Size, activity and catabolic diversity of the soil microbial biomass in a wetland complex invaded by reed canary grass
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Reed canary grass (Phalaris arundinacea, L.) invasion of wetlands is an ecological issue that has received attention, but its impact on soil microbial diversity is not well documented. The present study assessed the size (substrate-induced respiration), catabolic diversity (CLPP, community level physiological profiles) and composition (selective inhibition) of the soil microbial community in invaded (>95% P. arundinacea cover) and in non-invaded areas of a wetland occupied by native species grown either as a mixed assemblage (22 species) or as quasi-monotypic stands of Scirpus cyperinus (74% cover). The study also tested the hypothesis that decomposition of lignin- and phenolics-rich plant tissues would be fastest in soils exhibiting high catabolic diversity. Results showed that soil respiration, microbial biomass and diversity were significantly higher (P < 0.03; 1.5 to 3 fold) in P. arundinacea-invaded soils than in soils supporting native plant species. Fungal to bacterial ratios were also higher in invaded (0.6) than in non-invaded (0.4) plots. Further, canonical discriminant analysis of CLPP data showed distinct communities of soil decomposers associated with each plant community. However, these differences in microbial attributes had no effect on decomposition of plant biomass which was primarily controlled by its chemical composition. While P. arundinacea invasion has substantially reduced plant diversity, this study found no parallel decline in the size and diversity of the soil microbial community in the invaded areas.
KeywordsBiomass decomposition Microbial diversity Phalaris arundinacea Soil microbial biomass Wetlands
basal soil respiration
community level physiological profiles
microbial biomass carbon
residue quality index
soil organic carbon
The authors thank the Sycamore Land Trust for providing access to the study site; Andrew Mertz, of Indy Parks, for his help with the vegetation survey; Vince Hernly and Bob Hall for their support with field reconnaissance and well installation; and several interns from the Center for Earth and Environmental Science (IUPUI) who helped with field sampling.
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