Canopy precipitation interception in urban forests in relation to stand structure

Urban forests provide important ecosystem services. In terms of hydrological benefits, forest ecosystems in urban environments represent qualitative and quantitative filter for rainwater. We quantified the canopy interception in relation to urban forest stand structure and rainfall intensity in an urban transect of the mixed (upland) forest in the city centre, towards a riparian pine forest and a floodplain hardwood forest in the City of Ljubljana, Slovenia. Bulk precipitation in open areas and throughfall were measured with fixed rainfall collectors in each forest. Stemflow was estimated from a review of relevant literature. We found that canopy interception in selected urban forests was mainly affected by tree species composition and other stand structure variables, such as canopy cover and tree dimensions. Average annual canopy interception was highest in the mixed forest (18.0% of bulk precipitation), while the riparian pine forest had the lowest level (3.9% of bulk precipitation) and the floodplain hardwood forest had the intermediate level for interception (7.1% of bulk precipitation). The mixed forest exhibited the stand structure factors that contributed to the highest canopy interception among the studied forests: high assemblage of dominant coniferous trees, denser canopy cover and the highest growing stock. Furthermore, rainfall intensity has proven to be an important factor for the seasonal partitioning (comparing the leafed and leafless period) of canopy interception. A better understanding of precipitation interception processes in urban forests is needed to assist urban forest managing and planning, aiming at maximizing canopy interception for the mitigation of stormwater runoff and flooding in urbanized watershed.     

Learning about restoration of urban ecosystems: a case study integrating public participation,stormwater management,and ecological research

Restoration of ecosystem functions in urban environments is made challenging by 1) a public that often lacks understanding of ecological principles, 2) inadequate evidence of the effectiveness of restoration practices, and 3) difficulty integrating social and biophysical factors in studies of urban ecosystems. This paper describes a case study in which potential solutions to these challenges were explored. We facilitated collaborative learning through public participation in the design and implementation of an urban riparian buffer along a headwater stream in a neighborhood park, a process that was informed by ecological research. Learning outcomes were evaluated using surveys and qualitative assessment of discussion. Results indicated that participants’ knowledge about water quality problems associated with urbanization, stormwater, and nonpoint-source pollution increased, familiarity with stormwater management practices increased, and perceptions about the importance of stream ecosystem functions changed. In-stream monitoring of sediment delivery, as well as direct measurements of buffer infiltration capacity, provided early evidence of buffer effectiveness in prevention of sediment inputs to the stream and absorption of runoff from surrounding surfaces. This study provides a useful model for integration of collaborative learning through participation, ecological restoration, and ecological research in an urban setting. Elements deemed essential to success of this model included an opportunity for dialog focused on a specific natural feature, sustained interaction between participants and researchers, opportunities for hands-on participation by urban residents, and flexibility in restoration practice installation.     

Ecosystem services assessment of the urban forests of Addis Ababa,Ethiopia

Addis Ababa is a highland city with varied topography and landscape features. The mountains that surround the city are covered with urban forest of different types. These forests are providing various ecosystem services for the urban and peri-urban population of the city. Apart from surface temperature regulating function of the green spaces of Addis Ababa, no quantitative assessment of the carbon sequestration and soil protection ecosystem services provided by the urban forest has been conducted to date. The aim of this study was to assess selected ecosystem services such as carbon storage potential, habitat support and soil erosion protection provided by different categories of urban forest of Addis Ababa. The result showed that carbon density in the study area varied with forest categories viz. 293tons/ha, 142tons/ha and 132tons/ha in the dense, medium and open forest types respectively. The Shannon-Wiener diversity index is3.24 for Junipers dominated forest, 2.98 for mixed forest and 2.76 for Eucalyptus dominated forest. The formation of soil erosion features is significantly different among the Eucalyptus forest, Juniperus forest and Mixed forest where high incidence of soil erosion was recorded in the Eucalyptus forest. Therefore, irrespective of the environmental factors such as slope, aspect and elevation differences, there is an association between Eucalyptus forest cover and high soil erosion features. To ensure sustainable supply of ecosystem services and maintain a balanced urban environment, all green spaces in the city should be ecologically networked and diversified. Therefore, assessment of ecosystem services provided essential information for effective planning of the green space in terms of species composition and interconnectivity.     

