ORCID Profile
0000-0003-4801-8771
Current Organisation
University of Oxford
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Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-11589
Abstract: & & Based on Free Air Carbon Dioxide Enrichment (FACE) and other raised-CO& sub& & /sub& experiments (eCO& sub& & /sub& ), new hypotheses have been proposed to explain how the magnitude of the CO& sub& & /sub& fertilization effect on biomass and biomass production depends primarily on soil nitrogen and phosphorus availability [1,2]. To test whether these hypotheses and measurements from eCO& sub& & /sub& could explain the land carbon sink as independently determined from data and models, we combined a CO& sub& & /sub& response curve for biomass production with a simple two-box model of biomass and soil to simulate the evolution of the land carbon sink during the past century. Results were compared to Dynamic Global Vegetation Model (DGVM) results, as reported by the Global Carbon Project, and to results from inversion studies based on atmospheric CO& sub& & /sub& measurements. The interannual variability of the modelled land sink was realistic, dominated by the temperature dependence of heterotrophic respiration, and similar to DGVMs results. However, the magnitude of the derived land sink based on eCO& sub& & /sub& results was smaller, and its geographical distribution was different to DGVMs average. Sensitivity tests showed that these findings were robust to reasonable variations of parameter values. The smaller sink is due to the smaller amount of vegetation biomass increment documented by eCO& sub& & /sub& experiments in comparison with the mean predictions of DGVMs. A land sink closer to the observed one could be produced, however, when incorporating the hypothesis that nutrient-stressed plants export & #8220 excess& #8221 carbon (generated by increased photosynthesis, but unable to be used for growth) to the soil and that only a fraction of this excess carbon returns to the atmosphere.& This hypothesis requires further exploration but hints at a reconciliation between DGVMs that explain the land carbon sink without nutrient limitations, with experimental findings of (sometimes severe) restrictions on CO& sub& & /sub& fertilization due to nutrient stress.& & & & [1] Terrer et al. 2016, Science, 0.1126/science.aaf4610& & & & [2] Terrer et al. 2019, Nature Climate Change, 0.1038/s41558-019-0545-2& &
Publisher: Copernicus GmbH
Date: 28-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-8793
Abstract: & & Recent syntheses of elevated CO2& (eCO2) experiments provide critical information to quantify the effects of rising CO2& on vegetation. However, although the eCO2 effect on aboveground biomass (& #946 AGB) and soil carbon pool (& #946 Csoil) have been estimated, little has been known about the eCO2 effect on total net primary production (& #946 TNPP) - the sum of above and belowground - due to the difficulties of measuring NPP in eCO2 experiments. As a preliminary analysis of & #946 TNPP, we ran a thorough meta-analysis of global eCO2 experiments and found that (1) Most of the experiments reported a larger & #946 TNPP than & #946 AGB (2) Most of the experiments reported a larger eCO2 effect on belowground (roots) biomass (& #946 BGB) than total biomass (& #946 TB) (for AM mycorrhizal association only) (3) On average, seedling experiments reported a larger & #946 AGB than mature vegetation experiments. Aiming to improve estimates of & #946 TNPP we hypothesized that & #946 AGB could be underestimated due to short experimental time relative to biomass mean residence time, i.e., that & #946 AGB increases with experimental time. We proposed a set of simple first kinetics equation to derive & #946 TNPP with consideration of the imbalance between & #946 BGB and & #946 TB. We first validated the equations on experiments reporting both productivity and biomass before applying to other experiments. We found that, after the application, (1) On average, & #946 TNPP of seedling experiments are insignificantly different to & #946 TNPP of mature vegetation experiments (2) Compared with & #946 AGB, the relative importance of mycorrhizal on & #946 TNPP decrease, and soil CN ratio and soil phosphorus became the most important predictors. (3) The disagreement between experiments and models was smaller for & #946 TNPP than for & #946 AGB.& & &
Publisher: Springer Science and Business Media LLC
Date: 24-03-2021
DOI: 10.1038/S41586-021-03306-8
Abstract: Terrestrial ecosystems remove about 30 per cent of the carbon dioxide (CO
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Huanyuan Zhang-Zheng.