Vegetation Cover Change And Response To Climate Factors In Henan Province

Vegetation is provided with significant annual variation and seasonal changes. It is the nature "bond" which couples the soil, the atmosphere and the moisture. To some extent, it can represent the land cover change. This paper based on the RS&GIS technology, by using NOAA/AVHRR-NDVI data from 1982 to 2006. The average method, the difference method and the liner regression simulation method were used to analysis the spatial distribution and dynamic change of vegetation in Henan. And combined with appropriate climate data to analyze the relationship between NDVI and climate factors in recent 25 years by extracting each pixel's information. Main conclusions are as follows:(1) Vegetation cover of the research area trends to increase as a whole during 1982 to 2006 with a linear regression trend of 0.0016. The seasonal variation showed: NDVI in summer showed a slight downward trend, in the other seasons it showed upward trend. Spring is the most obvious increased season with the rate of 0.0034 and downward trend in summer to reduce the rate of 0.0008. The character of its spatial distribution showed:the western, eastern and southeastern in Henan displayed the good vegetation cover, but the middle was poor.(2) The yearly changes of NDVI of the different vegetation types are similarly, showed an increasing trend. Among them, two crops a year or two even for three crops, vegetation in deciduous fruit orchards are the most significant upward trends, evergreen coniferous forest vegetation is the most gentle upward trend. In spring the vegetation types are on the rise; In summer except type 23, all the other vegetation NDVI are showed downward trends, and type 12 is the most significant downward trend; Fall of the vegetation types are on the rise, but the trend is not obvious; In winter, the vegetation types are also on the rise, the upward trend of agriculture vegetation is obvious.(3) Inter-annual variability of temperature and NDVI inter-annual change in the overall trend is similar, which shows the temperature sensitivity of NDVI, also shows that temperature is not the only limiting factor of vegetation cover. There is a certain lag between the trends of annual change of NDVI and precipitation. Most of the year instead of NDVI decrease with the increase of precipitation.(4) The different vegetation types have the different response characteristics to climate change. The annual mean temperature variations have more impact on vegetation dynamics than the annual precipitation variation. Among them, the NDVI of type 23 had the highest correlation with temperature; NDVI of all vegetation types were negatively correlated with precipitation and the correlation is not high.