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The quality of plant community composition on US Fish and Wildlife Service (USFWS) lands in North Dakota and South Dakota has declined over the past several decades—the abundance of native species has decreased while the abundance of introduced species has rapidly increased. Extensive efforts have been made to improve plant community composition on USFWS prairies; however, there was not a unified approach to this end in North Dakota and South Dakota until the advent of the Native Prairie Adaptive Management (NPAM) program. The NPAM program provides decision support for the selection of management actions to improve plant community composition of tallgrass and mixed-grass prairies in the Northern Great Plains. We evaluated plant community composition on USFWS native tallgrass and mixed-grass prairie remnants enrolled in the NPAM program in North Dakota and South Dakota to examine effects of management on plant community composition. Our analysis suggests that incorporating certain management actions can improve plant community characteristics on the agency's tallgrass and mixed-grass prairies. We documented increased native species richness and decreased Bromus inermis (smooth brome) relative cover at sites that had been burned two or more times during a four-year period. In contrast, smooth brome relative cover was higher at sites managed by the exclusion of fire and intermittent light grazing or rest. Smooth brome is extremely invasive in native prairie remnants throughout the Northern Great Plains. Thus, our results have marked implications for managers working to reduce the prevalence of smooth brome on public and private lands.
Native ungulate grazers affect plant richness, with many studies examining grazer effects on community composition and structure. However, the effect of grazing on the demography of rare plant species is less well understood. Grazers are expected to benefit many plant species by suppressing the competitive dominant grasses and by scarifying and dispersing rare plant seeds. A goal in conservation biology is to quantify the most important threats to rare plant species and to determine how different types of management can improve their demographic outlook. Here, we provide results from two experimental studies that examine (1) the effect of ungulate grazer presence, and (2) the effect of a grass-specific herbicide treatment on the recruitment of a focal rare plant species. Our study demonstrates that both treatments effectively reduce the percent cover or height of the dominant grass species and increase the recruitment of the rare legume, Lespedeza leptostachya. If our results are generalizable to other grassland ecosystems and rare forb species, it suggests that reintroducing grazers may be critical to the management of rare plants in these ecosystems. However, in small remnant habitats where ungulate reintroductions are not possible, conservation efforts can more directly target the reduction of grass competitors using alternative methods.
Canada lynx (Lynx canadensis) were extirpated from Isle Royale in the 1930s. We conducted a population viability analysis (PVA) of a potential lynx reintroduction to better understand viability, uncertainty, and management options. We estimated that the 544-km2 island can support 30 lynx. The probability of 100-year population persistence was 0.36 for a model that simulated a decadal lynx-hare population cycle. A noncyclic model predicted a 0.73 probability of 100-year persistence. Inbreeding depression had a substantial negative effect on modeled persistence. Historically, periodic immigration of mainland lynx via an ice bridge probably reduced or prevented inbreeding depression on the island. The introduction of one male and one female lynx every 10 years increased the probability of 100-year persistence to 0.98 in the cyclic model. Occasional anthropogenic transfers of lynx to the island might be necessary because the frequency of ice bridge formation has decreased. However, our baseline models might underestimate viability because they used demographic rates from mainland studies where lynx were exposed to anthropogenic mortality. When we removed assumed anthropogenic mortality—which should be negligible on Isle Royale—the probability of 100-year persistence was 0.99 for the cyclic model, even without supplementation. Reintroducing lynx to Isle Royale appears feasible, assuming appropriate monitoring and management. Reintroducing lynx would restore a missing native species to Isle Royale and would increase our understanding of lynx ecology.
Land managers face the challenge of conserving medicinal plants that may be threatened by harvest pressure, often with limited biological information available to inform management decisions. Oshá (Ligusticum porteri) is an important medicinal plant whose roots are harvested as an herbal remedy for flu, sore throat, and other illnesses. However, little is known about population structure, root production, or the capacity of oshá to recover from harvest in different environmental contexts. We compared oshá population structure and root production within a gradient of canopy cover from meadow to forested habitat. We experimentally harvested roots of mature oshá plants and recorded oshá recolonization of pits created by root harvest. Prior to harvest, the number and percent cover of reproductive plants and the number of flowering stems per plot were higher in the meadow than in forested habitat. Canopy cover had a significant negative relationship to these variables, suggesting that oshá populations benefit from increased light availability. Average root weight per plant in meadow plots was three times higher than in forested plots. One year after harvest, the majority of all harvest pits across the canopy cover gradient were recolonized by oshá. Our results suggest that oshá population structure and root production are significantly influenced by canopy cover, but that plants have a high capacity for post-harvest recolonization under variable light conditions. These results demonstrate the need to account for environmental factors that influence population structure when addressing concerns about the overharvest of wild medicinal plants.
