Impacts of Change in Atmospheric CO2 Concentration on Larix gmelinii Forest Growth in Northeast China from 1950 to 2010

Although CO2 fertilization on plant growth has been repeatedly modeled to be the main reason for the current changes in the terrestrial carbon sink at the global scale, there have been controversial findings on the CO2 fertilization effects on forests from tree-ring analyses. In this study, we employed conventional dendrochronological tree-ring datasets from Northeast China, to detect the effect of CO2 fertilization on Larix gmelinii growth from 1950 to 2010. Among four sites, there were two sites exhibiting a significant residual growth enhancement at a 90% confidence level after removing the size, age and climaterelated trends of tree-ring indices. In addition, we found consistency (R from 0.26 to 0.33, p < 0.1) between the high frequency CO2 fluctuation and residual growth indices at two of the four sites during the common period. A biogeochemical model was used to quantitatively predict the contribution of elevated atmospheric CO2 on accumulated residual growth enhancement. As found in the tree-ring data, 14% of the residual growth was attributed to the CO2 fertilization effect, while climate was responsible for approximately the remainding 86%.