Edward S. DeKeyser

An index of plant community integrity: development of the methodology for assessing prairie wetland plant communities

Abstract We developed an Index of Plant Community Integrity (IPCI) for quantitatively assessing the quality of seasonal wetland plant communities. In 1998 and 1999, we sampled the plant communities of 46 seasonal wetlands in the Prairie Pothole Region (PPR) of central North Dakota, USA. We selected wetlands that represented a range of disturbance from well-managed native rangeland to heavily disturbed cropland. We delineated plant data into metrics of the data set (e.g. species richness, percentage of introduced and annual plants) and analyzed these metrics using principal components (PCs) and cluster analyses. Through analyses, five quality classes (Very good, Good, Fair, Poor, and Very poor) were determined. We then assigned ranges and scores for each metric based on the statistical analyses. By using this classification system, the plant communities of additional seasonal wetlands in the PPR can now be assessed and placed in quality classes for mitigation or ecological purposes, such as tracking the improvement of restored or reclaimed wetlands, wildlife habitat evaluation, hydrogeomorphic (HGM) assessment, and evaluation of other ecological functions.

Do geographically isolated wetlands influence landscape functions

Geographically isolated wetlands (GIWs), those surrounded by uplands, exchange materials, energy, and organisms with other elements in hydrological and habitat networks, contributing to landscape functions, such as flow generation, nutrient and sediment retention, and biodiversity support. GIWs constitute most of the wetlands in many North American landscapes, provide a disproportionately large fraction of wetland edges where many functions are enhanced, and form complexes with other water bodies to create spatial and temporal heterogeneity in the timing, flow paths, and magnitude of network connectivity. These attributes signal a critical role for GIWs in sustaining a portfolio of landscape functions, but legal protections remain weak despite preferential loss from many landscapes. GIWs lack persistent surface water connections, but this condition does not imply the absence of hydrological, biogeochemical, and biological exchanges with nearby and downstream waters. Although hydrological and biogeochemical connectivity is often episodic or slow (e.g., via groundwater), hydrologic continuity and limited evaporative solute enrichment suggest both flow generation and solute and sediment retention. Similarly, whereas biological connectivity usually requires overland dispersal, numerous organisms, including many rare or threatened species, use both GIWs and downstream waters at different times or life stages, suggesting that GIWs are critical elements of landscape habitat mosaics. Indeed, weaker hydrologic connectivity with downstream waters and constrained biological connectivity with other landscape elements are precisely what enhances some GIW functions and enables others. Based on analysis of wetland geography and synthesis of wetland functions, we argue that sustaining landscape functions requires conserving the entire continuum of wetland connectivity, including GIWs.

Geographically isolated wetlands: Rethinking a misnomer

We explore the category “geographically isolated wetlands” (GIWs; i.e., wetlands completely surrounded by uplands at the local scale) as used in the wetland sciences. As currently used, the GIW category (1) hampers scientific efforts by obscuring important hydrological and ecological differences among multiple wetland functional types, (2) aggregates wetlands in a manner not reflective of regulatory and management information needs, (3) implies wetlands so described are in some way “isolated,” an often incorrect implication, (4) is inconsistent with more broadly used and accepted concepts of “geographic isolation,” and (5) has injected unnecessary confusion into scientific investigations and discussions. Instead, we suggest other wetland classification systems offer more informative alternatives. For example, hydrogeomorphic (HGM) classes based on well-established scientific definitions account for wetland functional diversity thereby facilitating explorations into questions of connectivity without an a priori designation of “isolation.” Additionally, an HGM-type approach could be used in combination with terms reflective of current regulatory or policymaking needs. For those rare cases in which the condition of being surrounded by uplands is the relevant distinguishing characteristic, use of terminology that does not unnecessarily imply isolation (e.g., “upland embedded wetlands”) would help alleviate much confusion caused by the “geographically isolated wetlands” misnomer.

