Mahaney, W. M., K. A. Smemo, and K. L. Gross. 2008. Impacts of C4 grass introductions on soil carbon and nitrogen cycling in C3-dominated successional systems. Oecologia 157:295-305.
While recent research has focused on the effects of exotic plant species on ecosystem properties, less is known about how restoring individual native plant species, differing in biomass and tissue chemistry, may impact ecosystems. We examined how three native C4 prairie grasses affected soil C and N cycling 11 years after reintroduction into successional old-field communities dominated by non-native C3 grasses. The species examined in this study differ in traits that are expected to influence soil C and N cycling (biomass and tissue chemistry). Thus, we hypothesized that cycling rates would decrease, thereby increasing pool sizes in soils under C4 species compared under C3 species. As predicted, the C4 species had greater biomass and more recalcitrant tissue [higher C:N, acid detergent fiber (ADF):N] compared to the dominant C3 species. The three C4 species did not differ in tissue C:N, ADF:N, or root biomass, but Andropogon had more than twice the shoot biomass of Schizachyrium and Sorghastrum. Soils under the C4 species did not differ in inorganic N levels, but levels were lower than in soils under the C3 species, and soils under Andropogon had slightly lower in situ net N mineralization rates compared to those under C3 species. We found little evidence of larger surface soil C pools under C4 species versus C3 species after 11 years and no differences in subsurface soil C or N among species. The C4 species contributed a significant amount of C to both soil depths after 11 years. Our results demonstrate that C4 species reintroduction into old-fields can alter C and N cycling on relatively short timescales, and that individual C4 species differ in the magnitude of these effects. Improving our understanding of how species influence ecosystem properties is essential to predicting the ecosystem-level consequences of plant community alterations due to land use changes, global change, and species introductions.
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