Open AccessRecent trends in gross primary production and their drivers: analysis and modelling at flux-site and global scales
Author(s) -
Wenjia Cai,
Iain Colin Prentice
Publication year - 2020
Publication title -
environmental research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.37
H-Index - 124
ISSN - 1748-9326
DOI - 10.1088/1748-9326/abc64e
Subject(s) - primary production , eddy covariance , environmental science , atmospheric sciences , ecosystem respiration , representative concentration pathways , ecosystem , climatology , terrestrial ecosystem , flux (metallurgy) , carbon cycle , greenhouse gas , climate change , climate model , ecology , materials science , metallurgy , biology , geology
Gross primary production (GPP) by terrestrial ecosystems is the largest flux in the global carbon cycle, and its continuing increase in response to environmental changes is key to land ecosystems’ capacity to offset anthropogenic CO 2 emissions. However, the CO 2 - and climate-sensitivities of GPP vary among models. We applied the ‘P model’—a parameter-sparse and extensively tested light use efficiency (LUE) model, driven by CO 2 , climate and remotely sensed greenness data—at 29 sites with multi-year eddy-covariance flux measurements. Observed (both positive and negative) GPP trends at these sites were predicted, albeit with some bias. Increasing LUE (due to rising atmospheric CO 2 concentration) and green vegetation cover were the primary controls of modelled GPP trends across sites. Global GPP simulated by the same model increased by 0.46 ± 0.09 Pg C yr –2 during 1982–2016. This increase falls in the mid-range rate of simulated increase by the TRENDY v8 ensemble of state-of-the-art ecosystem models. The modelled LUE increase during 1900–2013 was 15%, similar to a published estimate based on deuterium isotopomers. Rising CO 2 was the largest contributor to the modelled GPP increase. Greening, which may in part be caused by rising CO 2 , ranked second but dominated the modelled GPP change over large areas, including semi-arid vegetation on all continents. Warming caused a small net reduction in modelled global GPP, but dominated the modelled GPP increase in high northern latitudes. These findings strengthen the evidence that rising LUE due to rising CO 2 level and increased green vegetation cover (fAPAR) are the main causes of increasing GPP, and thereby, the terrestrial carbon sink.