Seemingly Unrelated Mixed-Effects Biomass Models for Young Silver Birch Stands on Post-Agricultural Lands

Karol Bronisz,Lauri Mehtätalo

doi:10.3390/f11040381

Karol Bronisz, Lauri Mehtätalo

Open Access

https://doi.org/10.3390/f11040381

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Abstract

Secondary succession that occurs on abandoned farmlands is an important source of biomass carbon stocks. Both direct and indirect tree biomass estimation methods are applied on forest lands. Using empirical data from 148 uprooted trees, we developed a seemingly unrelated mixed-effects models system for the young silver birch that grows on post agricultural lands in central Poland. Tree height, biomass of stem, branches, foliage, and roots are used as dependent variables; the diameter at breast height is used as the independent variable. During model elaboration we used restricted cubic spline: 5 knots at the quantiles (0.05, 0.275, 0.5, 0.725, and 0.95) of diameter at breast height provided sufficiently flexible curves for all biomass components. In this study, we demonstrate the use of the model system through cross-model calibration of the biomass component model using tree height measured from 0, 2, 3, and 4 available extreme trees feature in the plot in question. A different number of extreme trees were measured for final model system and our results indicated that for all analyzed components, random-effect predictions are characterized by higher accuracy than fixed-effects predictions.

Highlights

Issues related to climate change have become increasingly important, as evidenced by the world’s strongest climate-energy policy agreed upon by the European Council in October 2014
One of the types of land that is not covered by official statistics is secondary succession, which occurs on abandoned farmlands and are an important source of biomass carbon stocks [3,4,5]
Using empirical data from 148 uprooted trees, we developed a seemingly unrelated mixed-effects models system for the young silver birch stands growing on post agricultural lands in central Poland

Summary

Introduction

Issues related to climate change have become increasingly important, as evidenced by the world’s strongest climate-energy policy agreed upon by the European Council in October 2014. The policy’s objective assumes that within the European Union (EU): (i) at least 32% of the energy demand is being covered by renewable energy sources and (ii) greenhouse gas emissions (from 1990 levels) will be cut by 40% by 2030 In this context, due to the area occupied and the amount of accumulated carbon, forest ecosystems play an important role. One of the types of land that is not covered by official statistics is secondary succession, which occurs on abandoned farmlands and are an important source of biomass carbon stocks [3,4,5] These areas are frequently subjected to appearance of pioneer forest tree species, such as silver birch (Betula pendula Roth.) [6,7]. By introducing rapid rotation in these areas, it is possible to increase the potential of fast growing silver birch stands, which can be assessed using a life cycle analysis [9]

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