A trade-off between plant and soil carbon storage under elevated CO2

Abstract

Terrestrial ecosystems remove about 30% of the CO 2 emitted by human activities each year 1 , yet the persistence of this carbon sink partly depends on how plant biomass and soil carbon stocks respond to future increases in atmospheric CO 2 2,3 . While plant biomass often increases in elevated CO 2 (eCO 2 ) experiments 4-6 , soil carbon has been observed to increase, remain unchanged, or even decline 7 . The mechanisms driving this variation across experiments remain poorly understood, creating uncertainty in climate projections 8,9 . Here, we synthesized data from 108 eCO 2 experiments and found that the effect of eCO 2 on soil carbon stocks is best explained by a negative relationship with plant biomass: when plant biomass is strongly stimulated by eCO 2 , soil carbon accrual declines; conversely, when biomass is weakly stimulated, soil carbon accumulates. This trade-off appears related to plant nutrient acquisition, whereby enhanced biomass requires mining the soil for nutrients, which decreases soil carbon accrual. We found an increase in soil carbon stocks with eCO 2 in grasslands (8±2%) and no increase in forests (0±2%), even though plant biomass in grassland responded less strongly (9±3%) than in forest (23±2%). Ecosystem models do not reproduce this trade-off, which implies that projections of soil carbon may need to be revised.

Climate change adaptation in and through agroforestry: four decades of research initiated by Peter Huxley

“…Belowground interactions that affect C storage in soils have been a major research interest in the past decades. Contrary to expectations of proportionality of aboveground biomass and soil C storage, a recent meta-review found that experimental effects of elevated CO 2 concentrations on soil carbon storage are inversely proportional to their effects on aboveground biomass (Terrer et al 2021). Positive effects on soil C were found in nutrientlimited situations with small aboveground biomass responses.…”

Forest management to increase carbon sequestration in boreal Pinus sylvestris forests

“…A potential problem with adaptation of forest management to increase soil C stocks is the possibility that a substantial part of the accumulated soil C stock may be lost after clear-felling (James and Harrison 2016;Nave et al 2010). Soil temperature and moisture are key factors controlling decomposition rates (Swift et al 1979), and clear-felling influence both (Jansson 1987), with a risk of destabilization of soil C. Below-ground C stocks also depend on plantsoil feedbacks and are expected to be sensitive to the removal of mycorrhizal trees at harvest (Kyaschenko et al 2017a). However, whether loss of mycorrhizal activity stabilize or destabilize the organic matter, remains unresolved (Frey 2019;Sterkenburg et al 2018).…”

Profiling of Plant Growth-Promoting Metabolites by Phosphate-Solubilizing Bacteria in Maize Rhizosphere

“…Some can secrete organic molecules from which plants gain resources for their growth directly [54]. For example, plants could use organic carbon as a carbon source [55]; moreover, they could absorb urea derivatives such as N-benzyl-N-isopropyl-N - [4-(trifluoromethoxy)phenyl]urea to supplement their nitrogen store [56]. Additionally, as signal molecules, some molecular organics (such as polyamines, phenolic acid, linolenic acid, etc.)…”