Vegetation Sampling for Wetland Delineation: A Review and Synthesis of Methods and Sampling Issues

Abstract

This document reviews sampling issues and methods for characterizing vegetation, with an emphasis on delineating wetland boundaries in accordance with Section 404 of the Clean Water Act. Numerous vegetation sampling methods have been developed, but no single approach is optimal for all sampling objectives, vegetation types, and ecological settings. Methods vary in relative precision, accuracy, and efficiency, although selection of methods should also explicitly consider sampling objectives, resources, and data requirements. Key considerations include the choice of metric(s), selection of sampling units, and logistical issues such as time required for sample collection. Common metrics include frequency, cover, and biomass,

Testing a rapid Floristic Quality Index on headwater wetlands in central Pennsylvania, USA

“…Treatments consisted of systematically removing the following taxa: (a) all Carex, (b) all grasses, (c) Carex and grasses, (d) all Third, we comparedC output based on all species present at a site (C all ) versus only dominant species (C dom ). Dominance was calculated using the 50/20 rule developed for wetland delineations which defines dominance as "the most abundant plant species (when ranked in descending order of abundance and cumulatively totaled) that immediately exceed 50% of the total dominance measure of the stratum, plus any additional species that individually comprise 20% or more of the total dominance measure for the stratum" (Gage and Cooper, 2010). In this way, we can use reference data to serve as a proxy for information typically collected during routine delineations, thus evaluating the efficacy of using delineation data to estimate wetland condition.…”

Field Testing New Plot Designs and Methods for Determining Hydrophytic Vegetation during Wetland Delineations in the United States

“…To measure plant community attributes, there are methods to determine the best plot size and shape for a specific study's purposes. Plot size is typically adjusted based on the objective of the study and the variance across all plots sampled for a specific community (Barbour et al 1999;Gage and Cooper 2010). For example, herbaceous species may be sampled in 1.0 m 2 plots when the vegetation community is dense and in continuous but larger plots when the vegetation is patchy or sparse.…”

Influence of wetland indicator status ratings on the extent of hydrophytic vegetation during wetland delineations

“…where S = sum of species cover. The HCI is designed to be an unbiased and easy field method for making vegetation determinations and follows methods outlined by Gage and Cooper (2010). Data collected for the HCI is consistent with standard scientific methods for vegetation analysis (McCune and Grace 2002).…”

“…The contrast between wetland and upland ecosystems may be abrupt or gradual and largely dependent on underlying environmental factors, such as topographic, geomorphic, and hydrologic conditions (Johnston and Naiman 1987, Naiman et al 1989, Strayer et al 2003. Discrete changes in topographic and geomorphic conditions can create distinct and narrow wetland-upland boundaries while gradual changes can create indistinct boundaries that may vary temporally (Kirkman et al 1998;Choesin and Boerner 2002;Gage and Cooper 2010). Gentle gradients and spatial heterogeneity of wetland environmental drivers reduce the magnitude of contrast between adjacent wetland and upland ecosystems, making discerning boundaries a challenging task for wetland delineators and practitioners (Johnston et al 1992;Kent et al 1997).…”

“…As a single factor in certain types of wetlands, boundaries of vegetation communities may be poor indicators of wetland boundaries. Vegetation composition can vary continuously or discretely, depending on abruptness of hydrologic gradients and the environmental tolerances of individual species (Whittaker 1953;Curtis 1955;Gage and Cooper 2010). Furthermore, vegetation community boundaries are largely a consequences of complex landscape factors (Whittaker 1953;Austin and Smith 1989;Kent et al 1997) and the differences between these adjacent systems.…”