Evaluating how variants of floristic quality assessment indicate wetland condition

Abstract

Biological indicators are useful tools for the assessment of ecosystem condition. Multi-metric and multi-taxa indicators may respond to a broader range of disturbances than simpler indicators, but their complexity can make them difficult to interpret, which is critical to indicator utility for ecosystem management. Floristic Quality Assessment (FQA) is an example of a biological assessment approach that has been widely tested for indicating freshwater wetland condition, but less attention has been given to clarifying the factors controlling its response. FQA quantifies the aggregate of vascular plant species tolerance to habitat degradation (conservatism), and model variants have incorporated species richness, abundance, and indigenity (native or non-native). To assess bias, we tested FQA variants in open-canopy freshwater wetlands against three independent reference measures, using practical vegetation sampling methods. FQA variants incorporating species richness did not correlate with our reference measures and were influenced by wetland size and hydrogeomorphic class. In contrast, FQA variants lacking measures of species richness responded linearly to reference measures quantifying individual and aggregate stresses, suggesting a broad response to cumulative degradation. FQA variants incorporating non-native species, and a variant additionally incorporating relative species abundance, improved performance over using only native species. We relate our empirical findings to ecological theory to clarify the functional properties and implications of the FQA variants. Our analysis indicates that (1) aggregate conservatism reliably declines with increased disturbance; (2) species richness has varying relationships with disturbance and increases with site area, confounding FQA response; and (3) non-native species signal human disturbance. We propose that incorporating species abundance can improve FQA site-level relevance with little extra sampling effort. Using our practical sampling methods, an FQA variant ignoring species richness and incorporating non-native species and relative species abundance can be logistically efficient, easily understood, and effective for wetland assessment.

Floristic Quality Assessment: a critique, a defense, and a primer

“…These are the basic, standard FQA measures (Swink and Wilhelm 1994). Of further note is that many variant FQA measures have been created, but these show either inconsistent, or decreased performance, compared to the standard measures (reviewed in Spyreas 2014, Kutcher andForrester 2018). Regional botanical experts pre-assign each plant species a C value.…”

“…Note that non-native species may or may not be included in either equation, with similar performance either way (Spyreas et al 2012). Of further note is that many variant FQA measures have been created, but these show either inconsistent, or decreased performance, compared to the standard measures (reviewed in Spyreas 2014, Kutcher andForrester 2018).…”

An Optimization Model for a Wetland Restoration Project under Uncertainty

“…To date, most researches on wetlands restoration focused on restorability assessment [19,20,21,22], suitability prediction [23,24,25,26], restoration site selection [27,28,29,30,31], and so on. Qu et al (2018) proposed a GIS-based Restorability Index (RESI) model and restoration plan to evaluate the wetland restorability of the Sanjiang Plain, which is the largest marsh area of China [32].…”

Effectiveness of different metrics of floristic quality assessment: The simpler, the better?

“…The index is based on native vascular plant species richness and on their mean CC to estimate habitat quality Wilhelm 1979, 1994;Miller and Wardrop 2006;Zinnen et al 2021a). Assuming that fewer native species indicate a greater environmental disturbance, alien species are not used to calculate the FQAI (Fennessy et al 1998;Kutcher and Forrester 2018). In recent years, a new "Adjusted FQAI'' index was developed to include alien species (Miller and Wardrop 2006;Raab and Bayley 2012;Ghoraba et al 2021).…”