2000—2016年中亚天山植被变化及气候分异研究

利用MODIS-NDVI产品生成中亚天山2000—2016年植被覆盖度,利用线性回归法和偏相关法分析了中亚天山植被时空变化特征及驱动因子。结果表明:中亚天山植被生长及变化趋势具有显著的区域分异性,纬度分区上,中天山和北天山西部植被覆盖度较高的草原、农田和森林在2000—2016年呈现退化趋势;南天山和北天山东部植被覆盖度较低的荒漠、草原和灌丛在同期表现出改善趋势,而中国境内的东天山与境外的西天山相比具有较低的植被覆盖度以及总体改善的变化趋势。中亚天山气候在2000—2016年显示出"暖湿化"特征,温度升高幅度(5. 9%)远大于降水增加幅度(1. 3%),温度、降水与植被覆盖度的显著相关比例为18. 0%和42. 6%,降水是中亚天山植被变化的主要气候驱动因素。以巴音布鲁克草原为代表的东天山部分草原受到过度放牧的影响而退化严重,建议加强植被退化区的生态修复与保护力度。

Vegetation dynamics in response to climate change in Tian Shan,Central Asia from 2000 to 2016

The Tian Shan plays a key role in the sustainable development of ecological environment in arid and semi-arid regions along the Silk Road Economic Belt as an important ecological barrier connecting the Central Asia and Xinjiang, China. Previous studies indicated that the global warming led to a series of ecological problems in Tian Shan, such as a decrease in snowfall rate, severe glacier melting, and significant grassland degradation. It has become an important and urgent task to monitor the dynamic changes of vegetation in the region and analyze its driving factors. Based on MODIS NDVI data, we calculated the Fractional Vegetation Coverage (FVC) of the Tian Shan from 2000 to 2016 using the harmonic analysis of time series (HANTS) algorithm and the dimidiate pixel model. The linear regression and partial correlation analysis were used to map the tempo-spatial variations of FVC and to analyze the correlation results with the precipitation and temperature. The major conclusions were drawn as follows: (1) The vegetation growth in Tian Shan had significant regional differentiation, the mean FVC in the northern, central and southern part of Tian Shan was 0.37, 0.49 and 0.26, respectively. In addition, the FVC value was 0.29 in the eastern Tian Shan, which is inside China, and 0.43 in the western Tian Shan, which is outside China. The FVC was higher on northern slope and western part. (2) There were 66.8% of the vegetation pixels displayed in an improving trend. The farmland and forest with the highest FVC showed degradation trend with the area proportions of 66% and 53%, respectively. However, the shrub-desert and shrubland with the lowest FVC showed improving trend with the area proportions of 88% and 74%, respectively. Moreover, the most widely distributed grassland has an improvement ratio of 64%. (3) The temperature and precipitation of Tian Shan were increased by 0.85 °C and 1.87 mm respectively during the time period from 2000 to 2016, which indicated equivalently an increment of 6.2% of the average temperature and an increment of 1.4% of the precipitation, respectively. (4) The correlation ratios of temperature and precipitation with the FVC were 18.0% and 42.6% respectively. The precipitation was the dominant factor affecting the change of vegetation in Tian Shan. (5) The vegetation in the typical regions like Bayinbuluke Grassland was greatly disturbed by overgrazing. We suggested that the ecological restoration in the vegetation degeneration area should be strengthened and the regional governments should make the reasonable plan for the sustainable tourism development.