| With global climate changes, spatial-temporal pattern of meteorological elements such as precipitation may be changed, and the frequency of extreme climate events will be increasing. As an important manifestation and result of global change, more and more attentions home and abroad are paid on drought and its relationship with ecosystem. It is not only good to enrich the theoretical underpinnings of meteorology, geography and so on, but also providing guiding significance to social economic development. Hei river basin is in the northwest arid and semi-arid region, with the rare rainfall and wicked environment. In recent years, serious and frequently occurred drought make the stability and diversity of ecosystem in Hei river basin be seriously threatened. The contradiction of environment protection and social economic development become increasing sharply. Therefore, this study takes Hei river basin as a research case. On foundation of the landscape pattern, spatiotemporal variations of drought are analyzed by using Z-index, which is calculated by the meteorological data of precipitation and temperature. Combined with Landsat TM and EOS MODIS image, the impact of drought on landscape pattern, NPP, carbon storage and service value of ecosystem are further investigated. On the basis of coupling relationship between drought and ecosystem, comprehensive evaluation index system of drought impact on ecosystem is constructed by AHP. The main conclusions are as follows:Under the typical pattern of MODS coupling ecosystem, spatial and temporal variations are reviewed in the distribution of climatic conditions and drought in Hei river basin. Most areas here are in the arid region, and the climate is becoming drier. Drought occurred cycle from1961-2010is2-4a, while the occurred frequency in each station is between26%-34%during the same years. Attack severity of drought is significant different too, the spatial distributions of it is higher in the middle and lower in the peripheral region.Spatial characteristics of landscape pattern, NPP, carbon storage and service value are obvious, which are strongly affected by drought. Pattern indexes such as AI, CONTAG, SHDI, and SHEI and so on have good correlations with aridity index. Climate in upper and middle reaches is relative humid, degrees of fragmentation; diversity and evenness here are much higher than lower reaches. Significant influenced by drought, average NPP in this basin is333.8406g/(m’-a). With drought forming more quickly, NPP is much more decreased. Carbon storage and carbon sink are also affected by the arid climate and environment. Distributions of them are reducing along the river, and with the higher value besides water. Carbon sink in drought years are lower than normal years, which are much lower when the degree of drought increases. Total ecological service value in Hei river basin is363.05billion RMB each year, with the highest service value of aquatic system. Service value per unit area in this basin is decreasing from upper to lower reaches.CEI constructed by indexes of drought situation, structure and function of ecosystem is distributed differently in the space. Affection of drought on ecosystem of lower reaches is much higher than upper and middle reaches. CEI value in Qilian is9.5375, which is the highest in the whole basin. Ecosystem there is relatively stable, with lowest affection from drought. CEI in middle reaches is decreased from west to east and south to north. Artificial oases such as Jiuquan are affected by drought slightly. Due to the lower precipitation and higher evaporation, CONTAG and AI in lower reaches are relatively higher, and ecosystem here is fragile under the drought threaten. |
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