Restoration practitioners balance the desire to use locally adapted plant materials with the uncertainty of what constitutes “local.” Provisional seed transfer zones are intended to guide managers on how far plant materials can be moved during revegetation with the assumption that all populations within a zone will show similarly adapted traits. There are multiple approaches to developing provisional transfer zones, including limiting transfer to specific populations, within ecoregions, within climatic zones, or within climatic zones within ecoregion; there is little information about which of these approaches is best or whether the best approach could vary by region. We used Pseudoroegneria spicata as a test species to assess (1) whether EPA Level III Ecoregion or population explained more variation in traits, and (2) which of four common provisional seed transfer zones (Ecoregion-only, Climate-only, USFS seed transfer zone, and Climate in Ecoregion) best explains trait variation. Plants from 14 populations and three ecoregions were grown in a common garden for two years; growth traits, final biomass, seed set, and mortality were measured. Ecoregion explained more variation than population for most growth traits and mortality; population explained more variation only for seed set. Only one of the three ecoregions showed strong trait differentiation. Out of the four provisional seed transfer zone models compared, we found the most support for models containing climate (Climate-only and Climate in Ecoregion). Findings suggest that Level III Ecoregions may be too broad for seed transfer and that managers should consider climate within ecoregion when making seed transfer decisions.
Cliffs harbor unique ecological communities while facing increasing pressure from human disturbances. How abiotic factors such as surface heterogeneity, slope, and aspect interact locally to drive variation in plant communities remains largely unknown. We surveyed the vascular plants, bryophytes, and lichens along 50 vertical transects throughout the Big South Fork National River and Recreation Area (Tennessee, USA) to characterize the vegetative community and to determine which factors influenced the distribution of cliff vegetation. Across all cliff face plots, the dominant lichen genus was Lepraria; the dominant vascular plant was Dennstaedtia punctilobula; and the dominant bryophyte was Dicranum montanum. We found several rare species including Cladonia pocillum, a boreal disjunct lichen; Vittaria appalachiana, Appalachian shoestring fern; and Cynodontium schisti, a rare bryophyte. Vascular plants, bryophytes, and lichens were each influenced by different environmental drivers. West-facing slopes supported high vascular plant diversity, low-angle slopes supported high bryophyte diversity, and faces with high surface heterogeneity supported high lichen diversity. Both plant and lichen communities varied widely by transect within and across sampling areas. Recreational rock climbing did not appear to influence community structure, possibly due to low levels of climbing traffic among our survey transects. Nonetheless, we overlapped our vegetative model with a simple spatial model of potential for rock climbing development to highlight specific areas of concern. Our predictive model of vegetative diversity was moderately accurate (ρ = 0.43), suggesting that surveying each cliff individually may be necessary for conservation efforts. In addition, our work indicated that preserving vegetation along the top of cliff faces should remain a focus of conservation efforts.
Fire management plans (FMP) are complex documents that receive little evaluation of whether their objectives are met. We evaluate the Archbold Biological Station (ABS) FMP for goals related to the fire regime (area burned, seasonality, severity, and fire return intervals). The goals include increasing the area burned with prescribed fires, burning more areas during the May–September natural (lightning) fire season, and maintaining variation in fire severity. The ABS FMP is based on the concept of modal fire-return intervals (FRI) for each vegetation type that allow for variation in FRI in space and time. Our analysis uses detailed spatial data (5-m grid) on vegetation, fire extent, and severity. From 1967 to 2014, ABS increased area burned with prescribed fires. Over time, a greater proportion of ABS was burned with lightning-season fires. Burns had variable but mainly high severity. Fire severity varied with vegetation but was consistent over time. Vegetation slated for frequent burns tended to be behind schedule, while rosemary scrub, slated for infrequent fire, was ahead of schedule. The intermediate scrubby flatwoods, which comprise the largest part of the ABS landscape, had a FRI distribution that matched the FMP. The combination of fire mapping, FRI targets, and GIS offers a verifiable and consistent method of tracking fire regime goals in an FMP. We discuss inevitable tradeoffs in managing fire for multiple species and vegetation types over a large landscape and we provide recommendations for FMP monitoring and evaluation that may be broadly applicable to fire-adapted vegetation.
