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Articles containing the keyword 'seemingly unrelated regression'

Category: Research article

article id 10627, category Research article
Christian Kuehne, J. Paul McLean, Kobra Maleki, Clara Antón-Fernández, Rasmus Astrup. (2022). A stand-level growth and yield model for thinned and unthinned even-aged Scots pine forests in Norway. Silva Fennica vol. 56 no. 1 article id 10627. https://doi.org/10.14214/sf.10627
Keywords: Pinus sylvestris; mortality; volume growth; seemingly unrelated regression; production forestry; system of equations
Highlights: The presented growth and yield model consists of component equations for dominant height, stem density, total basal area, and total stem volume; The component equations were fitted simultaneously using seemingly unrelated regression; The model is capable to forecast and compare outcomes of varying thinning regimes; The new component equations better represent the improved growing conditions for Scots pine in Norway.
Abstract | Full text in HTML | Full text in PDF | Author Info

Management of Scots pine (Pinus sylvestris L.) in Norway requires a forest growth and yield model suitable for describing stand dynamics of even-aged forests under contemporary climatic conditions with and without the effects of silvicultural thinning. A system of equations forming such a stand-level growth and yield model fitted to long-term experimental data is presented here. The growth and yield model consists of component equations for (i) dominant height, (ii) stem density (number of stems per hectare), (iii) total basal area, (iv) and total stem volume fitted simultaneously using seemingly unrelated regression. The component equations for stem density, basal area, and volume include a thinning modifier to forecast stand dynamics in thinned stands. It was shown that thinning significantly increased basal area and volume growth while reducing competition related mortality. No significant effect of thinning was found on dominant height. Model examination by means of various fit statistics indicated no obvious bias and improvement in prediction accuracy in comparison to existing models in general. An application of the developed stand-level model comparing different management scenarios exhibited plausible long-term behavior and we propose this is therefore suitable for national deployment.

  • Kuehne, Norwegian Institute of Bioeconomy Research, Division of Forestry and Forest Resources, P.O. Box 115, NO-1431 Ås, Norway E-mail: christian.kuehne@nibio.no (email)
  • McLean, Norwegian Institute of Bioeconomy Research, Division of Forestry and Forest Resources, P.O. Box 115, NO-1431 Ås, Norway E-mail: paul.mclean@nibio.no
  • Maleki, Norwegian Institute of Bioeconomy Research, Division of Forestry and Forest Resources, P.O. Box 115, NO-1431 Ås, Norway E-mail: kobra.maleki@nibio.no
  • Antón-Fernández, Norwegian Institute of Bioeconomy Research, Division of Forestry and Forest Resources, P.O. Box 115, NO-1431 Ås, Norway E-mail: clara.anton.fernandez@nibio.no
  • Astrup, Norwegian Institute of Bioeconomy Research, Division of Forestry and Forest Resources, P.O. Box 115, NO-1431 Ås, Norway E-mail: rasmus.astrup@nibio.no
article id 1559, category Research article
Karol Bronisz, Mike Strub, Chris Cieszewski, Szymon Bijak, Agnieszka Bronisz, Robert Tomusiak, Rafał Wojtan, Michał Zasada. (2016). Empirical equations for estimating aboveground biomass of Betula pendula growing on former farmland in central Poland. Silva Fennica vol. 50 no. 4 article id 1559. https://doi.org/10.14214/sf.1559
Keywords: silver birch; simplified and expanded models; seemingly unrelated regression
Highlights: We developed equations for aboveground biomass components of young silver birch stands on post-agricultural lands in central Poland for single tree level; Simplified equations were based exclusively on diameter at ground level or breast height, while expanded ones were based on the appropriate diameter and tree height; For large trees, diameter at breast height is a more appropriate explanatory variable than diameter at ground level; Biomass estimations based on models from neighboring countries were consistent with our results.
Abstract | Full text in HTML | Full text in PDF | Author Info

We determined empirical models for estimating total aboveground as well as stem, branches, and foliage dry biomass of young (age up to 16 years) silver birch (Betula pendula Roth.) growing on the post-agricultural lands. Two sets of allometric models for trees with a height below or above 1.3 m (small and large trees respectively) were developed. Simplified models were elaborated based exclusively on appropriate tree diameter (diameter at ground level for small trees, diameter at breast height for large trees), while expanded models also included tree height. Total aboveground biomass was estimated as the sum of biomass of all tree components. To assure additivity of the developed equations, the seemingly unrelated regression approach for the final model fitting was used. Expanded models in both tree groups were characterized by a better fit to the data (R2 for total aboveground biomass for small and large trees equaled 0.8768 and 0.9752, respectively). Diameter at breast height appeared to be a better predictor than diameter at ground level – simplified models had better fit for large trees (R2 for total aboveground biomass equals 0.9611) than for small ones (R2 = 0.7516). The developed equations provide biomass predictions consistent with available Latvian, Estonian, Finnish, Swedish, and Norwegian models for silver birch.

  • Bronisz, Laboratory of Dendrometry and Forest Productivity, Faculty of Forestry, Warsaw University of Life Sciences – SGGW, Nowoursynowska 159, 02-787 Warsaw, Poland E-mail: karol.bronisz@wl.sggw.pl (email)
  • Strub, Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30605, USA E-mail: strub@mcfns.com
  • Cieszewski, Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, 30605, USA E-mail: thebiomat@gmail.com
  • Bijak, Laboratory of Dendrometry and Forest Productivity, Faculty of Forestry, Warsaw University of Life Sciences – SGGW, Nowoursynowska 159, 02-787 Warsaw, Poland E-mail: szymon.bijak@wl.sggw.pl
  • Bronisz, Laboratory of Dendrometry and Forest Productivity, Faculty of Forestry, Warsaw University of Life Sciences – SGGW, Nowoursynowska 159, 02-787 Warsaw, Poland E-mail: agnieszka.bronisz@wl.sggw.pl
  • Tomusiak, Laboratory of Dendrometry and Forest Productivity, Faculty of Forestry, Warsaw University of Life Sciences – SGGW, Nowoursynowska 159, 02-787 Warsaw, Poland E-mail: robert.tomusiak@wl.sggw.pl
  • Wojtan, Laboratory of Dendrometry and Forest Productivity, Faculty of Forestry, Warsaw University of Life Sciences – SGGW, Nowoursynowska 159, 02-787 Warsaw, Poland E-mail: rafal.wojtan@wl.sggw.pl
  • Zasada, Laboratory of Dendrometry and Forest Productivity, Faculty of Forestry, Warsaw University of Life Sciences – SGGW, Nowoursynowska 159, 02-787 Warsaw, Poland E-mail: michal.zasada@wl.sggw.pl

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