Katalin Szlavecz

Beyond Urban Legends: An Emerging Framework of Urban Ecology, as Illustrated by the Baltimore Ecosystem Study

ABSTRACT The emerging discipline of urban ecology is shifting focus from ecological processes embedded within cities to integrative studies of large urban areas as biophysical-social complexes. Yet this discipline lacks a theory. Results from the Baltimore Ecosystem Study, part of the Long Term Ecological Research Network, expose new assumptions and test existing assumptions about urban ecosystems. The findings suggest a broader range of structural and functional relationships than is often assumed for urban ecological systems. We address the relationships between social status and awareness of environmental problems, and between race and environmental hazard. We present patterns of species diversity, riparian function, and stream nitrate loading. In addition, we probe the suitability of land-use models, the diversity of soils, and the potential for urban carbon sequestration. Finally, we illustrate lags between social patterns and vegetation, the biogeochemistry of lawns, ecosystem nutrient retention, and social-biophysical feedbacks. These results suggest a framework for a theory of urban ecosystems.

Ecosystem effects of non-native earthworms in Mid-Atlantic deciduous forests

In many mid-Atlantic forests where both native and non-native earthworms exist, it is the non-native species that are the dominant component of the soil macrofauna. Few earthworm ecology studies, however, focus attention on these forest systems in order to determine the relative ecological roles and potential interactions of the native and non-native earthworms. In a series of field samplings and experimental manipulations we collected data on the effects of earthworms on below-and aboveground ecosystem processes. Earthworm abundance and the ecological processes measured were dynamic in space and time across the range of study sites. Leaf litter decay rates doubled at sites that had abundant non-native earthworms. Earthworms also altered the abundance of soil fungi, the activity of extracellular enzymes, soil respiration, and the growth of tree seedlings but the effects varied among sites depending on differences in land-use history and forest age. Red oak seedling growth was less at sites that had abundant earthworms but tulip poplar and red maple seedlings grew equally well with and without abundant earthworms. These preliminary results suggest that non-native earthworms have significant ecosystem effects, even in forests where native earthworms still occur. Land use history, however, plays an important role in determining what those effects will be, and these effects are likely to be dynamic, depending on the abundance of non-native earthworms.

Wireless sensor networks for soil science

Wireless sensor networks can revolutionise soil ecology by providing measurements at temporal and spatial granularities previously impossible. This paper presents our first steps towards fulfilling that goal by developing and deploying two experimental soil monitoring networks at urban forests in Baltimore, MD. The nodes of these networks periodically measure soil moisture and temperature and store the measurements in local memory. Raw measurements are incrementally retrieved by a sensor gateway and persistently stored in a database. The database also stores calibrated versions of the collected data. The measurement database is available to third-party applications through various Web Services interfaces. At a high level, the deployments were successful in exposing high-level variations of soil factors. However, we have encountered a number of challenging technical problems: need for low-level programming at multiple levels, calibration across space and time, and sensor faults. These problems must be addressed before sensor networks can fulfil their potential as high-quality instruments that can be deployed by scientists without major effort or cost.

Belowground competition among invading detritivores

The factors regulating soil animal communities are poorly understood. Current theory favors niche complementarity and facilitation over competition as the primary forms of non-trophic interspecific interaction in soil fauna; however, competition has frequently been suggested as an important community-structuring factor in earthworms, ecosystem engineers that influence belowground processes. To date, direct evidence of competition in earthworms is lacking due to the difficulty inherent in identifying a limiting resource for saprophagous animals. In the present study, we offer the first direct evidence of interspecific competition for food in this dominant soil detritivore group by combining field observations with laboratory mesocosm experiments using 13C and 15N double-enriched leaf litter to track consumption patterns. In our experiments, the Asian invasive species Amynthas hilgendorfi was a dominant competitor for leaf litter against two European species currently invading the temperate deciduous forests in North America. This competitive advantage may account for recent invasion success of A. hilgendorfi in forests with established populations of European species, and we hypothesize that specific phenological differences play an important role in determining the outcome of the belowground competition. In contrast, Eisenoides lonnbergi, a common native species in the Eastern United States, occupied a unique trophic position with limited interactions with other species, which may contribute to its persistence in habitats dominated by invasive species. Furthermore, our results supported neither the hypothesis that facilitation occurs between species of different functional groups nor the hypothesis that species in the same group exhibit functional equivalency in C and N translocation in the soil. We propose that species identity is a more powerful approach to understand earthworm invasion and its impacts on belowground processes.

Ground Beetle (Coleoptera: Carabidae) Assemblages in Organic, No-Till, and Chisel-Till Cropping Systems in Maryland

Abstract Ground beetle assemblages were compared in organic, no-till, and chisel-till cropping systems of the USDA Farming Systems Project in Maryland. The cropping systems consisted of 3-yr rotations of corn (Zea mays L.), soybean (Glycine max L. Merr.), and wheat (Triticum aestivum L.) that were planted to corn and soybean during the 2 yr of field sampling (2001–2002). Each year, ground beetles were sampled using pitfall traps during three 9- to 14-d periods corresponding to spring, summer, and fall. A total of 2,313 specimens, representing 31 species, were collected over the 2 yr of sampling. The eight most common species represented 87% of the total specimens collected and included Scarites quadriceps Chaudoir, Elaphropus anceps (LeConte), Bembidion rapidum (LeConte), Harpalus pensylvanicus (DeGeer), Poecilus chalcites (Say), Clivina impressefrons LeConte, Agonum punctiforme (Say), and Amara aenea (DeGeer). Canonical variates analysis based on the 10 most abundant species showed that the carabid assemblages in the three cropping systems were distinguishable from each other. The organic system was found to be more different from the no-till and chisel-till systems than these two systems were from each other. In 2002, ground beetle relative abundance, measured species richness, and species diversity were greater in the organic than in the chisel-till system. Similar trends were found in 2001, but no significant differences were found in these measurements. Relatively few differences were found between the no-till and chisel-till systems. The estimated species richness of ground beetles based on several common estimators did not show differences among the three cropping systems. The potential use of ground beetles as ecological indicators is discussed.

