title: Competition and soil resource environment alter plant-soil feedbacks for native and exotic grasses.
abstract: Feedbacks between plants and soil biota are increasingly identified as key determinants of species abundance patterns within plant communities. However, our understanding of how plant-soil feedbacks (PSFs) may contribute to invasions is limited by our understanding of how feedbacks may shift in the light of other ecological processes. Here we assess how the strength of PSFs may shift as soil microbial communities change along a gradient of soil nitrogen (N) availability and how these dynamics may be further altered by the presence of a competitor. We conducted a greenhouse experiment where we grew native Stipa pulchra and exotic Avena fatua, alone and in competition, in soils inoculated with conspecific and heterospecific soil microbial communities conditioned in low, ambient and high N environments. Stipa pulchra decreased in heterospecific soil and in the presence of a competitor, while the performance of the exotic A. fatua shifted with soil microbial communities from altered N environments. Moreover, competition and soil microbial communities from the high N environment eliminated the positive PSFs of Stipa. Our results highlight the importance of examining how individual PSFs may interact in a broader community context and contribute to the establishment, spread and dominance of invaders.
authors.affiliation: Department of Environmental Science, Policy & Management, University of California Berkeley, 137 Mulford Hall, Berkeley, CA 94720-3114, USA Present address: Division of Biological Sciences, University of Montana, 32 Campus Dr HS104, Missoula, MT 59812, USA loralee.larios@mso.umt.edu.
authors.forename: Loralee
authors.initials: L
authors.lastname: Larios
authors.affiliation: Department of Environmental Science, Policy & Management, University of California Berkeley, 137 Mulford Hall, Berkeley, CA 94720-3114, USA Present address: EBIO, University of Colorado, Ramaley N122, Campus Box 334, Boulder, CO 80309-0334, USA.
authors.forename: Katharine N
authors.initials: KN
authors.lastname: Suding
keywords: Avena fatua; California grasslands; Stipa pulchra.; competition; exotic species; native species; nitrogen enrichment; plant–soil feedbacks