Population size estimates for plant species listed as threatened and endangered under the Endangered Species Act (ESA) are largely speculative. The lack of quantitative methods for assessing species abundance has contributed to ambiguity when assessing the status of ESA-listed species, including recognizing when species may be at an increased risk of extinction or determining when recovery has been achieved. In this paper we describe a sampling-based procedure used to estimate the minimum size of the greater Grand Valley population of the federally threatened Colorado hookless cactus (Sclerocactus glaucus). The estimation procedure applies plant density estimates derived from sampled macroplots to known habitat areas to obtain an estimate of the minimum population size for the entire area of occupation of the taxon. We found that previously reported population size estimates for the species were much lower than those resulting from our sampling-based approach.

Perched sand dunes are ecosystems vulnerable to anthropogenic influence along the Great Lakes, including Grand Sable Dunes in Pictured Rocks National Lakeshore along Lake Superior. Spotted knapweed (Centaurea stoebe) is a nonnative plant species that has colonized these dunes and spread into increasingly more areas of the ecosystem. I conducted plant surveys in areas with and without spotted knapweed in 2003, and then resurveyed those areas in 2018. Frequency of spotted knapweed increased in both areas surveyed. Additionally, dominance shifted with spotted knapweed becoming the most important species in the area originally invaded and third most important in the area originally uninvaded. There were approximately two-thirds of species shared between the two survey years, but many of the added species in 2018 were woody. Species richness increased between years, as did species diversity. Nonmetric multidimensional scaling ordination displayed community shifts as convergent succession. While the plant communities in the two areas were rather dissimilar in 2003, they converged as overlapping communities in 2018. Additionally, the shift between years in the area originally invaded was smaller compared to the shift between years in the area originally uninvaded. Due to the continuous evolution of plant communities within sand dune ecosystems, there is a need to monitor changes and quantify nonnative species spread patterns. Dominance by spotted knapweed may be facilitating dune stabilization and converging communities along a modified successional trajectory.

After the southern part of an old-growth, mesic southern forest dominated by Fagus grandifolia and Acer saccharum in southwestern Michigan, USA, had been clearcut, it was converted to a pasture. In 1919 grazing ceased on the pasture, and it and the old-growth forest to the north were protected as a natural area, later named Warren Woods State Park. At that time the pasture began to develop into a second-growth forest from root and stump sprouts and seeds. In 2014, 2018, and 2019, the tree species composition of the old-growth and second-growth forest was studied to answer the following questions: (1) How, when, and from where did the current species of the second-growth forest arrive? (2) Is there any evidence that the second-growth forest is trending toward the composition of the old-growth forest? (3) If so, what changes are predicted to occur? Data show that the second-growth forest has become a hardwood forest dominated by A. rubrum, Liriodendron tulipifera, Prunus serotina, and Quercus rubra with a subcanopy of A. saccharum and F. grandifolia. Finally, size class frequency distributions of F. grandifolia and A. saccharum, but not of the current canopy dominants, indicate that the second-growth forest may be trending toward the composition and structure of the old-growth forest that preceded it. As it does, tree species richness and diversity will decrease as basal area increases.

Pinus edulis–Juniperus osteosperma (piñon-juniper) woodlands in the southwestern United States are of high conservation value and are threatened by changing climate and increasing frequency of large, severe fires. We followed vegetation development after three recent fires (1989, 1996, and 2000) in Mesa Verde National Park (MEVE). Two types of piñon-juniper vegetation are found in MEVE: sprouting woodlands (SPW), dominated by species that resprout after injury, and obligate seeding woodlands (OSW), dominated by non-sprouting species. SPW stands showed greater resilience than OSW in terms of recovery of pre-fire structure and species composition, and vulnerability to invasion by nonnative plant species. After all three fires, plant cover increased more rapidly in SPW stands; all major pre-fire species were present within 2 y, and fewer nonnative species became established. Plant cover developed more slowly in OSW stands; nonnative plant species proliferated, in places being more abundant than the newly germinating native species. No reestablishment of piñon or juniper trees has been observed. If current trends persist, some portions of the burned SPW may be converted to a persistent shrubland type, while much of the burned OSW may be converted to a persistent, novel herbaceous vegetation type with a large component of nonnative species. Similar changes after fire can be expected in piñon-juniper woodlands like those in MEVE, which are widely distributed throughout the region.