REMOTE WETLAND ASSESSMENT FOR MISSOURI COTEAU PRAIRIE GLACIAL BASINS

Missouri Coteau prairie glacial wetlands are subject to numerous anthropogenic disturbances, such as cultivation, construction, and chemical inputs from upland land-use practices. High wetland density and temporal variability among these ecosystems necessitate synoptic tools for watershed-scale wetlands assessment and comprehensive monitoring. We developed a Geographic Information Systems (GIS) classification model for Missouri Coteau prairie glacial wetlands in North Dakota, USA and derived two indices that provide data salient to landscape-scale wetland assessment and monitoring. One, the Basin Buffer Index (BBI), delineates areas of natural vegetation that buffer waters from anthropogenic disturbance. The second, the Hydric Vegetation Index (HVI), delineates areas of hydric vegetation communities essential to prairie glacial wetland function. The model was developed by spectrally characterizing structural attributes common to glacial basins, such as hydroperiod, canopy architecture, and plant life-form and evaluating the potential for spectral detection of the natural vegetation buffers that surround these wetlands. Spectral separation among community zones in the green, red, and mid-infrared regions were evident in hyperspectral data and were convolved to fit multi-spectral satellite sensors. Model application using Landsat ETM+ and SPOT 5 satellite data over the central North Dakota study area produced classifications for buffer delineation and hydric community detection with 89 and 85% accuracy, respectively. By integrating remote sensing technology with those structural factors fundamental to wetland quality (i.e., land-use and natural vegetation buffers surrounding water bodies), we illustrate a method for evaluating wetland condition at a landscape scale.

Cool Season Invasive Grasses in Northern Great Plains Natural Areas

ABSTRACT: n Native prairie sites within the Northern Great Plains are being invaded by cool season invasive grasses despite utilizing even the most conservation-oriented management. Native prairie sites of the Knife River Indian Villages National Historic Site, located near the confluence of the Knife and Missouri Rivers in central North Dakota, were reassessed 23 years after the first assessment. The native prairie sites were initially assessed the summer of 1984 utilizing a modified Daubenmire technique which entailed randomly placing twenty-five ¼ m2 quadrats along transects at each native prairie site. Prior to 1976, native prairie sites were grazed by livestock; and after the National Park Service took ownership, sites were not grazed by livestock and were essentially left idle. The same technique was repeated during the summer of 2007 on the same native prairie sites surveyed in 1984, and comparisons were made between species composition of those sites in 1984 and 2007. Species composition of several sites across the landscape changed from containing a high percentage of native graminoids and forbs to containing a high percentage of invasive species such as smooth brome (Bromus inermis Leyss.) and Kentucky bluegrass (Poa pratensis L.). A few of the more xeric native prairie sites maintained a high percentage of native graminoids and forbs with minor changes in coverage. This study illustrates the emergence of invasive species and species composition changes under historic land use and climatic conditions and the roles that disturbances, such as grazing processes and fire, may play in maintaining native plant communities.

Enhancing Protection for Vulnerable Waters

Governments worldwide do not adequately protect their limited freshwater systems and therefore place freshwater functions and attendant ecosystem services at risk. The best available scientific evidence compels enhanced protections for freshwater systems, especially for impermanent streams and wetlands outside of floodplains that are particularly vulnerable to alteration or destruction. New approaches to freshwater sustainability - implemented through scientifically informed adaptive management - are required to protect freshwater systems through periods of changing societal needs. One such approach introduced in the US in 2015 is the Clean Water Rule, which clarified the jurisdictional scope for federally protected waters. However, within hours of its implementation litigants convinced the US Court of Appeals for the Sixth Circuit to stay the rule, and the subsequently elected administration has now placed it under review for potential revision or rescission. Regardless of its outcome at the federal level, policy and management discussions initiated by the propagation of this rare rulemaking event have potential far-reaching implications at all levels of government across the US and worldwide. At this timely juncture, we provide a scientific rationale and three policy options for all levels of government to meaningfully enhance protection of these vulnerable waters. A fourth option, a do-nothing approach, is wholly inconsistent with the well-established scientific evidence of the importance of these vulnerable waters.

DEVELOPING A WETLAND CONDITION PREDICTION MODEL USING LANDSCAPE STRUCTURE VARIABILITY

Recent studies found substantial variability in plant community integrity of wetlands in the Prairie Pothole Region (PPR) of central North Dakota, USA. We speculated that this variability might be connected to the nature of the surrounding landscapes and that a link might exist between landscape spatial metrics and wetland condition. We explored this potential link, using a case study in the PPR. A combination of remote sensing, geographic information systems (GIS), and landscape spatial metrics was used to: 1) examine the condition-landscape pattern relationship of temporary and seasonal wetlands, and 2) develop a landscape-level decision support tool for rapid assessment of wetland condition. We sampled 73 wetlands in the study area. We used the Index of Plant Community Integrity (IPCI) as our measure of wetland condition. A wetland landscape was defined by a 300 m radius circular area (0.283 km2) around each habitat. Quantitative characterization of landscape pattern was conducted using metrics computed from land cover categorization maps processed from multi-temporal Landsat satellite data. Ordination of wetland samples in a multivariate space of landscape metrics using non-metric multidimensional scaling revealed strong associations between wetland condition and 10 landscape metrics, primarily among seasonal wetlands. The Landscape Wetland Condition Analysis Model (LWCAM) was developed and validated for rapid quantitative assessment of wetland condition. The model was based on three landscape metrics considered most important for use in the PPR: 1) grassland percent core area of landscape, 2) grassland largest patch index, and 3) the number of patches per unit area. We concluded that surrounding natural grasslands and landscape fragmentation were the most important influences on the structure and plant community condition of wetland ecosystems.

