Drought-Induced Carbon and Water Use Efficiency Responses in Dryland Vegetation of Northern China.

Chengcheng Gang,Zhongming Wen,Liang Guo,Yi Zhang,Xuerui Gao,Mingxun Chen,Shouzhang Peng

doi:10.3389/fpls.2019.00224

Abstract

Given the context of global warming and the increasing frequency of extreme climate events, concerns have been raised by scientists, government, and the public regarding drought occurrence and its impacts, particularly in arid and semi-arid regions. In this paper, the drought conditions for the forest and grassland areas in the northern region of China were identified based on 12 years of satellite-based Drought Severity Index (DSI) data. The impact of drought on dryland vegetation in terms of carbon use efficiency (CUE) and water use efficiency (WUE) were also investigated by exploring their correlations with DSI. Results indicated that 49.90% of forest and grassland experienced a dry trend over this period. The most severe drought occurred in 2001. In general, most forests in the study regions experienced near normal and wet conditions during the 12 year period. However, grasslands experienced a widespread drought after 2006. The forest CUE values showed a fluctuation increase from 2000 to 2011, whereas the grassland CUE remained steady over this period. In contrast, WUE increased in both forest and grassland areas due to the increasing net primary productivity (NPP) and descending evapotranspiration (ET). The CUE and WUE values of forest areas were more sensitive to droughts when compared to the values for grassland areas. The correlation analysis demonstrated that areas of DSI that showed significant correlations with CUE and WUE were 17.24 and 10.37% of the vegetated areas, respectively. Overall, the carbon and water use of dryland forests was more affected by drought than that of dryland grasslands.

Highlights

Droughts have been frequently recorded due to climatic warming from elevated concentrations of greenhouse gasses
The ecosystem-scale carbon use efficiency, which is defined as the ratio of net primary productivity (NPP) to gross primary productivity (GPP), describes the capacity of an ecosystem to transfer the carbon from the atmosphere to vegetation biomass (DeLucia et al, 2007)
The dryland vegetation in northern China was deeply influenced by the drought during the 2000–2011 period, and forest and grassland reacted differently to drought conditions

Summary

Introduction

Droughts have been frequently recorded due to climatic warming from elevated concentrations of greenhouse gasses. This warming exacerbates water resource stress and poses a significant threat to food security and the sustainability of human activities in these areas (Vorosmarty et al, 2000; Rosegrant et al, 2003). The impacts of droughts on CUE and WUE have been widely reported in multiple scales (Webb et al, 1978; DeLucia et al, 2007; Liu Y. et al, 2015; Gang et al, 2016a). Further research is needed on the extent and duration of droughts as well as their impacts on the carbon and water cycles of dryland vegetation

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Conclusion