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Vegetation cover not just affects the habitability of the earth, but also provides potential terrestrial mechanism for
mitigation of greenhouse gases. This study aims at quantifying such green resources by incorporating multi-resolution
satellite images from different platforms, including Formosat-2(RSI), SPOT(HRV/HRG), and Terra(MODIS), to
investigate vegetation fractional cover (VFC) and its inter-/intra-annual variation in Taiwan. Given different sensor
capabilities in terms of their spatial coverage and resolution, infusion of NDVIs at different scales was used to determine
fraction of vegetation cover based on NDVI. Field campaign has been constantly conducted on a monthly basis for 6
years to calibrate the critical NDVI threshold for the presence of vegetation cover, with test sites covering IPCC-defined
land cover types of Taiwan.
Based on the proposed method, we analyzed spatio- temporal changes of VFC for the entire Taiwan Island. A bimodal
sequence of VFC was observed for intra-annual variation based on MODIS data, with level around 5% and two peaks in
spring and autumn marking the principal dual-cropping agriculture pattern in southwestern Taiwan. Compared to
anthropogenic-prone variation, the inter-annual VFC (Aug.-Oct.) derived from HRV/HRG/RSI reveals that the moderate
variations (3%) and the oscillations were strongly linked with regional climate pattern and major disturbances resulting
from extreme weather events. Two distinct cycles (2002-2005 and 2005-2009) were identified in the decadal
observations, with VFC peaks at 87.60% and 88.12% in 2003 and 2006, respectively. This time-series mapping of VFC
can be used to examine vegetation dynamics and its response associated with short-term and long-term
anthropogenic/natural events.
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