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The article presents a study which measures nitrate leaching and soil:atmosphere nitrous oxide flux in urban forests and grasslands in the Baltimore, Maryland metropolitan area. It states that the study aims to measure variation in nitrate leaching and nitrous oxide flux from different components of the urban landscape under a range of climatic conditions, and to understand the ecosystem properties controlling this variation. It notes that the transition of forests to urban grasslands increased nitrate leaching in Maryland from 20% to 170%, but the increase in urban grasslands have probably reduced nitrate leaching in the region over the past few decades.

Abstract: Forests embedded in an urban matrix are a useful venue for investigating the effects of multiple factors such as climate change, altered disturbance regimes and species invasions on forest ecosystems. Urban forests also represent a significant land area, with potentially important effects on landscape and regional scale nitrogen (N) and carbon (C) storage and flux. We measured forest community composition, litterfall, leaf area index, soil chemical properties, in situ net N mineralization and nitrification, soil and soil solution inorganic N pools, and soil:atmosphere fluxes of nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) in eight forest stands that differed in their exposure to urban atmospheric conditions and natural soil conditions (high versus low fertility). Our objectives were (1) to compare the influence of urban land use context and natural soil controls on forest composition and C and N cycling processes and (2) to evaluate the importance of “natural” N cycle processes relative to anthropogenic N fluxes in the urban landscape. Forest productivity and N cycling varied more with soil type than with proximity to urban land use, while forest composition and soil:atmosphere fluxes of CO2 and CH4 were more strongly influenced by exposure to an urban land use matrix and atmosphere. The magnitude of natural processes was important in the context of urban and suburban landscapes, i.e. production of, and annual variation in, inorganic N in forest patches was large relative to watershed-scale atmospheric deposition, fertilizer use and food/sewage fluxes that have been measured in other studies in these study landscapes. [Copyright &y& Elsevier]

The article features a study on carbon storage in soil in urban areas in the United States. Data available from measurements in Baltimore, Maryland are used to assess intercity variability of soil organic carbon (SOC) pools of six cities including Atlanta, Baltimore, Boston, Chicago, Oakland, and Syracuse. The net effect of urban land use conversion on SOC pools for the cities were calculated. The National Land Cover Database was used to extrapolate total SOC pools for each of the lower 48 US states and a comparison of these totals with aboveground totals of carbon storage by trees was done. The city analysis showed the importance of accounting for soils beneath impervious surfaces and in remnant patches of native vegetation.

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. [ABSTRACT FROM AUTHOR]

• Diverse soil habitats are an important component of urban green space heterogeneity. • High diversity of soil fauna reflects a variety of land covers and management types. • Mites and springtails showed similar trends along a disturbance gradient. Urbanization fundamentally alters soil physiochemical properties, but little is known on how this human effect alters soil biota. Microarthropods are important bioindicators due to their sedentary life form and sensitivity to environmental changes. Taxonomic richness, abundance, diversity, distribution of microarthropod communities were investigated in three urban land use types, remnant forests, low maintenance grass, highly disturbed open spaces, and were compared to deciduous forest stands outside the city, that served as reference. In general, habitats with more disturbed soil decreased the diversity of mites and springtails compared to the native vegetation sites. The leaf litter layer both in reference and remnant forests benefited the microarthropods through providing food resources and favorable habitats. Among soil properties soil organic carbon and bulk density had significant effects on mites (Acarina), while for springtails (Collembola), soil pH and soil moisture were significant factors. Soil temperature was the common significant constrained variable for both mites and springtails. Our study highlighted the effects of anthropogenic activities, especially that of soil disturbance in cities and the importance of retaining natural vegetation patches in urban green spaces. [ABSTRACT FROM AUTHOR]