Hotspots of recent drought in Asian steppes

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.

Land surface memory effects on dust emission in a Mongolian temperate grassland

“…The observed data showed that annual plant species increased more than perennial ones after drought years [ Shinoda et al, ]. Numerous studies have shown that grassland degradation has increased [ Mandakh et al , ; Nandintsetseg and Shinoda , ] and at the same time plant species composition has continually declined; moreover, shifts in from perennial to annual species have been induced by climate change (drought) [ Shinoda et al, ] and overgrazing in the Mongolian grasslands during recent decades [e.g., Jigmed , ; Tuvshintogtoh and Ariunbold , ; Hilker et al , 2013]. The model is unable to consider such changes in species and functional diversity of the plant community [e.g., Parton et al, ].…”

Dryland climate change: Recent progress and challenges

“…Multidisciplinary approaches to key linkages of complex natural and human systems have revealed that climate change impacts on such systems are often nonlinear, having a threshold or tipping point across which a catastrophic (and potentially nonresilient) change may occur in the system [see, e.g., Scheffer et al ., ]. For example, on the regional‐continental scale, such changes or thresholds are detected in the response of vegetation to drought [ Shinoda et al ., ], land‐surface to wind erosion or dust emission (i.e., threshold wind speed) [ Kurosaki et al ., ], and livestock mortality to dzud [ Tachiiri et al ., ; Tachiiri and Shinoda , ]. The satellite‐derived threshold wind speed was used to produce a novel semi‐real‐time wind erodibility (i.e., soil susceptibility to wind erosion) map available for a dust early warning system [ Kimura and Shinoda , ].…”

“…Shinoda et al . [] identified hot spots that exhibited nonresilient vegetation degradation after a multiyear megadrought in the Asian steppe using newly developed indices related to sensitivity and resilience (Figure ). Temperate grasslands surrounding the desert dust source regions are likely to be sensitive to the ongoing and projected expansion of Asian drylands and are significant or potentially significant dust sources [ Shinoda et al ., ; Nandintsetseg and Shinoda , ].…”

“…See the details in Shinoda et al . []. Nonresilient (potentially vulnerable) areas are denoted by red vectors indicating decreased vegetation despite increased precipitation during postdrought years, while resilient areas are indicated by blue vectors indicating increased vegetation during postdrought years.…”

“…Therefore, in response to the drying climate and potential risk of desertification, proactive planning and adaption strategies should be developed; furthermore, climate disaster management and countermeasures must be implemented based on projections of future climate hazards and insights into how and to what extent hazards and vulnerability of a local nature‐society system will jointly result in disasters. Some approaches have been used to detect dryland vulnerability [ Obasi , ; Guha‐Sapir et al ., ; Shinoda et al ., ], and some projects have been performed to develop comprehensive proactive countermeasures and policy recommendations to mitigate multidisaster impacts [ Applied Multi Risk Mapping of Natural Hazards for Impact Assessment (ARMONIA) , ; Shinoda , ].…”