Showing papers by "Peter S. White published in 2018"

Testing the effects of four urbanization filters on forest plant taxonomic, functional, and phylogenetic diversity.

Abstract: Ongoing urban development has significant effects on ecosystems, including changes to land cover, environmental conditions, and species' distributions. These various impacts may have opposing or interacting effects on plant communities, making it difficult to predict how plant biodiversity will respond to urban development. A frequently cited conceptual framework predicts how urban development influences plant taxonomic, functional, and phylogenetic diversity by simplifying multiple coincident effects of urbanization into four primary filters of biodiversity: habitat transformation, fragmentation, the urban environment, and human preferences. Each filter prevents some plant species from persisting in urban areas while promoting others, but species introductions according to human preferences are expected to cause a net increase in biodiversity while the other filters limit diversity. In this study, we used structural equation modeling to test these predictions and examine the relative importance of each filter on the taxonomic, functional, and phylogenetic diversity of riparian forest plant species sampled along an urban-to-rural gradient in the Research Triangle area of North Carolina. Most diversity measures declined with urbanization, but some (e.g., functional Rao's Q) increased with urbanization. We found support for some of the predicted relationships between urbanization filters and biodiversity, as well as some unexpected relationships, including positive effects of urban environments. Overall, urban environments and human preferences were stronger predictors than habitat transformation and fragmentation. Our approach could be used to test a general framework predicting the effects of urbanization on plant diversity across multiple cities and contribute to a more synthetic understanding of urban biodiversity.

Nativity and seed dispersal mode influence species’ responses to habitat connectivity and urban environments

Abstract: Aim Urbanization alters local environmental conditions and the ability of species to disperse between remnant habitat patches within the urban matrix. Nonetheless, despite the ongoing growth of urban areas worldwide, few studies have investigated the relative importance of dispersal and local environmental conditions for influencing species composition within urban and suburban landscapes. Here, we explore this question using spatial patterns of plant species composition. Location The Research Triangle area, which includes the cities of Raleigh, Durham, Chapel Hill and Cary, in central North Carolina, USA. Time period 2012–2014. Major taxa studied Vascular plants. Methods We sampled riparian forest plant communities along an urban‐to‐rural gradient and used redundancy analysis to identify predictors of species composition patterns for groups of species categorized by nativity and seed dispersal mode. We first compared the ability of different models of habitat connectivity (least‐cost paths that avoided urban land cover versus Euclidean and along‐stream distance) to explain spatial patterns of species composition. We then partitioned the variation in species composition explained by habitat connectivity models, local environmental conditions and measures of urbanization in the surrounding landscape. Results We found that several groups of native species were best explained by least‐cost path models that avoided urban development, suggesting that urbanization impedes dispersal within this landscape, particularly for short‐dispersed species. Environmental variables related to urbanization (e.g., temperature, stream incision) were important predictors of species composition for many species groups, but measures of urbanization in the surrounding landscape were more important for exotic than for native species. Main conclusions Our results demonstrate that urbanization influences plant species composition via its effects on both habitat connectivity and environmental conditions. However, the strength of these effects varies somewhat predictably across seed dispersal modes and between native and exotic species. These results highlight the importance of landscape‐scale planning for urban conservation. Read the full article in Global Ecology and Biogeography [1]. Associated SESYNC Researcher(s): blopez [2] DOI for citing: https://doi.org/10.1111/geb.12760 Source URL: https://www.sesync.org/nativity-and-seed-dispersal-mode-influence-species-responses-to-habitat-connectivity-and-urb an Links [1] https://onlinelibrary.wiley.com/doi/abs/10.1111/geb.12760 [2] https://www.sesync.org/users/blopez

Old-Growth Forests in the Southern Appalachians: Dynamics and Conservation Frameworks

Abstract: In the southern Appalachian Mountains, compositions, structures, and dynamics of forest communities vary across steep topographic gradients, such as elevation and slope aspect, position on slope, steepness, and slope shape (Whittaker 1956). For instance, in mesic sites, the forest transitions across elevations from lower elevation cove hardwoods and hemlock forests to higher elevation northern hardwoods and, where the mountains surpass approximately 1,680 meters, spruce-fir forests. At mid and low elevations, cove forests on protected sites transition to oak-dominated forests on drier soils and finally to pine and xeric hardwood forests on exposed south- to west-facing sites. Despite a long history of human influence, remnant old-growth forests have survived across these landscape gradients and now comprise, in aggregate, one of the largest totals for old-growth acreage in eastern North America (Davis 1996).

Senatorial epistolography from cicero to sidonius: emergence of a genre

Abstract: Although Cicero's letter collections were known and read throughout antiquity, traces of his influence on the style of later letter writers and on the organization of their epistolary collections seem to diminish steadily. What remains constant in the extant collections of Cicero, Pliny, Fronto, Symmachus, and Sidonius is the large number of correspondents represented, the preponderance of letters from the period of the writer's highest prestige, and the subject matter of the letters published, which highlights the familial and wider social connections of the writers and their political, financial, and literary interests. All five collections project the ethos and values of a senatorial class.