The direct and legacy effects of drying‐rewetting cycles on active and relatively resistant soil carbon decomposition

Abstract

Global climate change is expected to increase the frequency of drought and heavy precipitation, which could create more frequent drying‐rewetting cycles (DWC) in the soils. Although the DWC effects on soil organic carbon (SOC) decomposition have been widely studied, the effect of DWC and the subsequent legacy effect on the decomposition of different SOC pools is still unclear. We conducted a 128‐d laboratory incubation to investigate the DWC effects by using soils from old‐field for 15 years (OF, representing active SOC), bare‐fallow (BF)for 15 years, and BF for 23 years plus an extra 815‐d incubation (BF+, representing relatively resistant SOC). The experiment included nine 10‐d DWC of three treatments: (1) one mean constant‐moisture at 60% water‐holding capacity (WHC), (2) a mild DWC with 10‐d drying to 40% WHC and immediately rewetting to 80% WHC, and (3) a strong DWC with 10‐d drying to 20% WHC and immediately rewetting to 100% WHC. Following the DWC period (0–90 d), there was a 10‐d stabilization period (adjusting all treatments to 60% WHC), and then a 28‐d extended incubation under the constant moisture of 60% WHC. During the DWC period, the strong DWC had a strong effect on CO2 release compared with the constant‐moisture control, reducing the SOC decomposition of OF by 8% and BF by 10%, while increasing the SOC decomposition of BF+ by 16%. In addition, during the extended period, both mild and strong DWC significantly increased SOC mineralization of OF, but decreased that of BF and BF+. This legacy effect induced by DWC compensated for the changes in CO2 release during the DWC period, resulting in the minor response of SOC decomposition of OF and BF+ to the DWC during the entire incubation. Together, DWC could create both direct and legacy effects, and these effects vary with DWC intensity and SOC pools.

Microbial carbohydrate-active enzymes influence soil carbon by regulating the of plant- and fungal-derived biomass decomposition in plateau peat wetlands under differing water conditions

“…In addition, studies have demonstrated that moderate wet-dry alternation increases the soil microbial population and promotes soil organic carbon mineralization (Huang, 2012;Zhang S. et al, 2023), thereby accelerating the decomposition of soil active carbon pools (Wang et al, 2013;Meng et al, 2015), like the findings of this study. Changes in water conditions have significant effects on SOC and DOC stored in peatlands, and these effects are indirectly related to microorganisms; however, the exact relationship is unknown and needs to be confirmed through more targeted experiments.…”

Comprehensive increase in CO2 release by drying-rewetting cycles among Japanese forests and pastureland soils and exploring predictors of increasing magnitude

“…There is a non-significant trend in annual precipitation level during the same period (MEXT and JAM, 2020). This changing pattern in precipitation is often observed in the temperate region of the northern hemisphere (IPCC, 2021) and is related to increased fluctuation of soil water environments, especially DWCs, and consequent alterations in ecosystem functions (Borken and Matzner, 2009;Jin et al, 2023;Zhang et al, 2020Zhang et al, , 2023.…”

“…Carbon dioxide (CO 2 ) release from soil is an ecosystem process that is sensitive to DWCs (Birch, 1958;Borken and Matzner, 2009;Lee et al, 2002;Nagano et al, 2019;Unger et al, 2010Unger et al, , 2012Zhang et al, 2020Zhang et al, , 2023) and has substantial feedback potential to the ongoing climate change due to its magnitude reaching as much as seven times greater than anthropogenic CO 2 emission on a global scale (Bond-Lamberty and Thomson, 2010;Friedlingstein et al, 2020). The effects of DWCs on soil CO 2 release were first shown by Birch (1958) as the marked increase in soil organic matter (SOM) decomposition and CO 2 release after the rapid rewetting of dried soil, and has since been the subject of intensive investigation (Borken and Matzner, 2009;Kpemoua et al, 2023;Lee et al, 2002Lee et al, , 2004Miller et al, 2005;Nagano et al, 2019;Unger et al, 2010Unger et al, , 2012Xiang et al, 2008), including meta-analyses (Kim et al, 2012;Jin et al, 2023;Zhang et al, 2020).…”

“…However, it is still difficult to precisely quantify and predict the effects of DWCs on soil CO 2 release. The significant uncertainties in the effects of DWCs on soil CO 2 release include the inconsistent trends and sizes of effects likely due to the paucity of studies using constant moisture conditions equivalent to the mean water content during DWC incubation (Kpemoua et al, 2023;Zhang et al, 2020Zhang et al, , 2023. According to a meta-analysis by Zhang et al (2020) using 208 data from 34 sites in 29 reports, the effects of DWCs vary according to soil and water contents in continuous constant moisture conditions.…”

“…Another 29 data were calculated from the CO 2 release rates at the upper and lower ends of the range of constant moisture content, corresponding to the maximum and minimum water contents of DWC treatment, respectively (Zhang et al, 2020). In the experiment using three Alfisols from Chinese long-term experimental field studies, Zhang et al (2023) showed similar or somewhat lower CO 2 release in the DWC compared with the constant moisture conditions with the same mean water content for the DWC incubation. Using two Luvisols from French long-term field experiment sites, Kpemoua et al (2023) also showed similar features of changes in CO 2 release associated with DWCs, indicating the need for further comparison of CO 2 release between DWCs and constant moisture conditions with the same mean water content.…”