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Changes in the wetland vegetation growth patterns in large lakes on the Yangtze Plain

Hou, Xuejiao, Chen, Xiaoling, Liu, Weizhe, Feng, Lian, Ali, Tarig A.
International journal of remote sensing 2019 v.40 no.11 pp. 4290-4301
agricultural land, decision support systems, ecosystems, fertilizer application, image analysis, lakes, mineral fertilizers, moderate resolution imaging spectroradiometer, monitoring, normalized difference vegetation index, phenology, remote sensing, solar radiation, temperature, time series analysis, vegetation, wetlands
In this study, the vegetation emergence times (VET), an important phenological characteristics, were obtained for 25 large lakes on the Yangtze Plain between 2001 and 2014. This was carried out by extracting the normalized difference vegetation index (NDVI) time series from the moderate-resolution imaging spectroradiometer (MODIS) data using a decision tree method. This is the first comprehensive documentation of the changes in temporal and spatial distribution in wetland vegetation phenology for large lakes on the Yangtze Plain. The results showed that considerable changes in the VET occurred in 25 wetland ecosystems in the Yangtze Plain. Specifically, 76% of the lakes showed delayed trends in the VET, and 32% of them were statistically significant (p < 0.05). In contrast, 24% of the lakes displayed advanced trends in the VET and 17% of them were statistically significant (p < 0.05) over the past 14 years. An analysis of the driving factors of VET revealed that a VET change was more sensitive to temperature and sunshine duration than to precipitation for most of the lakes. The temperature in 1–2 months before VET had great effect on the vegetation growth, while such a pattern was not evident for sunshine duration for 5 months before VET. Furthermore, the amounts of chemical fertilizers used in nearby farmlands have also played an important role in the vegetation growth for some of the lakes. This record of change in vegetation phenology provides critical information for wetland ecosystem monitoring in the Yangtze Plain.