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Empirical models for estimating volume and biomass of poplars on farmland in Sweden

Hjelm, Birger (2015). Empirical models for estimating volume and biomass of poplars on farmland in Sweden. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2015:1
ISBN 978-91-576-8200-0
eISBN 978-91-576-8201-7
[Doctoral thesis]

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There is growing interest in establishing short-rotation poplar plantations in Sweden, primarily as a future feedstock for bioenergy. Cost-efficient planning and effective management of these plantations would be greatly facilitated by robust equations for estimating the taper, volume and height of poplar trees, and the biomass of poplar stumps and roots. Thus, the aim of the studies this thesis is based upon were to construct and evaluate such equations. Six equations were constructed: a stem taper equation, a stem volume equation, three stem height equations, and a stump and root biomass equation. The constructed taper and volume equations were compared with five and six published equations, respectively. The taper and volume equations are based on measurements of 69 and 72 trees, respectively, at 37 sites, the height equations on measurements of 117 trees at 40 sites, and the stump and root biomass equations on measurements of 72 stumps at six sites. All sites were located in central and southern Sweden (lat. 55-60° N). The mean age of the stands was 21 years (range 6-43 years) for the taper, volume and height analyses and 20 years for the stump/root biomass analysis.

The results confirm many previous findings that exponential equations provide the best descriptions and predictions of taper. A complex exponential equation presented by Kozak provided the best fit to the collected data. However, the constructed (polynomial) equation is recommended when a simpler model is required and larger bias is acceptable. Equations developed by Eriksson and Scott, and the constructed equation for estimating volume, provided the best fits to the volume data, but a constructed new equation is recommended for simplicity, as it only includes three parameters.

The diameter-height models were developed using a mixed model approach. The models included the stand variables mean diameter and age, and were improved by including a random site effect (to address variations among sites and provide locally calibrated estimates) which increased the R2 value from 0.87 to 0.96.

The stump and root biomass equations were based on a power equation with DBH as an independent variable. The R2 values were 0.93 and 0.80 for dry weight estimates of stumps and roots, respectively. The mean dry stump weight represented 21% of the mean stem weight. The total dry weight per hectare for stumps and for roots amounted to 34.9 and 12.0 tons, respectively.

Authors/Creators:Hjelm, Birger
Title:Empirical models for estimating volume and biomass of poplars on farmland in Sweden
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :2015
Depositing date:16 December 2014
Number of Pages:61
I.Hjelm, B. (2013). Stem taper equations for poplars growing on farmland in Sweden. Journal of Forestry Research 24: 15-22
II.Hjelm, B., Johansson, T. (2012). Volume equations for poplars growing on farmland in Sweden. Scandinavian Journal of Forest Research 27: 561-566
III.Hjelm, B., Mola-Yudego, B., Dimitriou, I., Johansson, T. (2014). Diameter-height models for rapidly growing poplar plantations on agricultural land in Sweden. Manuscript.
IV.Johansson, T., Hjelm, B. (2012). Stump and root biomass of poplar stands. Forests 3: 166–178
Place of Publication:Uppsala
Publisher:Department of Crop Production Ecology, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-576-8200-0
ISBN for electronic version:978-91-576-8201-7
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:K Forestry > K10 Forestry production
Subjects:(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 401 Agricultural, Forestry and Fisheries > Forest Science
(A) Swedish standard research categories 2011 > 4 Agricultural Sciences > 405 Other Agricultural Sciences > Renewable Bioenergy Research
Agrovoc terms:populus, bioenergy, biomass, volume, tree form, height, diameter, stems, stumps, forest mensuration, models, farmland, sweden
Keywords:poplar, bio-energy, short rotation forestry, taper equations, volume equations, diameter-height equations, stump biomass equations, mixed effect models
Permanent URL:
ID Code:11707
Faculty:NJ - Fakulteten för naturresurser och jordbruksvetenskap
Department:(NL, NJ) > Dept. of Crop Production Ecology
External funders:Skogssällskapet
Deposited By: PhDstudent Birger Hjelm
Deposited On:17 Dec 2014 09:33
Metadata Last Modified:10 Sep 2020 13:41

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