The effects of spatiotemporal patterns of atmospheric CO 2 concentration on terrestrial gross primary productivity estimation

A quantitative understanding of the global gross primary productivity (GPP) and its responses to increasing CO 2 levels is critical for quantifying the feedbacks of ecosystems to climate change. This study applied the daily boreal ecosystem productivity simulator (BEPSd) model to estimate the global GPP from 2000 to 2015, compare the estimated GPP with flux tower measurements and other GPP products to verify the estimation accuracy, and analyze the CO 2 fertilization effect and conducted a spatial analysis of the effects of the spatiotemporal distribution of the CO 2 concentration on the estimation of the GPP. The results showed that the estimates could capture the magnitude, amplitude, distribution, and variation in the GPP well compared with the flux tower measurements and other GPP products. In general, the terrestrial GPP increased as the atmospheric CO 2 concentrations increased; however, the CO 2 fertilization effect varied based on time and location and was constrained by climatic conditions. The increases in the lower latitudes were more significant than those in the middle and higher latitudes, and seasonal variation characteristics were observed in the middle and higher latitudes. Not considering the CO 2 fertilization effect could underestimate the global GPP and its trend, while not considering the spatiotemporal distribution of the CO 2 concentration could overestimate the global annual GPP. These results increase our understanding of the variations in carbon flux under future climate change, especially under the conditions of a changing atmospheric CO 2 concentration.