GeloriniPhD (PDF , 6973kb) - University of York

More documents

Recommendations

Info

INTRODUCTION resulting from inappropriate extrapolation of Eurocentric indicators of human impact, and partly from poor appreciation of the very significant climate changes in the relatively recent past (Verschuren, 2004; Verschuren and Charman, 2008). The fact remains that tropical ecosystems, which are exposed to climate change and/or anthropogenic disturbance, register similar environmental signatures, complicating the interpretation process. Transition from a woodland- to grassland-dominated environment can be attributed to either i) climate variability (increasing aridity, linked to natural fire frequency), ii) disturbance by large wild herbivores, iii) human interference (e.g., cultivation, pastoralism, logging, slash-and-burn practices), or iv) a complex interaction of these causal factors (e.g., Lamb et al., 2003; Vincens et al., 2003; Gillson, 2004; Ssemmanda et al., 2005; Rucina et al., 2010). Herbaceous pollen taxa such as Poaceae, Chenopodiaceae- Amaranthaceae and Urticaceae, may not only indicate pastoral activities (Taylor et al., 2005; Kiage and Liu, 2006), but are also common herbs in natural grasslands visited by large wild herbivores. Furthermore, evidence for agricultural activities is mainly supported by pollen records of ambiguously human-related plants, such as the oil palm and caster oil plant (e.g., Lamb et al., 2003; Darbyshire et al., 2003; Vincens et al., 2003; Rucina et al., 2010), which are also naturally abundant in East African vegetation as a pioneer tree and ruderal plant, respectively (Radcliffe-Smith, 1987; Maley and Chepstow-Lusty, 2001). Further compounding the problem, taxonomic identification of pollen types from crop plants cultivated in East Africa (i.e. sorghum, millet, banana, cotton, potatoes and rice) is impeded by morphological similarities between cultivated and wild species. The ~40 µm lower limit of the long axis diameter of European Cerealia pollen types (e.g., Andersen, 1979; Küster, 1988; Tweddle et al., 2005) is unfortunately not applicable to the tropics, since the pollen size ranges of tropical cereals, such as sorghum and teff may significantly overlap with those from tropical wild grasses (Bonnefille, 1972). At best, only maize pollen can be unambiguously distinguished from other Poaceae species (including wild grasses and cereals) mainly by their large size, although the diameter of fossil maize pollen (~60-85 µm) often falls below that of their modern counterparts (~85-125 µm) (Tsukada and Rowley, 1964). For example, in Uganda and Kenya maize is generally introduced as a crop by the late 19th century (Sprague, 1987; McCann, 2005), however maize pollen in sediment records is dated to the last 300 years (e.g., Lamb et al., 2003; Lejju et al., 2005; Taylor et al., 2005; Kiage and Liu, 2009). Due to the similar pollen morphology of many wild and cultivated species, cereals and other crops such as legumes, cassava/ manioc and cultivated banana, are unidentifiable in pollen records (e.g., Msaky et al., 2005; Kiage and Liu, 2006). Another major problem is related to the low pollen dispersal and production of many crop plants, being mostly insectpollinated or self-pollinated (maize excluded), limiting their abundance in pollen records. Pollen from exotic plantation trees, such as eucalyptus, cypress and pine are exclusively present in sediment records dated posterior to the early 20th century (e.g., Ssemmanda, unpublished CLANIMAE data; Kiage and Liu, 2009), when plantation forestry was stimulated to meet the growing demands of fuelwood and timber (Mclean, 1971). Phytolith records may capture anthropogenic signals as well, although evidence claiming to support a very early introduction of banana as a food crop in East Africa (Lejju et al., 2005; Lejju, 2006) has been strongly debated (e.g., Mbida et al., 2004; Vansina, 2004; Neumann and Hildebrand, 2009). As concerns East African charcoal records, high counts of macro- and microscopic charcoal concurrent with forest clearance are interpreted as human-induced (e.g. Thevenon et al., 2003; Lejju et al., 2005). However, drought episodes in savannah ecosystems may register a similar palaeoenvironmental signal (e.g., Duffin et al., 2008; Gillson and Ekblom, 2009). Thus, in summary, the visibility of anthropogenic activity in tropical African palaeoecological records is generally low, or biased. Patterns of human occupation Over the past 2500 years, eastern Africa has experienced an eventful history, with innovations in food production and . 26 .
