Birch stands growth increase in Western Siberia

摘要

Birch (Betula pendula Roth) growth within the Western Siberia forest-steppe was analyzed based on long-term (1897-2006) inventory data (height, diameter at breast height [dbh], and stand volume). Analysis of biometry parameters showed increased growth at the beginning of twenty-first century compared to similar stands (stands age = 40-60 years) at the end of nineteenth century. Mean height, dbh, and stem volume increased from 14 to 20 m, from 16 to 22 cm, and from similar to 63 to similar to 220 m(3)/ha, respectively. Significant correlations were found between the stands mean height, dbh, and volume on the one hand, and vegetation period length (r(s) = 0.71 to 0.74), atmospheric CO2 concentration (r(s) = 0.71 to 0.76), and drought index (Standardized Precipitation-Evapotranspiration Index, r(s) = -0.33 to -0.51) on the other hand. The results obtained have revealed apparent climate-induced impacts (e. g. increase of vegetation period length and birch habitat drying due to drought increase) on the stands growth. Along with this, a high correlation of birch biometric parameters and [CO2] in ambient air indicated an effect of CO2 fertilization. Meanwhile, further drought increase may switch birch stand growth into decline and greater mortality as has already been observed within the Trans-Baikal forest-steppe ecotone