The Vegetation GPP Spatiotemporal Dynamics In Wuhan City Based On Fusion Data

Gross primary production(GPP) is the total amount of organic carbon produced by vegetation per unit area in unit time. It determines the amount of primary energy flowing into the terrestrial ecosystem. The urban system is an important part of the terrestrial ecosystem, served as the main source of greenhouse gasses and other pollutants. Quantifying GPP of urban vegetation can lead to a better understanding of the impacts of the increasing CO2 emissions on urban environment, as well as the role of the urban system in the global and regional carbon cycle. However, it is difficult to obtain satellite data with very high spatial and temporal resolutions, limiting the potential of using remote sensing techniques to urban vegetation GPP. Data fusion techniques bridge the disparities in spatial and temporal availability of current satellite data, providing an innovative way to study the spatiotemporal dynamics of urban vegetation GPP.This study estimated vegetation GPP in Wuhan, Hubei from 2000 to 2013 based on STARFM-generated synthetic NDVI series, meteorological data, and land-cover maps. The spatiotemporal dynamics of urban vegetation GPP were studied, and the impacts of climate and land-cover changes on GPP dynamics were evaluated. The conclusions are as follows: 1. HANTS method can effectively reduce noises in NDVI time series. The improved NDVI time series demonstrated a more reasonable seasonal trend of vegetation. 2. The synthetic NDVI generated with STARFM based on data within 60 days were highly correlated with NDVI derived from Landsat images, with R2 greater than 0.72. The GPP estimates based on the synthetic data were within the reasonable range, and demonstrated the temporal dynamics. 3. During 2000-2013, the annual mean GPP of vegetation in Wuhan increased, but the annual total GPP decreased, and especially the downtown area showed a significant decrease in annual total GPP. 4. During 2000-2013, land-cover change may be the primary factor that led to the decrease in total GPP of vegetation in the study area. The change in meteorological variables resulted in the increase in annual mean GPP. Solar radiation was the controlling factor for GPP throughout the year. However, in winter, GPP was significantly affected by air temperature, while in summer precipitation was the main factors affecting GPP.