Effects of climate, disturbance, and species on forest biomass across Russia

We used detailed forest inventory data from 43 forests (3.5 x 10(3) - 115.2 x 10(3) stands each) and meteorological data from 30 weather stations located in proximity to these forests to assess the effects of disturbance and climate on biomass accumulation patterns across the forest zone of Russia. Chronosequences of biomass accumulation following disturbance were developed for each of the two to five dominant tree species in each forest using stand survey data collected by forest inventories in different regions of Russia between 1986 and 2003. These chronosequences represent changes in average live biomass of forest stands between age 10 and 210 years at 10-year intervals. The correlation of attributes of biomass accumulation (i.e., maximum biomass, biomass at age 40, and maximum biomass increment) with climatic and disturbance attributes was significant but weak (adjusted R-2 = 0.20-0.37). The effect of the most influential disturbance attributes (percent clear-cut and percent old forest) was as strong or stronger than the effect of climatic attributes (30-year averages of the sum of positive daily temperatures and climate moisture index). The effect of tree species was significant, but weaker than the effects of climate or disturbance. Combining climate, disturbance, and species attributes generally improved the models (adjusted R-2 = 0.37-0.53). The patterns of biomass change observed in chronosequences are influenced by the tendency of harvesting to target more productive forest stands of commercially valuable species, creating a disparity in productivity among the age cohorts. The apparent link between disturbance attributes of forests and biomass accumulation patterms in forest stands may be used to improve broad-scale modeling of changes in forest biomass with remotely sensed data.