Land trusts play an important role in private land conservation and afford some level of protection to 230,000 km² of land across the United States. In this study, we explored the potential for land trusts to contribute meaningfully to bird conservation. Based on survey responses of 626 land trusts, we found substantial regional variation in conservation strategies, barriers, and habitats protected. Land trusts used easements rather than purchasing land (i.e., fee acquisition) most often in the West (50% easement vs. 25% fee) and least in the Northeast (38% vs. 45%). The types of habitats protected also varied in ways that tracked regional patterns in land use and land cover. Across regions, 31% (Northeast) to 63% (Southeast) of land trusts included a city within service areas, highlighting the role land trusts may play in curbing urban sprawl. Land trusts throughout the United States used similar information sources to guide conservation decisions, with bird conservation plans used most frequently in the West (63%) and least in the Northeast (32%). Although roughly half of land trusts engaged in bird monitoring activities, human and fiscal resources were barriers to 60% or more of land trusts in each region. Overall, our study suggests that land trusts have untapped potential to contribute meaningfully to bird conservation and can benefit from engaging with birdwatchers and bird-focused organizations, monitoring birds on their properties, and pursuing grant opportunities related to bird conservation.

In Pennsylvania Baptisia australis var. australis is found along only four waterways: the Allegheny River, Youghiogheny River, Clarion River, and Red Bank Creek. Because of its limited distribution and small number of extant populations, the species is considered state-threatened in Pennsylvania. In addition, the riparian prairie habitat that Pennsylvania Baptisia australis var. australis is restricted to is also in decline and considered vulnerable. Because of these conservation concerns, insights into the natural history of the taxon in the state is valuable and will inform conservation efforts. Field surveys and fruit collections along the Allegheny River and herbarium collections were used to investigate and document granivory in Pennsylvania Baptisia australis var. australis, a phenomenon recorded in other parts of the species' range, but not previously reported on in Pennsylvania. Using a model of best fit, the number of seeds found in fruit was found to be significantly impacted by the presence of granivores. We also report that visual surveys of fruits in the field are found to be accurate assessments of the presence and potential impact of granivores. In turn, our results will inform the conservation and management of Baptisia australis var. australis populations in Pennsylvania and highlight the importance of field surveys in protecting threatened taxa.

Locating additional occurrences of at-risk species can inform assessments of their status and conservation needs (including potential legal protections). The perennial bearded beaksedge (Rhynchospora crinipes) ranges from Mississippi to North Carolina, but known occurrences are limited. Because of the species' apparent rarity, a model to identify areas with suitable habitat conditions for the species will allow conservationists to effectively prioritize and allocate scarce surveying resources. We used known occurrence records, a suite of environmental datasets, and four species distribution modeling techniques (generalized additive, GAM; maximum entropy, MaxEnt; generalized boosted, GBM; and weighted ensemble) to generate maps to inform surveys for R. crinipes. The ensemble approach improved predictive performance (AUC-PR = 0.95) compared to other techniques (individual model AUC-PR ranged from 0.7 to 0.8). We also obtained quantitative insights on the species' habitat relationships, including the likelihood of R. crinipes's presence near Atlantic white cedar (Chamaecyparis thyoides) habitat and floodplains, which is consistent with prior field observations. The ensemble model indicated that 3.6% of the study area could be suitable habitat, but only 0.38% had high suitability. Small stream riparian habitats and Atlantic swamp forests in Alabama, Florida, and Georgia had the highest proportion of suitable areas. Prioritizing surveys in areas with model-indicated high habitat suitability is expected to reveal additional R. crinipes occurrences. We suggest surveying efforts for other at-risk species may benefit from using an ensemble modeling approach to identify and prioritize survey areas and improve ecological knowledge of these species.

Sandsage prairie is a shrub-steppe ecological system of the Great Plains of North America in which sand sagebrush (Artemisia filifolia) is dominant and diagnostic. An estimated 5 million hectares of sandsage prairie occurs in discontinuous tracts across eight states in association with dune fields and other sandy habitat. This paper documents the biodiversity attributes of sandsage prairie, which is an ecological system of conservation concern due to range-wide declines in areal extent and ecological integrity. Sandsage prairie hosts many regional endemics, ecological specialists, and species of conservation concern at the state and global levels. It is particularly important to avian ecology in the Great Plains, with 14 species of endemic or obligate grassland birds utilizing sandsage prairie for breeding and/or foraging habitat. In many parts of its range, sandsage prairie is the only native vegetation of significant scale remaining on the landscape, providing islands of natural habitat critical to the support and persistence of biological diversity. These attributes make sandsage prairie a biodiversity hotspot for the central and southern Great Plains. Stewardship of sandsage prairie biodiversity requires preventing further loss, fragmentation, and degradation of existing occurrences as well as accommodating or restoring processes that drive the inherent heterogeneity of this unique ecological system.