MA Thesis Marije Vlaar 2007

Reconstruction of the Palaeoecology 

of the Eem Polder by 

means of dendrochronology, pollen 

and macrofossil analysis 

Marije Vlaar 

Master thesis Utrecht University, 2007 

Supervision: 

- Prof. dr. E. Jansma 

The National Service for Archaeology, Cultural 

Landscape and Built Heritage (RACM) 

Dutch Centre for Dendrochronology (Ring 

Foundation) 

- Prof. dr. G.J. van der Zwaan 

Utrecht University

Index ...........................................................................................................2 

Preface.......................................................................................................4 

Abstract.....................................................................................................6 

1. Introduction........................................................................................7 

2. Material and Methods.....................................................................9 

2.1 Location and site description...................................................9 

Geomorphological development of the Eem Valley 

2.2 Material: Sampling sites (Location 1 and 2).......................... 15 

2.2.1 Location 1, Groeneweg............................................... 15 

2.2.2 Location 2, Lodijk....................................................... 17 

2.3 Methods..................................................................................... 17 

2.3.1 Dendrochronology....................................................... 17 

General 

Calendars 

Sample preparation and the dating process 

Pointer years 

2.3.2 Pollen.............................................................................20 

General 

Sample preparation 

Counting and diagrams 

Comparison with known data 

2.3.3 Macrofossils...................................................................22 

General 


Analysis 

2.3.4 Radiocarbon dating........................................................23 

General 


3. Results and Interpretation.............................................................26 

3.1 Dendrochronological results.....................................................26 

Pointer years 

3.2 Pollen analysis............................................................................36 

Description of pollen diagram GP01 


3.3 Macrofossils................................................................................40 

3.4 Radiocarbon dating....................................................................41 

4. Discussion..............................................................................................43 

Dendrochronology 

Pointer Years 

Pollen and Macrofossil analysis 

2

5. Conclusions......................................................................................... 49 

Groeneweg 

Lodijk 

6. Further research............................................................................... 50 

7. References...........................................................................................51 

Appendix...................................................................................................55 

Appendix 1.......................................................................................55 

Appendix 2.......................................................................................56 

Appendix 3.......................................................................................59 

Appendix 4.......................................................................................61 

Appendix 5.......................................................................................67 

3

Preface 

After almost five years of studying Earth Sciences it was very pleasant to apply my 

knowledge during a final internship and to combine this with learning about a scientific 

discipline that was new to me. Starting my internship at the National Service for Archaeology, 

Cultural Landscape and Built Heritage (RACM), I discovered the field of dendrochronology, 

a method I had never worked with before. Coming from a background where time scales 

stretch out over millions of years, it was interesting to work with a dating method that is exact 

to the year. Besides the accuracy of dating, the dendrochronological analysis is also very 

understandable. Already during my first day I was able to date an old oak trunk. The 

combination of the study of dendrochronology with a pollen and macrofossil analysis 

supported my interest for palaeo-ecology and palaeo-botany. 

Prior to the different analyses that mostly occurred by using a microscope at the laboratory we 

accomplished some fieldwork in the Eem Polder. During these days we searched for tree 

remains and we sampled the soil for the pollen analysis. Large trunks were discovered in the 

field or were already collected by farmers. The practical activities of collecting, sawing and 

sampling made the fieldwork very pleasant as well. 

The last six months were very informative and interesting. This report is the result of all 

different analyses, discussions and interpretations. I never could have written this report 

without the help of many different people and I’m very grateful for their help and enthusiasm 

during this project. 

First of all I would like to thank my supervisor Esther Jansma (RACM, Ring Foundation). 

She introduced me to the field of dendrochronology and shared her enthusiasm about this 

science. She also performed many practical activities that were very useful during this 

research: the development of a new reference calendar was essential to date some of the trees 

by means of dendrochronology. It was very nice that she introduced different persons to me 

who were willing to participate in this research. Also, she had spent a lot of time on the 

revision of my thesis and she gave me useful comments to improve my report. I also want to 

congratulate her with her recent installation at Utrecht University as holder of a special chair 

dedicated to dendrochronology and palaeo-ecology of the quaternary. 

I could not have performed the pollen analysis without the help of Otto Brinkkemper 

(RACM). With great patience he taught me to determine all different vegetation species. He 

also scanned all samples on rare types and showed them to me to increase my knowledge. 

Besides the pollen analysis he dedicated a lot of his time to help me with many other 

problems and it was very pleasant to discuss some of the results together. 

Also, great regards go out to Marta Domínguez Delmás (Ring Foundation) for her very 

pleasant company, her help with dendrochronological problems and her comforting words 

especially during the last phase of this project. I want to thank Tamara Vernimmen (formerly 

of Ring Foundation) for her help with the macrofossil analysis and Elsemieke Hanraets 

(formerly of Ring Foundation) for her help with some dendrochronological measurements. I 

want to thank Bert van der Zwaan (Utrecht University) for his supervision, for bringing me in 

contact with Esther Jansma and for showing me the option of doing my final internship at the 

RACM. 

This whole project would not have existed without the enthusiasm of the Eem Polder 

volunteer group with Jantine Strating, Carla Vintges and Gerard Monkhorst. They started the 

project ‘Leefbaar Landschap’ in collaboration with the IVN (Association for natural and 

4

environmental education) to improve the public interest for the Eem Polder and were 

especially interested in the natural history of this area. Also the involved farmers, Kees van 

Valkengoed en Jan van Halteren were enthusiastic about this project. They showed us some 

tree remains that they found and tolerated that we excavated their grasslands. We couldn’t 

have performed the fieldwork without the help of Wim Jong (RACM). Due to his field 

activities I obtained some nice wood samples at the laboratory. Thanks to Hans van der Plicht 

(Centre for Isotope Research; University of Groningen) some wood and soil samples were 

radiocarbon dated. Despite the very busy schedule of his research centre he was willing to 

date my samples rapidly. He also welcomed me at his Centre of Isotope Research at the 

University of Groningen, showed me the laboratory and explained me the dating methods. 

The radiocarbon dating could not have been performed without Jos Deeben (RACM) who 

took care for the finances on behalf of the RACM. I want to thank the Laboratory of 

Palaeobotany en Palynology (Utrecht University) for giving me the opportunity to prepare the 

pollen and macrofossil samples, with a special thanks for Jan van Tongeren (Utrecht 

University) who performed most of the chemical treatments in their laboratory. Frans Bunnik 

(TNO-NITG) helped me with some problems during the pollen analysis and it was nice to 

discuss the vegetation history with him. I want to thank all other persons of the RACM who 

were interested in my project; Menne Kosian for giving me nice maps, Hans Peeters for 

literature and Ruud de Man for helping me to find my way in the beautiful library. 

Finally, I want to thank the National Service for Archaeology, Cultural Landscape and Built 

Heritage (RACM) and the Ring Foundation for giving me the opportunity to perform my final 

internship in a nice atmosphere and for using their facilities. 

5

Abstract 

The aim of this research is to reconstruct the palaeo-ecology of the Eem Polder by means of 

dendrochronology, pollen and macrofossils. Dendrochronology involves the study of annual 

ring-width variations through time. The tree-ring patterns in wood reflect the annual growth 

conditions, depending on different factors such as precipitation, temperature, hydrology, soil 

conditions and others. Synchronization of tree-ring patterns of sub-fossil wood with 

absolutely dated reference calendars makes it possible to date the trees. If trees can not be 

dated by means of dendrochronology, it is possible to date wood samples with the 

radiocarbon dating method. Pollen and macrofossil analyses are used to study the surrounding 

vegetation development. Together with the tree-ring pattern they contain information about 

the development of the soil on which the vegetation was growing. 

The Eem Polder is an area at the Eem Valley. This valley is formed during the Saalien period 

by ice sheets which covered large parts of Europe, including the northern part of the 

Netherlands. Tree remains are sampled at two different locations within the Eem Polder. At 

location Groeneweg two oaks (GFE01 and GFE02) are found in situ and they are dated by 

means of dendrochronology and radiocarbon. One of the studied oaks lived from 2719 until 

2570 BC and the other one from 2882 until 2581 BC. Synchronization with oaks from 

Ypenburg indicates that they were growing on an unsaturated substrate. The radiocarbon 

dates of GFE02 differ from the dendrochronological dates and it might be necessary to 

reconsider these radiocarbon dates. The tree-ring patterns of GFE01 and GFE02 show some 

simultaneous pointer years as the eight oaks from Ypenburg, caused by similar response to 

changing growth conditions. 

The pollen analysis that is performed on samples from the Groeneweg show a dominance of 

trees over herbs, indicating that the vegetation history of this area is characterized by the 

growth of a closed forest. Some macrofossil remains and also the appearance of clumps of 

pollen show the local appearance of species. Anthropogenic indicators are present in very low 

quantities indicating a minor influence of people in this area. The absence of water plants or 

peat forming plants confirm the unsaturated characteristic of the soil as shown by the studied 

oaks. From the results of the radiocarbon dating of three soil samples it turns out that the 

vegetation development took place during the Subboreal. The dates show that the studied oaks 

lived during the same period as the development of the studied profile occurred. The tree-ring 

pattern of GFE01 and GFE02 show that the trees died because of a sudden event and the 

preservation of the trees show that they were buried soon after their death. The pollen 

diagrams did not show any remarkable decrease of tree pollen during the studied period 

indicating that not the whole forest was influenced. 

Two oaks from location Lodijk are dated with a reference calendar build up with oaks that 

were growing in the province of Zuid-Holland. Oak LFE01 lived from 1678 until 1498 BC 

and LFE02 from 1688 until 1476 BC. The tree-ring patterns of the oaks show similarities with 

pointer years of 32 trees from the province of Zuid-Holland. Especially the rings formed 

during 1629 and 1628 BC were remarkable smaller. The trunks of LFE01 and LFE02 indicate 

that they were growing in a closed forest and other discovered root systems confirm this. The 

relation with undated pines from the same location is unknown, the stem form and shallow 

roots of these pines show that they were growing on a saturated, unstable substrate. In 

summary it can be stated that 5000 to 3000 years ago a closed-canopy forest grew in what 

now is called the Eem Polder. 

6

1. Introduction 

The surface on which we live is a treasure trove of earth’s own history. Sediments hold 

information about activities that once took place, a million years ago but also during the 

recent past. There are different ways to search for this information; from large glaciers in the 

mountains to the oceans floor, but also on smaller scales in our surrounding environment. 

The aim of this research is to reconstruct the palaeo-ecology of a part of the Eem Valley by 

performing a multi-proxy analysis on vegetation remains. Palaeo-ecological research 

concentrates on fossils and subfossils to reconstruct ecosystems of the past. This includes all 

organisms, their life cycle and natural environment. The study presented here only 

concentrates on subfossil vegetation remains to reconstruct the vegetation history. 

Knowledge about the palaeo-ecology of this valley is interesting from several points of view: 

From a biological point of view it is interesting to know which species were growing at a 

certain time and how their succession occurred. Looking at larger timescales, migration 

patterns of species through time are also interesting. 

From an archaeological point of view, vegetation history tells something about cultural 

development during certain periods. If vegetation patterns in the past change suddenly, it 

might be possible that people influenced the landscape by cutting trees or cultivating plants. 

Human migration and vegetation are also related; people only settle on areas which are 

attractive for them. 

There is also a natural-historical interest; many scientists research vegetation changes 

through time. There are several hypotheses about the Dutch palaeo-landscape. One of the 

theories states that the Dutch vegetation history was characterized by an open landscape with 

a mosaic of grasslands, shrubs and small tree groups. An autochthon fauna of herbivores 

prevented that the open landscape turned into a closed forest (Vera, 1997). 

Others state that the natural vegetation was characterized by a closed deciduous forest with 

oak (Quercus sp.), elm (Ulmus), lime (Tilia), ash (Fraxinus excelsior), beech (Fagus 

sylvatica), hornbeam (Carpinus betulus) and hazel (Corylus avallana) being the dominant 

species. The autochthon fauna of herbivores did not have influence on the succession of the 

forests. Rejuvenation took place in forest gaps originated by the collapse of single trees, 

following the gap-phase model of Watt (1947). 

This research is focused on a restricted area called the Eem Valley. This area received 

attention of public and scientists when farmers found tree remains perfectly preserved, lying 

half-buried under the surface. Because nothing was known about the age of the trees, we 

decided to conduct a dendrochronological research and found out when they had been living. 

In addition, to gather information about the ecological context in which the trees were 

growing, soils samples were taken and pollen and plant-macrofossils were analyzed. This 

multi-proxy approach provides information and gives more certainty about the vegetation 

history of this area. 

This research has attracted the attention not only of the farmers but also of some volunteers 

who want to improve the cultural interest for this area. By inserting information signs along 

roads for walkers and cyclists they want to promote the historical and natural value of this 

area. Some results of this research have been included on their information signs. 

7

To reconstruct the palaeo-ecology of the research area some questions should be answered: 

1. How many growth phases are represented in the different tree trunks that are found? 

- When did the trees germinate and die? 

- Do the tree-ring patterns or the shape of the trees give information about the 

environment in which they lived? 

2. Is it possible to relate the tree growth of the different phases to soil development? 

- How did the soil develop during the different phases? 

- On what kind of soil did the vegetation grow? 

3. Is it possible to discern relevant changes in the tree-growth pattern? How did the 

climatic conditions of that period affect the tree growth? 

- Do the growth patterns of the trees growing together in the Eem Valley 

resemble each other? 

- Do these patterns match with trees growing at the same time at other locations? 

- Were there major significant climatic changes during the growth period of 

these trees, and if so, are they recognizable in the growth pattern? 

4. What was the distribution and diversity of the surrounding vegetation during the 

different phases? 

- How is the vegetation related to time? 

- What plant species were present according to the palynological analysis? Is it 

possible to describe local and regional vegetation? 

- Is the vegetation development influenced by anthropogenic factors? 

- Does the palynological analysis agree with the dendrochronological research? 

- Is the distribution and diversity of vegetation related to any of the hypothesis 

about the natural Dutch palaeo-landscape? 

This study will try to answer these questions. After this introduction I will describe the 

‘Material and methods’ in chapter 2. First I will present the geomorphological development of 

the Eem Valley (chapter 2.1), followed by a description of how we sampled the two sites 

(chapter 2.2). The chapter will end with the different methods of dendrochronology, pollen 

and macrofossil analysis and radiocarbon dating (chapter 2.3). 

Chapter 3 will present the results of the dendrochronological research (chapter 3.1), the pollen 

analysis (chapter 3.2), the macrofossil analysis (chapter 3.3) and the radiocarbon dating 

(chapter 3.4). The results are discussed in chapter 4 and the conclusions are given in chapter 

5. I will end this report with some suggestions of further research (chapter 6), the references 

used for this report (chapter 7) and finally the appendixes. 

8

2. Material and Methods 

2.1 Location and site description 

The Eem Polder is situated in the Eem Valley and it belongs to a nature reserve called 

‘Arkemheen- Eemland’. Figure 1 shows the current perimeter of the nature reserve and the 

two locations (1 and 2) where the vegetation remains were collected. 

1 

2 

Border National 

Landscape 

Open Area 

Location Groeneweg 

Location Lodijk 

Figure 1: The Eem Polder is situated in the central part of the Netherlands. The two studied sites are within the 

nature reserve. 

Geomorphological development of the Eem Valley 

The development of the Eem Valley can be traced back to about 370.000 years ago, during 

the Saalien period. At that time ice sheets covered large parts of Europe, including the 

northern part of the Netherlands, with its southernmost boundary between Haarlem and 

Nijmegen. The Saalien period is characterized by a succession of relatively warm and cold 

periods, also called the ‘Saalien Complex Stage’, after Litt and Turner (de Mulder, Geluk, 

Ritsema, Westerhoff and Wong, 2003), with the coldest phase at the end of the period (Figure 

2). 

