Decomposition of urban atmospheric carbon in Sonoran Desert soils

Urban atmospheres can have high concentrations of particulate organic carbon (oC) but the rate and fate oC deposition in near-urban ecosystems are rarely quantified. We collected atmospheric particulate matter in Phoenix, AZ and applied these samples to Sonoran Desert soils in a series of laboratory incubation experiments. The addition of fine particulate matter (<2.5 μm aerodynamic diameter) increased microbial respiration in soils collected from the interspaces between desert shrubs. The increase in soil respiration was equivalent to 25% to 30% of the added oC. In contrast, we did not detect increases in respiration when coarse particulate matter (>2.5 μm aerodynamic diameter) was added to interspace soils, suggesting that coarse particulate oC is recalcitrant to microbial decomposition. Due to comparatively higher background levels of C mineralization, we rarely detected changes in microbial respiration when fine or coarse particulate oC was added to soils collected beneath shrub canopies. We measured total atmospheric C concentrations within and surrounding Phoenix and, using inferential methods, estimated rates of deposition that ranged from 0.02 to 0.58 mg C m⁻² d⁻¹ for fine particles and from 0 to 6.15 mg C m⁻² d⁻¹ for coarse particles. Results show that fine atmospheric particulate matter deposited at low rates downwind of Phoenix is a labile oC substrate for soil heterotrophs. In contrast, oC deposited at higher rates as coarse particulate matter may accumulate in soils due to slow microbial decomposition rates.     

Decomposition of tree leaf litter on pavement: implications for urban water quality

Leaf litter may be an important source of nutrients to stormwater and ultimately contribute to eutrophication of surface waters associated with urbanization. Thus, understanding decomposition and nutrient release from leaf litter that falls on impervious surfaces is important for stormwater management. However, few studies have examined leaf litter decomposition in the unique urban environment of the street gutter. We compared decomposition of leaf litter of five street tree species in a parking lot gutter in St. Paul, Minnesota, USA. In contrast to our expectations, comparisons with past studies revealed that litter decomposed more rapidly in the gutter than in nearby natural areas. And decomposition rates were as rapid as those measured in other urban settings (forests and streams), with most species losing 80 % of their initial mass after 1 year. Litter of most species had retained more than half of its initial N and P after 1 year. However, in contrast to N, litter P dynamics largely were uncoupled from litter mass dynamics, with litter P increasing and decreasing unpredictably over the year. Short-term (24 h) laboratory studies revealed that litter had the potential to lose a high fraction of its initial P, with high variation among species (from 27 to 88 %), and a smaller fraction of its initial N (<10 %) via leaching. Thus, street tree species may differ in their potential contributions to nutrients that are released during decomposition. Our results suggest that careful selection of street tree species and timely removal of litterfall have significant potential to reduce nutrient fluxes from streets to storm drains, particularly for P.     

Bird and butterfly communities associated with two types of urban riparian areas

We examined the distribution of birds and butterflies at two types of urban riparian areas in the metropolitan area of Denver, Colorado, USA. The sites consisted of relatively natural areas containing native woody vegetation, and those that had been highly modified with trees and shrubs removed and planted with lawn grass. Species richness of both butterflies and birds differed significantly between the two types of sites. Species richness, however, was not significantly correlated between birds and butterflies. Bird abundance was similar between site types but consisted of two assemblages. Brewer's blackbirds, common grackles, bank swallows, and mourning doves were abundant at wooded sites while American robins, European starlings, house sparrows, house finches, and mallards were more abundant at lawned riparian sites. Butterfly abundance was less at lawned sites. This contrast in bird and butterfly response to habitats suggests they respond to different habitats in distinct ways. Both taxon groups, however, were important discriminators between habitat types. Overall, butterfly and bird species richness was 44% less at highly modified riparian sites.     

Contrasting effects of urban habitat complexity on metabolic functional diversity and composition of litter and soil bacterial communities