The Significant Surface-Water Connectivity of “Geographically Isolated Wetlands"

We evaluated the current literature, coupled with our collective research expertise, on surface-water connectivity of wetlands considered to be “geographically isolated” (sensu Tiner Wetlands 23:494–516, 2003a) to critically assess the scientific foundation of grouping wetlands based on the singular condition of being surrounded by uplands. The most recent research on wetlands considered to be “geographically isolated” shows the difficulties in grouping an ecological resource that does not reliably indicate lack of surface water connectivity in order to meet legal, regulatory, or scientific needs. Additionally, the practice of identifying “geographically isolated wetlands” based on distance from a stream can result in gross overestimates of the number of wetlands lacking ecologically important surface-water connections. Our findings do not support use of the overly simplistic label of “geographically isolated wetlands”. Wetlands surrounded by uplands vary in function and surface-water connections based on wetland landscape setting, context, climate, and geographic region and should be evaluated as such. We found that the “geographically isolated” grouping does not reflect our understanding of the hydrologic variability of these wetlands and hence does not benefit conservation of the Nation’s diverse wetland resources. Therefore, we strongly discourage use of categorizations that provide overly simplistic views of surface-water connectivity of wetlands fully embedded in upland landscapes.

Evaluation of Restored and Native Prairie Pothole Region Plant Communities Following an Environmental Gradient

ABSTRACT: Historically, wetland and grassland ecosystems throughout the Prairie Pothole Region (PPR) of North America were shaped by fire, grazing, and alternating drought and deluge conditions. These historic disturbance patterns of the PPR have been altered by human modifications to the landscape. In recent years, managers have attempted to implement practices that simulate historic disturbance patterns in order to improve the diversity of structure and function in impacted ecosystems. This study evaluated the characteristics of restored and native wetland/grassland plant communities located within two National Wildlife Refuges (NWR) in the PPR of North Dakota. An extensive analysis of plant community composition following an environmental gradient was conducted in order to relate the composition and quality of wetland communities to the condition of adjacent upland grasslands and to compare the composition and quality of native and restored sites. Plant communities were evaluated using quadrat and transect methods and a Floristic Quality Index (FQI). Statistical analyses employed Nonmetric Multidimensional Scaling ordination and Multi-Response Permutation Procedure. We found wide variability in the composition and quality of the plant communities evaluated. Native plant communities were generally of higher quality than restored communities; also, plant communities located at Lostwood NWR generally contained more native components than those located at Tewaukon NWR. The results of this study show that restoration efforts, when properly managed, have the potential to improve the composition and quality of wetland and grassland plant communities. It is likely that the quality of the restored plant communities evaluated in this study will continue to improve with time and sustained management.

Does Increased Road Dust Due to Energy Development Impact Wetlands in the Bakken Region

The Bakken region of western North Dakota and Montana from January 2012 to December 2013 saw an increase of 3368 oil wells, causing a major increase in road dust emissions. A portion of the energy extraction in the Bakken occurs in the wetland rich Prairie Pothole Region, and there is little information on gravel road dust emissions or the ecological impacts. The objectives of this study were to (1) estimate surface loading of gravel road dust during different times of year and at different distances from the road, (2) evaluate dust loading effects on surface water quality, and (3) evaluate the impact of dust deposition on wetland soils. Ten wetlands were tested in the energy impacted area and ten in an adjacent area without energy development. There was a 355xa0% increase in dust loading 10xa0m from the road in the energy impacted area compared to an area without energy development; meanwhile, there was only a 46xa0% increase in dust loading 40xa0m from the road. This loading resulted in an annual deposition of 647xa0g/m2 of gravel road dust close to the road. However, the effect of dust loading on the water quality and soils of wetlands was minimal when compared to wetlands not impacted by increased gravel road dust. The finding of minimal effect on wetland resources from increased road dust fills a knowledge gap in the Bakken on how energy development alters the environment.