Leaf mesophyll structure and tree biomass of birches from different climatic zones in Northern Eurasia

In the context of global climate change, it is becoming increasingly important to study the adaptation of forest-forming species, assess their productivity and predict the transformation of forest ecosystems. Here we present the analysis of leaf mesophyll structure and tree biomass in populations of Betula pendula Roth and Betula pubescens Ehrh. along the global climatic transect representing the latitudinal distribution area of these species in Northern Eurasia. It has been shown that with distance from climatic optimum, biological productivity decreases and a structural rearrangement of leaf mesophyll based on a change in cell size and providing a positive carbon balance occurs. High correlations between photosynthetic cells volumes and stem biomass were found. It was concluded that mesophyll cells sizes underlie the structural adaptation of photosynthesis to climate, that determine birch productivity under changing growth conditions. The sizes of photosynthetic cells can be considered as a good predictors of woody species productivity and transformation of forest ecosystems under global climatic changes.