title: Can community structure track sea-level rise? Stress and competitive controls in tidal wetlands.
abstract: Climate change impacts, such as accelerated sea-level rise, will affect stress gradients, yet impacts on competition/stress tolerance trade-offs and shifts in distributions are unclear. Ecosystems with strong stress gradients, such as estuaries, allow for space-for-time substitutions of stress factors and can give insight into future climate-related shifts in both resource and nonresource stresses. We tested the stress gradient hypothesis and examined the effect of increased inundation stress and biotic interactions on growth and survival of two congeneric wetland sedges,Schoenoplectus acutusandSchoenoplectus americanus. We simulated sea-level rise across existing marsh elevations and those not currently found to reflect potential future sea-level rise conditions in two tidal wetlands differing in salinity. Plants were grown individually and together at five tidal elevations, the lowest simulating an 80-cm increase in sea level, and harvested to assess differences in biomass after one growing season. Inundation time, salinity, sulfides, and redox potential were measured concurrently. As predicted, increasing inundation reduced biomass of the species commonly found at higher marsh elevations, with little effect on the species found along channel margins. The presence of neighbors reduced total biomass of both species, particularly at the highest elevation; facilitation did not occur at any elevation. Contrary to predictions, we documented the competitive superiority of the stress tolerator under increased inundation, which was not predicted by the stress gradient hypothesis. Multifactor manipulation experiments addressing plant response to accelerated climate change are integral to creating a more realistic, valuable, and needed assessment of potential ecosystem response. Our results point to the important and unpredicted synergies between physical stressors, which are predicted to increase in intensity with climate change, and competitive forces on biomass as stresses increase.
authors.affiliation: Department of Environmental Science, Policy, and Management University of California Berkeley CA USA; Present address: Smithsonian Environmental Research Center 647 Contees Wharf Rd. Edgewater MD 21037 USA.
authors.forename: Lisa M
authors.identifier: 0000-0001-8565-3825
authors.initials: LM
authors.lastname: Schile
authors.affiliation: Department of Environmental Science University of San Francisco San Francisco CA USA.
authors.forename: John C
authors.initials: JC
authors.lastname: Callaway
authors.affiliation: Department of Environmental Science, Policy, and Management University of California Berkeley CA USA; Present address: Department of Ecology and Evolutionary Biology University of Colorado Ramaley N122 Campus Box 334 Boulder CO 80309 USA.
authors.forename: Katharine N
authors.initials: KN
authors.lastname: Suding
authors.affiliation: Department of Environmental Science, Policy, and Management University of California Berkeley CA USA.
authors.forename: N Maggi
authors.initials: NM
authors.lastname: Kelly
keywords: Schoenoplectus acutus; Schoenoplectus americanus; competition; facilitation; sea‐level rise; tidal wetlands