9

Figure 2: The Saalien Complex Stage is characterized by a variation of warm and cold periods 

(after de Mulder et al., 2003). 

The start of the Saalien (Stadial I after Zagwijn, 1973) was characterized by a scarce 

vegetation cover with birch (Betula sp.) and pine (Pinus sp.) trees and a more abundant cover 

of grasses (Poaceae) (de Mulder et al., 2003). The uncovered parts of the landscape were 

influenced by wind which deposited aeolian sediments. During the next stage, the so-called 

Hoogeveen Interstadial (Zagwijn, 1973), trees became more abundant, but birches and pines 

still were the dominant species (de Mulder et al., 2003). After the Hoogeveen Interstadial 

period a short colder period occurred again, which is called Stadial II (Zagwijn, 1973) (de 

Mulder et al., 2003). During this short cold phase the vegetation became more open again, 

and local aeolian sediments were formed. This cold period was followed by a warmer period 

called the Bantega Interstadial after a pollen analysis on material collected in Bantega. 

During the last and coldest phase of the Saalien (185.000-130.000 yr B.P.), ice sheets reached 

their maximum movement to the south creating depressions and ice-pushed ridges in the 

landscape. Figure 3 shows the maximum expansion of the ice sheets during this period, with a 

large glacial depression representing the Eem Valley. 

10

Figure 3: During the coldest phase of the Saalien, a glacial 

depression formed the Eem Valley (after de Mulder et al., 2003). 

Ice-pushed ridges are hills formed by the pressure of glaciers on sediments deposited 

previously. In contradiction, moraines are built up by sediments transported by the glaciers 

from elsewhere (de Mulder et al., 2003). In the Netherlands the Utrechtse Heuvelrug is the 

best known example of an ice-pushed ridge. 

Depressions are caused when ice sheets produce large amounts of melt water that erodes the 

substrate underneath. The ice will sink into the depression, where it will grow thicker and 

cause even more erosion. When finally the ice sheets melt, the depression will be filled with 

melt water and as a result a lake is formed. The most important depressions surrounded by 

ice-pushed ridges at the Dutch landscape were formed during the latest phase of the Saalien 

period. Examples are the Eem Valley, the IJsseldal and Nordhorn in Germany (de Mulder et 

al., 2003). 

After the Saalien period the Late Pleistocene starts which is divided into the Eemien 

(130.000-115.000 yr BP) and the Weichselien (115.000-10.000 yr BP) period. The Eemien 

period is called after the river Eem, which has also given its name to the Eem Valley and 

which ends into the IJssel Lake. During this period global temperature increased, causing 

large ice sheets in Northern Europe and North America to melt. As a result sea level rose to a 

level even higher than it is at present (de Mulder et al., 2003). 

11

Figure 4: The Eem Valley was flooded during the transgression 

phase of the Eemien (after de Mulder et al., 2003). 

The map in figure 4 shows the transgression phase of the Eemien, with large parts of the 

Netherlands, including the Eem Valley, flooded because of the high sea level. The ice cover 

during the Saalien influenced the morphology of the landscape and determined the influence 

of this marine transgression. The transgression phase caused deposition of marine sediments 

and along these areas peat development occurred on a large scale, mainly in the Eem Valley 

and in the Hunzedal (province of Drenthe) (de Mulder et al., 2003). 

The Weichselien is the latest glacial period: glaciers covered parts of northern Europe without 

reaching the Netherlands. The early Weichselien (115.000-73.000 yr BP) is characterized by a 

cold climate with an open landscape where pine and birch trees dominated. This cold stage 

also consisted of warmer periods during which forests developed, still dominated by birch and 

pine but with some spruce (Picea abies) present. In the southern part of the Netherlands oak 

formed an important part of the vegetation development. The middle-Weichselien (73.000- 

13.000 yr BP) started with a decrease of the global temperature, causing expansion of land ice 

on higher latitudes and a lowering of the sea level. The forests disappeared due to the low 

temperatures and erosion influences the landscape. 

The late-Weichselien (13.000-10.000 yr BP) is characterized by a variation of short warm and 

cold stages. It started with a relative warm stage with an open landscape dominated by birch. 

After a cold phase the vegetation recovered and pine trees took over the pioneer vegetation of 

birch and juniper (Juniperus communis) (de Mulder et al., 2003). During the latest 

millennium of the Weichselien temperature decreased again. 

12

During the Holocene (10.000 yr BP - present), melting of ice sheets in North-America and 

Scandinavia caused sea level to rise again. The North Sea, which dried during the 

Weichselien, was flooded and inundated larger parts of the Netherlands than it did during the 

transgression phase of the Eemien (de Mulder et al., 2003). The fast rise of the sea level 

ended about 7000 yr BP (Figure 5). When sea level rises, subsequently groundwater levels 

rises too, triggering environmental changes and influencing vegetation development (Peeters, 

2007). 

Figure 5: The fast sea level rise caused by melting of ice sheets ended 

7000 years BP (after de Mulder et al., 2003). 

The Holocene period is the most relevant period to this study because it is the first period in 

which people influenced the landscape. Important changes in the vegetation development 

occurred due to changes in the precipitation regime (de Mulder et al., 2003), but also because 

of cultural development. At the start of the Holocene vegetation developed as a natural 

response to climate and environment and was reflected by the succession of tree species 

(Figure 6). During the Preboreal birch was the most common species, after which pines 

became dominant. During the Atlanticum a mixed oak forest developed (de Mulder et al., 

2003). At the end of the Atlanticum culture developed towards permanent settlements and 

agriculture influenced the natural vegetation, which causes a relative decrease of trees and the 

first appearances of cultivated plants. During the Subboreal the decrease of trees and relative 

increase of herbs continued. During the Subatlatic the presence of natural vegetation came to 

an end and the natural landscape turned into a cultivated landscape. 

13

Figure 6: Vegetation development of the Late Weichselien and Holocene. This pollen diagram shows the general 

vegetation history of the Netherlands (after de Mulder et al., 2003). 

14

2.2 Material: Sampling sites (Location 1 and 2) 

The different sorts of vegetation remains used in this study were collected from various 

locations within the Eem Valley (Figure 1). Some of the remains were found in situ, buried in 

a grassland along the Groeneweg in Bunschoten (location 1). Other remains were gathered by 

a farmer along a highroad and on his grassland near the Lodijk in Bunschoten (location 2). 

The original location of the samples from the Lodijk is unknown. 

2.2.1 Location 1, Groeneweg 

Two large trees were identified in a grassland along the Groeneweg, because part of the 

trunks was visible in the adjacent ditch. These two trees are referred as GFE01 and GFE02 

(Groeneweg, Fossil oak, Eem Valley). The geographical coordinates (x;y) of GFE01 are 

155498.399; 472548.826 and those of GFE02 are 155473.385; 472559.495 (NedGraphics 

CAD/GIS). To determine the length and shape of the trees and the direction in which they 

were lying, metal sticks were inserted in the ground. With permission of the owner of the 

grassland a part of both trees was exposed by excavating (Figure 7a/b). In the exposed parts 

cross sections were cut with a chain saw. The thickest parts were cut into thinner samples at 

the laboratory (RACM) to make them fit under the microscope. From GFE01 two different 

sections were sawed, one closer to the roots and the other closer to the branches. From GFE02 

only one section was sawed. Because these trees were found in situ the surrounding sediments 

contain information about the environmental context of their growth. This information is 

present in the form of leaves, roots, seeds, pollen and spores. Right besides each stem, a 

sample of the profile was taken with a metal container (50x15x10 cm) (Figure 8a/b). These 

would cover the soil profile in which the trees were lying. The profiles are referred as GP01 

and GP02 (Groeneweg Profile) sampled near tree GFE01 and GFE02 respectively. Figure 9 

shows a schematic overview of the two trees and their location in the field. Their depth and 

the position of the profiles are shown in figure 10a and 10b. The two containers were stored at 

low temperatures to prevent decay of the material. 

Figure 7a: Tree GFE01. 

Figure 7b: Tree GFE02. 

Figure 8a: Profile GP01. 

Figure 8b: Profile GP02. 

15

Figure 9: A schematic overview of GFE01 and GFE02 in the grassland. Both trees were lying in the same 

direction. The black squares present the excavated parts with the sawed cross sections in white. The red lines 

present the location of the sampled soil profiles. 

Figure 10a: Schematic overview of GFE01 and its in situ location. 

Figure 10b: Schematic overview of GFE02 and its in situ location. 

16

Figure 11: LFE01 and LFE02 were collected by a farmer along 

a highway. 

2.2.2 Location 2, Lodijk 

At this location different trees were 

collected by a farmer. Two large trees 

were found along a highway where 

they became visible because of 

building activities (Figure 11). They 

are referred to as LFE01 and LFE02 

(Lodijk, Fossil oak, Eem Valley). 

LFE01 is 200 centimetre long and its 

diameter is 48 centimetre. LFE02 is 

255 centimetre long with a diameter 

of 37 centimetre. From LFE01 one 

cross section was taken, from LFE02 

two different ones. Other smaller tree 

fragments were gathered by the 

farmer on his land. Only the ones 

with enough rings for analysis were 

sampled. The original location of these samples is unknown because the trunks were moved 

prior to their discovery by the farmer and therefore no sediments were taken from this 

location. 

2.3 Methods 

To reconstruct the palaeo-ecology of the Eem Polder three different approaches were 

combined: 

1. The cross sections of trees were analyzed by means of dendrochronology 

2. In the soil sediments the content of pollen was analyzed 

3. A macrofossil analysis was performed by the determination of seeds, leaves, roots and 

small wood fragments 

2.3.1 Dendrochronology 

General 

The word dendrochronology is derived from the Greek words ‘dendron’ (tree), ‘chronos’ 

(time) and ‘logos’ (the science of) and it refers to the science that studies annual tree-ring 

variables through time (Grissino-Mayer, 2007). The main principles of dendrochronology are 

described in appendix 1 (Table 13). In temperate climate zones, tree species produce annual 

growth rings (a detailed explanation of tree growth and wood anatomy is described in 

appendix 2). Those tree rings will be wider or narrower depending on different factors such as 

precipitation, temperature, soil conditions and others. Tree-ring patterns of subfossil trees 

constitute a suitable record of proxidata for palaeoclimatological and ecological studies 

(Jansma, 2006). 

In Europe, oak (Quercus robur and Quercus petraea) is the most commonly used species for 

dendrochronological dating (Baillie, 1982). It is difficult to distinguish both species when 

remains of them are found. Only on living trees observation of the leaves and acorn cups may 

separate the two, but this can also be complicated because of the existence of hybrids (Baillie, 

1982). Despite of this, they can be used because of the common signal on environmental 

changes. When they are synchronized, the resulting calendars are useful for dating purposes. 

The growth pattern of oaks is influenced by climatic conditions that sometimes affected large 

areas. Because different oaks respond equally to annual climatic conditions, growth patterns 

17

of different oaks can be cross dated (Jansma, 1995). Cross dating is commonly used in 

dendrochronology. Tree-ring patterns of living trees can be matched with patterns of trees 

from earlier times, if a part of their growth pattern overlaps. Subsequently these growth 

patterns can be used to date older material (Figure 12). Doing so a dated chronology is 

developed and measurement series of an undated growth pattern can be dated with it. 

Figure 12: Wood can be dated by cross-dating 

if a part of their pattern overlaps (Grissino- 

Mayer, 2007). 

The last ring of the measurement series (the closest 

one to the outer part of the tree) will provide the 

closest date to the felling or death of the tree 

(Jansma, 1995). Because absolutely dated oaks do 

not extend further back than 12,000 years the 

dendrochronological dating method is restricted 

when it is used for absolute dating. Also, it is not 

always possible to date wood with this method for 

several reasons such as short tree-ring patterns, 

growth disturbances, reduced reaction on climate 

changes and the absence of reference calendars. 

However, for approximately the last 8,000 years 

dendrochronology has an advantage over all other 

dating methods, such as stratigraphy or 

radiocarbon dating, because it provides absolute 

dates, exact to the year (Jansma, 1995). 

Calendars 

Dated chronologies (also called calendars) are useful to match undated growth patterns. The 

calendars are built up by detrending and averaging cross dated series. Individual tree growth 

is dependent on different environmental factors which influence the ring-width series. The 

principle of aggregate tree growth (Appendix 1, table 13) is used to standardize individual 

tree-ring patterns. The oldest dated annual ring in the Dutch dataset was formed in 6025 BC. 

Following the overview from the national research agenda for archaeology (Jansma, 2006) 

dendrochronological data replication is described for eight consecutive archaeological 

periods. The overview of Dutch calendars described below is based on data available at the 

RACM and the Ring Foundation. The detailed overview of these periods is shown in 

appendix 3. 

1. 6025 – 2850 BC (Mid and New Stone Age) 

2. 2850 – 2000 BC (New Stone Age) 

3. 2000 – 800 BC (Bronze age) 

4. 800 – 12 BC (Iron age) 

5. 12 BC – AD 400 (Roman time) 

6. AD 400 – 1000 (Early Middle Ages) 

7. AD 1000 – 1500 (Mid and late Middle Ages) 

8. AD 1500 – 1950 (Early modern and modern time) 

18

Figure 13: The dendrochronology calendar 

contains two hiatus (Jansma, 2006). 

Unfortunately the existing calendars contain a 

couple of hiatus, periods for which no data is 

available (Figure 13). Different factors cause these 

hiatus. First, in order to develop useful calendars at 

least ten dated samples covering the same period 

are needed. Especially from prehistorically periods 

often not enough samples are available. Second, 

poor conservation of wood, the local absence of 

forests and felling activities decrease the 

availability of wood. 

Sample preparation and the dating process 

Prior to the dating of wood, samples have to be prepared. First the surfaces have to be 

cleaned. A thin surface layer is removed with a razor blade, making the rings along the radii 

visible. It is important to follow the direction of the radii and measure the ring widths 

perpendicular to tree-ring boundary. After cleaning, white chalk is put on the sample to fill 

the vessels and to enhance the contrast between early spring vessels and the denser summer 

wood (Appendix 2). The width of each individual ring is measured, starting from the first ring 

near the pith towards the last ring at the outside, using a measuring device that registers the 

ring-width sequences (Past 4, 2007). The tree-ring series are graphically displayed as a curve 

of ups and downs. The presence of sapwood rings or wane edge (Appendix 2) is registered for 

each sample. Whenever possible measurements are taken along different radii of the wood 

section and averaged into a mean curve per tree. The mean curve obtained from each tree has 

to be compared with existing chronologies for dating. Different statistical parameters describe 

the similarities between the curves; PV (Coefficient of Parallel Variation, also called 

Gleichläufichkeit (GL)), r (cross-correlation coefficient between two series) and t (the value 

resulting from a Students t-test on the highest value of r found when comparing the two 

series) (Jansma, 1995). PV calculates the fraction of ring widths that at a given position 

simultaneously show an increase or decrease relative to the previous ring width (Jansma, 

1995). The significance of this test depends on the overlap, a PV-value lower than 0.5 is not 

statistical significant. If the PV-value is 1 it means that the annual variation of ring widths is 

identical. 

‘The r is the correlation between the detrended series (x and y) and is estimated by: 

with n the number of values in each series, x i and y i the observed values in year i, x and y the 

mean of the series and S x and S y their standard deviation. To assess whether r xy deviates from 

zero, one uses the fact that the stochast has a Student distribution with (n-2) degrees of 

freedom’ (Jansma, 1995, pp 61). 

To produce a correct dendrochronological date the Students t-test must have a value of 5 or 

higher. 

