Rapid Buffer Assessment Fails to Predict and Classify Wetland Floristic Quality in Oklahoma

Abstract

Rapid field assessment indicators of ecological stress and disturbance may or may not reflect actual biological conditions. We tested the ability of rapidly assessed buffer quality to predict and classify wetland floristic quality across 106 sites in Oklahoma, USA. We used buffer zone metrics from a national-level rapid assessment tool (USA-RAM) to evaluate applicability at the state level. The rapid assessment relying on buffer quality did not relate predictably (linearly) with floristic quality, but the relationship improved after ecoregional stratification. Focusing on the Central Great Plains ecoregion with 55 wetlands sampled, we found 16 floristically intact sites and 13 floristically altered sites based on multivariate testing of the Floristic Quality Assessment Index and several component metrics. Distributions of buffer metrics across these sites were similar between the floristically intact and altered classes, suggesting potential for misclassification of wetland biological condition using rapid buffer assessment. Some of the disconnect may be attributed to bias in the buffer measurements and to using a national assessment protocol at the state level. Buffer metrics in the USA-RAM may offer little insight about wetland biological condition in some regions, and the use of such metrics should only complement direct bioassessments and not substitute for them.

Quantifying the extent of human disturbance activities and anthropogenic stressors in wetlands across the conterminous United States: results from the National Wetland Condition Assessment

“…Results from regional studies show mixed results regarding the strength of associations between wetland biota and human activities adjacent to wetlands and those at a larger landscape scale. Based on a study of 55 wetlands in the US Interior Plains state of Oklahoma, for example, Bried et al (2016) reported that the site-scale buffer disturbance evaluated by the NWCA disturbance index (140m-HDAI) was not a good predictor of the condition of wetland vegetation. In some regions, however, floral or faunal assemblages may be more strongly influenced by the type and proximity of overt human activities assessed by the NWCA disturbance measures.…”

Enhanced indicator species performance with increasing contextualization

“…Ecoregions are well established throughout the United States and capture broadly consistent climate‐soil‐vegetation‐landcover patterns over large areas (Stoddard, ). We previously found that splitting the CGP from other ecoregions helped to model wetland floristic quality and had more impact than separating depressional wetlands from riverine, seep, and lacustrine‐fringe wetlands (Bried et al, ; Jog et al, ). Others have recommended ecoregional specification of depressional wetland floristic quality in Oklahoma (Gallaway, Davis, Dvorett, & Tramell, ).…”

“…Plant checklists were accumulated from one‐time surveys (during 2012–2016) of 117 nonforested wetlands (Figure ). Sites were located from a variety of sources and spanned nine ecoregions, several major wetland classes, and a range of human disturbance (Bried et al, ; Jog et al, ). Many sites were targeted in the large depression‐rich Central Great Plains ecoregion (Figure ).…”

“…Vegetation surveys occurred from mid‐May to early August using plot‐based or census methods; the different methods appear to have negligible influence on wetland assessments in this study area (Bried et al, ). Plot‐based sampling followed the federal wetland condition assessment protocol (United States Environmental Protection Agency [USEPA], ).…”

“…Other shortcuts around assemblages, such as ignoring hard-to-identify taxa or focusing on dominant taxa only (Chamberlain & Brooks, 2016;Gianopulos, 2018), may be more time consuming and prone to bias than searching for a few indicator species. And nonbiological assessment methods (e.g., Fennessy, Jacobs, & Kentula, 2007) may be disconnected from species' habitats and ecological disturbances (Bried, Jog, Davis, & Dzialowski, 2016;Herlihy et al, 2019b;Swartz, Stuart, Foster, & Lindquist, 2016). Indicator species by contrast offer the dual advantage of being biologically explicit and relatively efficient.…”