根据安西极旱荒漠国家级自然保护区南部和北部2000 年、2003 年、2006 年、2009 年和2012 年的MODIS 影像数据和相关气象数据,对该保护区荒漠植被的归一化植被指数(NDVI)和比值植被指数(RVI)及水热因子(七月份均温、年均温和年均降水量)进行比较和相关性分析。结果表明:在2000 年至2012 年,该保护区南部植被的NDVI 和RVI 指数均随着时间推移持续升高;北部植被的NDVI 指数在2003 年达到最高值、2006 年明显下降、之后持续升高但均低于2003 年水平,而RVI 指数则总体呈逐渐升高的趋势。该保护区南部和北部的七月份均温和年均温均在2003 年最低、之后逐渐升高,其年均降水量变化趋势与北部NDVI 指数的变化趋势一致。相关性分析结果表明:该保护区南部和北部植被的NDVI 和RVI 指数间存在极显著正相关;南部植被的NDVI 和RVI 指数均与年均温、七月份均温和年均降水量呈显著或极显著正相关;北部植被的NDVI 指数仅与年均降水量呈显著正相关,其RVI指数与七月份均温和年均温呈极显著正相关。与该保护区南部相比,北部植被的NDVI 和RVI 指数均较低,年均温和年均降水量也较低,但七月份均温却较高。综合分析结果显示:与同期的水热因子变化相比,安西极旱荒漠国家级自然保护区南部和北部植被的NDVI 指数虽然具有较明显的时滞效应,但仍然能够较好地反映植被的生长状况;而它们的植被RVI 指数变化不明显,不适用于该保护区荒漠植被的影像研究。总体来看,该保护区的荒漠植被的生长缓慢但生长状况良好。

According to MODIS image data and related meteorological data in the south and north of Anxi Extra-Arid Desert National Nature Reserve in 2000, 2003, 2006, 2009 and 2012, comparison and correlation analysis on normalized difference vegetation index (NDVI) and ratio vegetation index (RVI)of desert vegetation and hydrothermic factors including mean temperature of July, annual mean temperature and annual mean precipitation of the reserve were done. The results show that from 2000 to 2012, NDVI and RVI indexes of vegetation in the south of the reserve increase gradually as time goes on. NDVI index of vegetation in the north reaches the highest value in 2003, decreases obviously in 2006, then increases continuously but all are lower than the level in 2003, while RVI index basically appears the trend of increasing gradually. Mean temperature of July and annual mean temperature in the south and north of the reserve all are the lowest in 2003, then increase gradually, change trend of their annual mean precipitation is consistent with that of NDVI index in the north. The result of correlation analysis shows that there are extremely significantly positive correlation between NDVI and RVI indexes of vegetation in the south and north of the reserve. Both of NDVI and RVI indexes of vegetation in the south have a significantly or extremely significantly positive correlation with annual mean temperature, mean temperature of July and annual mean precipitation. NDVI index of vegetation in the north only has a significantly positive correlation with annual mean precipitation, while RVI index has an extremely significantly positive correlation with mean temperature of July and annual mean temperature. Compared with the south of the reserve, NDVI and RVI indexes of vegetation in the north are lower, annual mean temperature and annual mean precipitation are also lower, but mean temperature of July is higher. The comprehensive analysis result indicates that compared with change of hydrothermic factors during the same period, although NDVI index of vegetation in the south and north of Anxi Extra-Arid Desert National Nature Reserve has an obviously time-lag effect, but it still can reflect well the vegetation growth status, while the change in their RVI index of vegetation is not obvious, so it is not suitable for image research of the reserve desert vegetation. Overall, the reserve desert vegetation grows slowly but its growth status is better.