Soil Type Modestly Impacts Bacterial Community Succession Associated with Decomposing Grass Detrituspheres

Abstract

Decomposition of plant residues has been widely studied; however, there is a lack of information on the dynamics of residue‐associated microbial taxa during decomposition and how it is affected by soil and residue types. It was hypothesized that distinct microbial communities from different soils would result in colonization of residues by different bacterial taxa and that there would be a shift in bacterial community structure during substrate degradation. A 2 × 2 factorial experiment with three replications was conducted consisting of Switchgrass (Panicum virgatum L.) and Rice (Oryza sativa L.) straw; two soil types (Sharkey and Marietta series); and four incubation periods (3, 23, 48, and 110 d; 25°C). Clone libraries were constructed from the unamended soils, pre‐incubation residues, and detritusphere (residues and adhering soil). Non‐metric multidimensional scaling of the detritusphere communities showed a large shift in the structure of the residue‐associated community following 3 d of decomposition. This shift coincided with disappearance of soluble C. Labile C availability appeared to be important for driving bacterial community succession during early colonization. At later stages of decomposition (Days 23–110), bacterial communities were less dynamic; however, there was partial segregation into two groups according to soil type. The relative abundance of Acidobacteria and Beta‐Proteobacteria were primarily responsible for community differences between the detrituspheres of the two soils. No effect on bacterial community dynamics and diversity due to residue type was observed. More striking was the relative similarity in bacterial types found to dominate the detrituspheres and point to the possibility that key functional community members are found widely in nature and that despite the huge diversity of soil bacteria, and some variation based on soil, a few dominant and widespread members came to the forefront during residue decomposition.