Functional diversity and composition of soil bacterial communities affect important soil biogeochemical processes. In natural and semi-natural ecosystems, variations in habitat complexity have been shown to significantly impact both litter and soil bacterial communities. However, this remains largely untested in urban ecosystems, where human management can lead to habitat complexity combinations unobserved in rural ecosystems. We established 10 research plots in low-complexity park, high-complexity park, and high-complexity remnant habitat types (n = 30) in Melbourne, Australia. The use of organic carbon substrates by soil and litter bacteria was measured using EcoPlates to investigate the effects of habitat complexity upon metabolic functional diversity and functional composition of bacterial communities of i) soil and ii) one-year old litter. Direct and indirect effects of habitat complexity, microclimate and decomposition status upon litter microbial functional diversity and composition were also modelled using path analysis. Soil bacterial communities had significantly higher functional diversity compared to litter bacterial communities, but no significant effect of habitat complexity was apparent. The functional composition of soil bacterial communities was not affected by habitat complexity. In contrast, the functional composition of litter bacterial communities in high complexity parks and remnants was significantly different from that in low-complexity parks. The functional composition of litter bacterial communities, but not their diversity, was directly affected by habitat complexity and microclimate as well as their indirect effects upon the decomposition status of litter. Human management of urban habitat complexity can alter the functional composition of litter and soil bacterial communities without affecting their functional diversity. While this can have significant impacts on bacteria-regulated processes and ecosystem services, it also suggests that urban bacterial communities might be able to adjust to further environmental and climatic changes affecting urban ecosystems.     

Being involved in the country: Productive ageing in different types of rural communities

Productive ageing recognises the contribution of older people to economic, social and cultural growth and helps build a sustainable community. Being involved in community life is good for individuals and good for society. However, we know very little about the participation of and contribution by people aged 50 and over in rural communities. This research aimed to develop a better understanding of productive ageing in different types of communities in rural Victoria, Australia. An anonymous self-complete postal questionnaire was distributed to a sample of households in twenty rural communities using the Australia Post Unaddressed Select Service. Those householders 50 years of age and older were invited to complete the survey. Data collected allowed examination of social and civic engagement, familiarity with community, the value placed on social relations by people aged 50 years and over, and how community involvement was linked to community sustainability. In particular it attempts to address the question ‘Does social and civic engagement differ across declining, stable and growing rural communities?’ Despite differences among rural communities, this study showed that older people develop and maintain strong community connections and well-functioning social capital and that participation in social activities was associated with feelings of being connected with community. It also identified health issues and lack of options as the main constraints on participation. A key message for policy makers is that older people play an important role in the sustainability of rural communities. There is much to be gained from actively supporting their participation in activities that are connected to ageing well.     

Trampling tolerance of understorey vegetation in different hemiboreal urban forest site types in Finland

The effects of trampling on the understorey vegetation were studied in boreal urban forests of different fertility in the greater Helsinki area, Finland. The three studied forest types in decreasing order of fertility were: 1) herb-rich heath forest, 2) mesic heath forest, and 3) sub-xeric heath forest. We inventoried the cover percentages of understorey vegetation in 40 herb-rich, 75 mesic and 40 sub-xeric biotopes located in 51 urban forests varying in size (0.6–502 ha). Cover percentages were compared to those of untrampled reference areas. In our study, trampling tolerance increased with increasing fertility of the forest type. Wear of understorey vegetation correlated positively with the number of residents (i.e. recreational pressure) around the forest patch. In general, understorey vegetation cover in all three forest types was lower than in the same forest types in untrampled reference areas. Ground layer cover in urban forests was less than half of that in reference areas. Mosses, lichens, and dwarf shrubs, especially Vaccinium vitis-idaea, proved to be sensitive to trampling and consequently decreased in cover. The cover of tree saplings, mainly Sorbus aucuparia, and some resilient herbs increased.     

Woody plant communities along urban,suburban, and rural streams in Louisville,Kentucky, USA

Anthropogenic changes in land use and cover (LULC) in stream catchments can alter the composition of riparian plant communities, which can affect ecosystem functions of riparian areas and streams from local to landscape scales. We conducted a study to determine if woody plant species composition and abundance along headwater streams were correlated with categorical and continuous LULC and environmental variables along an urban-to-rural gradient. These variables were calculated at different spatial scales (subcatchment level and within 0.5 and 1 km radii of plots) and used % impervious surface cover (ISC) and finer scale LULC classification levels to determine their ability to explain species composition, diversity, abundance, non-native provenance and wetland indicator status of four plant strata—canopy tree, tree sapling, tree seedling and shrub. At all scales, we found distinct riparian woody communities within land-use categories, with significant differences among shrub species. Fine-scale land-cover variables correlated with species composition of shrub, tree sapling and tree seedling strata, but not the canopy tree stratum. Celtis occidentalis and Acer negundo were ubiquitous but dominated riparian areas surrounded by development, while Asimina triloba was associated with forested rural riparian banks. Non-native shrubs, Lonicera maackii and Euonymus alatus, were indicative of areas surrounded by development, while the native shrub, Lindera benzoin, was associated with deciduous forest. Negative factor-ceiling relationships between canopy tree, sapling and tree seedling densities and % ISC were found, with abrupt declines above approximately 30 % ISC. Facultative wetland shrubs were not found above 30 % ISC. Streambank height, which was strongly negatively correlated with depth to the water table and positively correlated with cumulative catchment area, was negatively correlated with facultative wetland tree and shrub species. In addition, riparian tree sapling and seedling densities declined as the abundance of Lonicera maackii increased.     

