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Understanding the condition of natural resources in protected areas is fundamental to their management and preservation. Long-term monitoring can provide crucial data for managers to prioritize management actions and subsequently determine their effectiveness. In five national park units in the eastern United States, the National Park Service Inventory and Monitoring Program monitors rare riverscour communities—open habitats in which sun-loving plants grow over rocky substrates along high-gradient streams. Based on a decade of monitoring experience, we present recommendations for monitoring riverscour communities including sampling methodology, data collection methods, and subsequent management actions. Given increasing stressors from changing climate, invasive species, and altered hydrology, understanding how riverscour communities are changing is increasingly important to their protection.
Reed canarygrass (Phalaris arundinacea) is a grass species that can dominate wet meadow plant communities. This study investigated if grazing by cattle on restored wet meadows suppresses reed canarygrass, thereby promoting the restored plant community. This study was conducted at two locations in northwest Minnesota, one managed by The Nature Conservancy (TNC) and the other a Minnesota Board of Water and Soil Resources (BWSR) wetland bank site. Management practices used were a patch-burn grazing treatment on the TNC site and a high-density, short-duration grazing rotation system on the BWSR site. A pretreatment survey of total species canopy coverage was conducted before grazing followed by periodic surveys up to 7 y after grazing started. Both the patch-burn grazing and the grazing rotation system reduced reed canarygrass canopy cover by 49% compared to non-grazed control sites 5–7 y after grazing. With a reduction in reed canary grass canopy coverage due to grazing, the plant community moved toward a community with higher canopy coverage of Carex pellita that met restoration goals. Some of the species change was to grasses like Kentucky bluegrass (Poa pratensis), which is an exotic, invasive grass in prairies. The changed plant community held steady in native plant species richness or had an increase in native plant species richness. This study demonstrates grazing reduces the cover of reed canarygrass, while meeting restoration goals for wet meadows.
Multiflora rose (Rosa multiflora [MFR]) is an invasive, nonnative plant that has invaded many temperate forests across the eastern United States, often outcompeting native plants for sunlight and other resources. Herbicides can control MFR, but they can also reduce nontarget plant species and threaten aquatic ecosystems. In a black cherry-red maple forest in the Erie National Wildlife Refuge in Pennsylvania, the US Fish and Wildlife Service introduced prescribed goat-browsing as an exploratory control method. In four treatments, browsed, browsed/herbicide, cut/herbicide, and an unmanaged reference, we evaluated preliminary effects of these treatments on MFR and non-MFR herbaceous vegetation. For MFR, the browsed treatment had 56% lower leaf/stem mass ratios and 35% shorter stem lengths than the reference; the leaf/stem ratio in the cut/herbicide treatment was 55% lower than the reference. Stem density was not reduced because goats did not kill the MFR plants in this first year of treatment. The herbicide treatment had fewer non-MFR plants than the reference treatment. Light levels at ground level did not differ among the treatments. Overall, 33% of trees in the browsed treatment were affected by the goats, with 9% being completely girdled; red maple and ironwood were the most commonly browsed species. Preliminary results suggest that goats can be an effective control for MFR, however long-term success will be best evaluated after consecutive treatment seasons. Goats may increase tree mortality and shift tree species composition in stands dominated by trees with high browsing rates, but effects on diverse stands may be less pronounced.
Miller's witch-alder (Fothergilla milleri, Hamamelidaceae) is a newly described globally imperiled shrub that is known from disjunct populations in coastal Alabama, the panhandle of Florida, and one location in Georgia. Little is currently known about the natural history or ecology of the species. We conducted inventories of three populations of F. milleri in Alabama and Florida. A total of 3060 ramets were found; 45% were in one subpopulation ≤0.5 ha in area and 79% were in one population within an area of 4.5 ha. Low ramet counts in few locations makes the species particularly vulnerable to extinction due to stochastic events. Also, all seed capsules found within the surveys were infected by an aphid, which is possibly preventing sexual reproduction within the populations. Microsite habitat data indicated F. milleri grows in a unique transitional habitat between upland conifer forest and wetlands. The sites where extant populations of F. milleri inhabit tend to have acidic and well-drained soils with a high sand content. Further, many populations were under thick midstory vegetation. Thus, fire or other forms of removal may be needed to release those subpopulations before they may become shaded out. Lastly, a habitat suitability model was developed to better facilitate conservation efforts. However, only 0.5% of the study area was within the highest level of suitability. Fothergilla milleri is facing multiple threats that could lead to its extirpation from the wild, and direct and intense conservation action may be necessary to ensure F. milleri remains on the landscape.
The introduction of nonnative grazers and plants, as well as alterations to native fire regimes in grassland systems, can directly and indirectly affect the abundance of arthropods. In this study, we used sweep-net sampling at two sites occupied by the critically endangered Florida grasshopper sparrow (Ammodramus savannarum floridanus Mearns) in Osceola County, Florida, to assess how the abundance of all arthropods (orders pooled) and the four most common arthropod orders varied between native dry prairie and semi-improved cattle pasture habitat (2015–2016). We also examined the role of time since fire and fire season on arthropod abundance in both habitat types. The abundance of all arthropods, Hemiptera, Orthoptera, and Coleoptera was higher in pasture than dry prairie, but the mean body length of Orthoptera was smaller in pasture. Fire year and fire season did not affect arthropod abundance when data from both sites were combined. However, when examined separately, Orthoptera at the dry prairie site were more abundant in habitat burned in the current year than previous years, supporting the hypothesis that Florida grasshopper sparrows preferentially select recently burned prairies because they support greater resource availability. Orthoptera at the pasture site showed no significant response to fire year or season. This study is important because it is the first to compare arthropod prey abundance for Florida grasshopper sparrows across dry prairie and pasture habitat and has important implications for prescribed fire management.
