Abstract
Abstract. The net ecosystem productivity (NEP) is the estimates of net carbon exchanges between the vegetation-soil system and the atmosphere. Estimates of NEP could play important role in defining a terrestrial ecosystem as a net source and sink of atmospheric CO2. We model monthly NEP over India for past 26 years (1981–2006) by incorporating satellite observations of vegetation index together with other climatic parameters in to efficiency based terrestrial ecosystem model. Results depict large spatial and temporal variability of NEP over India. NEP climatology over India showed that this region sequestered annually 9.4 Tg C (at the rate of 2.54 gC m-2) and hence appeared to be a net sink of atmospheric CO2. Strength of the CO2 sequestration over the country has been increased during the study period with average linear growth rate of 1.8 TgC yr-2
Highlights
Plant biomass and soil organic matter contain about 2200 Gt C, two times more than that in the atmosphere
In this paper, high spatial resolution of satellite observations of Normalized Vegetation Index (NDVI) and other climatic data sources were used in a terrestrial biosphere model, the Carnegie– Ames–Stanford Approach (CASA; Potter et al 2003) to estimate the net ecosystem productivity (NEP) over Indian during 1981-2006
NEP is computed in the model for each year as the difference between net primary production (NPP) of vegetation and the respiration loss of CO2 by microbes in the soil (Rh) which excludes the effect of small-scale fires and other localized disturbances or vegetation regrowth patterns on carbon fluxes (Schimel et al, 2001)
Summary
Plant biomass and soil organic matter contain about 2200 Gt C, two times more than that in the atmosphere. The spatial and temporal variability of NEP could play an important role in the global carbon cycle and in variation of atmospheric CO2 concentration (Schimel et al 2000, 2001). Many of the studies revealed that global terrestrial ecosystem was a net carbon sink, but carbon uptakes and releases had large spatial and temporal variability due to the impacts of environmental and biological factors, such as climatic conditions, vegetation distribution, land use, etc (Fu and Wen, 1999). Understanding spatial and temporal variability of the carbon cycle is of great significance to estimate the variation of global terrestrial carbon sink. A few studies were carried out in the recent past to describe variability of NEP over the monsoon Asia including India (Titan et al 2003, Potter et al 2005), we believe that comprehensive analysis on spatial pattern of NEP and its seasonal and inter-annual variability in Indian terrestrial ecosystem were not been adequately investigated. The seasonal and interannual variability of NEP over the subcontinent was analyzed
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