Spatial-temporal variation of fraction of absorbed photosynthetically active radiation (FPAR) in Beijing during 2010-2012.

Abstract

In this study, the spatial distribution of fraction of absorbed photosynthetically active radiation (FPAR) of vegetation in Beijing during 2010-2012 was analyzed based on the MODIS-FPAR data with a resolution of 1 km and the functional classification of vegetation. The yearly dynamics of FPAR of different vegetation types were also investigated. Furthermore, the correlation between FPAR and leaf area index (LAI) was explored. The results showed that, there was a spatially descended trend from the northeast mountains to the central urban area of Beijing. The annual average FPAR of different vegetation types changed little during 2010-2012. These values varied in the ranges of 0.42-0.44, 0.38-0.39, 0.32-0.33, and 0.21-0.22 for coniferous forest, broadleaf forest, grassland, and crop, respectively. However, the range of variation was big for each vegetation type within the year. There was significant linear or logarithm relationship between FPAR and LAI of each vegetation type. Additionally, the smooth time series of MODIS-FPAR of vegetation types could better reflect seasonal variation, which was generated by Savitzky-Golay filtering in software Timesat.