Urban and wildland herpetofauna communities and riparian microhabitats along the Salt River, Arizona

Metropolitan areas are continually expanding, resulting in increasing impacts on ecosystems. Worldwide, riverine floodplains are among the most endangered landscapes and are often the focus of restoration activities. Amphibians and reptiles have valuable ecological roles in ecosystems, and promoting their abundance and diversity when rehabilitating riparian systems can contribute to reestablishing degraded ecosystem functions. We evaluated the herpetofauna community by measuring abundance, richness, diversity, and species-habitat relations along three reaches (wildland, urban rehabilitated, and urban disturbed reaches) varying in degree of urbanization and rehabilitation along the Salt River in central Arizona. We performed visual surveys for herpetofauna and quantified riparian microhabitat along eight transects per reach. The wildland reach had the greatest herpetofauna species richness and diversity, and had similar abundance compared to the urban rehabilitated reach. The urban disturbed reach had the lowest herpetofauna abundance and species richness, and had a similar diversity compared to the urban rehabilitated reach. Principal Component Analysis reduced 21 microhabitat variables to five factors which described habitat differences among reaches. Vegetation structural complexity, vegetation species richness, densities of Prosopis (mesquite), Salix (willow), Populus (cottonwood), and animal burrow density had a positive correlation with at least one herpetofauna community parameter, and had a positive correlation with abundance of at least one lizard species. Rehabilitation activities positively influenced herpetofauna abundance and species richness; whereas, urbanization negatively influenced herpetofauna diversity. Based on herpetofauna-microhabitat associations, we recommend urban natural resource managers increase vegetation structural complexity and woody debris to improve herpetofauna habitat when rehabilitating degraded riparian systems.     

Urban channel incision and stream flow subsidies have contrasting effects on the water status of riparian trees

The water relations of riparian trees are often closely tied to stream hydrology and channel morphology, which can be altered by urban development. In regions with limited precipitation, urban water use can generate or augment dry-season stream flows, potentially providing a water subsidy to riparian trees. However, urbanization is also associated with high storm flows that cause stream channel incision, or downcutting, which could limit the effect of flow subsidies by lowering riparian water tables. We investigated the effects of urban dry-season flow subsidies and stream channel incision on the water status of streamside trees in Sacramento, California, which has a Mediterranean climate with a distinct and lengthy dry season. For two common facultative riparian species, Quercus lobata (valley oak) and Fraxinus latifolia (Oregon ash), we analyzed both midday stem water potential (Ψ_stem) measurements and leaf carbon isotope signatures (?¹³C) to determine whether channel incision and dry-season flow had interacting effects on seasonal midday water stress and longer-term water use efficiency. We found that stream flow could substantially reduce dry-season water stress in both tree species, but only at low levels of channel incision. Leaf ?¹³C signatures for Q. lobata suggested increased water use efficiency in trees growing along incised streams and those lacking dry-season flow. Urban management decisions that affect both dry-season base flows and channel incision can thus influence the growth and health of riparian trees, potentially leading to broader changes in riparian ecosystems.

     

Evaluating the distribution of invasive woody vegetation around riparian corridors in relation to land use

Invasive species have been causing important and irreversible impacts to native species and communities of ecosystems. They distort ecosystem functions by degrading forest lands, wetlands, and agricultural habitats and replace the native vegetation and reduce biodiversity, forest productivity, and suitable wildlife habitat. To address disturbances caused by invasive species occurrence, further information is needed regarding the occurrence, extent, and dispersal of invasive species and how land use may increase the spread of these species. The objective of this study was to find the frequency and dominance of three invasive species common to riparian areas of east Alabama: Ligustrum sinense (Chinese privet), Elaeagnus pungens (silverthorn), and Triadica sebifera (Chinese tallow tree). Surveys of these species in riparian forests in and around Auburn, Alabama were conducted to show the relative extent of these shrubs and their relation to urban land use. It was expected to see the highest levels of invasive species in the city center with decreasing levels radiating outward into rural areas. Another objective was how urban land use may affect the presence-absence and prevalence of these non-native plant species within study sites. The results showed that around the city center and suburban lands, cover of both Chinese privet and silverthorn tended to increase. In contrast, Chinese tallow tree density percent cover showed an opposite trend with landscapes close to city center often having slightly less cover. This study shows that urban land use may be an important association with distribution of invasive plant species.     