城市社区文化建设的发展思路

社区作为城市中的基层组织,它的文化建设水平在一定程度上反映着城市的文化发展水平.社区文化是一种地域性的群众文化形态,它的文化行为的构成体现了社区居民的价值观、文化传统、社会心态以及审美情趣.搞好社区文化建设,有利于提高居民的精神境界,满足居民的精神需求,提高居民的文化素质,增强城市的综合竞争力,为经济发展和社会进步提供精神动力和智力支持,使城市快速持久地发展下去.     

Reporting and founding of child neglect in urban and rural communities

The community context in which child abuse and neglect takes place may influence both reporting and outcomes of investigations into such incidents. This study examines and contrasts urban versus rural community perceptions of neglect by lay citizens and protective service workers.     

Accumulation of deicing salts in soils in an urban environment

Examining rates of deicing salt accumulation and leaching in urban soils is important for understanding the distribution and movement of salt in the environment. We examined autumn concentrations of deicing salts in soils in a moderately dense urban landscape in eastern New York State. The study area contrasted to the isolated, rural highways examined in previous studies. While NaCl was the most abundantly applied salt, Mg²⁺ (apparently from MgCl₂, a secondary deicing salt) was the most abundant salt cation in soils. Moderate Na⁺ levels, and equivalent concentrations at depth and in surface samples, indicate that leaching of Na⁺ is rapid in this system. Leaching may ameliorate toxicity for land plants but accelerate inputs to aquatic systems. In contrast to rural highway studies, where salt levels declined rapidly with distance to pavement, Na⁺ remained elevated at the maximum distance measured. Airborne salt dispersal and dense networks of pavement likely contribute to widespread elevated salt levels. This semi-urban setting had salt levels high enough to be toxic to terrestrial plants and soil protozoa. Even moderate levels of development can have dramatic effects on salt inputs into soils and aquatic systems.

Health maintenance antecedents among older citizens in rural and urban communities

The evidence is clear that rural older people in most nations are less physically healthy than their urban counterparts. Research suggests that such differences may be due more to lifestyle characteristics, biological factors and environmental conditions than to access to, or utilization of, medical services. Utilizing a statewide sample of Idaho residents this study compares the characteristics of those people associated with a disease prevention/health maintenance model and those associated with the medical or disease oriented model. Results show some clear differences in characteristics between people utilizing the two models of health care.     

Vegetation composition and structure of woody plant communities along urban interstate corridors in Louisville,KY, U.S.A.

Urban forests adjacent to interstate corridors are understudied ecosystems across cities. Despite their small area, these forests may be strategically located to provide large ecosystem services due to their ability to act as a barrier against air pollutants and noise as well as to provide flood control. The woody vegetation composition and structure of forests adjacent to urban interstates is an important determinant of their ability to provide these services. However, these forest communities may be particularly susceptible to the introduction of exotic invasive species via the interstate and the surrounding city that can potentially alter current and future forest composition. The purpose of this study was to investigate the distribution of native and exotic woody vegetation and tree regeneration in forests along three interstate corridors in Louisville, KY, and to determine potential factors (e.g., traffic density) that are correlated with patterns in the woody vegetation community. We found the most important determinants of vegetation composition along these interstate corridors were the distance from the city center and the presence of an exotic invasive shrub, Amur honeysuckle (Lonicera maackii). Compared with forested plots within 10 km of the city center, plots further from the city center had 81% lower stem density of Amur honeysuckle, 96% higher tree seedling regeneration, and 51% greater woody plant species richness. The primarily native species composition of adult trees in forests alongside urban interstates in Louisville and the regeneration of native tree species provide optimism that these forests can maintain native species while experiencing multiple impacts from the interstate as well as from the surrounding city, emphasizing their important potential for maintaining natural forest functions across the urban landscape.     