. 27 . INTRODUCTION metallurgy mainly due to the emergence of trade networks, though foraging and traditional stone-tool technologies continued to prevail (Stahl, 2004). For decades, the spread of early farming and knowledge of iron working across sub- Saharan Africa (~500 BC-500 AD) has been regarded as having been conterminous with the expansion of Bantu-speaking farmers (e.g., Posnansky, 1968; Schoenbrun, 1993; Robertshaw and Taylor, 2000). However, it becomes increasingly clear that these processes of demographic, linguistic, economic and technological change may have developed independently of one another, probably through complex multi-cultural interactions at different time scales (Lane et al., 2007). At present, the debate about the origin and timing of first iron metallurgy in the Great Lakes region prior to the Bantu migration is ongoing (e.g., Alpern, 2005; Killick, 2009), however the idee fixe of an exclusively Bantu-related iron work introduction between ~800-400 BC remains hinted through the discussions. This example of begging the question is possible because of the limited multi-proxy archaeological data and poorly constrained radiometric dating, together with palaeoenvironmental hints of increasing agricultural activity from that period on (e.g., Schoenbrun, 1993; Sutton, 1995; Jolly et al., 1997; Taylor et al., 2000; Killick, 2009), as if by evidence of human activity fairly completing the historical picture. Nothing is farther from the truth: methodological deficiencies can unfortunately not be ignored and need to be regarded from a proper perspective, totally unrestrained from apriorisms. It can surely be argued that in tropical Africa the distinction between natural and cultural landscapes is not evident, because of significant climate-driven vegetation dynamics at both short and longer time scales, and relative mobility of indigenous people in response to the impacts of this climate change on land and water resources. How indigenous African people have interacted with climate-driven environmental changes and have modified landscapes to their food demands, has been dealt with in many reviews on the political, social, economic and cultural dimensions of East African pre-colonial and colonial societies (e.g., Smith, 1992; Connah, 1997; Schmidt, 1997; Robertshaw and Taylor, 2000; Taylor et al., 2000; Robertshaw et al., 2004; Stahl, 2004). Archaeological surveys have indicated that substantial occupation of the Interlacustrine area began from the ninth century AD, coeval with a pre-Medieval Warm Period of elevated rainfall (Robertshaw and Taylor, 2000). In the following centuries of region-wide drought, distinct subsistence patterns such as agro- and transhumant pastoralism developed, facilitating the occupation of dry (marginal) grasslands. Livestock keeping and crop cultivation were initially practiced in the same households, but soon became subject to class divergence (Stahl, 2004). Due to the emergence of long-distance trade networks (e.g., ivory, salt, iron, shell beads) elites started to consolidate power, leading to small chiefdoms (e.g., Ntusi and Munsa) (Robertshaw and Taylor, 2000). Wetter conditions after ~1250 AD resulted in increasing agricultural success (e.g., Engaruka; Holmgren and Öberg, 2006) and political stability (e.g., Bigo, Kibengo, Kibiro and Munsa). Around 1700 AD, however, major political economic changes occurred across the region, including the fall of the capital at Munsa (Robertshaw and Taylor, 2000). Nucleated villages were replaced by dispersed homesteads, and stratification between pastoral nobility and agricultural peasantry became more apparent in the Great Lakes region (Reid, 1996; Stahl, 2004; Robertshaw, 2010), a pattern that has mainly persisted into colonial and recent times. Unfortunately, much of East African history is mainly reconstructed from scarce archaeological remains and historical