内蒙古典型草原与荒漠草原NDVI对气象因子的响应

NDVI of Typical Steppe and Desert Steppe in Inner Mongolia in Response to Meteorological Factors

分析了内蒙古典型草原与荒漠草原NDVI的变化,探讨了干旱对NDVI的影响,建立了NDVI与气象因子的回归模型。结果表明:2000-2016年内蒙古典型草原与荒漠草原NDVI呈现波动变化,变异较小。干旱对典型草原区的羊草(Leymus chinensis)群落与大针茅(Stipa grandis)群落NDVI影响显著(P<0.05);与正常年份相比,干旱导致羊草群落与大针茅群落NDVI降低约23%。5-8月降水量和干燥度指数影响内蒙古典型草原羊草群落与大针茅群落NDVI;荒漠草原区羊草+短花针茅(Stipa breviflora)群落与沙生针茅(Stipa plareosa)群落NDVI的主要影响因子分别为年均气温与5-8月平均气温;5-8月降水量和年均气温是影响典型草原和荒漠草原NDVI的重要因子。基于气象因子的NDVI回归模型能够较好地对区域NDVI进行估测。生长季降水是影响典型草原NDVI的关键因素,而气温显著影响荒漠草原NDVI。在未来气候变化的背景下,内蒙古典型草原NDVI对干旱的响应会更加敏感。

The temporal variations of normalized difference vegetation index(NDVI) were analyzed using MODIS NDVI time series data in Inner-Mongolia typical steppe and desert steppe from 2000 to 2016. Effects of drought on NDVI for typical steppe and desert steppe were studied. The NDVI had a relatively small interannual variability, with C_V of 0.2 less for both typical steppe and desert steppe. The NDVI models of typical steppe and desert steppe were set up using stepwise regression combined with meteorological data, including annual rainfall, rainfall from May to August, mean annual temperature, mean temperature from May to August, annual aridity index and the aridity index from May to August were used in this study. The results showed that NDVI fluctuated in typical steppe and desert steppe from 2000 to 2016, and the typical steppe and desert steppe had low interannual coefficients of variation of NDVI. Compared to the normal year, drought significantly reduced NDVI by approximately 23% for Leymus chinensis community and Stipa grandis community of typical steppe, respectively. The main factors that affected NDVI for L. chinensis community and S. grandis community of typical steppe were mean precipitation from May to August and aridity index from May to August, respectively. NDVI for the L. chinensis+S. breviflora community and S. plareosa community of desert steppe were mainly affected by mean annual temperature and mean temperature from May to August, respectively. The key factors that affected NDVI were mean precipitation from May to August and mean annual temperature at the regional scale. We assessed the precision of NDVI models, and the high accuracy of NDVI models for typical steppe and desert steppe was observed. Precipitation during the growing season is the key factor that affects NDVI in typical steppe, and temperature significantly impacts on NDVI in desert steppe in Inner Mongolia. The results suggest that NDVI for typical steppe would be more susceptible to drought compared to desert steppe under future climate change scenarios.