19

Pointer years 

For studying the influence of climate on tree species, extreme ring widths in tree-ring series 

are a useful dendrochronological tool (Schweingruber, Eckstein, Serre-Bachet and Bräker, 

1990). Such extreme values are termed ‘event years’ and ‘pointer years’. An event year shows 

anomalous ring widths in a tree-ring series (Schweingruber et al., 1990) and a pointer year 

shows radial growth reduction or increase simultaneously replicated in several tree-ring series 

as a result of common forcing (Schweingruber et al., 1990). Several factors influence the 

appearance of event and pointer years, e.g. climate region, species, altitude (Desplanque, 

Rolland and Schweingruber, 1999). 

In this study pointer years of an existing dataset are compared to the ring patterns of the dated 

oaks (an overview of the datasets and their origin are shown in appendix 4). The dataset was 

selected because the chronologies of this dataset overlap in time with the dated trees of this 

research. The dataset contains several chronologies to make a statistical significant overview 

of pointer years. Their statistical comparison on pointer years was performed using the IPP 

Pointer Years Program, developed by Jansma (1991). 

The pointer years are compared on different significance levels; 

- 90% which requires a minimum of 5 ring sequences 



- 99.9% which requires a minimum of 13 ring sequences 

Using these four significance levels, the pointer years can then be visualized. 

2.3.2 Pollen 

General 

(Bennett and Willis, 2002) analyzed pollen content of sediments to investigate past climatic 

changes. At present, vegetation changes due to human impact, succession changes and biotic 

and abiotic factors also receive attention. Pollen analysis, more often referred as palynology, 

is concerned with the study of pollen, spores and other palynomorphs (plant and animal 

structures that are microscopic in size), both living as well as fossilized. Pollen grains are 

plants parts that contain a male nucleus for fertilization with the female nucleus in an ovule 

(Bennett and Willis, 2002). Spores are parts of ferns, mosses and fungi. Most pollen are 

dispersed either by wind, insects or water, plants with wind-dispersed pollen have the highest 

pollen production. Spores are wind-dispersed. 

That fraction of the pollen liberated into the atmosphere but not used for fertilization 

accumulates into sediments. Because the walls of pollen grains are very resistant against 

degradation, their preservation rate is high. The walls of pollen grains are built up of a 

mixture of cellulose and sporopollenin, both components are very resistant and chemically 

stable. The latter is resistant against most chemical and physical degradation, except oxidation 

(Bennett and Willis, 2002). This is an advantage because a large part of the pollen 

accumulated in anaerobic environments will be preserved. The other components of the 

sediments can be removed by chemical treatment in the laboratory, without dissolving the 

pollen. Birks and Birks (1980) described the main principles of palynology as follows: pollen 

and spores are produced in high abundances by plants and most of these produced 

palynomorphs accumulate in sediments. Pollen can be identified to various taxonomic levels. 

Because they are well mixed by atmospheric turbulence, the result is an uniform pollen rain in 

the sediments, where they are preserved in anaerobic environments. The pollen rain is a 

function of the composition of the vegetation. If pollen from sediments with a known age are 

20

identified, a vegetation reconstruction can be made in space and time. If many pollen samples 

are identified in a sequence of sediments, the vegetation changes throughout a period can be 

examined. And finally, using pollen spectra from different locations, it is possible to compare 

vegetation changes through time at different places. 


In preparation of the pollen analysis of the soil samples taken from the study sites at the 

Groeneweg, the surface of the profiles (GP01 and GP02) were cleaned to avoid contamination 

from surrounding sediments. Next, 12 samples at 4 centimetre intervals were taken from each 

container, starting from the bottom (Figure 14). Each subsample consists of 1 cm 3 material, 

taken from the middle part of the profile. All 24 samples were treated at the Laboratory of 

Palaeobotany and Palynology from Utrecht University to remove non-palynomorph organic 

matter and clastic sediments. Preceding this treatment a tablet with Lycopodium spore was 

added to each sample. The amount of Lycopodium in a sample can be used to estimate 

absolute pollen values. One Lycopodium tablet contains on average 18583 spores (Berglund 

and Persson, 2004) imbedded into the carbonate tablet. By adding hydrochloric acid (HCL) 

all carbonates (both of the tablet and of the sediments) were dissolved. Between all different 

steps of removing useless constituents with chemicals, the samples are homogenized, 

centrifuged and the added chemical is decanted. Some chemicals have more influence on the 

material when they are warmed up; therefore the samples were sometimes put in the dry-bath 

incubator to warm them. Homogenizing is important to ascertain that the chemicals have the 

same influence on the whole sample. It also avoids that heavier pollen grains sink down and 

escape the treatments. After removing the carbonates, potassium hydroxide (KOH) was added 

to remove organic debris. Unless pollen itself is also organic debris, this treatment will not 

solve the resistant wall of the grains. The remaining samples were sieved to remove the large 

material, and the sieved material, containing the pollen, was captured. From the remaining 

samples the silicates were removed using hydrogen fluoride (HF). Next to the silicates, the 

fluoride gels were removed with hydrochloric acid (HCL). Finally, the remaining organic 

matter was removed again using potassium hydroxide (KOH). The resulting samples mainly 

consist of palynomorphs. The samples were coloured with acetolysis. This makes it easier to 

recognize characteristics of certain pollen grains and removes finally the remaining organic 

matter except pollen grains. Before the samples were put on a microscope slide, glycerine was 

added, to prevent the samples from drying out on the slides. Due to the high density of 

palynomorphs one microscope slide for each sample was sufficient. 

Figure 14: Both profiles were divided into 12 samples from which the yellow labelled samples were selected for 

analysis. 

21

Counting and diagrams 

Due to time constraints not all 12 samples per container could be investigated. The selected 

samples for analysis are shown in figure 14. These samples were chosen to provide an 

overview of the whole profile and include the first and last sample. The palynomorphs were 

determined using a microscope at a magnification of 400x and for critical determinations a 

magnification of 1000x was used. During the analysis pollen and spores were classified and 

counted until a number of 300 tree pollen was reached. In addition, remarkable features such 

as fungi were registered. From a statistical point of view, counting until 300 tree pollen is 

enough to show the vegetation content of a sample (Bennett and Willis, 2002). After 

counting, the samples were scanned by O. Brinkkemper on pollen types not noticed before 

and these were included as rare types with ‘+’ (one specimen) or ‘++’ (more specimen) in the 

pollen diagrams. The amount of pollen and spores per samples were transformed to 

percentages and mapped in pollen diagrams against depth (Tiliagraph, 2001) 

Comparison with known data 

Pollen analysis can be useful to date sediments. In the Netherlands, a lot of research is done 

on vegetation development and a general vegetation history has been developed. This 

vegetation history is divided into several pollen zones, based on the first appearances or 

disappearances of certain species, e.g. the first appearance of beech in the Netherlands occurs 

around 2000 BC and the occurrence of beech pollen in a sample therefore indicates the date of 

the sediments after 2000 BC. The general overview is often used as a dating background. 

Three different samples from profile GP01 were radiocarbon dated and these dates were used 

to assign the vegetation to a time period. The radiocarbon dates were given as dates before 

present (BP) and were calibrated to dates before Christ (cal. BC) (Wincal25, Centre of Isotope 

Research at the university of Groningen). 

2.3.3 Macrofossils 

General 

Plant macrofossils are very helpful when reconstructing the vegetation history. In this study 

the term macrofossils refers to leaves, seeds, branches and roots. Compared to pollen, such 

remains are more sensitive to degradation, but when they accumulate into anaerobic 

conditions they will be well preserved. The advantage of macrofossil analysis over the 

analysis of pollen is that macrofossils represent the local vegetation because they have not 

become dispersed far from their source (Birks and Birks, 2006), whereas pollen can be blown 

in from elsewhere. 


To be able to relate the macrofossils to the pollen, the samples of macrofossils and pollen 

were taken at the same height in the profile. A slice of sediment was cut and the edges were 

removed to avoid contamination. To remove the material too small for macrofossil analysis, 

all samples were sieved using 250 and 125 μm mesh width. The volumes of the samples were 

measured before the samples were sieved. The resulting macrofossil samples were stored in 

demineralised water to avoid decomposition of the material. 

Analysis 

The macrofossil samples were analyzed on their content. The species in the fossil remains 

were determined and their number was estimated. Besides vegetation remains such as seeds, 

roots and leaves, also fragments of insects, fungi and charcoal were noted. Three samples 

from profile GP01 were analyzed by T. Vernimmen using a stereomicroscope at a 

22

magnification of 50x; (number 1 from the oldest part, number 6 from the middle part and 

number 12 from the youngest part). 

2.3.4 Radiocarbon dating 

General 

If wood can not be dated by means of dendrochronology, radiocarbon dating is a good 

12 13 

alternative. In nature, three different carbon isotopes exist, the two stable isotopes C and C 

14 14 

and the radioactive isotope C (Van der Plicht, 2006). C atoms are produced when cosmic 

particles from galaxies in outer space transform 14 N atoms in our atmosphere into radioactive 

14 C atoms, which then slowly decay (Ruddiman, 2002). Earth is protected against these 

cosmic rays by its magnetic field and therefore the atmospheric 14 C content is sensitive to the 

geomagnetic field strength and also to solar fluctuations (Kitagawa and Van der Plicht, 1998). 

14 C is added to the carbon cycle as CO 2 where it is used by living plants for their 

photosynthesis. Animals take up 14 C indirectly through their food. As soon as an organism 

dies, the exchange with CO 2 stops, and the remaining 14 C decays with a half lifetime of 5730 

years (Van der Plicht, 2006). By measuring the remaining 14 C content of a dead organism, the 

time that passes since its death can be estimated. 

Using the half lifetime of 14 C for dating is only possible if the half lifetime and the original 

concentration of 14 C are known, both being a problem within this method. When this method 

was first applied (1950) the half lifetime of 14 C was considered as 5568 year, but continuation 

of research showed that this half lifetime actually is 5730 years. Also, the atmospheric 14 C 

content is not constant because earth’s magnetic field and solar activity vary. Besides these 

two problems, isotope fractionation changes the 14 C content of organisms. To solve these 

problems a radiocarbon time scale was made, based on three principles (Van der Plicht, 

2006); 

- The original half-life time (from 1950) of 5568 years is used, instead of the actual half 

life time of 5730 years 

13 

- Fractionation is corrected using the stable isotope C 

14 14 

- C is measured relative to a standard, equal to the year 1950. C ages are given as BP 

(Before Present), where present is the year 1950. 

Because of these assumptions the created radiocarbon time scale is not equal to the calendar 

time scale, and the differences vary through time due to changing natural 14 C- content. 

Therefore the radiocarbon calendar has to be calibrated to an independent calendar. 

Radiocarbon calibration can be performed by 14 C dating of samples that also can be dated by 

an independent and preferably absolute dating method (Kitagawa and Van der Plicht, 1998). 

Tree rings are perfect samples for this purpose since they have an accurate annual time scale 

that can be dated by dendrochronology (Kitagawa and Van der Plicht, 1998). 

Dendrochronological calibration has been obtained back to 12.000 years. The calibration 

curve has been extended back to 26.000 BP, using dated corals (with 14 C and uranium 

isotopes) and laminated sediments from the Cariaco basin, in which the foraminifera (single 

celled organisms with calcareous tests) were dated (Reimer, Baillie, Bard, Bayliss, Beck, 

Bertrand, Blackwell, Buck, Burr, Cutler, Damon, Edwards, Fairbanks, Friedrich, Guilderson, 

Hogg, Hughen, Kromer, McCormac, Manning, Ramsey, Reimer, Remmele, Southon, Stuiver, 

Talamo, Taylor, Van der Plicht, and Weyhenmeyer, 2004). Recently different calibration 

curves have been obtained from varves, marine sediments and stalactites, extending the 

calibration curve back to 50.000 year BP. The only terrestrial 14 C samples used for this 

elongation are terrestrial remains such as roots, insects and leaves from laminated sediments 

of Lake Suigetsu in Japan (Kitagawa and Van der Plicht, 1998). 

23

Variations in the natural 14 C content cause fluctuations in the calibration curve. These 

fluctuations are called ‘wiggles’ (Van der Plicht, 2006) and although they complicate the 

calibration of 14 C dates, they can also be used to improve the accuracy of the radiocarbon 

dates. This is possible when several samples, with a known time period between them, are 

used. This method is called ‘wiggle-matching’ (Van der Plicht, 2006). This method is well 

suited when a piece of wood is not datable using dendrochronology. Because the time period 

between the rings is exactly known they from a chronology from which 14 C measurements can 

be obtained. Those measurements belong to a part of a calibration curve and are compared to 

the actual calibration curve to date the samples. 

Two different methods can be used; the conventional and the AMS-method (Van der Plicht, 

2006). The conventional method is based on radiometry and measures the radioactivity of the 

still present 14 C. For this method approximately 200 grams of carbon are needed and one 

measurement takes a few days. The AMS-method (Accelerator Mass Spectrometry) is based 

on mass spectrometry; elements of a sample are analyzed on their mass by giving them 

velocity, electrical charge and by separating them using a magnet. This method needs 1 mg of 

carbon, and measurements can be performed in less than one hour. Although the small sample 

fraction for the AMS-method is an advantage (it can date pollen, seeds and small 

macrofossils), the method also has some disadvantages; when using small samples the chance 

of contamination with other samples is larger and if the actual sample is not homogeneous, a 

small part of this sample might not be representative. Because of these disadvantages 

conventional measuring has the preference above the AMS-method when enough material is 

available (Van der Plicht, 2006). 


Besides the dendrochronological dating of wood, some wood and peat samples were dated 

using the radiocarbon method. From location Groeneweg, tree GFE02 was chosen, together 

with four samples from profile GP01. From location Lodijk four different pine samples were 

selected. 

Tree GFE02 was chosen because of 

its high number of tree rings, which 

enables dating the wood by 

‘wiggle-matching’. From this piece 

of wood every tenth ring was 

sampled, counting from the pith, 

ending with ring number 230 

(Figure 15) that represents 

sapwood. Exactly one ring per 

sample (with a minimum of 100 

milligrams) was cut out with a 

scalpel preventing the two 

surrounding rings being added to 

the sample. 

Figure 15: Subsamples of every tenth ring of tree GFE02 were radiocarbon dated. 

24

The pines did not contain enough tree rings for the ‘wiggle-matching’ method, but the AMSmethod 

could be performed. Because of the accuracy of the AMS-method, it was not 

necessary to measure exactly one ring. Counting rings from pine wood is more difficult than 

those of oaks because pines often form false rings. To select rings for radiocarbon dating one 

must be certain which rings were chosen. To make the dating more useful, some of the oldest 

rings were selected with a maximum of 5 rings. The rings of three different pine samples were 

subsampled for 14 C analysis: 

• LFE04: This sample contained at least 80 rings, but the oldest rings were difficult to 

measure and the exact amount was unclear. The subsample for 14 C dating contains 

ring 84 onwards with a maximum of 5 rings. 

• LFE07: This piece was characterized by a large part of reaction wood. Two different 

radii were measured, into two directions. Both of these radii correlate until ring 51, 

therefore rings 48 and 49 were chosen because these rings were obviously identifiable. 

• LFE08: Although this piece of wood contains 94 rings the outer rings were difficult to 

identify because they were very small and did not produce enough material for dating. 

Ring 70 till 74 were sampled because they were clearly visible. 

From profile GP01 four different samples were selected for radiocarbon dating. The first aim 

was to select macrofossils such as seeds, leaves or branches. But because most of the material 

was degraded, it was not possible to select complete macrofossils and three samples of bulk 

material had to be selected instead: sample 1 from the oldest part, sample 6 from the middle 

part and sample 12 from the youngest part. If roots were still recognizable, they were 

removed from the bulk material. Contamination of the bulk material with younger roots can 

cause 14 C ages to be too young (Yeloff, Bennett, Blaauw, Mauquoy, Sillasoo, Van der Plicht 

and Van Geel, 2006). Fortunately, in sample 12 also a branch was found, determined as 

Betula sp., and useful for radiocarbon dating. 

