Based On MODIS Time Series Data Of Forest Phenology In Temporal And Spatial Differentiation In Yangtze River Basin

Forest is an important component of terrestrial ecosystems, the forest as a special "convert" role in the lithosphere, and biosphere, soil circle and atmosphere circle. Forest phenology is an important indicator in climate and environment changes, there is evidence that the recent 100 year global climate change significantly, forest phenological response to climate change research has become a geography, ecology, environment and other multi-disciplinary research hot spot. This study using remote sensing technology for the 16 day maximum synthesis's time series MODIS EVI remote sensing data, and using Asymmetric Gaussian fitting, to getting EVI remote sensing image reconstruction of time series, Then, using dynamic threshold to extract the parameters of forest phenology in Yangtze river basin in 2002-2012, the parameters including:the forest phenology starting period of season (SOS), ending of growing season (EOS), the length of season (LOS) and forest EVI cumulates. Then, analysis the trend of time and space distribution pattern and annual variation for phenological parameters in Yangtze River basin and using the extracted forest phenological parameters with terrain?climate factor to have correlation analysis, the conclusion is as follows:(1) The forest phenology of spatial and temporal distributionForest phenology starting period in early February to mid-June, the most regions forest start period season basin between march to May in Yangtze river, in northwest forest starting period significantly later than east and south. The end of forest phenological period in mid-August to mid-December, and most of the region in the September to November, High altitude forests in northwestern end stage is earlier than in low altitude area of southern and eastern. Forest length of growing season in 113-305 days, with the north and west regions such as the length of growing season in 113-193 days, and other areas in 193-289 days. Forest growing season EVI cumulates space is uneven distribution, Among them, Daba?Qinling Mountains, Jiangnan hilly, eastern YunGui Plateau and so on, the forests phenological is dense. At the end of season the forest phenological, Jinsha River System, Han River System and Dalou Mountains have an early tendency.(2) The annual variation trend of forest phenologyForest phenological internal variation in 1-20 days in 2002-2012 years in Yangtze River Basin Forest growth starting period, Upper and middle reaches of Jinsha River, Sichuan Basin, the lower reaches of the Yangtze River, the forest phenological have ahead trend; While the middle and lower reaches of Minjiang River, Han River, Jiangnan hilly has a delay tendency, the Sichuan basin, Wujiang River System, the lower reaches of the Yangtze River System and other places has a delay tendency. The length of the growing season in the forest, Jinsha river, Minjiang River, Sichuan basin and other regions have extended trend; the Han River drainage and Dalou Mountains, had a shorten tendency. Forest growing season EVI cumulants, Jinsha River and Minjiang River, Sichuan basin, Wuling Mountains, Jiangnan regions have increased trendency; the downstream of Jinsha River and Minjiang River, the Han River and other regions have a decreasing trend.(3) The Yangtze River basin forest phenological phase and the relationship between climatesThe correlation analysis of the initial growth period and period average temperature and precipitation, which have significant negative correlation, the correlation coefficient R2 is 0.6326,0.6187. The forest phenological growth at the end of season period of the average temperature and precipitation for correlation analysis respectively is highly positive correlation with moderate positive correlation; the correlation coefficient R2 is respectively 0.7195,0.5161. Forest growing length of season and the average temperature and precipitation during the Phenological period are respectively high positively correlated and moderate positive correlation, and the correlation coefficient R2 values is respectively 0.701,0.4412. Overall, the Yangtze River forest phenological parameters affected by climate factors are significant.(4) The Yangtze River basin relationship between forest phenological parameters and the terrainForest starting of season, the end of season and the length of season respectively the correlation analysis with the elevation height, the correlation coefficient R2 is respectively 0.7083,0.6892,0.7064, so, the Yangtze River forest phenological space-time distribution difference is closely related to the height of the terrain.