Pectis imberbis is an endangered plant found in the Madrean Archipelago ecoregion of southern Arizona. Numerous, potentially interacting stressors, such as drought, shifting fire regimes, invasive species, and grazing by domesticated and wild ungulates, affect this species and region. We used Integral Projection Models (IPMs) to describe dynamics of the largest documented P. imberbis population. While collecting census data, we quantified impacts of species interacting with P. imberbis, including pollinators, Coues deer (Odocoileus virginianus couesi), and co-occurring vegetation, and evaluated their impact on P. imberbis population vital rates. Despite a large overall size (N = 794), the growth rate for this population was below replacement level (λ = 0.9519). Browse by Coues deer negatively impacted demographic vital rates. Woody species and perennial grasses afforded protection against browse, especially for small individuals, but in the absence of browse, coincidence with heterospecific vegetation decreased growth, survival, and reproduction of P. imberbis. We observed 12 taxa of invertebrates interacting with P. imberbis flowers, including native bees, flies, and wasps. Seed production by bagged flowers indicated that flowers are self-compatible. In summary, we detected a unique interplay between deer, which negatively impacted P. imberbis populations via browse, and vegetation, which reduced incidence of browse, while simultaneously depressing P. imberbis vital rates when no browse occurred. Findings suggest that shifts in community dynamics, such as introduction of invasive grasses or fluctuations in deer populations, could impact P. imberbis population trajectories. Management actions, including exclusion of herbivores and removal of invasive grasses, should be considered to aid species recovery.
Midwest oak savannas contain some of the highest plant diversity in the United States and are among the rarest terrestrial ecosystems globally. Consequently, understanding diversity patterns within these ecosystems is important for setting management and restoration goals. This study aimed to understand the role of canopy cover and heterogeneity in canopy cover in influencing plant alpha and beta diversity within oak savanna ecosystems. This study took place in the black oak savannas of the Indiana Dunes along the southern shores of Lake Michigan in NW Indiana, USA. We sampled twenty-nine 1000 m2 plots with gradients in canopy cover and canopy heterogeneity across the Indiana Dunes to examine the influence of canopy cover and canopy heterogeneity on plant diversity. Woody plant alpha diversity was highest in areas with a high canopy cover (>75%). C3 graminoids, C4 graminoids, and sedge alpha diversity were highest in low canopy cover areas (<25%). Forb and legume alpha diversity were highest with low to intermediate canopy cover (25–50% and 20–35%). Overall, plant alpha diversity was highest at intermediate canopy cover. High canopy heterogeneity was associated with high alpha diversity. There was no relationship between canopy cover or canopy heterogeneity with beta diversity. However, beta diversity was exceptionally high within all sites. An average canopy cover of 25–50% is the optimal cover for promoting high plant diversity across many functional groups. Still, low and high canopy cover sites are also important for maximizing diversity of some functional groups. Therefore, we recommend managing oak savannas for 25–50% canopy cover to maximize diversity, but where opportunities exist in large remnants of oak savanna, maintaining some areas with few trees and other areas with closed canopies can maximize diversity on a landscape scale.
We examined natural regeneration changes in an urban natural area forest, the Good Woods, Cobbs Creek Park, Philadelphia, Pennsylvania, after placement of exclusion fencing to prevent white-tailed deer (Odocoileus virginianus) browsing and unplanned North American beaver (Castor canadensis) felling. Seedlings (stem dbh < 2.5 cm, stump at 15 cm < 3.0 cm), saplings (stem dbh > 2.5–10 cm, stump at 15 cm > 3.0–11 cm), and trees (stem dbh > 10 cm, stump at 15 cm > 11 cm) were surveyed in 65 permanent 10 m × 10 m plots: 6 y after fencing placement to exclude white-tailed deer and 5 mo after the start of beaver felling. Overall seedling abundance increased by 5% while sapling populations grew by 20% and the number of trees expanded by 34% after white-tailed deer exclusion. Red maple (Acer rubrum) seedlings, tulip poplar (Liriodendron tulipifera) seedlings, and red oak (Quercus rubra) saplings increased significantly while pignut hickory (Carya glabra) and white ash (Fraxinus americana) seedlings decreased significantly. Seedling and tree losses to North American beaver felling were small (<2% for all seedlings and <3% for all trees). However, beaver felling caused a greater than 60% loss of saplings for red maple, black cherry (Prunus serotina), white oak (Quercus alba), and red oak. Less than 30% of the saplings were lost for pignut hickory, white ash, and tulip poplar. Urban North American beaver preferences for native species saplings paralleled rural beaver in the eastern United States. Our results indicate white-tailed deer exclusion fencing is an effective management method for increasing natural regeneration of both seedlings and saplings in an urban natural area forest when the fencing also effectively excludes North American beaver.
In any natural area, the seasonally changing needs and interactions of each individual species from the microbiota to plants, invertebrates, and vertebrates are largely unknown. Completing individual management plans and actions for every species is patently unachievable. Accepting this complexity and uncertainty, we submit that returning the formative interactions of water, fire, and predation/herbivory are the keys to sustaining habitats for all species, even those for which we have absolutely no data. We also contend that management of the interactions of natural processes that support an entire flora and fauna can be resolved with guidance from “tuning” plant species. Tuning plant species are those most affected when natural processes are altered. Analogous to tuning a violin for the best sound or an engine to run smoothly, tuning plant species guide the adjustment of processes. Tuning plants can teach us how the interactions of natural processes work in ecological systems and give direction for management practices.
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