The principle of space-for-time substitution in predicting Picea spp. biomass change under climate shifts

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.