Impact of drought on vegetation carbon storage in arid and semi-arid regions

Abstract

Drought is a common phenomenon in arid and semi-arid regions. In global carbon cycle, semi-arid ecosystem plays a crucial role in interannual variability and greening trend. The vegetation carbon storage and its relation with drought in India are not well understood. The impact of drought on vegetation carbon storage is investigated using Standardized Precipitation Evapotranspiration Index (SPEI) and CASA (Carnegie-Ames-Stanford Approach) derived Net Primary Production (NPP) during 2001–2013. A strong positive correlation is found between regional NPP and SPEI. CASA derived NPP shows good agreement (R2 = 0.57, significance > 95%) with field based observation in arid and semi-arid regions of Gujarat. A significant Increasing trend of 0.2 TgC Yr−1 (about 2 % per year) is observed during the period of 2001–2013. The highest decreased of 24% (2.79 TgC Yr−1) in NPP was found during 2002 and a notable increase of 17% (1.61 TgC Yr−1) was seen during 2013 due to consecutive drought and surplus rainfall years respectively. The study suggests that consecutive droughts have brought an immense impact on vegetation productivity. During the drought years, dry sub-humid region was the most vulnerable as it was dominated by agriculture land, while semi-arid region was less affected due to forest cover. Despite many droughts, some part of north-west and south-west regions had shown an increase in vegetation carbon storage, which indicates that these parts are not affected by the drought. The study also suggests that in addition to rainfall, heat wave also played a major limiting factor in vegetation productivity. The study will be useful in identifying the regions which are more vulnerable to drought. Present study, will also be helpful in combating the regional climate change as vegetation carbon storage is directly linked with agricultural productivity.