Warming‐induced global soil carbon loss attenuated by downward carbon movement

Abstract

Soil organic carbon (SOC) stored in world top 2 m soil depth is about two times of carbon in vegetation and the atmosphere combined (Batjes, 2016; Le Quéré et al., 2016), resulting in that a tiny change of global SOC stocks can substantially alter atmospheric CO 2 concentration therefore mitigating or amplifying climate change. Climate change, especially warming, has a substantial effect on SOC dynamics, while the direction and magnitude of this effect is still uncertain (Bond-Lamberty & Thomson, 2010; Crowther et al., 2016; Mahecha et al., 2010). Although the dynamics of SOC in the top soil layers (i.e. 0-0.2 m) in response to climate have been widely studied, much less studies have explored SOC dynamics extending to the whole-soil profile, particularly across large extents. Nevertheless, subsoil stores even more carbon than topsoil globally (Jobbágy & Jackson, 2000; Rumpel & Kögel-Knabner, 2011; Salome et al., 2010). It is required to understand how whole-soil SOC responds to climate change factors. This information is critical for a holistic understanding of soil carbon cycle-climate feedbacks and for the development of sound, unbiased strategies for whole-soil profile carbon management. Among climate change factors, warming is the most significant factor of concern as it affects SOC dynamics directly and

Temperature effects on carbon storage are controlled by soil stabilisation capacities

“…2b). While we focus on the top 50 cm, due to the potential for vertical profiles of soil C to be affected by temperature 22 , very similar results were observed for the top 20 cm (Supplementary Fig. 2).…”

Younger carbon dominates global soil carbon efflux

“…This may be largely due to cryoturbation‐induced redistribution of soil C in permafrost‐affected regions (Mishra et al, 2021), which might not be well represented by the process of vertical transport considered in this study. Soil profile C redistribution may play an important role in regulating a efflux (Luo et al, 2020). Indeed, our sensitivity analysis suggests that global average a efflux is increased by 72% (from 194 to 334 year) if vertical transport is not considered (Figure S5).…”

Beyond bulk: Density fractions explain heterogeneity in global soil carbon abundance and persistence

“…However, unless these iron-C associations are protected via subsequent occlusion or surface coating, they are likely vulnerable to dissolution if high moisture conditions resume (Chen et al, 2020). Another tension is that increased transport of dissolved organic C could lead to either less or more C at depth depending on whether those simple C molecules stimulate microbial decomposition ("priming"; Luo et al, 2020) or form mineral associations. The less positive response of C abundance to moisture in the free particulate fraction at depth (Figure S11) may reflect the priming effect.…”