The relevance of diversity—invasibility studies to the conservation of biodiversity has been questioned on grounds that species-rich assemblages may not deter invasion by competitively superior invaders. Few studies have compared the competitive effects of invaders on native species individually vs. in mixture. Using field experiments, we measured competition between an invasive grass, Microstegium vimineum, and six species of large native groundcover plants. We first examined whether planting six native species was more effective than planting an equivalent number of a single species in competitively suppressing Microstegium. Using a split-plot design, naturally occurring patches of Microstegium were treated with one of the two planting treatments or a control. We monitored Microstegium emergence and percent cover through 2015 and into the spring of 2016. We then tested the competitive effect of Microstegium on plantings of native species within Microstegium patches using a removal experiment in 2016. Although initial transplant survival was high in spring 2015, subsequent mortality during the growing season was also high in both planting treatments and, thus, there was no evidence of competitive suppression of Microstegium. In contrast, removal of Microstegium benefited the growth (and flowering) of native transplants in 2016, and all native species were more or less equally affected. These results suggest that neither high native diversity nor the presence of certain native species is likely to be effective in constraining the abundance of invaders demonstrated to have strong competitive effects on most or all native species under conditions that favor both native diversity and the invader.

Piratebush (Buckleya distichophylla, Santalaceae) is a dioecious, hemi-parasitic shrub endemic to the Blue Ridge Ecoregion of the Appalachian Mountains. The Poor Mountain Natural Area Preserve (PMNAP) in southwestern Virginia protects the densest known population of this rare plant. Permanent transects were set within this natural area to measure population density, size-class structure and health indicators, and to analyze their relationship to ecological parameters. Within PMNAP, there were 9 ± 2 piratebush per 100 m² of forest floor with a mean size of 4 ± 1 stems of 1.9 ± 0.6 cm diameter at ground height. Individual shrubs grew across a broad range of aspects, slopes (2–50%), and canopy cover (0–100%), exhibiting minimal crown death and a wide range of foliar color value. Weighted size class structure distribution was positively skewed, with low indication of recent seedling recruitment. Observed adventitious vegetative regeneration may mask the frequency of genetically distinct individuals, and indicate less genetic diversity within this population. Weighted size class was positively correlated to forest canopy cover (P < 0.001) and southerly aspect (P = 0.071). Foliar color value was positively correlated with canopy openness (P < 0.001) but neither weighted size class nor plant vigor. This study indicates that successful sexual reproduction within this piratebush population may be rare, and establishes a detailed baseline assessment of the largest extant piratebush population, enabling future study of factors relevant to the long-term viability of this species.

Ecological study of cliff environments has steadily increased in the last three decades. However, plant communities on many cliffs have yet to be investigated, and there remains uncertainty about the mechanisms that drive vegetation patterns on cliffs. On the Trapps cliff, a renowned rock-climbing destination within Mohonk Preserve, New York, we recorded tree species and surface micro-topography (“sloping.” “level,” “incut”) along seven rappel transects. In two study areas, we also sampled the ridge and talus areas above and below the cliff transects, and in one of those areas, we included a separate lateral survey along a prominent ledge on the cliff. We used estimated diaspore (seed or fruit) weights and chi-square analyses to test for association between diaspore weight class and topographic categories across the entire study. The cliff tree communities were dominated by mature pitch pine (Pinus rigida) and more frequent but smaller-diameter sweet birch (Betula lenta). Sweet birch, a species with lightweight, wind-dispersed seeds, was disproportionately frequent on the cliff and on sloping surfaces on the cliff, while heavier, gravity-dispersed diaspore species (especially oaks) were underrepresented on the cliff in general, but disproportionately associated with level micro-topography on the cliff. Our results suggest that diaspore weight and associated dispersal mechanisms may play a role in the assembly of cliff tree communities that are divergent from the ridge above, or talus below. Management implications include protecting adjacent plant communities (ridge, talus) that are likely diaspore sources that sustain plant communities on cliffs.

