Rationale of the winter temperature use in forecasting climate-related changes in the biomass of eurasian forests

Understanding the effects of climate change on tree growth is necessary to predict forest dynamics in future climate change scenarios. In this regard, the role of empirical models that adequately describe the variability of biological productivity of forests and allow predicting its change under the influence of climatic shifts is increasing. In the available publications, the contribution of climate variables to the explanation of biomass variability is either insignificant or zero, mainly due to the regional level of models. The modeling of the biomass of trees and stands performed at the Eurasian level showed the presence of a statistically significant contribution of winter temperature and average annual precipitation to the explanation of the variability of biomass indicators. However, the validity of using winter temperature instead of summer one in predictive models was questioned. The purpose of this work was to study the relationship of temperatures of different months in Eurasia and their changes in the latitudinal gradient from the tropics to the forest tundra in order to identify the month whose average temperature would be statistically significant in biomass models. To achieve this goal, the WorldClim version 2.1 climate database for the years 1970-2000 was used (https://worldclim.org/data/index.html). It is established that the average summer temperature provides a weak geographically distributed climatic signal, which is not capable of being extracted from the general dispersion of factors determining the biomass of trees and stands. On the contrary, the average January temperature represents a sufficiently strong geographically distributed climatic signal due to the high ratio of the total variance (or temperature range) to the residual one, which provided the statistical significance of the previously identified influence of winter temperatures on the biomass of trees and stands of forest-forming genera of Eurasia [4]. The average annual temperature, characterized by a high correlation with the January temperature, may be statistically significant in explaining the variability of biomass of trees and stands of Eurasia. The identification of this premise will be a subject of our further research.

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