基于SPOT NDVI的甘肃河东植被覆盖变化及其对气候因子的响应

Vegetation cover change and its response to climatic factors using SPOT NDVI in Hedong of Gansu Province

基于1998—2011年SPOT NDVI和年均气温、降水数据,采用植被覆盖度法、趋势分析法及相关分析法对甘肃河东地区植被覆盖时空变化及其对气温和降水的关系进行研究。结果表明:河东地区植被覆盖度南高北低,依次为陇南山区>甘南高原>陇东高原>陇中高原;近14年来植被覆盖度呈波动上升趋势,增速分别为陇南山区0.050 10 a-1、甘南高原0.009 10 a-1、陇东高原0.039 10 a-1、陇中高原0.023 10 a-1;植被覆盖轻度改善面积占37.20%,基本不变占59.75%,表明研究区植被覆盖稳中有所上升;河东地区植被NDVI与气温和降水的相关性各异,其中54.59%的地区植被NDVI与气温呈负相关,45.41%区域呈正相关;87.86%的地区植被NDVI与降水呈正相关,12.14%区域呈负相关;植被NDVI与降水正相关面积明显大于气温,说明降水是研究区植被生长的主导气候因子。

Spatio-temporal variations of the vegetation coverage and the correlation coefficient be- tween Normalized Difference Vegetation Index （NDVI） and temperature/precipitation were ana- lyzed based on SPOT NDVI and the yearly average temperature/annual precipitation data in He- dong region of Gansu Province during the period from 1998 to 2011 by using retrieval of vegeta- tion cover, linear regression and correlation analysis. The results showed that the vegetation cov- erage was higher in the south and lower in the north, and a descending order of the vegetation coverage was Longnan Coteau 〉 Gannan Plateau 〉 Longdong Plateau 〉 Longhzhong Plateau. In the recent 14 years （1998-2011）, NDVI showed an increasing trend, with increment magni- tudes at 0.05, 0. 009, 0. 039, and 0. 023 per decade in Longnan Coteau, Gannan Plateau, Longdong Plateau, and Longhzhong Plateau, respectively. The vegetation coverage in 37.20% of total area was slightly changed, and approximately 59.75% kept stable, which indicated that the vegetation coverage in the study area had increased but was still at a relatively stable level. The correlations between NDVI and temperature/precipitation were spatially various in Hedong re- gion. The correlation of NDVI with temperature was negative in 54.59% of the total area, and positive in the rest 45.41%, while its correlation with precipitation was negative for 12.14% of the total area, and positive for the other 87.86%. The area with positive correlation between ND- VI and precipitation was much larger than that with positive correlation between NDVI and tem- perature, indicating that precipitation was the main factor affecting vegetation growth in the study region