Study On Change Of NDVI For Different Vegetation Types Based On Spot Vegetation In Hainan

Vegetation as an important ecological factor is the bearer of climate change,showed positive feedback effect for climate change,and a reflection of the sensitive ecological indicator of environmental change.The research and monitoring in regional vegetation was great significance for vegetation protection especially the rational use of vegetation resources.Hainan is China's only tropical climate island with species richness,huge biomass and major tropical cash crops producing areas.With the development of remote sensing technology in recent decades,taking use of remote sensing data to observe vegetation dynamic changes,land use and vegetation coverage research has been very extensive,but use remote sensing data to study on Hainan Island in china for a long time sequence also few.Based on SPOT / VEGETATION 1km resolution data S10 analyzed spatial distribution of annual NDVI and inter-annual NDVI of different vegetation cover types with time units ten-day and year in recent ten-year in Hainan.The main conclusions were as follows:1) Based on the Savitzky-Golay filtering method,make use of cloud state data in remote sensing image,effective eliminated the noise caused by aerosol and cloud of NDVI time-series data in Hainan and obtained significant effect.Supplied high quality time-series data for further study.2) The largest significant fluctuations of annual NDVI average variation appeared in 2001 only 0.739 was the minimum period of the study,the NDVI value gradually increased from 2002 to 2007. Deviation analyzed the MNDVI concluded that the MNDVI reduced in 2001 74.5 percent region than 2000,reduced pixel mean value was -0.0401,while the increased average pixel was very low, only 0.008,indicating Hainan Island in poor vegetation growth in 2001,nearly three-quarters of the region,the best growth state of vegetation failed to meet the level of the previous year.65.3 percent region increased with mean value 0.0736 than previous in 2006.The inner-year NDVI variation were not appeared fine continuity although the vegetation is rich in resources,vegetation cover is higher in Hainan.The rose of NDVI variation curve of was gentler,slope of the down appeared large, indicate the vegetation of Hainan in growth state in the majority time during the year and the activities in the relatively high vegetation.NDVI showed significant volatility and exited in varying degrees in ten-year observation period.3) The growth of various vegetation types in central Hainan Island was better than any other districts and varied relatively stable.The vegetation growth condition is poor in eastern and northern and middle level in western and southern reflected the spatial distribution variation of various vegetation coverage types.Early gentle curve is green vegetation period,but this period relatively short in Hainan Island that generally maintained at 3 to 5-year and the steep variation of vegetation NDVI was a sign of the beginning of vegetation growth.Both various types vegetation NDVI cover and annual MNDVI curve had strong hierarchical structure,the NDVI value in the order of woodland＞high-coverage grassland＞shrub forest＞woodland＞the garden＞low-coverage grassland＞paddy field＞dry land. The annual average NDVI curve was smooth fluctuations from 1998 to 2004,but in 2005 appeared great fluctuation,contrary,annual average MNDVI showed no fluctuations in 2005,the result indicated various vegetation coverage types were recovering and got the individual annual average level.4) The spatial variation character of various vegetation covering typesHainan was divided into five parts(east,west,north,and south);all vegetation coverage curves showed strong layering.The curve of east and north appeared clear level with closed variation trend; except the western comer and the middle grass coverage in west and coverage in south lawn,other curves showed stability level;woodland and grassland of high coverage,coverage of cross-cutting the grass were intertwined,paddy field,dry land and garden showed consistent changes.Overall, paddy fields and dry land changes showed a good consistency,with the exception of the east and north,the whole year at the bottom of the other curves;forest land had a smooth change with smaller ups and downs,and at the highest level throughout the year.Overall,the improved vegetation coverage region was bigger than the vegetation degradation area.The improved area take 59.13percent of whole Hainan Island,the degradation region accounted for 21.70percent and the stability area occupied 16.92 percent.Mainly to a slight degradation of degradation,the main improvement is also a slight improvement,moderate improvement in the larger region.In recent ten years,the vegetation of whole Hainan showed improve trend.The vegetation growth in central state was stability;degradation was very evident in north area,and middle improve appeared in east and west coasts as well as west central and southern mountain areas. Significant improved region mainly in the south and west.