Trends and Variability of AVHRR-Derived NPP in India

Govindasamy Bala,Hosahalli Gangamani,Hirofumi Hashimoto,Rajiv Chaturvedi,Rama Nemani,Jaideep Joshi

doi:10.3390/rs5020810

Govindasamy Bala, Hosahalli Gangamani + Show 4 more

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https://doi.org/10.3390/rs5020810

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Abstract

In this paper, we estimate the trends and variability in Advanced Very High Resolution Radiometer (AVHRR)-derived terrestrial net primary productivity (NPP) over India for the period 1982–2006. We find an increasing trend of 3.9% per decade (r = 0.78, R2 = 0.61) during the analysis period. A multivariate linear regression of NPP with temperature, precipitation, atmospheric CO2 concentration, soil water and surface solar radiation (r = 0.80, R2 = 0.65) indicates that the increasing trend is partly driven by increasing atmospheric CO2 concentration and the consequent CO2 fertilization of the ecosystems. However, human interventions may have also played a key role in the NPP increase: non-forest NPP growth is largely driven by increases in irrigated area and fertilizer use, while forest NPP is influenced by plantation and forest conservation programs. A similar multivariate regression of interannual NPP anomalies with temperature, precipitation, soil water, solar radiation and CO2 anomalies suggests that the interannual variability in NPP is primarily driven by precipitation and temperature variability. Mean seasonal NPP is largest during post-monsoon and lowest during the pre-monsoon period, thereby indicating the importance of soil moisture for vegetation productivity.

Highlights

Terrestrial net primary productivity (NPP) is one of the most important ecosystem variables that have been studied extensively during the last 40 years [1]
0.83 peta grams of carbon (PgC)·y−1 and 0.03 PgC·y−1 which are less than the CASA-model estimate of 1.42 PgC·y−1 and
Since all available global scale NPP products are model based, it is important to recognize that trends and variability estimated from these products are likely more reliable and consistent than the mean values

Summary

Introduction

Terrestrial net primary productivity (NPP) is one of the most important ecosystem variables that have been studied extensively during the last 40 years [1]. It is a fundamental ecological variable, because it measures the terrestrial carbon dioxide assimilation, but it indicates the type (e.g., crops, forests) of the land surface area and status of a wide range of ecological processes. Global ecosystem models provide the basis for computing a satellite-based estimate of NPP These models range from simple ones based on light use efficiency (LUE) to more mechanistic models based on “Soil-Vegetation-Atmospheric-Transfer” (SVAT) schemes designed to capture variability in biospheric processes

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Conclusion