Wayne C. Zipperer

Ecosystem processes along an urban-to-rural gradient

In order to understand the effect of urban development on the functioning of forest ecosystems during the past decade we have been studying red oak stands located on similar soil along an urban-rural gradient running from New York City ro rural Litchfield County, Connecticut. This paper summarizes the results of this work. Field measurements, controlled laboratory experiments, and reciprocal transplants documented soil pollution, soil hydrophobicity, litter decomposition rates, total soil carbon, potential nitrogen mineralization, nitrification, fungal biomass, and earthworm populations in forests along the 140 × 20 km study transect. The results revealed a complex urban-rural environmental gradient. The urban forests exhibit unique ecosystem structure and function in relation to the suburban and rural forest stands; these are likely linked to stresses of the urban environment such as air pollution, which has also resulted in elevated levels of heavy metals in the soil, the positive effects of the heat island phenomenon, and the presence of earthworms. The data suggest a working model to guide mechanistic work on the ecology of forests along urban-to-rural gradients, and for comparison of different metropolitan areas.

Coupling biogeochemical cycles in urban environments: ecosystem services, green solutions, and misconceptions

Urban green space is purported to offset greenhouse-gas (GHG) emissions, remove air and water pollutants, cool local climate, and improve public health. To use these services, municipalities have focused efforts on designing and implementing ecosystem-services-based “green infrastructure” in urban environments. In some cases the environmental benefits of this infrastructure have been well documented, but they are often unclear, unquantified, and/or outweighed by potential costs. Quantifying biogeochemical processes in urban green infrastructure can improve our understanding of urban ecosystem services and disservices (negative or unintended consequences) resulting from designed urban green spaces. Here we propose a framework to integrate biogeochemical processes into designing, implementing, and evaluating the net effectiveness of green infrastructure, and provide examples for GHG mitigation, stormwater runoff mitigation, and improvements in air quality and health.

Down by the riverside: urban riparian ecology

Riparian areas are hotspots of interactions between plants, soil, water, microbes, and people. While urban land use change has been shown to have dramatic effects on watershed hydrology, there has been surprisingly little analysis of its effects on riparian areas. Here we examine the ecology of urban riparian zones, focusing on work done in the Baltimore Ecosystem Study, a component of the US National Science Foundation’s Long Term Ecological Research network. Research in the Baltimore study has addressed how changes in hydrology associated with urbanization create riparian “hydrologic drought” by lowering water tables, which in turn alters soil, vegetation, and microbial processes. We analyze the nature of past and current human interactions with riparian ecosystems, and review other urban ecosystem studies to show how our observations mirror those in other cities.

THE APPLICATION OF ECOLOGICAL PRINCIPLES TO URBAN AND URBANIZING LANDSCAPES

gene sequencers through advanced computers and networking to global-observing satellites-coupled with keen scientific curiosity present an opportunity for unprecedented advances. Together, we can make ecological science a mainstay of sustainability. While pursuing that goal, we need to ensure that our best efforts are made available to society along the way. The time of science remaining in its ivory tower is long gone. And, ecological science is at the center of so many of the major crises affecting the planet todaydeforestation, biodiversity loss, land degradation, fisheries decline, coastal pollution, climate change. As scientists, we have a special responsibility not just to increase our understanding of these issues, but also to assess and predict, help evaluate, and, in turn, support decision makers and society at large in averting worst-

Urban tree cover: an ecological perspective

Analysis of urban tree cover is generally limited to inventories of tree structure and composition on public lands. This approach provided valuable information for resource management. However, it does not account for all tree cover within an urban landscape, thus providing insufficient information on ecological patterns and processes. We propose evaluating tree cover for an entire urban area that is based on patch dynamics. Treed patches are classified by their origin, structure, and management intensity. A patch approach enables ecologists to evaluate ecological patterns and processes for the entire urban landscape and to examine how social patterns influence these ecological patterns and processes.

Adopting a modern ecological view of the metropolitan landscape: the case of a greenspace system for the New York City region

Abstract Concern about environmental quality and the long-term livability of urban areas is now a driving paradigm for planning professionals. Although a modern ecological framework exists, inappropriate or outdated concepts continue to be used in the context of land-use decision making. These classical concepts emphasize a static view of the landscape and focus on short term planing of single sites. The modern framework emphasizes a dynamic view of a biologically rich urban environment with a focus on interactions among multiple sites across temporal scales. We summarize this framework by presenting five key ecological principles—content, context, dynamics, heterogeneity and hierarchy—and use the New York City Metropolitan Area as a case study to illustrate how these principles might be applied to achieve specific planning goals. We additionally use the case study as reference in providing some guidelines to more effectively incorporate the modern ecological framework in future planning.

