Effects of Drought Disturbance on Forest Biomass in Southwestern China

Forest growth is easily influenced and disturbed by extreme climate change. Exploring the spatial and temporal changes of forest biomass and its response to climate change is of significant importance to assess the carbon dynamics of terrestrial ecosystem. During 2009-2012, continuous severe drought happened in southwestern China, and large-scale extreme drought occurred in 2009 and 2010. Although previous studies have revealed the responses of vegetation to the drought in southwestern China, there is no study on quantifying the effects of drought disturbance on forest biomass. In this study, annual forest Biomass Carbon Density (BCD) was estimated first using forest resources statistics of China (1984-2013), the Global Inventory Modeling and Mapping Studies (GIMMS) Normalized Difference Vegetation Index (NDVI) and elevation data in southwestern China. Then the effects of drought disturbance on forest biomass were evaluated through correlation analysis combined with the Palmer Drought Severity Index (PDSI) data. The results showed that: (1) the accuracy of forest BCD was enhanced by using Inventory-satellite-based method, and the accuracy reached R2=0.86 (P<0.001); (2) from 2000 to 2013, the mean BCD in southwestern China was 38.66 Mg C/ha, and was increasing annually with rate of 0.102 Mg C/ha; (3) forest BCD continuously declined due to the drought from 2010 to 2012, and in the extreme drought year 2010, BCD anomaly reduced to -1.004 and returned to 0.371 in 2013. Our results indicate that drought disturbances could significantly impact the forest biomass and the carbon dynamics of terrestrial ecosystem.