All samples were send to the Centre of Isotope Research at the university of Groningen 

(Figure 16) where they were dated using the AMS-method. 

Figure 16a: The Accelerator Mass Spectrometry 

measuring device. 

Figure 16b: The conventional measuring device. 

25

3. Results and Interpretation 

3.1 Dendrochronological results (Ring rapport number 2007060) 

The two trees found in situ at location 1 (Figure 1) were both determined as oak (Quercus 

robur/petraea.). Unfortunately, synchronization of GFE01 with reference calendars did not 

give a significant result. Because both tree patterns have a significant comparison (α = 

0.0001), the dated tree GFE02 is used as a reference to date GFE01 (Table 1). The 

dendrochronological analysis showed that they were living in the same period: GFE01 from 

2719 until 2570 BC and GFE02 from 2882 until 2581 BC. The graphical comparison between 

GFE01 and GFE02 is shown in figure 17 and in more detail in figure 18, their common 

interval is 139 rings. The grey vertical areas represent the percentage of parallel variation 

(PV) (Chapter 2.3.1). 

Because GFE01 did not contain sapwood rings or wane edge, the exact date of death of the 

tree is unknown and can only be estimated. Date of death estimations (Jansma, 2007) give 22 

± 7 sapwood rings for this tree. If the last heartwood ring of the sample would be measured, 

the date of death of the tree would be included in the interval –2570 + (22 ± 7). However, the 

number of heartwood rings missing towards the sapwood is unknown. Therefore it only can 

be said that the tree died after –2570 + (22 - 7) = - 2555 

Table 1: GFE01 is dated with GFE02 as a reference, both trees show a significant comparison. 

Tree Number Start End Date Sapwood THO GL Overlap Significance Reference 

of rings Year Year of estimation 

(α) chronology 

(BC) (BC) death 

(BC) 

after 

GFE01 150 2719 2570 2555 22 ± 7 6.461 69.780 139 0.0001 GFE02 

Figure 17: Graphical comparison of GFE01 (orange) and GFE02 (purple). The y-axis (logarithmic) shows the 

ring width (mm -2 ) and the x-axis gives the calendar year. The grey areas represent the PV. 

26

Figure 18: A detailed overview of the corresponding part of GFE01 (orange) and GFE02 (purple). The y-axis 

(logarithmic) shows the ring width (mm -2 ) and the x-axis gives the calendar year. The grey areas represent the 

PV. 

GFE02 is dated by synchronization with YPFKLSt (α = 0.0002) (Table 2). Table 3 shows the 

information of the used reference chronology. GFE02 contained 25 sapwood rings, but no 

wane edge. Calculations of the date of death (Jansma, 2007) gave an sapwood estimation of 9 

± 8 rings. The last measured sapwood ring is from 2581 BC. The date of death of GFE02 can 

be calculated as: -2581 + (9 ± 8) = 2572 ± 8. This means that the date of death of GFE02 is 

after 2580 BC and because there are no heartwood rings missing, the tree died before 2564 

BC. The graphical synchronization between GFE02 and YPFKLSt is shown in figure 19, with 

the grey areas presenting the PV. 

Tree 

Table 2: GFE02 is dated with reference calendar YPFKLSt 

Number 

Number 

Start 

End 

Date of 

Sapwood 

of rings 

of 

Year 

Year 

death 

estimation 

sapwood (BC) 

(BC) 

(BC) 

rings 

GFE02 302 25 2882 2581 2580 / 

2564 

between 

THO 

GL 

Overlap 

Significance 

(α) 

Reference 

chronology 

9 ± 8 5.485 62.150 247 0.0002 YPFKLSt 

Table 3: Information about the used reference chronology 

Reference Country Province Number 

chronology 

YPFKLSt The Netherlands Zuid- 

Holland, 

Ypenburg 

Start Year End Year Author 

of rings (BC) (BC) 

247 2860 2614 E. Jansma, 2007, 

based on data by 

Van Daalen 

(2001) 

27

Figure 19: Graphical comparison between GFE02 (green) and YPFKLSt (blue). The y-axis (logarithmic) shows 

the ring width (mm -2 ) and the x-axis gives the calendar year. The grey areas represent the PV. 

The tree-ring patterns of GFE01 and GFE02 were averaged into a site chronology (GFE1_2). 

The graphical synchronization of GFE1_2 (2882 – 2570 BC) with the reference calendar of 

YPFKLSt is shown in figure 20. The statistical results in table 4 shows that GFE1_2 and 

YPFKLSt synchronized together (α = 0.0002). 

Figure 20: Synchronization of the site chronology GFE1_2 (green) with the reference chronology YPFKLSt 

(blue). The y-axis (logarithmic) shows the ring width (mm -2 ) and the x-axis gives the calendar year. The grey 

areas represent the PV. 

Table 4: Results of the dendrochronological comparison of site chronology GFE1_2 with the reference 

chronology YPFKLSt. 

Site Number Start End Date of death THO GL Overlap Significance Reference 

Chronology of rings Year Year (BC) after 


(BC) (BC) 

GFE1_2 313 2882 2570 2555 5.992 62.550 247 0.0002 YPFKLSt 

28

The trees referred to as LFE01 and LFE02 from location 2 

(Figure 1) were also determined as oaks (Quercus 

robur/petraea). The trunks were characterized by the 

absence of branches; on both trees only one branch-growth 

was visible (Figure 21). Dendrochronological analysis 

indicates that these trees were living in the same period: 

LFE01 from 1678 until 1498 BC and LFE02 from 1688 

until 1476 BC. These dendrochronological dates are the 

result of the synchronization with reference calendar 

NLVEEN04 (α = 0.0001) 

Figure 21: The trunks showed 

one branch-growth. 

The ring pattern of LFE01 shows a normal growth pattern 

with juvenile wide rings at the beginning, followed by smaller rings due to the aging effect 

when the tree grows older. The ring pattern of LFE02 shows at the first beginning small ring 

widths where after a normal growth pattern appears, with the aging effect of small older rings. 

After 1582 BC the ring widths become remarkable smaller and subsequently it recovers from 

1566 BC onwards, showing wider rings. 

The ring widths of both trees were measured and compared to reference calendars. The best 

synchronization for both trees was found with the reference chronology NLVEEN04 (Table 

5). Table 6 shows the information of the reference chronology NLVEEN04. The samples did 

not contain sapwood or wane edge and the exact date of death of the trees is estimated. 

According to Jansma (2007) the sapwood estimation for sample LFE01 would be 25 ± 9 

rings. The number of heartwood rings missing towards the sapwood is unknown. Therefore it 

only can be said that the tree died after –1498 + (25-9) = -1482. Proceeding in the same 

manner, the sapwood estimations of LFE02 would be 28 ± 10. Again the number of 

heartwood rings till the first sapwood is unknown and it only can be stated that the tree died 

after –1476 + (28-10) = -1458. 

Table 5: Results of the dendrochronological comparison of LFE01 and LFE02 with the reference chronology 

NLVEEN04. 

Tree Number Start End Date of Sapwood THO GL Overlap Significance Reference 

of rings Year Year death (BC) estimations 


(BC) (BC) (after) 

LFE01 181 1678 1498 1482 25 ± 9 6.408 68.230 181 0.0001 NLVEEN04 

LFE02 213 1688 1476 1458 28 ± 10 6.887 65.730 213 0.0001 NLVEEN04 

Table 6: Information about the used reference chronology 

Reference Country Province Number Start Year End Year Author 

chronology 

of rings (BC) (BC) 

NLVEEN04 The Netherlands Zuid- 

Holland 

1601 2258 658 E. Jansma, 

1997 

29

Figure 22 shows the visual synchronization between LFE01 and LFE02. Their common 

interval is 181 rings, equal to the total amount of rings of LFE01. The graphical 

synchronization of LFE01 and LFE02 with the reference chronology NLVEEN04 is shown in 

figure 23 and 24 respectively. The site chronology LFE1_2 is the mean tree-ring pattern of 

LFE01 and LFE02. The results of the synchronization of LFE1_2 with NLVEEN04 are 

shown in table 7. The visual synchronization of this site chronology with the reference 

NLVEEN04 is shown in figure 25. 

Figure 22: The tree-ring pattern of LFE01 (orange) and LFE02 (purple) do synchronize together with a common 

interval of 181 rings. The y-axis (logarithmic) shows the ring width (mm -2 ) and the x-axis gives the calendar 

year. The grey areas represent the PV. 

Figure 23: Synchronization of the dated sample LFE01 (green) with the reference chronology NLVEEN04 



30

Figure 24: Sample LFE02 (green) is also dated with the reference chronology NLVEEN04 (blue). The y-axis 

(logarithmic) shows the ring width (mm -2 ) and the x-axis gives the calendar year. The grey areas represent the 

PV. 

Table 7: Results of the dendrochronological comparison of site chronology LFE1_2 with the reference 

chronology NLVEEN04. 

Site 

Number 

Start 

End 

Date of THO 

GL 

Overlap 

Significance 

Reference 

Chronology 

of rings 

Year 

Year 

death 

(α) 

chronology 

(BC) 

(BC) 

(BC) 

(after) 

LFE 213 1688 1476 1458 7.671 66.430 213 0.0001 NLVEEN04 

1_2 

Figure 25: Synchronization of the site chronology LFE1_2 (green) with the reference chronology NLVEEN04 



31

Besides LFE01 and LFE02 also some other small 

trunks were discovered but they were not useful for 

dendrochronology because the nearby root system 

deformed the tree rings. This root system was 

characterized by shallow roots (Figure 26) and the 

absence of deep taproots. Besides these trunks, many 

root systems were discovered in situ near the place 

where the oaks were found. 

Figure 26: A shallow root system. 

The small pieces of wood collected by the farmer on this land were determined as pine (Pinus 

sylvestris). Some of the collected pine trees showed remarkable growth of the stems. The 

bended forms (Figure 27) are also called ‘saber tooth growth’ (personal communication E. 

Jansma). Unfortunately none of these samples could be dated by dendrochronology. Table 8 

shows an overview of the pine trees which were measured. 

Table 8: Pine samples were 

measured on their tree rings. They 

could not be dated by means of 

dendrochronology. 

Tree Number Date 

of rings 

LFE04 97 Undated 



Figure 27: ‘Saber tooth growth’ 

32

Pointer years 

The tree-ring patterns of the samples GFE01 and GFE02 were compared graphically with a 

pointer year graph obtained from 8 trees that lived during the same period but in a different 

area (Ypenburg, province of Zuid-Holland). These 8 trees were selected because they had a 

significant correlation with the oaks from location 1. The results are plotted in figure 28 and 

29 respectively. The pointer years require a minimum sample number (Appendix 4, Table 14). 

The results are given on four different significance levels (Appendix 4, Table15). The bars on 

the positive part of the graphic show the positive pointer years (parallel increased growth), 

whereas the negative part of the graphic shows the negative pointer years (parallel decreased 

growth). Table 16 (Appendix 4) shows which tree measurements from Ypenburg are 

included. 

99% 

95% 

90% 

99.9% 

99% 

95% 

90% 

90% 

95% 

99% 

99.9% 

Figure 28: The ring width pattern of GFE01 compared to pointer years of 8 trees. The bars show the pointer 

years on different significance levels (90, 95, 99 and 99.9 %). The shortest bars show the lowest significance 

level and the longest bars show the highest significance level. 

99.9% 

99% 

95% 

90% 

90% 

95% 

99% 

99.9% 

Figure 29: The ring width pattern of GFE02 compared to pointer years of 8 trees. The bars show the pointer 

years on different significance levels (90, 95, 99 and 99.9 %). The shortest bars show the lowest significance 

level and the longest bars show the highest significance level. 

The pointer years of 8 oaks from Ypenburg and two oaks from the Eem Polder show 

similarities but it is obvious that the statistical results of the comparisons are not highly 

significant. This is caused by the small amount of trees that is used for the analysis and not by 

an less significant event. During the growth of GFE01 only three pointer years were showed 

33

y the 8 trees from Ypenburg. This is not a statistical result, but the result of a small overlap 

between the tree-ring pattern of GFE01 and of the trees from Ypenburg. 

The tree-ring patterns of the samples LFE01 and LFE02 were compared graphically with a 

pointer year graph obtained from 32 trees from different locations in the province of Zuid- 

Holland. The tree-ring patterns of LFE01 and LFE02 are plotted with the pointer years of 

these 32 trees (Appendix 4, table 17) in figure 30 and 31 respectively. Table 18 (Appendix 4) 

shows the original location of these trees and table 19 (Appendix 4) shows which tree 

measurements are included. 

99.9% 

99% 

95% 

90% 

90% 

95% 

99% 

99.9% 

Figure 30: The ring width pattern of LFE01 (pink curve) compared to pointer years (bars) of 32 trees. The bars 

show the pointer years on different significance levels (90, 95, 99 and 99.9 %). The shortest bars show the lowest 

significance level and the longest bars show the highest significance level. 

99.9% 

99% 

95% 

90% 

90% 

95% 

99% 

99.9% 

Figure 31: The ring width pattern of LFE02 (pink curve) compared to pointer years (bars) of 32 trees. The bars 

show the pointer years on different significance levels (90, 95, 99 and 99.9 %). The shortest bars show the lowest 

significance level and the longest bars show the highest significance level. 

34

Table 9: Pointer years with a 99.9% significance level, 

three positive and four negative pointer years. 

Pointer years with a 99.9% significance level based on 32 

trees (province of Zuid-Holland) 

Positive Pointer Year (BC) Negative Pointer Year (BC) 

1660 1629 

1605 1628 

1582 1602 

1594 

Table 9 summarizes the positive and negative pointer years of the 32 trees from the province 

of Zuid-Holland on a 99.9% significance level. When only concentrating on these pointer 

years, the tree pattern of LFE01 shows some similarities. The first positive pointer year (1660 

BC) coincidence with an remarkable wider ring of LFE01. Also the positive pointer years 

from 1605 and 1582 BC show a sudden increase in ring width. The negative pointer years of 

1629 and 1628 are remarkable because they present two following years. LFE01 also shows 

smaller rings during both years. The negative pointer year from 1602 BC coincidence with a 

sudden decrease in ring width and although less obvious, also the ring width formed in 1594 

BC decreases. The tree-ring pattern of LFE01 also show some notable ring width changes that 

are not accomplished with pointer years of the 32 trees like a remarkable smaller ring at 1658 

BC and a remarkable wider ring at 1655 BC. 

The tree-ring pattern of LFE02 also shows many similarities with the pointer years of the 32 

trees from the province of Zuid-Holland. The positive pointer year from 1660 BC 

coincidences with a small ring width increase whereas the other pointer years are more similar 

with ring width changes of LFE02. Obviously, the tree-ring pattern of LFE02 shows a trend 

of smaller rings between 1580 and 1550 BC, only corresponding with one negative pointer 

year at 1569 BC. 

35

3.2 Pollen analysis 

The pollen analyses performed on the samples from Groeneweg (GP01 and GP02) resulted in 

two pollen diagrams (Figure 34a/b). The determined species are divided into several groups 

(upland trees, wetland trees, anthropogenic indicators, herbs, spores, scalariform perforation 

plate of wood, types and indeterminable pollen). Both figures show the lithology column of 

the profile with sand on the lower part and peat representing the major part of the profile. 

Some samples from profile GP01 were radiocarbon dated and these dates are visible in the 

figure. The radiocarbon dates were calibrated to calendar years, also plotted in the figure. 