The urban watershed continuum: evolving spatial and temporal dimensions

Urban ecosystems are constantly evolving, and they are expected to change in both space and time with active management or degradation. An urban watershed continuum framework recognizes a continuum of engineered and natural hydrologic flowpaths that expands hydrologic networks in ways that are seldom considered. It recognizes that the nature of hydrologic connectivity influences downstream fluxes and transformations of carbon, contaminants, energy, and nutrients across 4 space and time dimensions. Specifically, it proposes that (1) first order streams are largely replaced by urban infrastructure (e.g. storm drains, ditches, gutters, pipes) longitudinally and laterally within watersheds, (2) there is extensive longitudinal and lateral modification of organic carbon and nutrient retention in engineered headwaters (3) there are longitudinal downstream pulses in material and energy exports that are amplified by interactive land-use and hydrologic variability, (4) there are vertical interactions between leaky pipes and ground water that influence stream solute transport, (5) the urban watershed continuum is a transformer and transporter of materials and energy based on hydrologic residence times, and (6) temporally, there is an evolution of biogeochemical cycles and ecosystem functions as land use and urban infrastructure change over time. We provide examples from the Baltimore Ecosystem Study Long-Term Ecological (LTER) site along 4 spatiotemporal dimensions. Long-term monitoring indicates that engineered headwaters increase downstream subsidies of nitrate, phosphate, sulfate, carbon, and metals compared with undeveloped headwaters. There are increased longitudinal transformations of carbon and nitrogen from suburban headwaters to more urbanized receiving waters. Hydrologic connectivity along the vertical dimension between ground water and leaky pipes from Baltimore??s aging infrastructure elevates stream solute concentrations. Across time, there has been increased headwater stream burial, evolving stormwater management, and long-term salinization of Baltimore??s drinking water supply. Overall, an urban watershed continuum framework proposes testable hypotheses of how transport/transformation of materials and energy vary along a continuum of engineered and natural hydrologic flowpaths in space and time. Given interest in transitioning from sanitary to sustainable cities, it is necessary to recognize the evolving relationship between infrastructure and ecosystem function along the urban watershed continuum.     

Pond age and riparian zone proximity influence anuran occupancy of urban retention ponds

Urbanization is widespread throughout the United States and negatively affects many wildlife populations. However, certain urban features, such as retention ponds, may provide habitat for some species, such as amphibians. This study examines the influence of riparian zone proximity and pond age on retention pond occupancy by anurans. We identified and estimated the age of 25 retention ponds near Charlotte, North Carolina, USA and used a geographic information system to determine the distance to the nearest riparian zone. Occupancy modeling indicated that anuran presence decreased with increasing distance to riparian zone. Pond age also appeared to be an important factor, but the effect varied among species. Although the results of this study demonstrate the potential value of retention ponds to anurans, it is important to be conservative in estimating the ability of these ponds to sustain amphibian populations in urbanized regions.     

Vegetation structure along urban ephemeral streams in southeastern Arizona

Riparian areas in Arizona are being encroached upon by urban developments. This study investigated the impacts of different urban housing densities on riparian vegetation structure along ephemeral streams. Nine sites representing three levels of housing density were selected within the town of Marana, located in southeast Arizona. The housing densities were categorized as high (7–8 houses ha^?1), moderate (2.5–4.5 houses ha^?1), and low (< 1.5 houses ha^?1). Each treatment had three replications. The urban developments were relatively young (less than 15 years). No significant differences were found among the treatments for the tree variables (density, height, mean canopy volume and total canopy volume) or the herbaceous vegetation variables (species richness, percentage of introduced species and percentage of ground cover). However, the shrub variables (mean density, mean height, mean canopy volume, total canopy volume and species richness) showed some significant differences. Shrub density and species richness was significantly greater adjacent to ephemeral channels than just three meters upland. In addition, whitethorn acacia shrubs were significantly taller and larger adjacent to the stream channels in the high and moderate housing density sites than in the low housing density sites. Creosote shrubs showed the opposite trend. Increased runoff in the more heavily urbanized streams may have promoted the growth of the facultative riparian species (whitethorn acacia) but not the non-riparian species (creosote). Overall, in these young developments, vegetation was resilient across the levels of urbanization explored in the study.     

