Spatial assessment of vegetation vulnerability to accumulated drought in Northeast China

Drought is considered as one of the main forces driving current and likely future ecosystem productivity loss and vegetation mortality. Therefore, understanding where, when and which vegetation type would be most vulnerable to drought is a prerequisite for developing effective adaptation strategies. Based on accumulated standardized precipitation index calculated from April and normalized difference vegetation index obtained from satellite images, we evaluated regional vegetation vulnerability across Northeast China to drought at different stages of summer (June, July and August), when plant growth is highly affected by drought conditions. The findings indicated that vegetation vulnerability to drought varied noticeably with vegetation growth stages and geographical areas. Vegetation growth at early stage (up to June) was most vulnerable to accumulated drought, while it was least vulnerable until the period of peak greenness (in August). A similar spatial pattern of drought vulnerability was observed in different vegetative stages, with higher vulnerability in the west, south and some parts of northeast east of the study region. The pattern is closely associated with land use types. Generally, cropland, wetland and saline and alkaline land showed a much higher vulnerability, as vegetation growing on them had low ground cover and was more affected by accumulated drought conditions. Our results identified the vegetative growth stages and growing areas likely to exhibit high vulnerability to drought and might help improve the basis both for vegetation management and for the development of specific drought adaptation options.