Hotspots of recent drought in Asian steppes
Hotspots of recent drought in Asian steppes
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DOI：
10.1007/s10113-013-0464-0
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发表时间：
2014-02
影响因子：
4.2
通讯作者：
M. Shinoda;B. Nandintsetseg;Urianhai Galzuud Nachinshonhor-;Hiroshi Komiyama
中科院分区：
文献类型：
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作者：
M. Shinoda;B. Nandintsetseg;Urianhai Galzuud Nachinshonhor-;Hiroshi Komiyama
本研究的目的是确定热点的亚洲草原，容易受到广泛的干旱事件在北方半球在1999-2002年期间，使用新提出的指数植被对干旱的反应（敏感性和弹性）。干旱敏感性被定义为从干旱前到干旱阶段植被对降水减少的反应，而恢复力被定义为从干旱到干旱后阶段对降水增加的反应。因此，敏感性和恢复性指数SI和RI类似地表示为植被相对于降水的归一化变化。我们还开发了新的区域调整指数SIrandRIr，做植被动态的区域间比较。在一般情况下，弹性（RIrorRI）大于敏感性（SIrorSI）在整个地区，而他们有类似的幅度在潮湿的地区（森林草原）。这种在荒漠草原/草原区出现的SIr <RIr的不对称响应，可以用植物种类组成的年际变化（即，2003年干旱后，一年生/多年生物种比例较大）。在草原区，中国区在干旱后年份的恢复力明显高于蒙古区。这可能是由于较大的年度/常年的比例，但并不强烈相关的放牧压力。对这些指数进行的空间和时间分析发现，尽管降水量增加，但受干旱影响的植被条件没有恢复力，和/或植被的长期稳定性受到威胁。
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 indicesSIandRIare similarly expressed as normalized change of vegetation relative to that of precipitation. We also develop new regionally adjusted indicesSIrandRIr, to do an interregional comparison of vegetation dynamics. In general, the resilience (RIrorRI) was larger than sensitivity (SIrorSI) over the entire region, whereas they had similar amplitudes over a wetter region (forest steppe). This asymmetric response ofSIr<RIr, 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.