Top-down and sideways: Herbivory and cross-ecosystem connectivity shape restoration success at the salt marsh-upland ecotone

PLoS One. 2021 Feb 22;16(2):e0247374. doi: 10.1371/journal.pone.0247374. eCollection 2021.

Abstract

Wetland restoration provides remarkable opportunities to understand vegetation dynamics and to inform success of future projects through rigorous restoration experiments. Salt marsh restoration typically focuses on physical factors such as sediment dynamics and elevation. Despite many demonstrations of strong top-down effects on salt marshes, the potential for consumers to affect salt marsh restoration projects has rarely been quantified. Recently, major restoration projects at the Elkhorn Slough National Estuarine Research Reserve in central California, USA provided an opportunity to examine how herbivory influences restoration success. We quantified the strength of consumer effects by comparing caged to uncaged plantings, and compared effects among plant species and sites. We used camera traps to detect which herbivores were most common and how their abundance varied spatially. Beyond characterizing consumer effects, we also tested management strategies for reducing negative effects of herbivory at the restoration sites, including caging, mowing, and acoustic playbacks of predator sounds. We found extremely strong consumer effects at sites with extensive stands of exotic forbs upland of the high marsh; uncaged restoration plants suffered heavy herbivory and high mortality, while most caged plants survived. Brush rabbits (Sylvilagus bachmani) were by far the most frequent consumers of these high marsh plants. Our work thus provides the first evidence of mammal consumers affecting salt marsh restoration success. Mowing of tall exotic forb cover adjacent to the marsh at one restoration site greatly reduced consumption, and nearly all monitored plantings survived at a second restoration site where construction had temporarily eliminated upland cover. Playbacks of predator sounds did not significantly affect restoration plantings, but restoration efforts in marsh communities vulnerable to terrestrial herbivory may benefit from concurrent restoration of predator communities in the upland habitats surrounding the marsh. A landscape approach is thus critical for recognizing linkages between terrestrial and marine vegetation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Ecosystem
  • Herbivory / physiology*
  • Plants
  • Rabbits
  • Wetlands

Grants and funding

Funding of ESNERR staff (KW, AW, and others who supported the project) was provided by a grant from NOAA’s Office for Coastal Management. Whistlestop and Hester Marsh restoration projects were coordinated by ESNERR’s Tidal Wetland Program and funded by grants from California Department of Water Resources, California Department of Fish and Wildlife, California Coastal Conservancy, USFW National Coastal Wetlands Conservation, Ocean Protection Council, and the Wildlife Conservation Board to the Elkhorn Slough Foundation on behalf of ESNERR. Funding for KET was provided by ESNERR, the Ecology and Evolutionary Biology Department at the University of California, Santa Cruz (UCSC), the Future Leaders in Coastal Science Award (Division of Physical & Biological Sciences, UCSC), the Jean H. Langenheim Graduate Fellowship, and the Hardman Native Plant Award. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.