Biodiversity on the Urban Landscape

This essay, which provides an overview of recent urban biodiversity research, highlights the field’s basic principles by drawing from specific results that have emerged from the Baltimore Ecosystem Study (BES). Because in urban ecosystems, the structure of plant and animal communities are jointly determined by both anthropogenic and natural processes, cities provide an opportune setting to examine general ecological questions concerning community disturbance, patch dynamics, and species invasion. The study of urban habitats also introduces new theoretical questions that are posed by the extreme heterogeneity of the landscape, and the division of land into multiple parcels, each under separate ownership and control. From an applied perspective, urban areas potentially serve as venues for educating the public on the value of biodiversity and for promoting certain species assemblages that are likely to provide ecosystem services and improve the quality of life of nearby human residents. Urban biodiversity researchers face a number of daunting methodological challenges, including (a) the task of integrating community dynamics from the local scale to the regional scale (the metacommunity approach) and (b) clearly isolating evolutionary changes in species that have become adapted to the urban environment.

A global comparison of surface soil characteristics across five cities: a test of the urban ecosystem convergence hypothesis

Abstract As part of the Global Urban Soil Ecology and Education Network and to test the urban ecosystem convergence hypothesis, we report on soil pH, organic carbon (OC), total nitrogen (TN), phosphorus (P), and potassium (K) measured in four soil habitat types (turfgrass, ruderal, remnant, and reference) in five metropolitan areas (Baltimore, Budapest, Helsinki, Lahti, Potchefstroom) across four biomes. We expected the urban soil characteristics to “converge” in comparison to the reference soils. Moreover, we expected cities in biomes with more limiting climatic conditions, or where local factors strongly affect soil characteristics, would exhibit the greatest variance across soil types within and among cities. In addition, soil characteristics related to biogenic factors (OC, TN) would vary the most because of differences in climate and human efforts to overcome limiting environmental conditions. The comparison of soils among and within the five cities suggests that anthropogenic, and to a lesser degree native, factors interact in the development of soils in urban landscapes. In particular, characteristics affected by anthropogenic processes and closely associated with biogenic processes (OC, TN) converged, while characteristics closely associated with parent material (K, P) did not converge, but rather diverged, across all soil habitat types. These results partially supported the urban ecosystem convergence hypothesis in that a convergence occurred for soil characteristics affected by climatic conditions. However, the divergence of K and P was unexpected and warrants adjusting the hypothesis to account for variations in anthropogenic effects (e.g., management) that may occur within soil habitat types impacted by humans.

LUMBRICUS FRIENDI COGNETTI, 1904 A NEW EXOTIC EARTHWORM IN NORTH AMERICA

Abstract Soil fauna of the Baltimore-Washington Metropolitan Area, MD was assessed as part of the Baltimore Ecosystem Study Long Term Ecological Research Site. The majority of earthworm species were European exotics, and one of them Lumbricus friendi Cognetti, 1904 proved to be a new species to the fauna of North America. The species is very similar to L. terrestris, thus a comparative description of the two species is given.

Native and exotic earthworms affect orchid seed loss.

Invasion by non-native earthworms is a world-wide problem. Earthworms affect plants by ingesting seeds and burying them in the soil. Orchids include 10% of the worlds plant species and have some of the smallest seeds, making them particularly vulnerable to earthworm ingestion. We found that earthworms decreased seed viability in the orchid Goodyera pubescens and buried some seeds too deeply for them to form associations with the fungi they require to grow. This leads to loss of approximately 50% of orchid seeds and may slow orchid colonization of forests that are proceeding through succession.

Asian pheretimoid earthworms in North America north of Mexico: An illustrated key to the genera Amynthas , Metaphire , Pithemera , and Polypheretima (Clitellata: Megascolecidae)

The invasion of the pheretimoid earthworms in North America, especially the genera Amynthas and Metaphire, has raised increasing concerns among ecologists and land managers, in turn increasing the need for proper identification. However, the commonly used keys to this group are more than 30 years old with outdated taxonomic information and are based primarily on internal morphology. The requirement of significant amount of taxonomic expertise and dissection, even from the first entry of the key, has prevented broader use of these keys. As a result, many publications in the United States have used Amynthas spp. to represent the group without identifying the species. We present here a new key and diagnoses for the 16 pheretimoid earthworm species recorded in North America north of Mexico, including four genera: Amynthas (10), Metaphire (4), Pithemera (1), and Polypheretima (1). The descriptions were based on published records with modifications following inspection of specimens archived at the National Museum of Natural History, Smithsonian Institution, Washington, D.C. Photos of external and internal characters, including male pores, spermathecal pores, genital markings, spermathecae, prostate glands, and intestinal caeca, are presented to help identification. A summary of current knowledge about the ecology and historical context is provided for each species. We also highlight the previously overlooked and potentially common and widespread co-occurrence of three species-A. agrestis, A. tokioensis, and M. hilgendorfi-and point out that many recent claims of invasion of A. agrestis need to be re-evaluated for potential misidentification.