基于MODIS NDVI的辽河保护区成立前后植被覆盖时空动态研究

以2010年成立以自然生态恢复为主的辽河保护区为研究对象,基于中分辨率成像光谱仪(MODIS)获取的500米分辨率的归一化植被指数(NDVI)数据,研究了辽河保护区成立前(2000—2009年)和成立后(2010—2015年)植被覆盖时空动态。结果表明:(1)2000—2015年NDVI呈现持续增加趋势;2000—2009年NDVI的年际增加主要发生在夏季,2010—2015年NDVI的年际增加主要发生在春季和冬季。辽河保护区成立后春季NDVI的逐年增加有利于该区域防风固沙功能的提升。(2)季节尺度上,2000—2009年春季降水量与春季和夏季NDVI显著正相关,夏季气温与夏季NDVI显著负相关;2010—2015年仅夏季NDVI动态受春季气温和夏季日照时数变化的影响。(3)月尺度上,气温是影响辽河保护区NDVI变化的主要气候因素,2000—2015年NDVI动态对气温变化的响应存在1个月的滞后期;2000—2009年NDVI动态对降水变化的响应存在1个月的滞后期,2010—2015年则无滞后效应。(4)2000—2009年影响NDVI动态的人类活动主要为农田耕作;辽河保护区成立后,河岸带封育区内的自然恢复和小型人工湿地建设促进了NDVI增加,大型人工湿地建设和人工经营牧草地对NDVI动态无显著影响。

Spatial-temporal dynamics of vegetation cover before and after establishment of Liaohe River Reserve based on MODIS NDVI

Liaohe River Reserve was established in 2010, and recovered primarily by natural ecological restoration. Based on the 500 metres normalized difference vegetation index (NDVI) extracted from the moderate resolution imaging spectroradiometer (MODIS) images, we examined the spatial-temporal dynamics of NDVI before (2000-2009) and after (2010-2015) establishment of Liaohe River Reserve. The results showed that:(1) annual NDVI increased from 2000 to 2015. The interannual increase in NDVI mainly occurred in the summers of 2000-2009, and in springs and winters of 2010-2015. The significant increase of spring NDVI from 2010 to 2015 promoted the improvement of the ecosystem sand fixation service. (2) At the seasonal scale, during 2000-2009, spring precipitation was positively correlated with spring and summer NDVI. Summer temperature was negatively correlated with summer NDVI. During 2010-2015, only the variation in summer NDVI was associated with spring temperature and summer sunshine duration. (3) At the monthly scale, temperature was the dominant factor affecting NDVI variation of the Liaohe River Reserve, and temperature change had a lag effect of one month on NDVI variation during 2010-2015. NDVI variation during 2000-2009 was significantly linked to precipitation change with a lag time of one month, but variation in 2010-2015 had no time lag effect. (4) Farming practices were the dominant anthropogenic factors affecting NDVI dynamics during 2000-2009. After the establishment of Liaohe River Reserve, natural restoration and construction of small artificial wetlands promoted the increase of NDVI, whereas the construction of large artificial wetlands and artificial pastures had no significant influence on NDVI dynamics.