Located southwest of Houston, Texas, the Columbia Bottomlands comprise a significant complex of the bottomland hardwood forest ecosystem. As the largest expanse of forest adjacent to the Gulf of Mexico in Texas, the Columbia Bottomlands are critical stopover and staging habitat for Nearctic—Neotropical migratory landbirds. They have been cleared to less than one-quarter of their historical extent of 283,000 ha. Restoration of bottomland forests has predominantly focused on planting just a few heavy-seeded, mast-producing species, such as oaks (Quercus spp.) and hickories (Carya spp.), but such active restorations often fail to meet management objectives of vertical structural complexity, unevenly aged trees, standing dead snags, and coarse woody debris, and do not adequately develop into quality habitat for birds and other wildlife. This study investigates the potential for passive restoration—colonization via natural dispersal—to restore previously cleared areas of bottomland floodplains. Vegetation surveys were conducted in passively restored second-growth forest of varying ages within the Columbia Bottomlands to quantify the structure and composition of vegetation regrowth, and compared to a nearby old-growth stand. At 18–20 y old, the Dance Bayou Site resembled a young forest with open areas of dense vines. At approximately 50–72 y old, the Sweeny Site had characteristics of a mature forest, with vertical structural complexity, unevenly aged trees, standing snags, coarse woody debris, and a greater richness of woody plant species than a nearby old-growth stand. The passively restored sites adequately recruited heavy-seeded species. Passive reforestation has great potential in the Columbia Bottomlands.

After decades of fire suppression in eastern North America, land managers now are prioritizing prescribed fire as a management tool to restore or maintain fire-adapted vegetation communities. However, in long—fire-suppressed landscapes, such as the central and southern Appalachians, it is unknown how bats will respond to prescribed fire in both riparian and upland forest habitats. To address these concerns, we conducted zero-crossing acoustic surveys of bat activity in burned, unburned, riparian, and non-riparian areas in the central Appalachians, Virginia, USA. Burn and riparian variables had model support (ΔAICc < 4) to explain activity of all bat species. Nonetheless, parameter estimates for these conditions were small and confidence intervals overlapped zero for all species, indicating effect sizes were marginal. Our results suggest that bats respond to fire differently between upland and riparian forest habitats, but overall, large landscape-level prescribed fire has a slightly positive to neutral impact on all bats species identified at our study site post—fire application.

In support of natural resource agencies in Canada, the United States, and Mexico, we report on a series of component analyses and an updated Landscape Conservation Design for temperate grassland conservation. We targeted 12 major grassland ecosystem types that occur across the Great Plains and Chihuahuan Desert regions. Component analyses included (1) documenting long-term trends in extent by grassland type, (2) identifying species of concern associated with the major grassland types, (3) documenting current protected areas including each grassland type, (4) assessing landscape intactness and connectivity among grassland areas, and (5) identifying Grassland Potential Conservation Areas (GPCAs) to advance grassland conservation. Most severe declines in grassland extent have occurred in tallgrass prairie types, followed by mixed-grass, shortgrass, and semi-desert grasslands. Similar trends by type were documented for landscape intactness and connectivity. Some 174 species of vertebrates, invertebrates, and plants considered by NatureServe as critically imperiled, imperiled, or vulnerable are strongly associated with these grassland types, and 103 are listed under protective legislation in one or more countries. Just 1.2% of historic extent for all types combined is currently found within designated protected areas. A total of 177 GPCAs were identified to represent grassland type diversity in areas least likely to conflict with other land uses. Within identified GPCAs, type-specific representation varied from a low of just 1% of historic extent for Texas Blackland Tallgrass Prairie to a high of 27% for Western Great Plains Sand Prairie. Combined across all 12 grassland types, 15% of historic extent is represented.

“The genetic memory of complex ecosystems that has evolved over millennia does not adapt well to changing management styles, varied objectives, nor different organizational philosophies.”

Adopted from Dr. Gerould Wilhelm, Conservation Design Forum