Experimental flooding shifts carbon, nitrogen, and phosphorus pool distribution and microbial activity

Abstract

Abstract Flooding transforms the soil environment, impacting small-scale controls on mineral associated carbon (C), nitrogen (N) and phosphorus (P) stabilization and mobilization. Yet during flood events, mineral associated C, N, and P may not respond in the same way, such that soluble C, N, and P concentrations and stoichiometry may change with unknown consequences for microbial activity. Using a laboratory incubation approach, we investigated how flooding impacts C, N, and P pool distribution and microbial activity across a 1-week flood event and after drying. We found that all three mineral associated pools responded dynamically to flooding, increasing and decreasing throughout the flood with a net increase of 5.9% in mineral associated C and 32.5% decrease in residual P. However, mineral associated C, N, and P each shifted at different temporal points, indicating that they are likely responding to separate destabilization mechanisms working at different temporal scales. The soluble C and N responses to flooding contrasted the mineral associated pool’s response, increasing by 57% and decreasing by 72% respectively at the beginning of the flood which remained post-flood. However, soluble P behaved more similarly to the mineral associated pool. The microbial community maintained and even increased their exo-cellular activity throughout the flood period, responding most strongly to changes in available P. Our research demonstrates that the mineral associated pool is sensitive to short-term flooding altering the composition and quantity of water extracted compounds and microbial activity.