ORIGINAL PAPER Soil organic carbon pools and composition in a wetland complex invaded by reed canary grass Jonathan S. Bills & Pierre-Andre Jacinthe & Lenore P. Tedesco Received: 9 January 2010 / Revised: 7 June 2010 / Accepted: 17 June 2010 / Published online: 6 July 2010 # Springer-Verlag 2010 Abstract Reed canary grass (Phalaris arundinacea) invasion is prevalent in wetlands and riparian fringes, and due to differences in vegetative growth and residue quality relative to native species, P. arundinacea invasion could result in measurable effect on soil organic carbon (SOC) pools and composition. To examine these ques- tions, plant biomass and soil samples were collected from areas invaded by P. arundinacea and areas colonized either by a native sedge Scirpus cyperinus or a mixed assemblage of 22 native species in a south-central Indiana (USA) wetland. Plant biomass composition (C, N, cellu- lose, lignin, and phenolics), total and water-extractable SOC pools were determined. S. cyperinus biomass contained (g kg -1 biomass) significantly (P <0.05) more lignin (142.5 vs 72), phenolics (29.2 vs 11.2), and cellulose (260.5 vs 164.8) than P. arundinacea biomass. These constituents were also more abundant in mixed native plant material than in P. arundinacea biomass. Decomposition of plant biomass was related to residue composition with P. arundinacea shoot biomass decom- posing 1.6 times faster than S. cyperinus material. SOC pools (Mg C ha -1 , 0–30 cm) were larger under P. arundinacea (28.3) than under either S. cyperinus (23.9) or the mixed native species (21.8). Thus, the greater recalcitrance of native plant biomass did not translate into larger SOC pools. Furthermore, water-extractable organic C, N, and carbohydrates were significantly higher in the surface layer of soils supporting P. arundinacea than in native species. These results therefore indicate a clear effect of P. arundinacea invasion on the cycling and composition of soil organic matter at the study site. Keywords Plant invasion . Soil organic carbon pools . Mixed native grass species . Extractable soil carbohydrates Introduction Reed canary grass (Phalaris arundinacea) is an herbaceous species that has invaded riparian fringes and wetlands throughout the USA and Canada. During the dormant season, P. arundinacea often stores nonstructural carbohy- drates (e.g., fructose, glucose, sucrose, and starch) in its rhizomes which allows for early and prolific tillering the following spring (Lavergne and Molofsky 2004). As a result of the shading created by these abundant tillers, P. arundinacea generally eliminates most competing plant species, leading to the formation of low-diversity vegeta- tion communities. Non-invasive species generally produce lesser amounts of biomass and have shorter vegetation growth periods than P. arundinacea (Kercher et al. 2004). These physiological traits could contribute to greater SOC stocks in areas invaded by P. arundinacea. Studies comparing the effects of invasive species on nutrient cycling and C cycling are generally inconclusive. While some studies reported increased SOC stocks with plant invasion (Saggar et al. 1999; Hook et al. 2004; Liao et al. 2007), the reverse has also been found (Evans et al. 2001; Fornara and Tilman 2008). Jandl et al. (2007) argued that plant species occupying different ecological niches can complement each other and, compared with monotypic stands, generally lead to greater SOC pools in the long- term, especially in communities that include deep rooted species. Fornara and Tilman (2008) also reported greater J. S. Bills : P.-A. Jacinthe (*) : L. P. Tedesco Department of Earth Sciences, Indiana University–Purdue University Indianapolis (IUPUI), 723 W. Michigan Street, SL 122, Indianapolis, IN46202, USA e-mail: pjacinth@iupui.edu Biol Fertil Soils (2010) 46:697–706 DOI 10.1007/s00374-010-0476-6