Abstract
Past changes in gross primary productivity (GPP) were assessed using historical satellite observations based on the Normalized Difference Vegetation Index (NDVI) from the Advanced Very High Resolution Radiometer (AVHRR) onboard the National Oceanic and Atmospheric Administration (NOAA) satellite series and four terrestrial biosphere models to identify the trends and driving mechanisms related to GPP and NDVI in Asia. A satellite-based time-series data analysis showed that approximately 40% of the area has experienced a significant increase in the NDVI, while only a few areas have experienced a significant decreasing trend over the last 30 years. The increases in the NDVI are dominant in the sub-continental regions of Siberia, East Asia, and India. Simulations using the terrestrial biosphere models also showed significant increases in GPP, similar to the results for the NDVI, in boreal and temperate regions. A modeled sensitivity analysis showed that the increases in GPP are explained by increased temperature and precipitation in Siberia. Precipitation, solar radiation and CO2 fertilization are important factors in the tropical regions. However, the relative contributions of each factor to GPP changes are different among the models.
Highlights
Asia, which is characterized by a rapidly growing economy, human-induced disturbances, and climate changes, is an important region for understanding global terrestrial carbon cycles [1,2,3].Siberian regions have experienced a 1.0–2.0 °C increase in temperature from 1961 to 2004 [4]
As inputs; only the Tropical Asia South region did not exhibit a difference in the trend significance likely due to uncertainties in the solar radiation data used for BEAMS models
Based on the analysis of the four terrestrial biosphere models and the satellite-based Normalized Difference Vegetation Index (NDVI) data, we found that the detected NDVI trends are mostly consistent with model-based gross primary productivity (GPP) trends in Asia
Summary
Asia, which is characterized by a rapidly growing economy, human-induced disturbances, and climate changes, is an important region for understanding global terrestrial carbon cycles [1,2,3]. Siberian regions have experienced a 1.0–2.0 °C increase in temperature from 1961 to 2004 [4]. China and India have recently experienced rapid economic growth and a large increase in CO2 emissions. CO2 emissions in China and India accounted for 28% and 7%, respectively, of the global. Many regions, for example, China, Southeast Asia, and South. Asia, have experienced land-use changes, including changes in the use of cropland and forest areas [6,7]. An accurate estimate of the magnitude of temporal GPP changes is required to quantify and predict terrestrial carbon budgets
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