Usoltsev V. А., Tsepordey I. S., Chasovskikh V. P. Tree Biomass of Two-Needled Pines in Eurasia: Additive Models in Climatic Gradients

The analysis of studies on the relations between tree and forest stand biomass and climatic conditions revealed a wide variety of independent variables and their combinations involved as predictors. There are significant contradictions and uncertainties found in modeling of dependences of tree and stand biomass upon temperature and precipitation using both empirical and process-based models. The database on biomass of 2100 single trees of two-needled pines (subgenus Pinus L.) of Eurasia compiled by the authors, enables to design for the first time a trans-Eurasian harmonized model on the tree biomass structure and to estimate quantitatively the influence of January temperatures and annual precipitation on tree biomass. The harmonization is achieved with additivity of biomass component composition, which means that the total of biomass components (stems, branches, foliage, roots) derived from component equations is equal to the result obtained using a common biomass equation. It is stated, that in cold climatic zones any increase in precipitation leads to a corresponding decrease in the biomass values, but in warm zones – to its increase. In wet areas, the rise in temperature causes an increase of biomass values, but in arid areas – their reductions. Geometric view of this model represented by a «propeller-shaped» surface is consistent with the results formerly revealed by the other authors in Russia on local and regional levels. The proposed transcontinental model of additive structure of tree biomass makes it possible to predict a change of biomass structure in relation to simultaneous increase or decrease of January temperature and annual precipitation. The development of such models for basic forest-forming species grown in Eurasia enables one to forecast any changes in the biological productivity of forest cover of Eurasia in relation to climate change.