Vegetation cover change and its response to climatic factors using SPOT NDVI in Hedong of Gansu Province
Spatio-temporal variations of the vegetation coverage and the correlation coefficient between Normalized Difference Vegetation Index (NDVI) and temperature/precipitation were analyzed based on SPOT NDVI and the yearly average temperature/annual precipitation data in Hedong region of Gansu Province during the period from 1998 to 2011 by using retrieval of vegetation cover,linear regression and correlation analysis.The results showed that the vegetation coverage 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 magnitudes 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 region.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 NDVI and precipitation was much larger than that with positive correlation between NDVI and temperature,indicating that precipitation was the main factor affecting vegetation growth in the study region.
国家科技期刊平台
NSTL
万方数据
维普
