Hotspots of recent drought in Asian steppes

Masato Shinoda,Urianhai Galzuud Nachinshonhor,Hiroshi Komiyama,Banzragch Nandintsetseg

doi:10.1007/s10113-013-0464-0

Abstract

The present study aims to identify hotspots on the Asian steppe that were vulnerable to widespread drought events in the Northern Hemisphere during 1999–2002, using newly proposed indices of vegetation response (sensitivity and resilience) to drought. Drought sensitivity is defined as vegetation response to decreased precipitation from pre-drought to drought phases, and resilience is defined as response to increased precipitation from drought to post-drought phases. Thus, the sensitivity and resiliency indices SI and RI are similarly expressed as normalized change of vegetation relative to that of precipitation. We also develop new regionally adjusted indices SI r and RI r , to do an interregional comparison of vegetation dynamics. In general, the resilience (RI r or RI) was larger than sensitivity (SI r or SI) over the entire region, whereas they had similar amplitudes over a wetter region (forest steppe). This asymmetric response of SI r < RI r , which manifested over the desert steppe/steppe regions, is explained by interannual change of plant species composition (i.e., larger ratio of annual/perennial species for the post-drought year of 2003). As for the steppe region, the Chinese section had much higher resilience during the post-drought year compared with the Mongolian one. This may be attributable to the larger annual/perennial ratio, but is not strongly related to grazing pressure. Spatial and temporal analyses of the indices identified locations where there was not resilience from drought-affected vegetation conditions despite increased precipitation, and/or where long-term stability of vegetation is under threat.

Highlights

The new field of sustainability science has emerged since the late 1990s (e.g., Kates et al 2001; Clark and Dickson 2003)
The present study aims to identify hotspots on the Asian steppe that were vulnerable to widespread drought events in the Northern Hemisphere during 1999–2002, using newly proposed indices of vegetation response to drought
The multiyear drought highlighted here, which was the severest on the continental scale over the past three decades, provided a unique experimental opportunity in an earth laboratory to explore drought impact on the terrestrial ecosystem

Summary

Introduction

The new field of sustainability science has emerged since the late 1990s (e.g., Kates et al 2001; Clark and Dickson 2003). Vulnerability is a function of the character, magnitude, and rate of climate change and variation to which a system is exposed, its sensitivity and adaptive capacity. Given this background, the present paper develops a method to systematically measure the degree of ecosystem vulnerability to climate change (especially drought) on the continental scale. Vulnerability is considered to comprise three components, namely exposure, sensitivity, and resilience. This analysis defines the combination of the latter two components for a region as forming its vulnerability. This is because there is no strategy for eliminating exposure of regional vegetation to unusual weather by measures such as moving its location on a yearly basis, as with animals

Methods

Results

Conclusion