sources affiliated to elite groups during pre-colonial and colonial times. Archaeological records from pre-colonial periods (prior ~1880 AD) remain lacking, partly due to low archaeological visibility of the temporary settlements occupied by pastoralists, leaving few materials behind once the open-air site is abandoned (Robertshaw, 1978; Banning and Kohler-Rollefson, 1992). Also the difficulty of distinguishing between hunter-gatherer and pastoral archaeological sites causes a major interpretive problem in studies of prehistoric Africa (Shahack-Gross et al., 2003; Mutundu, 2010). Besides, most archaeological sites are located away from palaeoecological reconstruction sites, making it difficult to relate observed changes in habitat directly to human patterns of resource use (Lane, 2010). Historical written sources from pre-colonial times are rare, making historiographical support of current culture-historical hypotheses inadequate. The few extant written sources, which frequently served the interests of the colonial state and European settler colonies,
Page 3: 2011 Thesis submitted in partial fu
Page 7: Voorwoord . 7 . VOORWOORD Aarde, wa
Page 10: DANKWOORD / ACKNOWLEDGEMENTS door K
Page 14 and 15: TABLE OF CONTENTS A.1. Septated spo
Page 17 and 18: Abstract . 17 . ABSTRACT In tropica
Page 19 and 20: Introduction . 19 . INTRODUCTION
Page 21 and 22: . 21 . INTRODUCTION Atlantic Ocean
Page 23 and 24: 1 Figure 2 Global Land-Cover 2000 m
Page 25: Fig. iv. Rainfall variation in east
Page 29 and 30: . 29 . INTRODUCTION analysis of fos
Page 31 and 32: . 31 . INTRODUCTION (iv) illuminate
Page 33 and 34: . 33 . INTRODUCTION Coniochaeta spe
Page 35 and 36: . 35 . INTRODUCTION university pres
Page 37 and 38: . 37 . INTRODUCTION Mumbi, C.T., Ma
Page 39 and 40: . 39 . INTRODUCTION lipids in an eq
Page 41 and 42: . 41 . CHAPTER 1 Diversity and ecol
Page 43 and 44: Equator b 0° Altitude (m) a >3000
Page 47 and 48: 1.3.1. Descriptions and illustratio
Page 49 and 50: Type HdV-1005: Brachydesmiella sp.
Page 51 and 52: Type HdV-1020 (Plate II) . 51 . CHA
Page 55 and 56: Type HdV-1051 (Plate III) . 55 . CH
Page 63 and 64: RefeRences . 63 . CHAPTER 1 Diversi
Page 69: . 69 . CHAPTER 1 Diversity and ecol
Page 72 and 73: CHAPTER 2 Modern non-pollen palynom
Page 74 and 75: CHAPTER 2 Modern non-pollen palynom
Page 76 and 77:
CHAPTER 2 Modern non-pollen palynom
Page 78 and 79:
Page 80 and 81:
Page 82 and 83:
Page 84 and 85:
Page 86 and 87:
Page 88 and 89:
Page 90 and 91:
Page 92 and 93:
Page 94 and 95:
Page 96 and 97:
Page 98 and 99:
Page 100 and 101:
Page 102 and 103:
Page 104 and 105:
Page 106 and 107:
Page 108 and 109:
Page 110 and 111:
Page 112 and 113:
Page 114 and 115:
Page 116 and 117:
Page 118 and 119:
Page 120 and 121:
Page 122 and 123:
Page 124 and 125:
Page 126 and 127:
Page 128 and 129:
CHAPTER 3 Effects of Land use on th
Page 130 and 131:
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
Page 138 and 139:
Page 140 and 141:
Page 142 and 143:
Page 144 and 145:
Page 146 and 147:
Page 148 and 149:
Page 150 and 151:
Page 152 and 153:
Page 154 and 155:
Page 156 and 157:
Page 158 and 159:
Page 160 and 161:
Page 162 and 163:
CHAPTER 4 Validation of non-pollen
Page 164 and 165:
Page 166 and 167:
Page 168 and 169:
Page 170 and 171:
Page 172 and 173:
Page 174 and 175:
Page 176 and 177:
Page 178 and 179:
Page 180 and 181:
Page 182 and 183:
Page 184 and 185:
Page 187 and 188:
General discussion and conclusion .
Page 189 and 190:
. 189 . GENERAL DISCUSSION AND CONC
Page 191 and 192:
Page 193 and 194:
Page 195:
Page 198 and 199:
SAMENVATTING beperkingen (i.v.m. de
Page 200 and 201:
APPENDICES Appendix I. Raw NPP data
Page 202 and 203:
APPENDICES Mahuhura Kitere Katanda
Page 204 and 205:
Page 206 and 207:
Page 208 and 209:
Page 210 and 211:
Page 212 and 213:
APPENDICES Appendix II. Raw NPP dat
Page 214 and 215:
APPENDICES L. Chibwera Identificati
Page 216 and 217:
APPENDICES L. Chibwera Identificati
Page 218 and 219:
APPENDICES Appendix III. Raw NPP da
Page 220 and 221:
APPENDICES L. Kanymukali Identifica
Page 222 and 223:
APPENDICES L. Kanymukali Identifica
Page 224:
Photograph by Bob Rumes Front cover
show all

GeloriniPhD (PDF , 6973kb) - University of York

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?