Land-use history and contemporary management inform an ecological reference model for longleaf pine woodland understory plant communities

PLoS One. 2014 Jan 23;9(1):e86604. doi: 10.1371/journal.pone.0086604. eCollection 2014.

Abstract

Ecological restoration is frequently guided by reference conditions describing a successfully restored ecosystem; however, the causes and magnitude of ecosystem degradation vary, making simple knowledge of reference conditions insufficient for prioritizing and guiding restoration. Ecological reference models provide further guidance by quantifying reference conditions, as well as conditions at degraded states that deviate from reference conditions. Many reference models remain qualitative, however, limiting their utility. We quantified and evaluated a reference model for southeastern U.S. longleaf pine woodland understory plant communities. We used regression trees to classify 232 longleaf pine woodland sites at three locations along the Atlantic coastal plain based on relationships between understory plant community composition, soils (which broadly structure these communities), and factors associated with understory degradation, including fire frequency, agricultural history, and tree basal area. To understand the spatial generality of this model, we classified all sites together and for each of three study locations separately. Both the regional and location-specific models produced quantifiable degradation gradients-i.e., progressive deviation from conditions at 38 reference sites, based on understory species composition, diversity and total cover, litter depth, and other attributes. Regionally, fire suppression was the most important degrading factor, followed by agricultural history, but at individual locations, agricultural history or tree basal area was most important. At one location, the influence of a degrading factor depended on soil attributes. We suggest that our regional model can help prioritize longleaf pine woodland restoration across our study region; however, due to substantial landscape-to-landscape variation, local management decisions should take into account additional factors (e.g., soil attributes). Our study demonstrates the utility of quantifying degraded states and provides a series of hypotheses for future experimental restoration work. More broadly, our work provides a framework for developing and evaluating reference models that incorporate multiple, interactive anthropogenic drivers of ecosystem degradation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Agriculture*
  • Biodiversity*
  • Conservation of Natural Resources
  • Ecosystem*
  • Models, Biological*
  • Pinus / classification*
  • Pinus / physiology*

Grants and funding

This study was funded by the Strategic Environmental Research and Development Program (Project RC-1695) and by funds provided to the Department of Agriculture, Forest Service, Savannah River, under Interagency Agreement DE-AI09-00SR22188 with the Department of Energy, Aiken, SC. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.