Abstract:

A lot of studies have demonstrated that the NDVI and vegetation cover conditions showed a significant positive correlation,which could well reflect the status of vegetation cover.Thus,NDVI was subsequently used to study the changes in vegetation spatial and temporal dynamics.In this paper,we made use of the SPOT VEGETATION NDVI data between July and August from 1998 to 2011,computed two months NDVI average for each year,thereby generated the NDVI time series file of 14 years.We processed the NDVI time series file,extracted information and analyzed it,so as to reflect the vegetation growth conditions in Hubei Province as well as monitor and study the dynamic changes and trends of vegetation cover during vegetation growth peak in Hubei Province.The study area was divided into weak vegetation coverage area (NDVI value from 0 to 013),sparse vegetation cover area (NDVI value from 013 to 03),low vegetation cover area (NDVI value from 03 to 045),medium vegetation cover area (NDVI value from 045 to 06),high vegetation cover area (NDVI value from 06 to 075),dense vegetation cover area (NDVI value from 075 to 1) by vegetation cover partition method,to monitor the dynamic change of each vegetation cover areas during these 14 years.The results showed that with the exception of the dense vegetation cover area,vegetation area ratio in the other vegetation cover areas was basically stable,and the change extent was not great.They all increased firstly and then reduced,while the dense vegetation cover area showed decreased change in 1998 to 2002,and increased change from 2003 to 2011.Overall,the vegetation cover ratio of the study area had little change.After the analysis of vegetation cover dynamic change,we made use of the MannKendall trend analysis method to research on change trends of vegetation cover over 14 years.The results showed that the majority of the study area showed no significant change in trend,1655% of the region showed increasing trend,033% of the region showed decreasing trend.In order to analyze the influence factors of vegetation cover changes in Hubei Province,we collected the relevant statistic data about urban development,population and vegetation composition in Hubei Province from 1998 to 2011,researched on the relationship between the above factors and vegetation cover.The results showed that the urban sprawl,population growth and vegetation composition of the study area during these 14 years did not changed tremendously,so vegetation cover could be protected and vegetation cover was relatively stable.Through the above analysis,the study results based on vegetation cover areas method and the MannKendall trend analysis method were basically the same,indicating that the two methods could reflect the changes in vegetation cover from the vegetation cover status and trends angle dynamics.Besides,the two methods were an effective way to study temporal and spatial change of regional vegetation cover