2000—2016年云南地区植被覆盖时空变化及其对水热因子的响应

Spatio-temporal patterns of vegetation coverage and response to hydrothermal factors in Yunnan Province,China

基于2000—2016年MODIS-NDVI数据,利用趋势分析法以及线性相关分析等方法对云南地区植被月变化趋势、年际变化趋势进行详细分析;探讨植被覆盖变化与主要气候水热因子的关系。结果表明:研究区大部分地区植被覆盖良好,年NDVI的平均值为0.55,其中NDVI较高值(>0.8)区域主要分布于南部,而西北部和中部城市地区NDVI值较低;自2000年开始,研究区NDVI总体呈显著(P<0.05)增加趋势,年NDVI的变化斜率为0.0036,植被覆盖呈增加趋势的区域占研究区总面积79.80%;不同季节(春、夏、秋、冬)和生长季的植被状况均呈良性发展趋势;湿润指数和水热综合因子在滇西北与NDVI多呈负相关,在滇中地区以正相关为主;春、夏、秋3个季节NDVI受降水影响较大,而冬季NDVI则受气温影响较大;受降水影响较大的区域主要分布在中部和南部,受气温影响较大区域主要分布在滇西北、滇东北地区; NDVI在不同月份对气候因子的滞后时间存在差异,NDVI与当月气温的相关性强于与当月降水的相关性,植被生长对气温的响应无明显滞后效应,对降水存在3个月的滞后期。

The spatio-temporal patterns of vegetation coverage in Yunnan Province from 2000 to 2016 were analyzed using moderate resolution imaging spectrometer (MODIS) normalized difference vegetation index (NDVI) data. Maximum value composites, linear regression methods, and partial correlation analyses were used to investigate the monthly and annual NDVI variations, analyze the spatial distribution and changes in the NDVI, and examine the relationships between the NDVI and climatic factors. The results showed that the average NDVI value for Yunnan Province was 0.55 from 2000 to 2016. The higher NDVI values (>0.8) were mainly distributed in the southern part of Yunnan Province. In contrast, the northwest part and central urban region had lower NDVI. Annual NDVI increased significantly from 2000 to 2016 (P < 0.05), and the slope of the trend line was 0.0036. The seasonal NDVI and the growing season NDVI also showed increases. Autumn had the fastest NDVI growth rate (0.0063), followed by spring (0.0044), winter (0.0042), and summer (0.0010). The increasing rate of NDVI in the growing season (0.0025) was higher than that in summer. The vegetation improvement area was significantly greater than the degradation area, and the area of increasing trend accounted for 79.80% of the total vegetation coverage. The area of increased vegetation coverage was mainly concentrated in the northeast and east regions, and the decreased vegetation area was mainly concentrated in northwest and central regions. Precipitation had a crucial effect on the NDVI variation in spring, summer, and autumn, but temperature was the main controlling factor in winter. There was a clear difference in the relationships between NDVI and temperature and precipitation among different months of the growing season, and there was a time lag in the response of NDVI to precipitation.