Gross primary production of global forest ecosystems has been overestimated

Abstract

Coverage rate, a critical variable for gridded forest area, has been neglected by previous studies in estimating the annual gross primary production (GPP) of global forest ecosystems. In this study, we investigated to what extent the coverage rate could impact forest GPP estimates from 1982 to 2011. Here we show that the traditional calculation without considering the coverage rate globally overestimated the forest gross carbon dioxide uptake by approximately 8.7%, with a value of 5.12 ± 0.23 Pg C yr−1, which is equivalent to 48% of the annual emissions from anthropogenic activities in 2012. Actually, the global annual GPP of forest ecosystems is approximately 53.71 ± 4.83 Pg C yr−1 for the past 30 years by taking the coverage rate into account. Accordingly, we argue that forest annual GPP calculated by previous studies has been overestimated due to the exaggerated forest area, and therefore, coverage rate may be a required factor to further quantify the global carbon cycle.

Photosynthetic productivity and its efficiencies in ISIMIP2a biome models: benchmarking for impact assessment studies

“…For example, an isotopic study by Welp et al (2011) implied that global GPP is much higher than the values obtained by flux and satellite studies. In contrast, an analysis by Ma et al (2015) implied that previous studies have overestimated global forest GPP because of an incorrect assumption of forest coverage change. Terrestrial ecosystem models have been successfully adopted in carbon cycle studies, but large uncertainties remain in their estimates (Anav et al 2015, Schwalm et al 2015.…”

Spatiotemporal patterns of terrestrial gross primary production: A review

“…However, direct measurements of GPP do not exist because no observation techniques are available to quantify this process at the right spatial scale [ Ma et al ., ]. Using photosynthesis measurements at leaf level is not that straightforward because of difficulties in controlling environmental conditions of gas exchange chambers or physical placement of a cuvette on a leaf (or a chamber over a plant) that may produce biases and artifacts [ Baldocchi , ].…”

Effects of Anthropogenic Activity on Global Terrestrial Gross Primary Production

“…The largest and the most uncertain contributor to interannual global carbon uptake variability is land (Bousquet et al, 2000;Friedlingstein et al, 2014;Intergovernmental Panel on Climate Change IPCC, 2013). The largest land carbon flux is gross primary production (GPP; Beer et al, 2010;Ma et al, 2015). GPP cannot be directly measured at large scales (Ma et al, 2015;Welp et al, 2011).…”

“…The largest land carbon flux is gross primary production (GPP; Beer et al, 2010;Ma et al, 2015). GPP cannot be directly measured at large scales (Ma et al, 2015;Welp et al, 2011). Thus, GPP estimates are typically based on upscaling in situ observations, satellite remote sensing, and terrestrial biosphere models (TBMs).…”