Proceedings World Bioenergy 2010

BIOMASS FUNCTIONS FOR YOUNG SCOTS PINE-DOMINATED FOREST
K. Ahnlund Ulvcrona 1 , U. Nilsson 2 , T. Lundmark 3
1
Vindeln Experimental Forests, Svartberget Research Station, Swedish University of Agricultural Science, SE-922 91
Vindeln, Sweden
2
Southern Swedish Forest Research centre, Swedish University of Agricultural Science, SE-230 53 Alnarp, Sweden
3
Forest Ecology and Management, Swedish University of Agricultural Science, SE-901 83 Umeå, Sweden
Kristina.ulvcrona@esf.slu.se
ABSTRACT: The aim of this study was to develop predictive biomass functions for young stands of Scots pine-dominated
forests in northern Sweden. Above ground biomass was destructively sampled, and biomass functions for all tree fractions
(e.g. stem including bark, branch and foliage) were developed, based on independent variables. Functions to estimate dry
weight of the whole tree were also developed. No significant regressions could be found for the dead branch fraction. DBH
for sampled trees in this study was in the range of 11 - 136 mm (Pinus sylvestris), 10 - 121 mm (Picea abies L. Karst) and 9 –
113 mm (Betula spp.).
Keywords: bioenergy strategy, biomass characteristics, forestry residues
1 INTRODUCTION
Global emissions of greenhouse gases from the use of
coal and oil need to be reduced. Consequently, there is a
need for further development of more environmentally
friendly energy sources [1]. In the future, it may be
possible to use biofuel to satisfy some of the global
energy demand, and therefore knowledge that supports
the development of new silvicultural regimes is also
required. Studies have shown that wood quality and
branch characteristics tend to improve when Scots pine
(Pinus sylvestris) is thinned at a greater stand height [2].
To meet the increasing demand for raw material from the
forest, biomass growth has to increase. A high stem
density results in high biomass production [3]. Dense,
young forest can thus contribute to this increasing
demand for raw material. Terrestrial vegetation can also
be a CO 2 sink that may mitigate greenhouse gas
emissions.
An increased interest in small stems as well as branches
for biomass harvest has led to the need for biomass
functions suitable for these stands. The aim of this study
was to find biomass functions based on easily measured
variables (DBH and height) for the estimation of DW
(dry weight) biomass.
2 MATERIAL AND METHODS
2.1 The sites
Biomass was sampled at six different sites (Renfors,
Degerön, Kulbäcksliden, Gagnet, Lillarmsjö and Unbyn;
table 1). The sites are all young self-regenerated pinedominated
mixed forest. Four of the sites (Renfors,
Degerön, Kulbäcksliden and Gagnet) used for biomass
sampling are part of a factorial experiment comparing
thinning/no thinning combined with three different levels
of fertilization. The field experiment was established in
1997 and 1998 (Gagnet) after the first biomass sampling.
The sizes of the experimental plots are 30 x 30 m or 45 x
20 m, and each plot is surrounded by a 5 m buffer zone.
Table 1. The sites for biomass sampling
Site Latitude Altitude H100 (m)
Renfors 64.22 190 18
Degerön 64.15 175 20
Kulbäcksliden 64.17 170 20
Gagnet 63.25 125 24
Lillarmsjö 63.97 220 21
Unbyn 65.70 20 19
2.2 Sample trees
The trees for biomass sampling were randomly
sampled from each DBH-class in the stand, but damaged
trees were not chosen.
In total, 387 trees were included in this destructive
above-ground biomass study, of which 54 were from the
pre commercial thinning (PCT)-treatment. The first
samples were taken in June 1997 (Renfors, Degerön,
Kulbäcksliden), June 1998 (Lillarmsjö) and August 1998
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