Abstract
Climate change is intensifying the global water cycle, with increased frequency of drought and flood. Water is an important driver of soil carbon dynamics, and it is crucial to understand how moisture disturbances will affect carbon availability and fluxes in soils. Here we investigate the role of water in substrate-microbe connectivity and soil carbon cycling under extreme moisture conditions. We collected soils from Alaska, Florida, and Washington USA, and incubated them under Drought and Flood conditions. Drought had a stronger effect on soil respiration, pore-water carbon, and microbial community composition than flooding. Soil response was not consistent across sites, and was influenced by site-level pedological and environmental factors. Soil texture and porosity can influence microbial access to substrates through the pore network, driving the chemical response. Further, the microbial communities are adapted to the historic stress conditions at their sites and therefore show site-specific responses to drought and flood.
Highlights
Climate change is intensifying the global water cycle, with increased frequency of drought and flood
We expected pore-water dissolved organic carbon (DOC) to increase in the droughtincubated soils, since drought-induced increases in ionic strength are known to destabilize adsorbed C from mineral surfaces[12,22]
The Washington soils showed increased pore-water DOC across all three treatments (Table 2), suggesting a strong sampling effect, i.e., merely sampling and incubating these soils contributed to C destabilization
Summary
Climate change is intensifying the global water cycle, with increased frequency of drought and flood. The timing and distribution of precipitation are projected to change under climate change, increasing the frequency of drought in some locations and extreme inundation events, including storms and storm surges, in others[1,2] Such extreme moisture conditions drive key soil processes in ways we cannot currently predict[3,4]. Antecedent moisture conditions have been shown to exert an overwhelming effect on the moisture response of soil carbon dioxide (CO2) fluxes[5,6,7], including the increased CO2 fluxes that occur during rewetting[8,9,10] The mechanisms behind this amplified respiration response, often described as the “Birch effect”, remain ill-defined, as this is a complex phenomenon arising from various physicochemical and biochemical destabilization processes that collectively increase microbial oxidation of soil organic carbon (SOC)[9,11,12,13]. We sampled soil cores at three locations from different climatic regions, with different drought/flooding regimes, and with soils of varying physicochemical properties: a silty soil from Caribou-Poker
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call