Sentinel wetlands in Cuyahoga Valley National Park: II. Condition trends for wetlands of management concern, 2008–2018

Bingham, Sonia; Young, Craig

doi:10.36967/2301705

Twenty important management areas (wetlands of management concern) and reference wetlands compose the sentinel wetlands at Cuyahoga Valley National Park. These wetlands are monitored more intensively than other wetlands in the program. This is the second report in a two-part series, designed to summarize the results from intensive vegetation surveys completed at sentinel wetlands from 2008 to 2018. The first report (Bingham and Young 2023) characterized the conditions in each wetland and provided baseline reference information for other reports and site-specific projects. In this report, we examine results from five selected metrics more closely within and across three natural wetlands of management concern groups (restoration wetlands, mitigation wetlands, and rare habitat wetlands) using the reference wetlands as overall benchmarks. We used the Ohio Rapid Assessment Method (ORAM) to evaluate habitat in the sentinel wetlands. In addition, a total of 37 long-term sample plots were established within these wetlands to monitor biological conditions over time using vegetation as an indicator. Multiple plots were located in larger wetland complexes to capture spatial differences in condition. Vegetation was intensively surveyed within the plots using the Vegetation Index of Biotic Integrity (VIBI), where all plant species are identified to the lowest taxonomic level possible (genus or species). The sample plots were surveyed twice, and the five evaluation metrics included the VIBI score, Floristic Quality Assessment Index (FQAI), percent sensitive plant species, percent invasive graminoids, and species richness. For the analysis, VIBI plot locations were rank ordered based on their 2018 scores, the range and average for each metric was examined across the wetlands of management concern groups and plotted against reference wetlands for comparison, and the two survey years (pre-2015 and 2018) were plotted against each other for substantial changes from the established baseline. Across the sample plot locations, VIBI scores ranged from a low of 7 (Stanford Run SF1) to a high of 91 (Columbia Run 554). The top scoring plots were at four reference wetlands (Stumpy Basin 526, Virginia Kendall Lake 241K, Columbia Run 554, and Boston Mills 683) and one rare habitat wetland (Beaver Marsh BM3). All of these plots fell within an excellent condition range in one or both survey years. They each have unique habitats with some specialized plant species. The majority (24) of the sentinel wetlands plots ranked within the poor or fair ranges. These include the three mitigation wetlands: Brookside 968, Rockside RS2, and Krejci, as well as all plots within the Pleasant Valley and Stanford Run wetlands. Most of the large wetlands had dramatic condition differences within their boundaries— effected by pollution sources, land-use modifications, and/or invasive species in some areas more than others. We documented these wide condition ranges at Fawn Pond, Virginia Kendall Lake, Beaver Marsh and Stumpy Basin, but the most pronounced within-wetland differences were at Virginia Kendall Lake, which had a 58-point difference between the highest and lowest scoring plot. Fawn Pond is in good condition at most plots and scored very high in comparison to other wetlands within the riverine mainstem hydrogeomorphic class. The average and range of most metric scores were notably different across the four different wetlands groups. Average values at rare habitat wetlands plots were similar to reference plots for VIBI and FQAI scores, percent invasive graminoids, and percent sensitive metrics. Krejci KR1 and Fawn Pond FP3 had unusually high percent cover of sensitive species (31.0% and 27.9%, respectively) for the mitigation and restoration groupings. However, average overall metric scores across the restoration and mitigation wetlands were generally very low, with Stanford Run being the lowest scoring restoration wetland and Brookside being the lowest scoring mitigation wetland. With restoration efforts completed, the expectation is that mitigation wetlands should be performing much higher. Two of the three mitigation wetlands sites are not meeting the mitigation benchmarks that were created for them by the US Army Corp of Engineers and the Ohio Environmental Protection Agency. Contractor reports state that the wetlands met the criteria within the first five years of establishment. However, upon release from monitoring and maintenance, invasive species have gradually re-established, which has led to condition deterioration over time, and lower metric scores. VIBI scores stayed the same or improved (only slightly in many cases) in the majority of plots (67.6%) between survey years. The Krecji mitigation wetlands had the largest improvement in VIBI scoring. Scores at six plots decreased by at least 10 points from the baseline survey. Two of the park’s most beloved wetlands, Beaver Marsh (at one location) and the Stumpy Basin reference plot, had the two most notable declines in VIBI scores. In 2018, 11 plots (29.7%) had greater than 25% invasive graminoid cover (e.g. cattail, common reed grass, reed canary grass) and 18 plots (48.7%) experienced an increase in invasive graminoid cover between survey years. A marked increase (>10% cover) in invasive graminoids was documented at eight locations (Rockside 1079RS2, Beaver Marsh BM5, Fawn Pond FP3 and FP4, Brookside 968, Stumpy Basin SB1, and two other Pleasant Valley plots: 1049 and 969). These trends are likely to continue, and biological conditions are expected to deteriorate at these wetlands in response. Regardless of invasive species increases, many of the wetlands showed remarkable resilience over the last decade with fairly stable VIBI categories.

Sentinel wetlands in Cuyahoga Valley National Park: II. Condition trends for wetlands of management concern, 2008–2018

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