Provincial and cosmopolitan: floristic composition of a dryland urban river

High rates of intercontinental exchange of plant species have caused scientists to ask whether floristic areas with similar environments are undergoing global homogenization. We focused on riparian forests of the urban Salt River (Sonoran Desert, USA) to ask: (1) Is the forest dominated by cosmopolitan or provincial elements? (2) Which trees planted in the irrigated cityscape have established along the river? (3) Which types of restoration interventions have favored provincial species? We surveyed tree abundance, size and vigor in belt transects among five reaches that differed in degree of restoration, and obtained data on tree species composition of the urban landscape and pre-development riparian zone. Our results reveal the urban riparian forest to have many cosmopolitan elements, owing in part to spillover of trees from the cultivated cityscape (e.g., Acacia stenophylla, Vitex agnus-castus). Global spread of some regional (Neotropical) riparian taxa (e.g., Parkinsonia aculeata, Prosopis) also has contributed to the cosmopolitan status. Yet, the forests retain a distinct regional signature. Unintentional restoration of winter floods has allowed for regeneration of Salix gooddingii, a vernally-adapted provincial pioneer, although its long-term survivorship is restricted to limited micro-sites (storm drain outfalls). Urbanization-related changes in stream hydrogeomorphology explain increases in some regional species (e.g., Washingtonia spp.) that historically were excluded from the river.

Reaches restored by planting, weeding, watering, and geocountouring had the greatest abundance of provincial species and greatest floristic similarity to historic conditions.

     

Feeding,growth, and trophic position of redbreast sunfish (Lepomis auritus) in watersheds of differing land cover in the lower Piedmont,USA

One pervasive outcome in the urbanization of an ecosystem is the proliferation and numerical dominance of select tolerant organisms that are often native to the system yet with reduced relative abundances in less-disturbed conditions. As a result of high variation in environmental conditions between urbanized and non-urbanized systems, it is possible that the functional role of a ubiquitous organism is context dependent. Such is the case for redbreast sunfish (Lepomis auritus) in small streams in many parts of the Piedmont of the southeastern USA. To investigate this hypothesis, we evaluated the feeding, growth, and trophic position of redbreast sunfish in 3 streams of increasing levels of watershed urbanization (forested, suburban, urban) in the Lower Piedmont of western Georgia, USA. Through gut contents analysis, we found that sunfish consumed primarily Chironomidae (Diptera) larvae across all streams. However, fish in the suburban stream consumed more terrestrial prey than fish in the forest and urban streams, which corresponded to lower aquatic prey abundances in the suburban stream. Although there was no difference in mean fish age among streams, otolith analysis revealed that fish in the urban stream were larger at age than those in the forest stream. Last, stable isotope analysis revealed that fish in the urban stream occupied a lower trophic position than the other 2 streams. These results suggest that despite the fact that the primary prey resource was similar for sunfish in each stream, their potential functional role, as evidenced by size at age and trophic position, is context dependent.