The genesis,classification, and mapping of soils in urban areas

This paper discusses the concept of soil in both urban and rural environments, and along the urban-rural land use gradient, to illustrate the obvious need to increase our understanding of urban soils. Spatial variability of the urban landscape is illustrated with "Soil series - Urban land complexes" from Baltimore County, Maryland. The World Reference Base for Soil Resources (ISSS-ISRIC-FAO, 1994) proposed Anthrosol and Regosol major soil groups are discussed to show modern approaches to soil classification and to illustrate how the classification of urban soils is essentially undeveloped. Models of soil genesis help identify the processes and functions of the soil system. A conceptual model using Jenny's (1941) state factor approach for human impact on soil formation details the "anthroposequence." The benchmark anthroposequence model may be applied to studying soil systems along urban-rural land use gradients. The process of "anthropedogenesis" is supported to quantify the role of human activity in changing the "natural" direction of soil formation. Future directions of soil research in the urban landscape should involve large scale soil mapping (e.g. 1:6000), benchmark anthroposequences, improved soil classification, and refined characterization of the role of human activities in soil formation.     

Structural landscape changes in urban and peri-urban agricultural systems of two West African cities and their relations to ecosystem services provided by woody plant communities

Urban Ecosystems - High urbanization pressure in Sub-Saharan Africa led to changes in the composition and configuration of rural and peri-urban agricultural production systems and to the...     

Urban Morphology types and open space distribution in urban core areas

Urban cores are primarily associated with economic activity: they are places where people live, work and engage in a range of leisure activities. Natural elements within the environment are recognised as having an important role in promoting quality of life. An investigation into the urban character of Manchester City Centre (UK) combining an analysis of the surface cover with the mapping of urban morphology types (UMTs) shows the extent to which green space permeates the built matrix. Around 20% of the urban core was covered by evapotranspiring surfaces. UMTs were differentiated along axes which were characterised by the intensity of grassland management and the density of building. The results presented here contribute to the on going debate around the development of cities and the relationship between the natural and built environments and provide guidance for those challenged with designing these environments.     

Three categories of urban green areas and the effect of their different management on the communities of ants,spiders and harvestmen

Urban green areas have become an important tool for biodiversity conservation in cities. However, land use and the different management practices applied to these areas determine their effectiveness as biodiversity refuges within cities. In our study, we compare the biodiversity of three bioindicator groups of arthropods (ants, spiders and harvestmen) found in eleven urban green sites in Warsaw (Poland). The studied sites represent three categories of management: botanical gardens, public parks and urban woodlands. Our aim was to determine the effect of the type of management (as urban green categories) on arthropod communities in urban areas.

     

Habitat origins and microhabitat preferences of urban plant species

Urban vegetation is commonly described as dominated by weedy species that are adapted to human disturbance. In this study, we determined the original (pre-agriculture) habitats of urban plant species sampled quantitatively in the spontaneous vegetation of a university campus in Halifax, Nova Scotia (eastern Canada). We sampled 11 distinct patch types corresponding to different built forms. Differences in vegetation among patch types were related in part to environmental variables such as soil moisture and light availability. The urban vegetation was dominated by species from rocky habitats such as cliffs and talus slopes, with lesser representation from grassland and floodplain habitats. When compared to a null model of species origins based on the global area and species richness of different original habitats, species from rock outcrops and grassland habitats were overrepresented in the urban vegetation. These results contrast with the received view that cities represented highly “unnatural” ecosystems: built form appears to replicate the habitat templates required by rock outcrop species. Urban ecological theory should incorporate the replication of habitat analogs by built forms in addition to the creation of ecologically novel habitats.     

Forest structure and anthropogenic disturbances regulate plant invasion in urban forests

Urban forest ecosystems, the structure, and functions therein are subjected to anthropogenic disturbances. Native and sensitive species from those forests might be lost due to such disturbances. At the same time, supplemented anthropogenic resources might create opportunities for exotic and invasive species. Although invasive species are considered one of the major threats to the urban biodiversity and ecosystems, the research on invasion dynamics in the Himalayas has primarily focused on the impacts of invasion on forest structure and productivity. This study aims to understand the influence of forest structure and anthropogenic factors in invasion success that are poorly covered in the existing literature. We selected 11 urban forest patches for the study considering the presence-absence of selected invasive species and structural attributes. We used Principal Component Analysis (PCA) to reduce co-linearity in the covariates and generalized linear mixed effects model (GLMM) to identify the factors affecting invasion success. We found that forest structural attributes, namely, tree diameter, height and canopy cover, and anthropogenic disturbances regulate invasion success in urban forests. This implies that maintaining urban forest structural attributes, especially the stands with large-sized trees, is essential to control invasion in the context of urbanization.