Drying-rewetting cycles alter carbon and nitrogen mineralization in litter-amended alpine wetland soil

Abstract

Wetting-drying cycles can influence decomposition of litter and soil organic carbon (SOC) and their mineralization, but such effects have seldom been explored in alpine wetland soils. We conducted a 120-day incubation experiment with alpine wetland soils to which we added litter or not. These soil samples were assigned to two constant moisture treatments (60% or 100% soil water-holding capacity, WHC) or to a wetting-drying treatment that cycled between 60% and 100% WHC. Drying-rewetting cycles significantly accelerated carbon (C) mineralization and nitrogen (N) immobilization compared to soil under saturated soil moisture conditions. Litter addition greatly increased C mineralization and N immobilization, but the intensity of mineralization was regulated by soil moisture through microbial biomass. A significantly negative relationship between C and N mineralization became more pronounced when litter was added. Thus, drying-rewetting cycles can alter C and N mineralization, and this effect can strongly depend on litter in alpine wetlands. This indicates that future climate change could affect C stocks in alpine wetland soil through altering moisture and litter production.

Nitrogen availability regulates topsoil carbon dynamics after permafrost thaw by altering microbial metabolic efficiency

“…Moreover, soils in swamp meadow exhibit the highest C content among the soils of various grassland types on the plateau 52 , with a SOC density comparable to that of the high-latitude permafrost regions (65.0 vs. 58.2 kg C m −2 ) 52 . However, unlike arctic and subarctic permafrost regions, where the microbial activity in organic soil is solely N limited 21 , soil microbial activity in swamp meadow is co-limited by C and N availability, as indicated by the low soil C concentration and C:N ratio 40 , 55 (C limitation) combined with negative net N mineralization rate 23 , 24 and the high ratio of N immobilization to total gross N mineralization 25 (N limitation). More importantly, in contrast with the shallow root distribution in arctic tundra ecosystems 10 , 29 , 56 , approximately 81% of plant roots are distributed in the top 30 cm of the soil in the swamp meadow (Supplementary Fig.…”

Soil Carbon, Nitrogen, and Phosphorus Cycling Microbial Populations and Their Resistance to Global Change Depend on Soil C:N:P Stoichiometry

“…When disturbances cease, nutrient biogeochemical cycling and C transformations depend solely on the remaining microbial populations. For example, organic matter decomposition, N mineralization, and nitrification appear to have a strong capacity to recover from drying and rewetting events (12)(13)(14). This resilience may be regulated by taxonomic groups that possess the functional capacity to synthesize enzymes that mitigate deleterious effects (15,16).…”

Controls on mineral-associated organic matter formation in a degraded Oxisol

“…5e, f), indicating that the variability of soil moisture and O2 may critically affect the efficiency of C retention in this degraded Oxisol. Although some studies have reported the effects of DRW cycles on SOC dynamics in soils with residue amendment, they focused on C and N mineralization (Gao et al, 2016;Yemadje et al, 2017), not on the formation of mineral-associated C. To link litter decomposition with SOC stabilization in the mineral soil matrix, Cotrufo et al (2013) developed the Microbial Efficiency-Matrix Stabilization framework which proposed that most mineral-associated C is of microbial origin. Short-range-ordered Fe oxides also function as an important regulator for the formation of mineral-associated C in Fe-rich soils (Kleber et al, 2005).…”