Trends and Variability of AVHRR-Derived NPP in India

Abstract

In this paper, we estimate the trends and variability in Advanced VeryHigh Resolution Radiometer (AVHRR)-derived terrestrial net primaryproductivity (NPP) over India for the period 1982-2006. We find anincreasing trend of 3.9% per decade (r = 0.78, R-2 = 0.61) during theanalysis period. A multivariate linear regression of NPP withtemperature, precipitation, atmospheric CO2 concentration, soil waterand surface solar radiation (r = 0.80, R-2 = 0.65) indicates that theincreasing trend is partly driven by increasing atmospheric CO2concentration and the consequent CO2 fertilization of the ecosystems.However, human interventions may have also played a key role in the NPPincrease: non-forest NPP growth is largely driven by increases inirrigated area and fertilizer use, while forest NPP is influenced byplantation and forest conservation programs. A similar multivariateregression of interannual NPP anomalies with temperature, precipitation,soil water, solar radiation and CO2 anomalies suggests that theinterannual variability in NPP is primarily driven by precipitation andtemperature variability. Mean seasonal NPP is largest duringpost-monsoon and lowest during the pre-monsoon period, therebyindicating the importance of soil moisture for vegetation productivity.