ECOSYSTEM ECOLOGY - ORIGINAL PAPER Impacts of C 4 grass introductions on soil carbon and nitrogen cycling in C 3 -dominated successional systems Wendy M. Mahaney Æ Kurt A. Smemo Æ Katherine L. Gross Received: 28 November 2007 / Accepted: 28 April 2008 / Published online: 21 May 2008 Ó Springer-Verlag 2008 Abstract While recent research has focused on the effects of exotic plant species on ecosystem properties, less is known about how restoring individual native plant spe- cies, differing in biomass and tissue chemistry, may impact ecosystems. We examined how three native C 4 prairie grasses affected soil C and N cycling 11 years after reintroduction into successional old-field communities dominated by non-native C 3 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 C 4 species compared under C 3 species. As predicted, the C 4 species had greater biomass and more recalcitrant tissue [higher C:N, acid detergent fiber (ADF):N] compared to the dominant C 3 species. The three C 4 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 Sorgha- strum. Soils under the C 4 species did not differ in inorganic N levels, but levels were lower than in soils under the C 3 species, and soils under Andropogon had slightly lower in situ net N mineralization rates compared to those under C 3 species. We found little evidence of larger surface soil C pools under C 4 species versus C 3 species after 11 years and no differences in subsurface soil C or N among species. The C 4 species contributed a significant amount of C to both soil depths after 11 years. Our results demonstrate that C 4 species reintroduction into old-fields can alter C and N cycling on relatively short timescales, and that individual C 4 species differ in the magnitude of these effects. Improving our understanding of how species influence ecosystem properties is essential to predicting the ecosys- tem-level consequences of plant community alterations due to land use changes, global change, and species introductions. Keywords Stable carbon isotope ratio  Andropogon gerardii  Bromus inermis  Elymus repens  Old-field Introduction Human activities, such as land use change and the intro- duction of exotic species, are altering biodiversity on a global scale (Lawton and May 1995; Pimm et al. 1995; Chapin et al. 2000; Hooper et al. 2005). However, the ecological implications of such shifts in plant species dis- tributions and abundances are poorly understood. A number of studies have shown that the introduction of an exotic species can dramatically and rapidly alter ecosystem properties (Vitousek and Walker 1989; Evans et al. 2001; Mack and D’Antonio 2003), but few studies have focused on the reverse: how the reintroduction of native species affects ecosystem properties (sensu Hooper et al. 2005) and whether individual native species differ in their impact on these properties. This study examined how the Communicated by Alan Knapp. W. M. Mahaney (&)  K. L. Gross W.K. Kellogg Biological Station and Department of Plant Biology, Michigan State University, Hickory Corners, MI, USA e-mail: mahaneyw@kbs.msu.edu K. A. Smemo The Holden Arboretum, Kirtland, OH, USA K. A. Smemo Department of Biology, Case Western Reserve University, Cleveland, OH, USA 123 Oecologia (2008) 157:295–305 DOI 10.1007/s00442-008-1063-5