Effects of Vegetation, Corridor Width and Regional Land Use on Early Successional Birds on Powerline Corridors

Powerline rights-of-way (ROWs) often provide habitat for early successional bird species that have suffered long-term population declines in eastern North America. To determine how the abundance of shrubland birds varies with habitat within ROW corridors and with land use patterns surrounding corridors, we ran Poisson regression models on data from 93 plots on ROWs and compared regression coefficients. We also determined nest success rates on a 1-km stretch of ROW. Seven species of shrubland birds were common in powerline corridors. However, the nest success rates for prairie warbler (Dendroica discolor) and field sparrow (Spizella pusilla) were <21%, which is too low to compensate for estimated annual mortality. Some shrubland bird species were more abundant on narrower ROWs or at sites with lower vegetation or particular types of vegetation, indicating that vegetation management could be refined to favor species of high conservation priority. Also, several species were more abundant in ROWs traversing unfragmented forest than those near residential areas or farmland, indicating that corridors in heavily forested regions may provide better habitat for these species. In the area where we monitored nests, brood parasitism by brown-headed cowbirds (Molothrus ater) occurred more frequently close to a residential area. Although ROWs support dense populations of shrubland birds, those in more heavily developed landscapes may constitute sink habitat. ROWs in extensive forests may contribute more to sustaining populations of early successional birds, and thus may be the best targets for habitat management

The intersection of ecological risk assessment and plant communities: an analysis of Agrostis and Panicum species in the northeastern U.S.

Ecological risk assessments for grass species with novel traits are advisable, or required, in order to identify potential environmental harms prior to large-scale cultivation. Credible risk assessments are built upon knowledge of the communities that could be negatively affected by crop-to-wild gene flow, new weeds, or invasive plants. This study focused on two cultivated grasses with different life histories: the exotic, weedy Agrostis stolonifera (creeping bentgrass) and the native Panicum virgatum (switchgrass). Vascular plant communities were analyzed in 190 transects (50 m) in ten habitat types across two ecoregions (inland and coastal) in the northeastern U. S. Ordination plots and dendrogram analysis showed clustering of inland plant community assemblages within habitat types, while coastal plant communities were similar across the habitats studied. Agrostis and Panicum species had unequal distribution across the habitat types and ecoregions. Agrostis species were more common in the inland ecoregion and habitats receiving moderate management or disturbance events. In both ecoregions, A. stolonifera had high co-occurrence values with other exotic Agrostis species, suggesting potential for interspecific gene flow. P. virgatum was most common in inland roadside and wasteland habitats, but was distributed equally in the three coastal habitats. Co-occurrence between P. virgatum and congenerics was infrequent, although one transect had both P. virgatum and the state-listed coastal species Panicum amarum. This is the first study to characterize Agrostis and Panicum plant communities and distribution providing the basis for ecological risk assessments, coexistence-strategies, and geographic exclusion zones

Coastal eutrophication as a driver of salt marsh loss

Salt marshes are highly productive coastal wetlands that provide important ecosystem services such as storm protection for coastal cities, nutrient removal and carbon sequestration. Despite protective measures, however, worldwide losses of these ecosystems have accelerated in recent decades1. Here we present data from a nine-year whole-ecosystem nutrient-enrichment experiment. Our study demonstrates that nutrient enrichment, a global problem for coastal ecosystems2,3,4, can be a driver of salt marsh loss. We show that nutrient levels commonly associated with coastal eutrophication increased above-ground leaf biomass, decreased the dense, below-ground biomass of bank-stabilizing roots, and increased microbial decomposition of organic matter. Alterations in these key ecosystem properties reduced geomorphic stability, resulting in creek-bank collapse with significant areas of creek-bank marsh converted to unvegetated mud. This pattern of marsh loss parallels observations for anthropogenically nutrient-enriched marshes worldwide, with creek-edge and bay-edge marsh evolving into mudflats and wider creeks5,6,7. Our work suggests that current nutrient loading rates to many coastal ecosystems have overwhelmed the capacity of marshes to remove nitrogen without deleterious effects. Projected increases in nitrogen flux to the coast, related to increased fertilizer use required to feed an expanding human population, may rapidly result in a coastal landscape with less marsh, which would reduce the capacity of coastal regions to provide important ecological and economic services