Regional contribution to variability and trends of global gross primary productivity

Abstract

Terrestrial gross primary productivity (GPP) is the largest component of the global carbon cycle and a key process for understanding land ecosystems dynamics. In this study, we used GPP estimates from a combination of eight global biome models participating in the Inter-Sectoral Impact-Model Intercomparison Project phase 2a (ISIMIP2a), the Moderate Resolution Spectroradiometer (MODIS) GPP product, and a data-driven product (Model Tree Ensemble, MTE) to study the spatiotemporal variability of GPP at the regional and global levels. We found the 2000-2010 total global GPP estimated from the model ensemble to be 117 ± 13 Pg C yr −1 (mean ± 1 standard deviation), which was higher than MODIS (112 Pg C yr −1 ), and close to the MTE (120 Pg C yr −1 ). The spatial patterns of MODIS, MTE and ISIMIP2a GPP generally agree well, but their temporal trends are different, and the seasonality and inter-annual variability of GPP at the regional and global levels are not completely consistent. For the model ensemble, Tropical Latin America contributes the most to global GPP, Asian regions contribute the most to the global GPP trend, the Northern Hemisphere regions dominate the global GPP seasonal variations, and Oceania is likely the largest contributor to inter-annual variability of global GPP. However, we observed large uncertainties across the eight ISIMIP2a models, which are probably due to the differences in the formulation of underlying photosynthetic processes. The results of this study are useful in understanding the contributions of different regions to global GPP and its spatiotemporal variability, how the model-and observational-based GPP estimates differ from each other in time and space, and the relative strength of the eight models. Our results also highlight the models' ability to capture the seasonality of GPP that are essential for understanding the inter-annual and seasonal variability of GPP as a major component of the carbon cycle.

Improving Estimates of Gross Primary Productivity by Assimilating Solar‐Induced Fluorescence Satellite Retrievals in a Terrestrial Biosphere Model Using a Process‐Based SIF Model

“…The positive trend of the model was decreased from 0.56 to 0.43 GtC.yr −2 for both 1990–2009 and 2001–2009 periods. It is hence in closer agreement with mean linear trends estimated in the literature from several models (for instance 0.41 GtC/yr 2 both over the period 1990–2009 in Anav et al () and over the period 2000–2010 in Chen et al (), 0.35 GtC.yr −2 over the 1981–2010 period in Ito et al (), 0.39 GtC.yr −2 over 2000–2013 in Zhang et al ()), but departs from the higher positive trend of FLUXSAT (1.35 GtC/yr 2 over 2001–2009). That positive trend in ORCHIDEE is due to the fertilization effect of increasing CO 2 atmospheric concentrations to which the model is sensitive (Sun et al, ), although moderated by a downregulation effect that mimics the role of nitrogen limitation on photosynthesis in the version used, and to the increasing surface temperatures (Anav et al, ).…”

“…That positive trend in ORCHIDEE is due to the fertilization effect of increasing CO 2 atmospheric concentrations to which the model is sensitive (Sun et al, ), although moderated by a downregulation effect that mimics the role of nitrogen limitation on photosynthesis in the version used, and to the increasing surface temperatures (Anav et al, ). In parallel, the interannual variation (IAV) was increased from 1.67 to 1.93 GtC.yr −1 over the 1990–2009 period, which remains higher than FLUXCOM IAV (0.31); over 2001–2009 however, ORCHIDEE‐GPP IAV was decreased from 1.43 to 1.19 GtC/year which is closer to that estimated in FLUXSAT (1.25 GtC/year) but departs from the mean IAV of an ensemble of land surface models during the 2000–2010 period in Chen et al () (1.48).…”

Changes in the Shadow: The Shifting Role of Shaded Leaves in Global Carbon and Water Cycles Under Climate Change

“…Although a great number of global estimates of the two largest fluxes in terrestrial ecosystems, gross primary production (GPP) and evapotranspiration (ET), are currently available, they do not converge on spatial distributions nor in long-term trends (Anav et al, 2015;Beer et al, 2010;Chen et al, 2017;He, Chen, Croft, et al, 2017;Jiang & Ryu, 2016;Jung et al, 2010Jung et al, , 2011Knauer et al, 2017;Mao et al, 2015;Mu et al, 2011;Zeng et al, 2012;Zhang, Peña-Arancibia, et al, 2016). So far, no analysis has been conducted on the trends of GPP and ET components for sunlit and shaded leaf groups.…”

Key ecological parameters of immotile versus locomotive life Фундаментальные экологические параметры неподвижной и передвигающейся жизни

“…For mature steady-state vegetation death of plant parts should be compensated by net primary production P. Net primary production P = P с of mature vegetation is, in the form of dead plant matter, consumed by the immotile heterotrophs to sustain their respiration (1). According to observations [20,[22][23][24], gross primary productivity F exceeds net primary productivity P by approximately twofold. Therefore, net primary productivity P с of mature steady-state vegetation approximately coincides with the respiration of the mature vegetation layer l c :…”