PJB-2020-460
Are there differences in the response of Betula spp. and Quercus spp. tree biomass to changes in temperatures and precipitation? A special reference on additive models
Vladimir Andreevich Usoltsev
Abstract
Oaks and birches are deciduous genera, and both are capable of vegetative renewal. But their ecological niches do not coincide in many ways. If birch trees are distributed throughout the Northern hemisphere, from the subtropics to the tundra, the areas of oak habitat are mainly confined to the oceanic climate. Accordingly, their responses to climate change can vary greatly. In our study, the first attempt is made to compare the changes in the additive component composition of tree biomass of Betula spp. and Quercus spp. according to trans-Eurasian hydrothermal gradients using the unique Eurasian database of harvest data on single-tree biomass compiled by the authors. Since climate variables are geographically determined, it can be expected that the development of allometric biomass models, including not only the age, height and stem diameter as independent variables, but also climate indices, will allow to isolate and quantify some changes in the biomass structure of equal-aged and equal-sized trees in relation to climate variables and will provide climate-sensitivity of such models. The propeller-shaped 3-D pattern common to the components of birch biomass is stated: in cold zones, an increase in precipitation leads to a decrease in biomass, and in warm zones– to its increase. Accordingly, in moisture-rich areas, the temperature increase causes biomass increase, and in arid areas – its decrease. But in oaks, the propeller-shaped surfaces are turned in the opposite direction, which means that the reactions of the biomass of all components to changes in both temperatures and precipitation are directly opposite to the corresponding reactions in birch. As one moves from warm to cold zones, the value of the R/S ratio for birches decreases by 44% and for oaks increases by 112 %. The results presented need to be accounted for as the first approximation only. There is the problem of unknown response of tree biomass to climate shifts in the context of the disproportion of adaptation lags, one of which lasted for thousands of years and determines the current relationship of vegetation and climate zoning, and the other occurs abruptly over the past decades.
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