The diagrams present percentages of the total amount of determined species, plotted against 

depth below NAP (Dutch Ordnance Datum). Two different graph styles are plotted in the 

diagram; the dark-grey colour shows the actual percentages of the graph, whereas the hatched 

graphs are 10 times exaggerated to make the presence of species visible. The first graph 

shows a cumulative diagram (percentages) of the upland trees, wetland trees and herbs. Pollen 

sums present the absolute total of upland trees, wetland trees and herbs. Rare types which 

were added to the diagram after scanning the samples are presented by the ‘+’ and ‘++’ 

symbols. Appendix 5 shows the absolute concentration of upland trees, wetland trees and 

herbs together. This absolute curve is calculated by making use of the added and counted 

Lycopodium spores per sample relative to the counted pollen. The diagrams show no obvious 

vegetation changes, i.e. a sudden increase, decrease, appearance or disappearance of species, 

therefore the diagram is not divided into separate pollen zones. 


Tree species (both upland and wetland) represent the most dominant group in this diagram. 

The most dominant trees within the upland trees are hazel (Corylus avellana) and oak 

(Quercus sp.), with a minor dominance of birch (Betula). These three species have a rather 

constant appearance in the vegetation, although at the upper part hazel increases and oak 

decreases slightly. In the lowest part, lime (Tilia) has its highest appearance and after its 

amount decreases lime is present at a constant low amount. The same pattern applies for elm 

(Ulmus), although this species has even lower quantities. Pine (Pinus sylvestris) is constantly 

present with low numbers. Ash (Fraxinus excelsior), ivy (Hedera helix), holly (Ilex aquifolia) 

and mistletoe (Viscum album) all appear as rare types at the lower part and the first three 

appear along the profile with small quantities or as rare types. Pollen grains of ivy, holly and 

mistletoe are shown in figure 32. 

Figure 32a: Ivy 

(Hedera helix) 

Figure 32b: Holly (Ilex 

aquifolia). The left 

picture shows the polar 

view 

Figure 32c: 

Mistletoe 

(Viscum album) 

Woodbine (Lonicera periclymenum) is counted in the lowest sample and appears furthermore 

as a rare type several times. Finally, in the upper part a pollen grain of beech (Fagus 

sylvatica) was counted. Alder (Alnus sp.) is by far the most dominant wetland tree with a 

constant occurrence through the column. From alder and oak also some clumps of (immature) 

pollen were found (Figure 33). Willow (Salix) appears a couple of times. 

36

Herbs (including anthropogenic indicators) play a minor role in this vegetation. The most 

common herbs are heath (Ericales) and grasses. Spores were also determined in low 

quantities but present in all samples. Scalariform perforation plates appear in the middle and 

upper part. They are most probably from alder, but birch is also possible. One type of fungi 

(type 2, Gelasinospora) was found in this profile. 


Trees (upland and wetland) are also the most dominant group of 

species in profile GP02, with a higher abundance of upland trees in 

comparison with profile GP01. Hazel and especially oak are the most 

dominant upland species and they show an opposite appearance. 

Again some clumps of oak and alder pollen grains (Figure 33) were 

found. Birch is constantly present with a large increase in the upper 

part. Pine, lime and elm are constantly present, but in low quantities. 

Whereas beech occurred in GP01 only in the upper part, in GP02 it 

appears only in the lowest part. Ash, ivy and holly appear in low 

quantities along the profile, sometimes noticed as rare types. 

Figure 33: clumps of 

oak pollen. 

Woodbine and hornbeam (Carpinus) both were observed once as rare types. Alder represents 

again the most dominant wetland tree, with some occurrence of willow and bog myrtle 

(Myrica gale). The herbs (including anthropogenic indicators) are the minor group in this 

diagram, with again heath and grasses being the most frequent species. Some spores were 

determined, but they appear in low quantities along the profile. Scalariform perforation plates 

appear only in the upper part. Three different fungi types were determined, with a striking 

abundance of type 112 (Cercophora) in the highest part of the profile. 

37

Salix 

Ilex 

Asteraceae liguflorae 

Asteraceae tubuliflorae 

Alisma 

Apiaceae 

Caryophyllaceae 

Cyperaceae 

Ericales 

Vaccinium-type 

Galium-type 

Humulus lupulus 

Hydrocotyle 

Poaceae 

Potentilla-type 

Solanum dulcamara 

Sparganium erectum-type 

Typha latifolia 

Dryopteris-type 

Polypodium-type 

Pteridium-type 

Sphagnum 

Scalariform perforation plate 

v. Geel type 2 

Indet 

Indet. corroded 

Indet. folded 

Pollensum 

Artemisia 

Chenopodiaceae 

Plantago lanceolata 

Succisa 

Viscum album 

Alnus 

Tilia 

Tilia platyphyllos 

Ulmus 

Lonicera peridymenum 

Quercus 

Pinus 

Upland trees 

Wetland trees 

Herbs 

Betula 

Corylus 

Fagus 

Fraxinus 

Hedera 

Depth below NAP (mm) 

3875 ± 40 2350 BC 

2400 BC 

2600 BC 

4125 ± 35 2725 BC 

2800 BC 

3000 BC 

4475 ± 40 3185 BC 

1300 

1350 

1400 

1450 

1500 

1550 

1600 

1650 

1700 

1750 

1800 

Lithology 

Eemv alley, GFE01 

20 40 60 80 100 

20 

Humus Sand 

Figure 34a: pollen diagram of GP01 

20 40 

Upland Trees 

20 40 

Wetland Trees 

Anthropogenic indicators Herbs 

Spores Perf. Plate Types Indet. 

368 

352 

432 

350 

1360 

415 

Analysis: Marije Vlaar, 2007 

Radiocarbon Dates (BP) 

Ca lendar age

Myrica 

Salix 

Analysis: Marije Vlaar, 2007 

Plantago lanceolata 

Apiaceae 

Calystegia 

Cyperaceae 

Ericales 

Vaccinium-type 

Filipendula 

Galium-type 

Humulus lupulus 

Hydrocotyle 

Nuphar lutea 

Poaceae 

Potentilla-type 

Ranunculus 

c.f. Scr ophulariac eae 

Solanum dulcamara 

Sparganium erectum-type 

Typha latifolia 

Dryopteris-type 

Polypodium-type 

Pteridium-type 

Sphagnum 

Scalariform perforation pl ate 

Type 2 (Gelasinospora) 

Type 112 (Cercophora) 

Type 368 (Podospora) 

Indet 

Indet. folded 

Indet. corroded 

Pollensum 

1150 

1200 

1250 

1300 

1350 

1400 

1450 

1500 

1550 

1600 

20 40 60 80 100 

39 

Artemisia 

Asteraceae tubuliflorae 

Chenopodiaceae 

Eu-Rumex 

Alnus 

Tilia 

Ulmus 

Eemvalley, GFE02 

Upland trees 

Wetland trees 

Herbs 

Betula 

Carpinus 

Corylus 

Fagus 

Fraxinus 

Hedera 

Ilex 

Lonicera peridymenum 

Pinus 

20 

20 

Upland Trees 

20 40 60 80 

20 

Wetland Trees 

Anthropogenic indicators Herbs 

Spores Perf. Plate Types 

Indet. 

371 

368 

380 

619 

400 

393 

375 

20 

20 

20 

Quercus 

Humus Sand 

Dept h below NAP (mm) 

Lithology 

Figure 34b: Pollen diagram of GP02

3.3 Macrofossils 

The macrofossil analysis was carried out on three different subsamples from profile GP01. 

The selected subsamples were derived from the upper, middle and lower part of the profile 

(sample 12, 6 and 1 respectively). The estimation of the abundance of macrofossils per 

sample shows that the vegetation remains were not preserved well and that most of them were 

degraded. Some stem fragments were determined as common reed (Phragmites australis) 

although the determination was not described with certainty. Besides the macrofossil study on 

samples from the profile, also some pine wood was found in the field above the samples 

profile. The fossil content of the youngest sample (12) is the highest, containing also charcoal 

and insect remains. Table 10 shows the results of the macrofossil analysis of the three 

samples. 

Table 10: analysis of macrofossils 

Sample Volume Content Estimated number Determined 

number 

1 

(cm 

) 

39 Small root fragments 11-50 

Wood (root) 1 Betula sp. 

Small stem fragments 1-10 

Large stem fragments 1-10 Phragmites 

Cenococcum (fungi) 51-100 

6 41 Small root fragments 11-50 

Wood (root fragments) 1-10 Betula sp. 


Small branch fragments 1-10 

Cenococcum (fungi) 1-10 

12 33 Small root fragments 1-10 


Large stem fragments 1-10 Phragmites 

Wood (branch) 1-10 

Betula sp. 

Nodes 1-10 

Bark fragments 1-10 

Seeds 40 Betula sp. 

Beetle fragments 1-10 

Charcoal 1 

Cenococcum (fungi) 1-10

3.4 Radiocarbon dating 

In a first attempt both oaks GFE01 and GFE02 could not be dated by dendrochronology and 

therefore wood samples were sent for radiocarbon analysis. Both trees synchronized together 

(Figure 17) and by dating one of the trees, the age of the other tree can be assessed. From the 

23 samples of GFE02 which were sent to the Centre of Isotope Research, 6 were selected for 

AMS-dating. The dates were given as dates Before Present (BP) and by wiggle-matching 

these dates were transformed to dates Before Christ (BC). The dates (BP) were given with a 

40 year threshold for accuracy. Two different options were given as a result of the wigglematching 

(Figure 35a/b), depending on the goodness of fit (Chi 2 fitvalue). 

Figure 35a: Wiggle-match result, option 1. 

Chi 2 fitvalue: 0.895 

Figure 35b: Wiggle-match result, option 2. 

Chi 2 fitvalue: 0.980 

Table 11: The two wiggle-match options results in two different dates 

Ring number GrAnumber 

Age (BP) Calibrated calendar Age (BC) Calibrated calendar Age (BC) 

Wiggle-match 1, figure 34a Wiggle-match 2, figure 34b 

10 35608 4090 ± 40 2734 2815 

50 35609 4165 ± 40 2684 2765 

100 35610 4160 ± 40 2634 2715 

150 35613 4045 ± 40 2584 2665 

200 35616 4050 ± 40 2534 2615 

230 35615 4040 ± 40 2504 2585 

The two different options of the wiggle-match also resulted in two different dating for the tree 

as shown in table 11. According to the wiggle-match with the lowest Chi 2 fitvalue (option 1) 

the oldest measured ring (number 10) was formed in 2734 BC and the youngest measured 

ring (number 230) was formed in 2504 BC. The other wiggle-match result (option 2) showed 

that ring number 10 was formed in 2815 BC and ring number 230 in 2585 BC. 

The dendrochronological date of the last measured ring of GFE02 (ring number 302) showed 

that it was formed in 2581 BC. According to the two wiggle-match results ring 302 was 

formed in 2432 BC (option 1) or in 2513 BC (option 2). 

41

From profile GP01 four samples were dated by the AMS- radiocarbon dating method. The 

results show that the profile was formed between 4475 ± 40 and 3875 ± 40 year BP. The 

radiocarbon dates (BP) were calibrated to calendar years (BC) (Wincal25, Centre of Isotope 

Research at the University of Groningen). First a 2σ range was calculated from which the 

average age (cal BC) of the samples was calculated (Table 12). The depth-age relation of this 

profile is given in figure 36. This rather linear relation (0.6 mm/ year) is used to assume a 

constant accumulation rate of sediments through time and to deduce calendar ages for the 

whole profile. 

Table 12: 14 C dates of profile GP01 

Sample GrAnumber 

Age (BP) 2σ range (cal Average age (cal Material 

BC) 

BC) 

GP01-1 35440 4475 ± 40 3026-3342 3185 Peat 

GP01-6 35441 4125 ± 35 2579-2871 2725 Peat 

GP01-12 35444 3875 ± 40 2208-2476 2350 Peat 

GP01-12 35445 3855 ± 40 

Branch (Betula sp.) 

Age (cal. BC) 

-2200 

-2400 

-2350 

-2600 

-2725 

-2800 

-3000 

-3185 

-3200 

1250 1305 1360 1415 1470 1525 1580 1635 1690 1745 1800 

Depth below NAP (mm) 

Figure 36: Depth-age model of the analyzed profile. 

42

4. Discussion 

Dendrochronology 

The oaks found at the Lodijk (LFE01, 1678-1498 BC, date of death after 1482 BC and 

LFE02, 1688-1476 BC, date of death after 1458 BC) lived during a more recent period than 

the oaks found near the Groeneweg (GFE01, 2719 – 2570 BC, date of death after 2555 BC 

and GFE02, 2882 – 2581 BC, date of death between 2580 and 2564 BC). The shape of the 

trunks and the tree-ring patterns of the trees contain information about their growth 

conditions. The branchless character of LFE01 and LFE02 gives information about their 

direct surrounding: diminished branching and enhanced stem elongation is typical of crowded 

trees to avoid shading (Weinig, 2000), which indicates that both trees were growing in a 

closed forest with competition for light and space. The tree-ring pattern of LFE01 did not 

show any remarkable growth conditions, but its pattern displays the aging effect 

(Schweingruber, 1996). The tree-ring widths of LFE02 show some remarkable patterns which 

can be caused by stressed growth conditions. The stress periods can be due to different factors 

such as temperature changes, soil characteristics and fungi or viruses (Pedersen, 1998). 

The discovery of several root systems near the location where LFE01 and LFE02 were found 

might indicate that more trees were growing during this period (ca. 1700-1450 BC). The 

absence of taproots on some pine trunks indicates a high groundwater level. The development 

of deep taproots versus wide spreading roots depends on the depth of the groundwater table 

(Callaway, 1990). This implies that these trees were growing on a saturated soil where 

taproots cannot develop. The branchless trunks and the abundant root-systems in the field 

indicate that the trees possibly were once part of a closed forest. The preservation conditions 

must be perfect to conserve these trees such a long time. Aerobic conditions speed up the 

decomposition process (Kristensen, Ahmed and Devol, 1995). These trees were preserved in 

oxygen-free conditions and therefore hardly degraded. 

The dendrochronological analysis of GFE01 and GFE02 was complicated because the trees 

did not date with any of the existing reference calendars. The reference calendars used to date 

Dutch oaks are compiled from measurements on oaks that were mostly growing on humid 

soils such as bogs. These oaks are also known as bog oaks and their ring patterns often 

contain obvious growth depressions lasting for a decade or more (personal communication E. 

Jansma). The ring-width patterns of GFE01 and GFE02 show a rather constant growth, 

without remarkable growth reductions. The fact that the oaks from the Groeneweg could not 

be dated with the existing references calendars based on bog oaks could indicate that the oaks 

from location 1 were growing on less saturated substrates. The local growth conditions of the 

oaks from the Groeneweg were different from the environmental factors that steered the 

growth of the oaks that served as building blocks of the existing ‘wet’ reference calendars. 

In a second attempt to date the undated trees from the Groeneweg, a new chronology was 

compiled, using data from previous research on an ancient forest in Ypenburg (62 oaks 

growing from 3000 until 2500 BC; Van Daalen, 2001). These eight trees were chosen because 

they gave a significant date with the oaks from location 1. If more measurement series of oaks 

from Ypenburg were inserted into the calendar, the Ypenburg material became dominant in 

the calendar and the match with the series from location 1 decreased. The obvious reason is 

that the local growth at Ypenburg was not identical to those at location 1. The dated oaks 

from Ypenburg presumably grew on dunes and although peat development occurred on a 

large scale during that time, it did not reach these topographic highs (Van Daalen, 2001). The 

fact that the two oaks from location 1 could not be dated with bog oak chronologies, but 

43

synchronize well with the Ypenburg oaks that grew on less saturated soils, indicates that the 

oaks from location 1 also grew on unsaturated soils. Although the growth environment of the 

oaks clearly cannot be characterized as a bog, the trunks were preserved in peat. Both buried 

trees were very large and GFE02 also contained easily degradable sapwood rings, which 

means that the burying of the trunks and the development of the peat must have been taken 

place before the trees died or soon after their death. The absence of plant species that 

characterize peat development is in contrast with the peat layers in which the trunks were 

found. The trees were probably growing on a very humus-rich soil and somehow the 

environment changed and increased the conservation of the trunks. The tree-ring patterns do 

not show any sign of coming death (illness or death by old age, expressed in narrow ring 

widths), so the trees probably died because of a sudden external event. The results of this 

study do not shed any light on the chronological relationship between the start of the peat 

development on this location on the one hand, and the dying-off of the trees and their 

subsequent sedimentation in the soil on the other hand. 

