Determining vegetation metric robustness to environmental and methodological variables.

Land managers need reliable metrics for assessing the quality of restorations and natural areas and prioritizing management and conservation efforts. However, it can be difficult to select metrics that are robust to sampling methods and natural environmental differences among sites, while still providing relevant information regarding ecosystem changes or stressors. We collected herbaceous-layer vegetation data in wetlands and grasslands in four regions of the USA (the Midwest, subtropical Florida, arid southwest, and coastal New England) to determine if commonly used vegetation metrics (species richness, mean coefficient of conservatism [mean C], Floristic Quality Index [FQI], abundance-weighted mean C, and percent non-native species cover) were robust to environmental and methodological variables (region, site, observer, season, and year), and to determine adequate sample sizes for each metric. We constructed linear mixed effects models to determine the influence of these environmental and methodological variables on vegetation metrics and used metric accumulation curves to determine the effect of sample size on metric values. Species richness and FQI varied among regions, and year and observer effects were also highly supported in our models. Mean C was the metric most robust to sampling variables and stabilized at less sampling effort compared to other metrics. Assessment of mean C requires sampling a small number of quadrats (e.g. 20), but assessment of species richness or FQI requires more intensive sampling, particularly in species-rich sites. Based on our analysis, we recommend caution be used when comparing metric values among sites sampled in different regions, different years, or by different observers.

Development of a modified floristic quality index as a rapid habitat assessment method in the northern Everglades.

Floristic quality assessments (FQA) using floristic quality indices (FQIs) are useful tools for assessing and comparing vegetation communities and related habitat condition. However, intensive vegetation surveys requiring significant time and technical expertise are necessary, which limits the use of FQIs in environmental monitoring programs. This study modified standard FQI methods to develop a rapid assessment method for characterizing and modeling change in wetland habitat condition in the northern Everglades. Method modifications include limiting vegetation surveys to a subset of taxa selected as indicators of impact and eliminating richness and/or abundance factors from the equation. These modifications reduce the amount of time required to complete surveys and minimizes misidentification of species, which can skew results. The habitat characterization and assessment tool (HCAT) developed here is a FQA that uses a modified FQI to detect and model changes in habitat condition based on vegetation communities, characterize levels of impact as high, moderate, or low, provide predictive capabilities for assessing natural resource management or water management operation alternatives, and uniquely links a FQI with readily accessible environmental data. For application in the northern Everglades, surface water phosphorus concentrations, specific conductivity, distance from canal, and days since dry (5-year average) explained 67% of the variability in the dataset with > 99.9% confidence. The HCAT approach can be used to monitor, assess, and evaluate habitats with the objective of informing management decisions (e.g., as a screening tool) to maximize conservation and restoration of protected areas and is transferable to other wetlands with additional modification.

Evaluating Composition and Conservation Value of Roadside Plant Communities in a Grassland Biome.

In the context of roadside revegetation activities in rural regions, revegetation objectives commonly are to establish plant communities with a diversity of species that would otherwise be absent on the predominantly agricultural landscape. To determine the efficacy of revegetation in providing plant communities of high biodiversity value, we quantified species richness, floristic quality, and success in seeding efforts. We evaluated the outcome of roadside seedings conducted by Nebraska Department of Transportation (NDOT) for five NDOT landscape regions spanning Nebraska. Our assessment occurred on average 13.2 years (range: 10-17) post-revegetation, thus, providing insight into what established plant communities can be expected after a decade or more. Biomass production declined on an east to west gradient, but the component species responsible for this gradient were unique to each region. We found species richness was greatest in the western regions of Nebraska with the Sandhills supporting the highest richness. This rangeland-dominated region exhibited the highest floristic quality index, a tool commonly used to identify areas of high conservation value. Our findings indicate that the roadside vegetation is landscape-dependent in that neighboring plant communities influence botanical composition of roadside vegetation. Thus, less diverse seeding mixtures could be used on roadsides with a diversity of desirable native plant species in neighboring land (i.e., Sandhills rangeland). Conversely, in roadsides surrounded by cropland or plant communities with many non-native, weedy species, seeding complex mixtures with a diversity of desirable and highly competitive native species is likely necessary. Nebraska roadsides are viewed as a resource where plant communities with a diversity of native grassland species can be established; however, persistence of many seeded, native species is minimal (mostly forbs) because of the competiveness of both seeded and invasive grasses.

Reinventory of the vascular plants of Mormon Island Crane Meadows after forty years of restoration, invasion, and climate change.

The majority of tallgrass prairie has been lost from North America's Great Plains, but remaining tracts often support significant biodiversity. Despite permanent protections for some remnants, they continue to face anthropogenic threats including habitat fragmentation, invasive species, and climate change. Conservationists have sought to buffer remnants from threats using prairie restoration but limited research has assessed such practices at the landscape-level. We reexamine the flora of Mormon Island, the largest tract of lowland tallgrass prairie remaining in the Central Platte River Valley (CPRV) of Nebraska, USA, nearly 40-years after it was initially inventoried and following widespread restoration. We also conducted preliminary inventories of nearby Shoemaker Island and adjacent off-island habitats using an ecotope-based stratified random sampling approach. We examined change at Mormon Island between 1980-1981 and 2015-2020 and compared it to adjacent conservation lands using a number of vegetation indices. We documented 389 vascular plant species on Mormon Island, 405 on Shoemaker Island, and 337 on off-island habitats from 2015-2020, which represented an increase in native and exotic species richness on Mormon Island compared to 1980-1981 results. Floristic quality index (FQI) values increased at Mormon Island between 1980-1981 and 2015-2020. Paradoxically, the distribution of exotic-invasive species also expanded. Mormon Island from 2015-2020 was more similar to Shoemaker Island and off-island habitats from 2015-2020 than Mormon Island from 1980-1981. Widespread restoration introduced a number of high conservation value species native to Nebraska but novel to the CPRV, which improved FQIs despite increased exotic species invasion. These concurrent trends appear to have driven biological homogenization across the study area. Restoration did not fully buffer Mormon Island from exotic species invasion but it may have partially mitigated the impact considering the persistence of most native species across a 40-year period. We recommend using "local ecotype" seed for restorations to preserve distinctive local communities.

[FQA: A method for floristic quality assessment based on conservatism of plant species]. / FQA:一种基于物种保守性的植物区系质量评价方法.

FQA, which uses the conservatism of plant species for particular habitats and the species richness of plant communities, is a rapid method for the assessment of habitat quality. This method is based on species composition of quadrats and coefficients of conservatism for species which assigned by experts. Floristic Quality Index (FQI) that reflects vegetation integrity and degradation of a site can be calculated by a simple formula and be used for space-time comparison of habitat quality. It has been widely used in more than ten countries including the United States and Canada. This paper presented the principle, calculation formulas and application cases of this method, with the aim to provide a simple, repeatable and comparable method to assess habitat quality for ecological managers and researchers.