No abstract

Forest ecosystems, as sinks of atmospheric carbon, play an important role in reducing CO2 emissions and preventing annual temperatures from rising. On the other hand, climate change entails changes in the structure and functions of all the biota, including forest cover. Therefore, we attempted to model Betula spp. ecosystem biomass and annual net primary production (NPP) (t ha-1) using the data from 650 forest stands for biomass, 245 for NPP and biomass, as well as climate data on the Trans-Eurasian hydrothermal gradients. The model involves regional peculiarities of age and morphology of the forests. It is found that the reaction of birch biomass and NPP structure on temperature and precipitation corresponds to the principle of limiting factors by Liebig-Shelford but in different proportions for different species. Since the minimum values of biomass and NPP occur in regions with minimum precipitation and minimum temperature, these two factors are limiting in terms of biomass and NPP of birches. The same phenomenon is typical for firs, partly typical for spruces and very differ for larches and pines. The development of such models for basic forest-forming species grown in Eurasia will give possibility to predict any changes in the biological productivity of forest cover of Eurasia in relation to climate change.

Although forest ecosystems play an essential role in climate stabilization, current climatic shifts might cause striking changes in their biological productivity, which, in turn, affects the biosphere function of forests. Studies of the relationship between the biomass of trees and stands and hydrothermal indicators (temperature and precipitation) have usually been carried out at local or regional levels. It is still unknown how climate changes affect tree and stand biomass along transcontinental gradients. Therefore, the goals of this study were (a) to test if the law of the limiting factor holds for tree and stand biomass of Picea spp. at the transcontinental level of Eurasia in relation to temperature and precipitation, and (b) to apply the principle of space-for-time substitution to document the use of the derived tree and stand biomass climate-sensitive models for predicting temporal biomass changes. The results revealed that at a tree level spruce aboveground biomass increased with a temperature increase in moisture-rich regions, whereas in moisture–deficient regions it was reduced. Similarly, precipitation reduction at a constant average January temperature caused a reduction in aboveground biomass in warm regions, while in cold regions its increase was revealed. At a stand level, we also revealed an increase in biomass with increased precipitation amount in warm regions. The study suggested that the principle of space-for-time substitution was clearly manifested on biomass quantity of spruce at both individual tree and forest stand levels.