PARENT SESSION
Tuesday, August 8, 1:30-5:00 pm
COS 42 - Microbial ecology
Chickasaw, Mezzanine Level, Cook Convention Center
Presiders: L Aldrich-Wolfe

Differentiating effects of leaf litter and roots on shifts in soil microbial communities and enzyme activities beneath native and invasive plants.

Yu, Shen^*,1, Vor, Tosten², Elgersma, Kenneth¹, Ehrenfeld, Joan¹, ¹ Rutgers, The State University of New Jersey, New Brunswick, NJ² University of Gottingen, Busgenweg, Gottingen, Germany

ABSTRACT- Plant root inputs (exudation and root turnover) and leaf litter are two substantial feedbacks of photosynthetic products to soil which theoretically cause shifts in soil microbial communities and enzyme activities. Soil microorganisms and enzymes drive soil nutrient cycling, feeding back to plant growth. Efficient positive feedback has been hypothesized as one of the mechanisms by which invasive plants supplant native species. However, the relative importance of above-ground and below-ground effects on the microbial community is unknown. We have conducted a greenhouse experiment to differentiate effects of leaf litter and root exudation of two native (Vaccinium corymbosum and Viburnum acerifolium) and two invasive plants (Berberis thunbergii and Microstegium vimineum). Pots with a field-collected uninvaded soil received seedlings of one of the four species or only litter of one of the species. Soil microbial community and nutrient-cycling-linked enzyme activities were analyzed using PLFA, chloroform-fumigation-extraction and microplate methods after plant growth (two successive generations) and leaf litter decomposition (11 months). Both plant growth and leaf litter decomposition shifted the composition and function of the soil microbial community, including microbial biomass C/N ratios and bacteria/fungi ratios, but in opposite ways. Soil enzyme activities (acid phosphatase and -glucosidase) were greater in planted soil than in litter-only soils, whereas phenol oxidase showed the opposite trend. The invasive plants induced greater soil urease activity than their leaf litter did, but native plants reversed. These results demonstrate that plant-driven effects on soil communities and processes are a combination of different influences from roots and whole plants and from litter only. We suggest that models of plant-soil interaction based on litter characteristics should be revised to reflect the differing effects of whole plants and their litter.

Key words: soil microbial community and enzyme activities, invasive and native plants, plant-soil interaction and leaf litter decomposition