     

Invasive weeds in urban riparian zones: the influence of catchment imperviousness and soil chemistry across an urbanization gradient

The riparian zones of urban waterways are frequently degraded by weed invasions. This study examined the effects of different levels of catchment imperviousness, as a surrogate for the extent and intensity of urbanisation, on invasive weeds and soil physical and chemical attributes. The study was conducted adjacent to waterways in the partly urbanised Georges River catchment in south western Sydney. Vegetation and soil sampling was undertaken in the riparian zone of 10 freshwater streams in non-urban (low imperviousness), peri-urban (moderate imperviousness) and urban (high imperviousness) sub-catchments. Soil samples were tested for a suite of physical and chemical properties (moisture, bulk density, organic matter, pH, salinity, phosphorus, potassium and calcium). Increased levels of sub-catchment imperviousness and urbanisation were associated with higher weed coverage and elevated soil geochemical attributes. One of the most interesting findings in this study was that urban soil calcium concentrations were over 2000 times greater than soils collected from non-urban catchments. The BIOENV procedure identified soil pH, salinity, calcium, organic matter, moisture and catchment imperviousness to be important environmental factors associated with variation in riparian vegetation. The single factor of soil pH was most highly correlated with variations in riparian vegetation. Soil pH was approximately 1.5 units higher in urban compared to non-urban riparian soils. We speculate that there is a link between urban concrete materials, urban soil and water contaminants and riparian weed invasion. We also recommend further study into the contribution of urban concrete materials on the geochemical contamination of riparian soils.     

Ecological integrity in urban forests

Ecological integrity has been an umbrella concept guiding ecosystem management for several decades. Though plenty of definitions of ecological integrity exist, the concept is best understood through related concepts, chiefly, ecosystem health, biodiversity, native species, stressors, resilience and self-maintenance. Discussions on how ecological integrity may be relevant to complex human-nature ecosystems, besides those set aside for conservation, are growing in number. In the case of urban forests, no significant effort has yet been made to address the holistic concept of ecological integrity for the urban forest system. Preliminary connections between goals such as increasing tree health, maintaining canopy cover, and reducing anthropogenic stressors and the general notion of integrity exist. However, other related concepts, such as increasing biodiversity, the planting of native species, and the full meaning of ecosystem health beyond merely tree health have not been addressed profoundly as contributors to urban forest integrity. Meanwhile, other concepts such as resilience to change and self-maintenance are not addressed explicitly. In this paper we reveal two camps of interpretation of ecological integrity for urban forests that in turn rely on a particular definition of the urban forest ecosystem and a set of urban forest values. Convergence and integration of these values is necessary to bring a constructive frame of interpretation of ecological integrity to guide urban forest management into the future.     

Some simple tools for communicating the biophysical condition of urban rivers to support decision making in relation to river restoration

This paper illustrates a set of simple tools that may be used to assess and communicate the biophysical condition of river and riparian habitat in urban catchments. The tools are based upon information collected using the Urban River Survey (URS), a habitat survey designed for application to 500?m stretches of urban river corridor, and comprise (i) a series of aggregate indices, (ii) three classifications relating to the materials, habitat and vegetation characteristics of urban river stretches, which contribute to an overall score, the Stretch Habitat Quality Index (SHQI), and (iii) two environmental gradients which define a URS matrix of engineering:habitat associations. This toolkit may be used to gather and exchange knowledge about urban river habitat quality to a wide range of specialist or non-technical stakeholders and local community members. It may be used to provide information at the catchment and reach scales to support stakeholder discussions and decision making relating to initial site selection for restoration works; to post project appraisal; and to track changes in river character across space and through time. Example applications of the tools are provided using URS surveys undertaken on tributaries of the River Thames within London in comparison with an archive of previous surveys from three other urban river systems. These tools are being validated in London as part of a larger interdisciplinary research project that is testing the suitability of this type of approach in the context of the London Rivers Action Plan, Water Framework Directive, and urban green space regeneration.     

Southern two-lined salamanders in urbanizing watersheds

Forested riparian buffers are an increasingly common method of mitigating the negative effects of impervious surface cover on water quality and wildlife habitat. We sampled larval southern two-lined salamanders (Eurycea cirrigera) in 43 streams, representing the range of impervious surface cover and forested riparian buffer width across Wake County, NC, USA. Larval abundance decreased with increasing impervious surface cover in the upstream catchment, but was not affected by buffer width. This is likely a result of an incomplete buffer system and culverts or other breaches along streams. Larval abundance increased with detritus cover in the stream to a threshold and then decreased as detritus continued to increase. As percent pebble substrate in the stream increased, especially in perennial streams, larval salamander abundance also increased. We suspect salamanders were unable to migrate with the water column during dry periods in intermittent streams with sedimented interstices below the surface, resulting in low abundances. A combination of increased peak flows and sedimentation, reduced base flow, and chemical changes likely reduces the abundance of salamanders in urban and suburban streams. We suggest creation of catchment-wide, unbreached buffers to maintain the integrity of stream habitats in urbanizing watersheds.     