To evaluate the effects of Amur honeysuckle (Lonicera maackii) removal on arthropod abundance and taxon richness, we sampled arthropods in seven removal plots and seven control plots in urban parkland in Louisville, Kentucky, in the first and third years after removal. We found no differences in overall abundance between invaded and removal plots in the first year after management, although removal plots had 12%–16% higher taxon diversity than invaded plots. Three years after management, invaded plots had 46% higher ground-dwelling arthropod abundance and 31% higher taxon richness, partly explained by other shrubs in managed plots. Herbivores were 91% more abundant in removal plots. Our results suggest that honeysuckle removal can have small effects on the entire arthropod community, but an increase in herbivore abundance should be expected following removal of this unpalatable invasive species.
Changes in drilling practices in the oil and gas industry have opened new regions to energy development across much of the United States, including areas that have large holdings of public lands of high conservation value. Using satellite images and GIS techniques, we measured public land use changes in the Fayetteville Shale, a region in north-central Arkansas that has undergone rapid natural gas development in the last 10 years. These public lands showed less development of gas infrastructure compared to the larger gas field, which is mostly privately owned. Gas activities led to less natural forest loss and edge habitat creation in public lands compared to private lands. However, one large public land property (Gulf Mountain Wildlife Management Area) showed much more development compared to the overall gas field (about 20% higher). This disparity was most likely due to differences in regulation and controversial leases that were allowed for this wildlife management area early in the Fayetteville Shale development. These results show that natural gas development can occur around public lands of high conservation value without large land use and habitat impacts, but we suggest such an outcome relies upon effective management practices and wise decision-making by public officials. In the case of Gulf Mountain Wildlife Management Area, strategic well-pad and pipeline placement could have substantially reduced impact to natural areas.
Protected areas have been established under the premise of static distribution of different ecosystems and species, but this assumption is becoming invalid due to climate change. Under non-static conditions, some adaptable nonnative species will enter into protected areas, while some native species will no longer be able to sustain ecological functions. In this case, it is a challenge to determine if species that expand their distribution due to climate change (climate-induced species) should be regarded as “alien species” and be removed or not. We approached the challenge of how to treat climate-induced species in protected areas by conducting a literature survey together with a case study in the largest terrestrial national park in Japan (Daisetsuzan National Park). According to both surveys, there is considerable difference in the attitudes of researchers and practitioners. Practitioners tend to think that climate-induced species should be removed only if they are harmful and realistically removable. Continued discussion on climate-induced species is needed to develop and implement a consistent response.
Exotic African warm-season forage grasses were first introduced into the Americas in the 16th century, and have become invasive in many areas. In Florida, 16 exotic grasses are considered invasive, with the majority originating in Africa and introduced as forages. The high propensity of Africa warm-season grasses to become invasive may be related to the same characteristics that are associated with their value as forages, including adaptability to a wide range of abiotic conditions, rapid establishment, persistence in the environment with minimal husbandry, high productivity under grazing pressure, and adaptation to disturbance. The majority of African warm-season grasses in Florida reproduce vegetatively, a trait known to be associated with invasiveness, and many have been widely planted leading to high propagule pressure and opportunities to invade a variety of niches. In spite of a long history of introduction and promotion in Florida, few African forage grasses are in use today, while many have become invasive. The benefit/cost ratio appears to be tilted in the direction of environmental and economic costs, with minimal benefits. We support newly enacted restrictions on the importation of potentially invasive plants into the USA, and suggest the establishment of a more comprehensive and transparent system for tracking past and future introductions.
A significant portion of world food supply depends on the action of pollinators, which for most crops are primarily domesticated and “wild” bees. Over 75% of pollinator value in the USA accrues through the actions of domesticated honey bees. However, the number of commercial honey bee colonies in the USA has been declining for seven decades due to parasitic arthropods, diseases, and various stresses. The recognition that honey bees, and the crops they service, are vulnerable has accelerated the search for alternative species of bees for pollination of selected crops. Foremost among potential alternatives are native solitary species such as Osmia lignaria propinqua, the “Blue Orchard Bee” (BOB), whose use as a pollinator of almonds, cherries, and apples is increasing. The BOB occurs on public lands managed by the USDA Forest Service, and the USDI Bureau of Land Management and National Park Service. BOBs are targets of “trappers” who place mostly unauthorized “trap-nests” of various designs on public lands. Several problems result from this “Tragedy of the Commons” situation: (1) the unsupervised removal of target bee species from their role in maintaining healthy ecosystems as pollinators of native plants; (2) the removal, as bycatch, of many nontarget species of bees and wasps that also employ trap-nests to rear their progeny; and (3) the shipping of these bees into areas where they do not occur naturally. We argue that unauthorized trap-nesting on public lands should be prohibited and offer several proposals to legalize commercial trap-nesting at a reduced level.