Compared to dendrochronology the radiocarbon dates of the wood, which were performed 

before the oaks could be dated with the reference calendar from Ypenburg, give a different 

date for the oaks. Two different wiggle-match options show a difference of 149 (± 40) years 

with the dendrochronological date and the other option gives a difference of 68 (± 40) years. 

It is difficult to explain this large difference between the radiocarbon and dendrochronological 

dates. The statistical results of the dendrochronological dates are very significant and 

therefore there are no doubts about their accuracy. The software used for wiggle-matching 

lacks proper statistical foundation. It does not make clear if the match fits within the 

dendrochronological dating. Probably radiocarbon measuring with a higher resolution, e.g. 

every tenth ring instead of every fiftieth ring, will increase the statistical certainty about the 

measurement and may even change the wiggle-match results. 

Regarding the dating of pinewood, the main problem is the absence of good reference 

calendars in the Netherlands. A problem with the pines is their relative young age, which 

results in measurement series containing too few rings for statistical comparisons and cross 

dating. The remarkable stem form (‘saber-tooth growth’) of some pines is the result of 

stabilization after subsiding of the unstable substrate. Because the pines could not be dated by 

dendrochronology, samples were sent to the Centre of Isotope Research at the University of 

Groningen for radiocarbon dating. Unfortunately the results are not yet available due to the 

busy schedule of this research centre. The ecological past of the pines and their relation to the 

oaks from location 2 are still unknown. 

Pointer Years 

If tree-ring patterns from a certain location follow the pattern of pointer years from trees 

growing elsewhere, it may imply that the same environmental factors have influenced the 

vegetation on a large scale. It is difficult to explain why the pointer years of oaks growing in 

the Eem Valley correspond with the pointer years of oaks growing in the province of Zuid- 

Holland. There is little known about environmental or climatic changes in the period during 

which these trees were living. However, some discussion exists about the pointer years from 

1629 and 1628 BC. There is some evidence that a volcanic event influenced at least the 

northern hemisphere during this time. Ice cores from Greenland, bristlecone frost rings from 

North-America and Irish oak minimum-growth events show that there was a large volcanic 

dust-veil event in 1628 BC (Baillie, 1989). Some scientists suggest that these phenomena are 

related to the dating of the Thera (Santorini) eruption (Baillie, 1991). Thera is a volcanic 

island in the Mediterranean and belongs to Greece. However, none of the evidences specifies 

44

which volcanic eruptions were actually involved and therefore it cannot be proven that the 

1628 BC event was connected to the (undated) Thera eruption (Baillie, 1989). One of the 

problems to be solved is the link between a volcanic dust event and reduced oak growth in 

northern Europe. These oaks are hardly affected by cooling or low pressure anomalies, both a 

result of major eruptions, but it is possible that the oaks were responding to raised water 

tables (Baillie, 1989). Because of a time lag between volcanic eruptions and the resulting 

environmental changes elsewhere, it may be possible that the eruptions took place a couple of 

years before the occurrence of growth responses in European oaks (Baillie, 1989). Volcanic 

eruptions in the past may have caused large-scale environmental changes on which trees 

throughout the world reacted. The main problem is that it is unknown what kind of eruption 

influenced the 1628 BC event and if this was really the Thera-eruption. 

At 1629 and 1628 BC the 32 trees from Zuid-Holland and the two oaks from location 2 (Eem 

Polder) show negative pointer years. If the volcanic eruption from 1628 BC has influenced 

the growth of these trees, it is surprising that the preceding year (1629 BC) already shows a 

negative pointer year. This pointer year can not be related to an event that happened a year 

later. In addition, one would expect the reduced growth to last after the volcanic event of 1628 

BC, because of lagged environmental response and the fact that tree growth would need some 

time to recover. This lagged response does not show up in the material. There must have been 

a general environmental impact (or combination of factors) that for two years negatively 

influenced the growth of the 32 trees from Zuid-Holland and the two oaks from the Eem 

Polder, but the reason for this reduced growth can not be rashly ascribed to the Thera eruption 

of 1628 BC. 

Pollen and Macrofossil analysis 

To reconstruct the appearance of the surrounding vegetation near the oaks which were 

discovered in situ, pollen and macrofossil analysis were performed. General pollen zones of 

the Netherlands are used to relate the vegetation history to time. The exclusion of local 

circumstances within these overviews should be considered when these overviews are used as 

a dating method. During the pollen analysis of this study several species were noticed as a 

time indicator. According to chronostratigraphic pollen zones of (Bastiaens, Brinkkemper, 

Deforce, Maes, Rovekamp, Van den Bremt and Zwaenepoel, 2006) the pollen samples from 

the Eem Polder presented a vegetation development from the Early-Atlantic period (7000- 

5500 yr BC). The division of pollen zones from (Bastiaens et al, 2006) are based on a 

previous developed overview from (Berendsen and Zagwijn, 1984). The addition of new 

species as time indicators to the overview of (Berendsen and Zagwijn, 1984) are based on 

more recent research on pollen, but also on the analysis of seeds and wood remains (Bastiaens 

et al, 2006). 

According to the pollen zones of (Bastiaens et al, 2006) oak and alder are the most dominant 

species during the Early-Atlantic. Lime and elm are also abundant and ivy, mistletoe and 

holly are present. Furthermore, pine trees are present but in low quantities (Bastiaens et al, 

2006). The transition to the Late-Atlanticum is characterized by the first appearance of 

cultivated species. During the next stage, the Subboreal, European yew (Taxus baccata) 

appears, lime and elm are no longer abundant, hazel increases in appearance and cultivated 

plants are common. The Subboreal ends with the appearance of beech (Bastiaens et al, 2006). 

Another general pollen zone overview is presented by de Jong (1983). This overview 

describes the pollen zones with less detail. The Atlanticum is characterized by the occurrence 

of more than 5% elm, alder and oak are dominant and pine appears in low quantities. The 

45

transition to the Subboreal is defined by a decrease of elm and the appearance of cultivated 

species. The first occurrence of beech represents the end of this period. 

Because of some important indicators such as ivy, mistletoe and holly and because of the 

absence of cultivated plants and European yew, the results of the pollen analysis of this study 

were interpreted as pointing to the Early-Atlanticum (7000-5500 yr BC). However, the 

radiocarbon analysis of three soil samples from the profile points out that the profile dates 

from 3185 to 2350 yr BC (Subboreal). Although it might be possible that the radiocarbon 

dates are too young due to the presence of roots in the bulk material, after these results the 

date based on the general pollen zones was regarded with more caution. According to 

(Bastiaens et al, 2006) the presence of European yew and cultivated plants is an important 

characteristic of the Subboreal. Both indicators were not noticed in the studied pollen samples 

but their absence can be the result of the local influences. European yew pollen is a difficult 

species for analysis because it is sensitive to folding and fracturing. Because this species does 

not appear in high quantities, local factors may influence its appearance. A detailed palaeoecological 

study on micro- and macrofossils from the Borchert (North-Eastern part of The 

Netherlands) resulted in a pollen diagram dated from 10.000 to 1300 yr BP (Van Geel, 

Bohncke and Dee, 1980). In this diagram European yew is not present during the whole 

period. Another palaeo-ecological study on sediments from Ilperveld (Western Netherlands) 

resulted in a pollen diagram dated from about 3000 to 1000 yr BC (Bakker and Van 

Smeerdijk, 1981). Again European yew is not found during the whole period. This may 

indicate that this species should not be put out as an important time indicator. There are also 

examples in the Netherlands of pollen analysis that contain pollen of European yew. A pollen 

diagram from the ‘Dommelvalley’ (North Brabant) contains European yew pollen during the 

Subboreal period (Janssen, 1972). They appeared during clearance phases, at a time when the 

forests were less dense (Janssen, 1972). Other time indicators according to (Bastiaens et al, 

2006) for the Early-Atlanticum are ivy, mistletoe and holly which are not classified at the 

Late-Atlanticum and the Subboreal. However, the palaeo-ecological study from the Borchert 

(Van Geel et al, 1980) showed that these species continued their appearance through these 

periods and therefore could also be present in the studied samples from the Eem Polder. The 

appearance of elm in the profile from the Eem Polder agrees with the Subboreal period of de 

Jong (1983). According to his pollen zones elm should be present with more than 5% during 

the Atlanticum and with low quantities during the Subboreal. In both profiles from the Eem 

Polder elm appears with low quantities, indicating the Subboreal period. Finally, according to 

both pollen zones of (Bastiaens et al, 2006) and de Jong (1983) the Subboreal is characterized 

by the presence of cultivated plants. The profiles from the Eem Polder show some 

anthropogenic indicators, but in very low quantities. This could also be caused by local 

factors such as the absence of people in this area during this period. The discussed time 

indicators and the comments on the general pollen zones assume that the three radiocarbon 

dates of the profile are correct. 

Both pollen diagrams show a very high amount of trees (upland and wetland) relative to the 

herbs. This implies that the abundant trees formed a closed forest in which herbs could not 

develop because of shading. The most dominant tree species in this forest were hazel, oak and 

alder. Pollen dispersal in trees is a combination of local dispersion and long-distance transport 

(Streiff, Ducousso, Lexer, Steinkellner, Gloessl and Kremer, 1999). The clumps of 

(immature) pollen constitute the gravity component and indicate local occurrence of the 

corresponding taxa. Clumps of pollen seem to be associated with local or extra-local pollen 

deposition (Janssen, 1986) implying local appearance of oak and alder in this site. The pollen 

analysis from the ‘Dommelvalley’ (Janssen, 1972) shows that European yew only appears 

during clearance phases when the forest was less dense. The density of the forest from the 

46

Eem Polder might explain why European yew did not appear in this vegetation. Besides very 

abundant trees as hazel, oak and alder, also pine appears constantly in this pollen diagram, 

although with very low quantities. Pollen of pine trees is susceptible to long-distance dispersal 

and due to the high pollen production of pines it is difficult to determine the presence of pine 

on a local scale (Eide, Birks, Bigelow, Peglar, and Birks, 2006). Hence, plant macrofossils of 

pines are useful to refine and correct the pollen analysis of pine trees (Birks and Birks, 2000). 

Because the pollen percentages of pines are very low in both diagrams, pine trees were not 

abundant in the forest. However, remarkable pine macrofossils were found above the sampled 

profile. This means that pine trees were locally present and probably their dominance 

increased in time. Only three samples from profile GP01 were analyzed. The macrofossil 

remains determined as birch indicate that this tree was locally present. The older samples (1 

and 6) only contain birch roots which could be grown in after the peat formation and are no 

proof the local appearance of this species. If macrofossil remains of common reed occur in the 

profile it is difficult to explain why this species is not noticed during the pollen analysis. This 

species was also found above the sampled profile and could indicate the formation of peat and 

the presence of a high groundwater table. Charcoal could indicate ancient anthropogenic fires 

although clearance of vegetation is not visible in the pollen diagrams. Analysis of more 

samples may not increase the knowledge of the macrofossils because these three samples 

show that the material was largely degraded. 

Some of the herbs are grouped as anthropogenic indicators according to (Behra, 1981). Both 

pollen zones overviews of (Bastiaens et al, 2006) and (Jong, 1983) show that the Subboreal is 

characterized by the presence of cultivated species. The anthropogenic indicators from the 

Eem Polder appear in very low quantities and important indicators for agriculture such as 

cereals are absent. If the pollen diagrams of the Eem Polder present a closed forest it might 

explain why anthropogenic indicators such as cereals are missing. This would not necessarily 

mean the cereals were not growing in the surrounding environment; they release little pollen 

and the dispersal zone is very limited (Edwards, Whittington, Robinson and Richter, 2005). It 

is possible that people influenced the area around the forest by cultivating plants and that 

pollen of this species could not reach the forest area because of its density. The pollen 

diagrams most likely show an extra-local vegetation history of a closed forest where herbs 

could not develop and in which surrounding vegetation could not disperse their pollen. 

The peat layer from which the vegetation remains were sampled prevented decaying of the 

organic material and stored it for many years. As the tree-ring patterns of GFE01 and GFE02 

and their synchronization with the oaks from Ypenburg shows, the substrate on which the 

oaks were growing was not very saturated. The absence of water plants and the low 

abundances of typical peat bog species such as peat moss (Sphagnum), confirm that the forest 

grew on a relatively dry substrate. Every year the abundant trees dropped their leaves and the 

substrate probably turned into a very humus-rich soil. The high absolute number of pollen in 

this profile indicates either a slow accumulation rate of soil layers or an extraordinary pollen 

release from the vegetation. The calibrated radiocarbon dates can be used to estimate the 

accumulation rate of the sediments in the profile. From these dates it is assumed that the 

accumulation rate was rather constant (± 0.6 mm/year). At a certain time the humus rich soil 

turned into a peat bog, but the results of the pollen analysis do not show when exactly this 

happened. 

The growth of the oaks GFE01 and GFE02 occurred during the same period as the 

development of the profile in which they were found. The oak pollen curve of GP01 does not 

show a sudden decrease and this might indicate that there was no event that influenced the 

47

death of many trees. The profile of GP02 does show a decrease of oak pollen in the upper 

part. At the same part the amount of Cercophora increases. This fungus does not only appear 

on dung, but also on decaying wood (Van Geel et al, 1980). Profile GP02 is not dated but 

according to the NAP-depths relative to GP01 the decrease of oak pollen and the increase of 

the fungi probably happened after the death of the studied oaks. 

The results of this study are relevant to our understanding of the natural vegetation in the 

Netherlands. The evidence of branchless tree trunks, abundant root systems and a very high 

tree ratio relative to herbs or anthropogenic indicators points at the previous existence in the 

Eem Polder of a closed deciduous forest. At least locally this finding disagrees with the 

hypothesis stated by Vera (1997) that the environment in the Netherlands was characterized 

by an open landscape. Although both phases of tree growth identified in the Eem Polder 

indicate that a closed forest existed, it is possible that the results only have a restricted 

geographical bearing. Therefore the general assumption that the Dutch natural vegetation was 

characterized by an open landscape with widely distributed single trees cannot be refuted 

based on the results presented here. 

48

5. Conclusions 

The different trees that were studied during this research have been living during two different 

time periods. The oaks from location Groeneweg (GFE01 and GFE02) died after 2555 and 

between 2580 and 2564 BC respectively, while the oaks from the Lodijk (LFE01 and LFE02) 

died after 1482 and 1458 respectively. 

Groeneweg 

The studied oaks at Groeneweg grew on a relatively dry substrate. The oaks could not be 

dated by synchronization with oaks that grew in wet circumstances and have been preserved 

in Dutch bogs, but they gave a significant correlation with oaks from Ypenburg which also 

grew on an unsaturated soil. The absence of waterplants or plant species that characterizes 

peat formation confirmed that the trees at Groeneweg were growing on an unsaturated soil. 

Their synchronization with oaks from Ypenburg showed that the growth patterns of the trees 

reflect regional growth conditions, while the pollen analysis showed local conditions. 

