Monitoring Dynamics of Grassland Vegetation in Poyang Lake National Nature Reserve,using Modis Imagery
نویسنده
چکیده
The particular flood recessional ecosystem in Poyang Lake provides young and high quality grasses in late autumn and wintertime, and attracts millions of migratory birds to over winter. Grasslands along the lakes within Poyang Lake National Nature Reserve (NNR) have a remarkable phenology. So far, little attention has been paid to this dynamics of phenology. This thesis aimed to describe and investigate the seasonal patterns of the recessional grassland vegetation and how are these related to environmental variables (elevation, water level and air temperature). Normalized Difference Vegetation Indices (NDVI) derived from time-series MODIS was applied to investigate the phenological patterns of grassland vegetation. Huisman-Olff-Fresco model II (HOF model II) was employed to detect the response of the grassland vegetation to environment variables. The results revealed a strong negative relationship between the cover percentage of Carex and elevation and a positive relationship between the length of Carex and elevation, with R was 0.317 and 0.381 respectively. Time series NDVI showed clear seasonal phenological patterns of Carex. The phenology dynamics was attributed to the fluctuation of water level and air temperature between years. It revealed that NDVI of Carex has a negative relationship with water level and a positive relationship with cumulative air temperature respectively. * Corresponding author.
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