Deforestation patterns and their effects on forest patches

Five identifiable patterns of deforestation are recognized - internal, indentation, cropping, fragmentation, and removal - and each has a distinct effect on habitat quality of forest patches in the eastern United States. By overlaying land use maps from 1973 and 1981 for three counties in the State of Maryland (Prince Georges, Anne Arundel, and Wicomico), changes in the interior core area and edge length of individual patches were measured. Forest interior declined by 23.8 km2 in Anne Arundel, 16.3 km2 in Prince Georges, and 8.4 km2 in Wicomico. Within Anne Arundel and Prince Georges Counties, deforestation increased edge length by 52.1 km and 31.2 km, respectively, whereas, within Wicomico, it decreased edge length by 8.7 km. Differences among counties resulted from current land use patterns, percentage of forest cover, and the dominant deforestation pattern.

Methods for spatial and temporal land use and land cover assessment for urban ecosystems and application in the greater Baltimore-Chesapeake region

Understanding contemporary urban landscapes requires multiple sets of spatially and temporally compatible data that can integrate historical land use patterns and disturbances to land cover. This paper presents three principal methods: (1) core analysis; (2) historic mapping; and (3) gradient analysis, to link spatial and temporal data for urban ecosystems and applies their use in the Baltimore-Chesapeake region. Paleoecological evidence derived from the geochronology of sediment cores provides data on long-term as well as recent changes in vegetative land cover. This information, combined with contemporary vegetation maps, provides a baseline for conducting trend analyses to evaluate urbanization of the landscape. A 200-year historical land use database created from historical maps, census data, and remotely sensed data provides a spatial framework for investigating human impacts on the region. A geographic information system (GIS) integrates core analyses with historic data on land use change to yield a comprehensive land use and land cover framework and rates of change. These data resources establish the regional foundation for investigating the ecological components of an urban ecosystem. Urban-rural gradient analyses and patch analyses are proposed as the most appropriate methods for studying the urban ecosystem as they link ecological and social patterns and processes for varying degrees of urbanization.

Species composition and structure of regenerated and remnant forest patches within an urban landscape

Regenerated and remnant forest patches were inventoried in Syracuse, New York, USA to determine differences in structure, species composition, human disturbances, and landscape context. Patches had similar mean stem diameter, total stem density, and total basal areas, but differed with respect to diameter distribution, disturbance regime, landscape context, and occurrence of introduced species. In regenerated patches, 23 introduced species were inventoried and they accounted for 48% of relative density. In remnant patches, only seven introduced species were inventoried and they accounted for 17% of the relative density. Cluster analyses identified two community types for remnant patches—sugar maple and black oak—and three for regenerated patches—sugar maple, Norway maple, and boxelder. For remnant patches, Rhamnus cathartica dominated the small diameter class in the black oak cluster, and Acer saccharum dominated the small diameter class in the sugar maple cluster. For regenerated patches, introduced species—A. platanoides and R. cathartica—dominated the small diameter class in the Norway cluster, and a mixture of native and introduced species—A. negundo, R. cathartica, A. saccharum, and Rhus typhina—dominated the small diameter classes in the sugar maple and boxelder clusters. Functionally, land covers containing remnant and regenerated patches, such as vacant lots and greenspaces, had the highest net rate of carbon sequestration (848.7 mt/ha/yr).

Testing and classification of individual plants for fire behaviour: plant selection for the wildland–urban interface

Knowledge of how species differ in their flammability characteristics is needed to develop more reliable lists of plants recommended for landscaping homes in the wildland-urban interface (WUI). As indicated by conflicting advice in such lists, such characterisation is not without difficulties and disagreements. The flammability of vegetation is often described as having four components (ignitability, combustibility, sustainability and consumability). No standards or generally recognised test procedures exist for evaluating these components in plants. Some measurements of flammability include times for ignition, rate of flame spread, flame height and heat release rate. Often, the fire behaviour characteristics of a plant are derived from its physical and chemical characteristics. Thermogravimetric analysis and other thermal analyses of ground samples have long been used to characterise the thermal degradation of vegetation. More recently, researchers have used the oxygen consumption methodology to measure the heat released due to combustion of the vegetation. Although oxygen consumption calorimetry is an improvement in characterising plant flammability, translation of laboratory results to field conditions can be problematic and tests can be expensive.