According to the pollen, the oaks were growing in a closed forest with a dominance of oak, 

hazel and alder. Herbs could not develop because of shading by the closed canopy. In 

addition, anthropogenic indicators were almost absent, which indicates a minor influence of 

people on this area. The pollen diagrams did not show a remarkable decrease of the 

appearance of species, implying that the forest did not suffer any dramatic changes or 

clearances. This vegetation reconstruction showed the local appearance of plant species and 

from this study the regional vegetation development or the geographical distribution of the 

forest is unknown. The tree patterns of the oaks showed that the trees died because of a 

sudden event, whereas the constant amount of tree pollen indicated that this event did not 

influenced the whole forest or even a substantial part of it. Because the trees were preserved 

well, one of them even still retaining its sapwood rings, it is possible that peat development 

started before the death of the trees. This study does not clarify how the change from an 

unsaturated soil into peat development took place, when this occurred and on what scale it 

affected the forest near the Groeneweg. 

Lodijk 

The studied oaks sampled at the Lodijk also were growing in a closed forest, which is 

indicated by the fact that the trunks were relatively branchless. Also, near the original location 

of the studied oaks more root systems were found, implying that at some point in time more 

trees were growing at this location. Because the age of these root systems is unknown, it is 

unclear if these trees were growing during the same period as the studied oaks. The 

morphology of some root systems indicates a high groundwater level and a saturated soil. The 

tree-ring patterns of the studied oaks show that they grew unhindered by any remarkable 

stress. Their tree-ring patterns show wider and narrower rings that occur synchronously with 

pointer years in the patterns of trees which grew in the province of Zuid-Holland. Remarkable 

reduced growth occurred during 1629 and 1628 BC. From this study it is not clear if these 

growth reductions are caused by the eruption in 1628 BC of the volcano Thera. 

The results of the radiocarbon dating of the pines are not accomplished yet. The relation 

between the pines and the oaks from the Lodijk is still unknown. Some pines showed ‘saber 

tooth growth’, indicating that they were growing on an unstable substrate. 

49

6. Further Research 

After finishing this research on the vegetation history of the Eem Polder some questions still 

remain. Therefore it is recommendable to perform further research in this area to extend the 

knowledge about vegetation history. In both locations near the Groeneweg and near the 

Lodijk further research questions can be proposed, but also more knowledge is required about 

a possibly relationship between the two locations. 

The reconstruction of the vegetation history indicated that a closed forest dominated the 

landscape at both study sites, but little is known about the geographical distribution of these 

forests. It is likely that the vegetation reconstruction presented the local occurrence of the 

vegetation development and therefore it would be interesting to find out on what scale the 

forests developed. It might be possible that the forests were distributed over a large area and 

maybe they migrated through the landscape. By searching for more tree remains at both 

locations the distribution of the forest can possibly be studied. The forest near the Groeneweg 

grew about 1000 years earlier than the forest near the Lodijk but possibly there is a relation 

between the two. Because the tree remains from the Lodijk used during this study were not 

found in situ, nothing is known about the surrounding vegetation development in this area. If 

in situ tree remains can be localized, a pollen analysis should be performed at this location 

too. Furthermore, the relation between the collected pines and oaks from the Lodijk is still 

unknown. By dating the pines this relationship can be revealed and the remarkable growth 

forms of the pines can also explain the growth conditions of the oaks. 

The pointer year analysis indicated that the tree-ring patterns of the studied trees show 

similarities with trees growing in the province of Zuid-Holland. Maybe it is possible to reveal 

what kind of growth conditions were responsible for these similarities and if remarkable 

environmental changes occurred during this period. 

There are also some questions left about the downfall of the forest discovered near the 

Groeneweg. According to the pollen analysis no decrease in tree pollen occurred during the 

studied period and no remarkable event influenced the whole forest. But because both trees 

were preserved very well the burying of the trees must have happened soon after their death. 

This implies that peat development already started and it would be logical that more trees 

suffered from the increased saturation of the soil. Maybe it is possible that on a local scale no 

peat developed and the humus-rich soil characterized the substrate. Information about this can 

be obtained by biochemical research on the soil profile. More information about the soil 

development and the relation with the downfall of single trees or the whole forest is needed to 

discover the sequence of events. To investigate the influence of changes in soil development 

on the forest a pollen analysis should be performed on younger soil samples to discover a 

decrease of trees. Also dendrochronological research on other tree remains might answer 

questions about environmental changes and other tree-ring patterns may indicate stress 

conditions of growth. 

The difference between the radiocarbon and the dendrochronological dating of the oaks from 

the Groeneweg should be explained in more detail. Maybe it is possible to revise the 

radiocarbon dates by studying the significance of the statistics used with this dating method. 

To two locations in the Eem Polder are very interesting for further research and hopefully 

more details about the vegetation history of this area can be discovered. Also, besides these 

two locations it is likely that more tree remains can be collected from many other locations 

50

within the Eem Polder. Further research can hopefully complete the reconstruction of the 

palaeo-ecology of the Eem Polder. 

7. References 

Baillie, M.G.L. (1982). ‘Tree-ring dating and Archaeology’. In Varley, G.C., and Gradwell, 

G.R. 1962. The effect of partial defoliation by the Caterpillars on the Timber 

Production of oak trees in England. XI Internationaler Kongress fur Entomologie 

Wien 1960, Sonderdruck aus den Verhandlungen, Bd II, pp. 211-14. 

Baillie, M.G.L. (1989). ‘Proceedings of the third International Congres, Santorini’. 

Baillie, M.G.L. (1991). ‘Marking in Marker Dates: Towards an Archaeology with historical 

Precision’. World Archaeology, volume 23, issue 2, pp 233-243. 

Bakker, M. and Smeerdijk, D.G. van. (1981). ‘A palaeo-ecological study of a late Holocene 

section from ‘Het Ilperveld’, Western Netherlands’. Review of Palaeobotany and 

Palynology, 36, pp 95-103. 

Bastiaens, J., Brinkkemper, O., Deforce, K., Maes, B., Rovekamp, C., Bremt, P van den, 

Zwaenepoel, A. (2006). Inheemse bomen en struiken in Nederland en Vlaanderen, 

herkenning, verspreiding, geschiedenis en gebruik. Amsterdam, Boom. 

Behra, K. (1981).’The interpretation of anthropogenic indicators in pollen diagrams’. The 

Journal of Ecology, volume 76, issue 3, pp 903. 

Bennett, K.D. and Willis, K.J. (2002). Pollen. In, J.P. Smol, H.J. B. Birks and W.M. Last 

(eds.) Tracking Environmental Change Using Lake Sediments, Volume 3: Terrestrial, 

Algal, and Siliceous Indicators. Kluwer Academic Publishers, Dordrecht. 

Berendsen, J.H.A, & W.H. Zagwijn. (1984). ‘Some conclusions reached at the symposium on 

geological changes in the western Netherlands during the period 1000-1300 AD.’ 

Geologie en Mijnbouw 63, pp 225-229. 

Berglund, B. And Persson, T. (2004). Information on spore tablets Retrieved from 

http://www.geol.lu.se/personal/tsp/Ly483216Eur.pdf. 

Birks, H.H and Birks, H. J. B. (2000). Future Uses of Pollen Analysis Must Include Plant 

Macrofossils. Journal of biogeography, volume 37, issue 1, pp 31-35. 

Birks, H.J.B. and Birks, H.H. (1980). Quaternary palaeoecology. New Jersey, 

The Blackburn Press. 

Birks, H.J.B. and Birks, H.H. (2006). ‘Multi-proxy studies in palaeolimnology’. Vegetation 

history and Archaeobotany, volume 15, issue 4, pp 235-251. 

Callaway, R.M.(1990). ‘Effects of soil water distribution on the lateral root development of 

three species of Californian oaks’. American Journal of Botany, volume 77, issue 11, 

pp 1469-1474. 

Cook, E.R. and Kairiukstis, L.A. (1990). Methods of dendrochronology. Applications in the 

51

environmental sciences. Dordrecht, Kluwer Academic Publishers. 

Daalen, S van. (2001). Een reconstructie van het moerasbos te Ypenburg. MSc thesis, 

University of Wageningen 

Desplanque, C., Rolland, C. and Schweingruber, F.H. (1999). ‘Influence of species and 

abiotic factors on extreme tree ring modulation: Picea abies and Abies alba in 

Tarentaise and Maurienne (French Alps)’. Trees, volume 13, issue 4, pp 218-227 . 

Edwards, K.J., Whittington, G., Robinson, M. and Richter, D. (2005). ‘Palaeoenvironments, 

the archaeological record and cereal pollen detection at Clickimin, Shetland, 

Scotland.’ Journal of archaeological science, volume 32, issue 12, pp 1741-1756. 

Eide, W., Birks, H.H., Bigelow, N.H., Peglar, S.M. and Birks, H.J.B. (2006). ‘Holocene forest 

development along the Setesdal valley, southern Norway, reconstructed from 

macrofossils and pollen evidence.’ Vegetation history and archaeobotany, volume 15, 

issue 2, pp 65-85. 

Fritts, H.C. (1976). Tree rings and climate. London, Academics. 

Geel, B van, Bohncke, S.J.P. and Dee, H. (1980). ‘A palaeo-ecological study of an upper late 

glacial and Holocene sequence from ‘De Borchert’, The Netherlands.’ Review of 

Palaeobotany and Palynology, 31, pp 367-448. 

Henri D. Grissino-Mayer, Department of Geography, The University of Tennessee, from: 

http://web.utk.edu/~grissino (2007). 

Jansma, E. (1995). Rememberings. The development and application of local and regional 

tree-ring chronologies of oak for the purpose of archaeological and historical 

research in the Netherlands. PhD dissertation, University of Amsterdam. 

Jansma, E. (2006). Dendrochronologie, NoaA Chapter 3 (versie 1.0), (www.noaa.nl), 1-40. 

Jansma, E., (2007). Datering, herkomst en bouwvolgorde van De Meern 4. In: T. de Groot & 

J.-M.A.W. Morel (red.), 2007: Het schip uit de Romeinse tijd De Meern 4 nabij 

boerderij de Balije, Leidsche Rijn, gemeente Utrecht. Waardestellend onderzoek naar 

de kwaliteit van het schip en het conserverend vermogen van het bodemmilieu. 

Amersfoort, RACM. 

Janssen, C.R. (1972). ‘The palaeo-ecology of plant communities in the Dommel Valley, 

North Brabant, Netherlands.’ The Journal of Ecology, volume 60, issue 2, pp 411-437. 

Janssen, C.R. (1986). ‘The use of local pollen indicators and of the contrast between regional 

and local pollen values in the assessment of the human impact on vegetation.’ 

Quarternary research,16, pp 80-96. 

Jong, J de. 1983. Chronostratigraphic subdivision of the Holocene in the Netherlands. 

52

Kitagawa, H. and van der Plicht, J. (1998). ‘Atmospheric Radiocarbon Calibration to 45.000 

yr B.P.: Late Glacial Fluctuations and Cosmogenic Isotope Production.’ Science, 

volume 279, issue 5354, pp 1187-1190. 

Kristensen, E., Ahmed, S.I. and Devol, A.H. (1995). ‘Aerobic and Anaerobic decomposition 

of organic matter in marine sediment: Which is fastest?’ Limnology and 

oceanography, volume 40, issue 8, pp 1430-1437. 

Mauseth, J.D. (1998). Botany, an introduction to plant biology. University of Texas, Austin. 

Sudbury, Jones and Bartlett Publishers. 

Mulder, E.F.J. de, Geluk, M.C., Ritsema, I.L., Westerhoff, W.E. and Wong, T.E. (2003). De 

ondergrond van Nederland. Groningen, Wolters Noordhoff. 

Pedersen, B.S. (1998). ‘The Role of Stress in the Mortality of Midwestern Oaks as Indicated 

by Growth prior to Death;. Ecology, volume 79, issue 1, pp 79-93. 

Peeters, J.H.M. (2007). Hoge vaart-A27 in context: Towards a model of Mesolithic – 

Neolithic land use dynamics as a framework for archaeological heritage management. 

PhD dissertation, University of Amsterdam. 

14 

Plicht, J. van der. (2006). De C methode, NoaA Chapter 4 (versie 1.0), (www.noaa.nl), 1-25. 

Reimer, P.J., Baillie, M.G.L., Bard, E., Bayliss, A., Beck, J.W., Bertrand, C.J.H., Blackwell, 

P.G., Buck, C.E., Burr, G.S., Cutler, K.B., Damon, P.E., Edwards, R.L., Fairbanks, 

R.G., Friedrich, M., Guilderson, T.P., Hogg, A.G., Hughen, K.A., Kromer, B., 

McCormac, G., Manning, S., Ramsey, C.B., Reimer, R.W., Remmele, S., Southon, 

J.R., Stuiver, M., Talamo, S., Taylor, F.W., Van der Plicht, J. and Weyhenmeyer, C.E. 

(2004). ‘IntCal04 terrestrial radiocarbon age calibration, 0-26 cal. KYR BP.’ 

Radiocarbon 46, pp 1029-1058. 

Ruddiman, F.W.(2002). Earth’s climate: past and future. New York, W. H. Freeman and 

company. 

Ruelle, J., Yamamoto, H. and Thibaut, B. (2007). ‘Growth stresses and cellulose structural 

parameters in tension and normal wood from three tropical rainforest angiosperm 

species.’ Bioresources, volume 2, issue 2, pp 235. 

Schweingruber, F.H. (1996). Tree rings and environment dendroecology. Berne, Paul Haupt 

Publishers. 

Schweingruber, F.H., Eckstein, D., Serre-Bachet, F. and Bräker, O.U. (1990). ‘Identification, 

presentation and interpretation of event years and pointer years in dendrochronology.’ 

Dendrochronologia 8, 9-38. 

Streiff, R., Ducousso, A., Lexer, C., Steinkellner, H., Gloessl, J. And Kremer, A. (1999). 

‘Pollen dispersal inferred from paternity analysis in a mixed oak stand of Quercus 

robur L. and Q. petraea (Matt.) Liebl.’ Molecular Ecology, volume 8, issue 5, pp 831, 

11p. 

53

Vera. F.W.M. (1997). Metaforen voor de Wildernis. Eik, Hazelaar, rund en paard. ’s- 

Gravenhage, Ministerie van Landbouw, Natuurbeheer en Visserij. 

Watt, A.S. (1947). ‘Pattern and process in the plant community’. Journal of Ecology, 

35, 1-22. 

Weinig, C. (2000). ‘Differing selection in alternative competitive environments: shadeavoidance 

responses and germination timing.’ Evolution, volume 54, issue 1, pp 124- 

136. 

Yeloff, D., Bennett, K.D., Blaauw, M., Mauquoy, D., Sillasoo, U., van der Plicht, J. and van 

Geel, B. (2006). ‘High precision 14C dating of Holocene peat deposits: A comparison 

of Bayesian calibration and wiggle-matching approaches.’ Quaternary geochronology, 

volume 1, issue 3, pp 222-235. 

Zagwijn, W.H. (1973). ‘Pollenanalytic studies of Holsteinian and Saalien beds in the northern 

Netherlands’. Mededelingen Rijks Geologische Dienst, Nieuwe serie 24, pp 139-156. 

54

Appendix 

Appendix 1 

Table 13 (Grissino-Mayer, 2007) 

Principle 

The Uniformitarian Principle 

The Principle of Limiting Factors 

The Principle of Aggregate Tree Growth 

Explanation 

‘The present is the key to the past’, stated by 

James Hutton in 1785; by knowing the 

relationship between tree-rings and climate at 

present, it is possible to make climate 

reconstructions of the past using tree-rings of 

old, long-lived trees. 

The environmental variable that is most 

limiting for plant growth, determines the 

conditions of the plant; if tree growth is 

limited by precipitation, trees will not grow 

faster than allowed by the amount of rainfall, 

and ring-width is a function of precipitation 

(Fritts, 1976). 

Individual tree growth can be described as a 

function of different environmental factors, 

both human and natural, that effect the tree 

growth. This is given as the function: 

R t= A t + C t + δD1 t + δD2 t + Et 

R t = the observed ring-width series 

A t = the age-size related trend in ring width 

C t = the climatically related environmental 

signal 

D1 t = the disturbance pulse caused by a local 

endogenous disturbance 

D2 t = the disturbance pulse caused by a 

standwide exogene disturbance 

E t = the largely unexplained year-to-year 

variability not related to other signals 

(Cook and Kairiukstis, 1990). 

The Principle of Ecological Amplitude 

Using this formula we assume that A t, Ct and 

E t are always present, while D1 t and D2t are 

only present (δ=1) if a disturbance had 

occurred at a certain year, and not present 

(δ=0) if no disturbances occurred (Cook and 

Kairiukstis, 1990). 

The ecological amplitude refers to the area in 

which tree species can grow and reproduce. 

This principle is used within 

dendrochronology because the most useful 

trees are found near the margins of their 

natural range, determined by latitude, 

longitude and elevation. 

55

Appendix 2: Tree growth and wood anatomy 

There are two fundamental types of plant bodies: the primary plant body (herbaceous plants 

that only undertake primary growth) and the secondary plant body (trees or shrubs with 

secondary growth that produce wood and bark) (Mauseth, 1998). 

Plants contain two types of vascular tissue, xylem and phloem, which both are types of 

transport tissue. Xylem conducts water and minerals and phloem distributes sugars and 

minerals (Mauseth, 1998). Water and minerals enter the xylem in the roots and are conducted 

upwards to the leaves and stems, travelling through dead cells. Once it enters in the right 

location, the water evaporates and the minerals are absorbed (Mauseth, 1998). The phloem 

consists of living cells that pick up sugars from areas where they are abundant and transport 

them to areas where they are needed. Both types of vascular tissues exist in primary and 

secondary plant bodies. The vascular cambium is a thin layer of cells located between the 

wood and the bark (Figure 37). When active (during the growing season) it produces xylem 

towards to inside and phloem or bark towards the outside (Baillie, 1982). The growing season 

on temperate climates ranges from March to late September. 

Figure 37: Anatomy of a tree stem. 

56

At the beginning of the growing season the cambium of deciduous trees produces large 

vessels to provide the newly grown leaves with transport canals; these vessels are also called 

spring vessels (Figure 38). As the growing season proceed and the tree is full of adult leaves, 

stability becomes the major priority and the cambium produces small and compact cells that 

will provide strength to the whole structure. This type of wood is called summerwood (Figure 

38) (Mauseth, 1998). At the end of the growing season cell division stops; the last cells are 

formed as heavy fibers with thick secondary walls. The spring vessels and the summerwood 

together represent the growth of one year, also called an annual ring (Mauseth, 1998). 

Spring vessels 

Summerwood 

Spring vessels 

Figure 38a: Spring vessels 

(white cells) and 

summerwood (brown bands) 

together represent one annual 

ring 

Figure 38b: a detailed picture 

of spring vessels and 

summerwood 

The width of individual growth rings may vary greatly from year to year as a function of 

environmental factors such as light, temperature, rainfall and available soil. The forming of 

spring vessels is dependent on the reserves of the tree built up in previous years and the 

summerwood is dependent on the food supplies of the particular year during which the 

summerwood formation takes place. The width of the spring vessels varies little from year to 

year, which means that the variation of ring widths in deciduous trees in fact represents the 

variation in the summerwood width. 

The obvious ring pattern, the long lifetime and the annual character of oaks are advantages for 

dendrochronology. In the cross sections of oaks, two zones can be distinguished: the centre, 

almost always darker in colour than the outer wood, is called heartwood. The outer section, 

usually moister and lighter in colour is called the sapwood. These two regions exist because 

vessels can break as the result of freezing, wind vibration, insects and other factors. If a 

column is broken, it makes no sense to pull water in for transport and the vessel usually never 

conducts water again. Therefore surrounding parenchyma cells push protoplasm through the 

pit into the vessels, forming a plug called tylosis that will seal them off (Mauseth, 1998). 

These changes make the heartwood more durable, less penetrable and more protected against 

decay by organisms. The sapwood contains living parenchyma and waterfilled conducting 

vessels, full of xylem sap. A new layer of sapwood is formed every year, and one annual ring 

is converted into heartwood on average each year (Mauseth, 1998). The thickness of the 

sapwood of oaks is more or less constant, making it useful for dendrochronological research. 

The wane edge is the last ring under the bark, presenting the last year of growth. It is possible 

to date the death of a tree exactly if the wane edge is still present. Despite the fact that it is 

very unusual to find complete oak trunks from the past, including all sapwood rings and bark, 

it is possible to estimate the original amount of sapwood rings, and thus to estimate the death 

of the tree. 

57

Coniferous trees may not form a ring along the total circumference of the stem if they are 

influenced by extreme weather (Fritts, 1976). When this happens, the ring is missing along 

the radii of a tree-ring series. It is also possible that growth conditions temporarily become 

poor before the end of the growing season. During this period vessels grow smaller with 

thicker walls. When conditions improve again during the same season, cells are formed larger 

with thinner walls. These intra-annual growth bands are also referred as false rings (Fritts, 

1976). Trees are not only influenced by climatological factors, but also on abiotic ones. Trees 

react on mechanical stress such as wind exposure, soil movement or shading. If the substrate 

on which a tree grows moves, the tree will respond to restore verticality. Trees are able to 

bend their trunk by the formation of stressed wood, called reaction wood, to stabilise or reach 

for light (Ruelle, Yamamoto and Thibaut, 2007). If ring widths of coniferous trees are 

measured for dating or climatological research one should be aware of missing rings, false 

rings or reaction wood. 

58

Appendix 3: Overview of archaeological periods describing dendrochronological calendars, 

based on dendrochronological research until 2004 (Jansma, 2006). 

6025 - 2850 BC 

The dendrochronological dataset of this period contains 95 measurements of oaks from 

natural habitats in ancient peat bogs and river areas. It also contains 7 measurements on oaks 

from a road and a bridge made of wood through a peat bog. From cover-sand areas at the 

eastern and southern Netherlands no wood data are available. Chronologically, the data set of 

this period contains two hiatus: 5467 - 5121 BC and 4557 - 3643 BC. 

2850 - 2000 BC 

The dendrochronological dataset of this time interval contains 115 measurements of oaks 

from natural habitats in ancient peat bogs and 10 measurements from archaeological sites. 

The dataset covers the whole period, without any hiatus. The oaks of this dataset grew on 

different soils (also sand-cover areas) but their geographical distribution is restricted; 66 

series are derived from Ypenburg and a cluster of oaks from the southern area of the province 

of Zuid-Holland. 

2000 - 800 BC 

This dendrochronological dataset contains 83 measurements of oaks from natural habitats 

(peat bogs) mostly from the western past of the Netherlands. It contains 5 measurements of 

oaks from archaeological sites. Except for the western part of the Netherlands, this period 

must yet be described dendrochronologically. 

800 - 12 BC 

Measurements of 103 oaks from natural habitats and 22 oaks from archaeological sites cover 

this whole period. Within this dataset especially the northern and eastern part of the 

Netherlands and the province of Zeeland are not presented adequately. 

12 BC - AD 400 

For this period an extraordinary amount of dendrochronological measurements are available; 

296 measurements from native Roman context (5 silver fir, 14 ash, 277 oak), 290 from 

military context (26 elm and ash, 264 oak), 16 from civil context (oak), 33 from religious 

context (oak) and 62 from natural context (26 beech, 36 oak). The northern part of the 

Netherlands is not presented well in this dataset. 

AD 400 - 1000 

This period contains 179 measurements from archaeological context (oaks) and 62 

measurements from natural context (12 beech, 50 oak). The dataset covers the whole period, 

but the native material found in situ dates no later than AD 570. The Dutch calendar of native 

oaks found in situ here reaches its chronological end. In this dataset the northern part of the 

Netherlands and the province of Zeeland are not presented well. 

AD 1000 - 1500 

From this period 464 archaeological measurements are available (2 pine, 3 ash, 20 silver fir, 

439 oak). The eastern part of the Netherlands is not presented well in this period. 

During this period large amounts of wood were imported, and therefore the material is not 

useful to develop native calendars. The data are useful to determine the origin of transported 

wood and to develop regional import calendars. 

59

AD 1500 - 1950 

The archaeological dataset of this period contains 245 measurements (2 beech, 2 pine, 8 silver 

fir, 233 oak). Besides this a lot of data are available from monumental buildings still present. 

Some of these data overlap with the time span represented by the growth rings in living oaks. 

But the data are in many cases not native and therefore not very useful for indigenous 

calendars and climatological research directed at the Netherlands. 

60

Appendix 4 

Table 14: Minimum sample amount vs. significance 

n 99.9 99 95 90 

1 - - - - 

2 - - - - 

3 - - - - 

4 - - - - 

5 - - - 97 

6 - - 98 92 

7 - - 94 88 

8 - - 91 85 

9 - 98 88 83 

10 - 96 86 81 

11 - 93 84 79 

12 - 91 82 78 

13 100 89 81 77 

14 98 88 80 75 

15 96 87 79 75 

16 94 85 78 74 

17 93 84 77 73 

18 92 83 76 72 

19 90 82 75 71 

20 89 81 74 71 

21 88 80 74 70 

22 87 80 73 70 

23 87 79 73 69 

24 86 78 72 69 

25 85 78 72 68 

26 84 77 71 68 

27 84 77 71 68 

28 83 76 70 67 

29 82 76 70 67 

30 82 75 70 67 

31 81 75 69 66 

32 81 74 69 66 

33 80 74 69 66 

34 80 74 68 66 

61

Table 15: Pointer years of 8 trees from Ypenburg 

JAAR No % Min/Max a 

-2794 5 100% - 

-2791 6 100% + ** 

-2790 6 100% + ** 

-2776 6 100% - ** 

-2774 6 100% + ** 

-2772 7 100% - ** 

-2770 7 100% + ** 

-2764 7 100% + ** 

-2762 7 100% - ** 

-2759 7 100% - ** 

-2758 7 100% - ** 

-2754 7 100% + ** 

-2746 7 100% + ** 

-2744 7 100% + ** 

-2738 8 88% + 

-2737 8 88% - 

-2735 8 100% + ** 

-2734 8 100% + ** 

-2721 7 100% - ** 

-2715 7 100% + ** 

-2697 7 100% + ** 

-2680 5 100% + 

****** : z = 3.30 and certainty 99.9% 

**** : z = 2.57 and certainty 99% 

** : z = 1.96 and certainty 95% 

- : z = 1.64 and certainty 90% 

90.0% certainty: 14 maxima and 8 minima 



99.9% certainty: -2 maxima and -2 minima 

Time span =-2889 - -2658 

62

Table 16: A total of 10 trees were compared to determine pointer years. 

Dated studied 

chronologies 

GFE010 

GFE020 

Ypenburg 

ypf201 

ypf602 

ypf061 

ypf131 

ypf221 

ypf231 

ypf241 

ypf733 

63

Table 17: Pointer years of 32 trees from the province of Zuid-Holland 

JAAR No % Min/Max a JAAR No % Min/Max a 

-1699 7 100% + ** -1585 16 88% - **** 

-1689 10 90% + ** -1584 16 75% - 

-1687 11 91% - ** -1582 16 94% + ****** 

-1686 11 82% - -1569 13 92% - **** 

-1683 11 82% - -1557 9 89% + ** 

-1679 11 91% + ** -1549 8 88% - 

-1675 11 91% + ** -1544 6 100% - ** 

-1673 14 86% + ** -1543 6 100% - ** 

-1670 14 93% - **** -1538 6 100% + ** 

-1669 14 93% + **** -1534 6 100% + ** 

-1668 14 79% - -1522 7 100% + ** 

-1667 14 93% - **** -1511 7 100% - ** 

-1664 14 86% + ** -1509 8 88% + 

-1660 14 100% + ****** -1503 8 88% + 

-1653 14 86% - ** -1495 8 88% - 

-1652 14 86% + ** -1485 7 100% - ** 

-1651 14 86% + ** -1470 6 100% - ** 

-1648 14 86% - ** -1458 9 89% + ** 

-1646 14 93% - **** -1455 9 100% - **** 

-1643 14 86% + ** -1453 9 100% - **** 

-1640 15 80% - ** -1446 9 89% - ** 

-1638 15 80% + ** -1445 9 89% + ** 

-1637 15 80% - ** -1435 10 100% - **** 

-1633 16 81% - ** -1434 10 100% - **** 

-1632 16 75% + -1429 10 90% + ** 

-1629 16 100% - ****** -1425 8 88% + 

-1628 16 94% - ****** -1423 8 88% - 

-1625 15 87% + **** -1420 8 100% - ** 

-1624 15 80% + ** -1417 8 88% - 

-1622 15 93% + **** -1414 8 88% - 

-1621 15 93% - **** -1413 8 88% - 

-1618 16 75% + -1407 8 88% - 

-1617 16 75% - -1404 10 100% + **** 

-1615 16 75% - -1392 9 89% + ** 

-1613 16 88% + **** -1390 8 100% + ** 

-1611 16 75% - -1385 9 100% - **** 

-1608 16 81% - ** -1383 10 90% - ** 

-1605 16 94% + ****** -1381 11 91% + ** 

-1604 16 81% + ** -1373 13 92% - **** 

-1602 17 94% - ****** -1372 13 77% - 

-1601 17 76% - -1368 13 85% + ** 

-1599 17 82% + ** -1367 13 77% - 

-1597 17 88% + **** -1361 13 77% + 

-1594 17 100% - ****** -1360 13 77% - 

-1593 17 76% - -1358 13 85% - ** 

-1591 17 82% + ** -1357 13 92% + **** 

-1588 16 81% + ** -1356 13 85% + ** 

-1587 16 88% - **** -1355 13 77% + 

-1353 13 77% - 

64

****** : z = 3.30 and certainty 99.9% 

**** : z = 2.57 and certainty 99% 

** : z = 1.96 and certainty 95% 

- : z = 1.64 and certainty 90% 





Time span = -1701 - -1350 

Table 18: The original location of the 32 trees from the province of Zuid-Holland 

Site name Start Year End Year Locations 

(BC) (BC) 

Site1c_b -1748 -767 Ouderkerk a/d IJssel 

Papendrecht 

Site 1b -2256 -1141 

Papendrecht 

Papendrecht 

Sliedrecht 

Alphen a/d Rijn 

Bodegraven 

Gouderak 

Hazerswoude-Rijndijk 

Hazerswoude 

Hazerswoude 

Oudewater 

Zoeterwoude dorp 

65

Table 19: A total of 34 trees were compared to determine pointer years, 

32 tree measurements from the province of Zuid-Holland were included. 

Dated studied Site1c_b Site 1b 

chronologies 

LFE010 

LFE020 

OKf082 

PAf041 

PAf071 

PAFB20 

PAFo31 

PAFo81 

PAF141 

PAF152 

SCf161 

afe142 

bof021 

bof041 

gof011 

gof020 

gof031 

gof051 

gof061 

gof071 

gof081 

hrf030 

hwf030 

hwf041 

hwf111 

hwf181 

hzfn11 

ouf022 

ouf032 

ouf040 

ouf061 

zdf040 

zdf070 

zwf042 

66

Appendix 5: absolute pollen diagrams 

Eem Eemvalley, Valley, GFE01 GP01 

1300 

Total concentration 

Eemvalley, GFE02 

Eem Valley, GP02 

1150 

Total concentration 

1350 

1200 

1400 

1250 

1450 

1300 

1500 

1350 

Depth 

1550 

Depth 

1400 

1600 

1450 

1650 

1500 

1700 

1550 

1750 

1800 

2000 4000 

(* 1000) 

1600 

500 1000 1500 

(* 1000) 

67

MA Thesis Marije Vlaar 2007

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