Ichthyofauna diet changes in response to urbanization: the case of upper Paranapanema River basin (Brazil)

Alterations in stream environments can alter fish food availability, but there is little research data related to the impacts of urbanization on fish diets in tropical streams. Thus, we sought to compare the diet of ten fish species in urbanized and non-urbanized streams reaches. Fish stomach contents were obtained for four urban and five non-urban stream reaches from two medium-sized cities. We verified the similarity of diet composition from urbanized/non-urbanized streams. In-stream features mainly related to the substrate highlighted a perturbation gradient: gravel, pebbles and cobbles were associated to the wider urban reaches while silt were representative in the narrow pools from non-urban streams. Fishes changed their diet in response to urban and non-urban treatments. Omnivorous fishes consumed more detritus and Chironomidae and less terrestrial adult insects in urban reaches, while invertivorous fish consumed more terrestrial adult insects and Trichoptera larvae in the non-urbanized stream reaches. Although the management of the physical structure of streams in Brazil has been basically focused on riparian reforestation, our results suggest that a restoration plan for urban streams cannot be limited to reforestation of its surroundings, but also need to consider the physical structure of the channel, especially the substrate, which contributes to promote in-stream variability.     

Local and landscape drivers of arthropod abundance,richness, and trophic composition in urban habitats

Urban green spaces, such as forest fragments, vacant lots, and community gardens, are increasingly highlighted as biodiversity refuges and are of growing interest to conservation. At the same time, the burgeoning urban garden movement partially seeks to ameliorate problems of food security. Arthropods link these two issues (conservation and food security) given their abundance, diversity, and role as providers of ecosystem services like pollination and pest control. Many previous studies of urban arthropods focused on a single taxon (e.g. order or family), and examined either local habitat drivers or effects of landscape characteristics. In contrast, we examined both local and landscape drivers of community patterns, and examined differences in abundance, richness, and trophic structure of arthropod communities in urban forest fragments, vacant lots, and community gardens. We sampled ground-foraging arthropods, collected data on 24 local habitat features (e.g., vegetation, ground cover, concrete), and examined land-cover types within 2 km of 12 study sites in Toledo, Ohio. We found that abundance and richness of urban arthropods differed by habitat type and that richness of ants and spiders, in particular, varied among lots, gardens, and forests. Several local and landscape factors correlated with changes in abundance, richness, and trophic composition of arthropods, and different factors were important for specific arthropod groups. Overwhelmingly, local factors were the predominant (80 % of interactions) driver of arthropods in this urban environment. These results indicate that park managers and gardeners alike may be able to manage forests and gardens to promote biodiversity of desired organisms and potentially improve ecosystem services within the urban landscape.     

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.     

Conifer growth and reproduction in urban forest fragments: Predictors of future responses to global change?

Global change has a large and growing influence on forests, particularly in urban and urbanizing areas. Compared to rural forests, urban forests may experience warmer temperatures, higher CO₂ levels, and greater nitrogen deposition, with exacerbated differences at urban forest edges. Thus, comparing urban to rural forests may help predict future effects of global change on forests. We focused on the conifer western red-cedar (Thuja plicata) to test three hypotheses: at urban forest edges, relative to rural forests and urban forest centers, trees experience 1) higher temperatures and nitrogen levels, 2) lower seedling recruitment, and 3) greater growth. We additionally tested anecdotal reports that 4) tree seedling recruitment in urban and rural forests is much lower than in ??pristine?? old-growth forests. To test these hypotheses, we quantified air temperature, soil nitrate, adult T. plicata growth and seedling recruitment in five urban and three rural parks at both forest edges and centers. We also quantified T. plicata recruitment at five old-growth ??pristine?? sites. Temperatures were highest at urban forest edges, and soil nitrate was highest in urban forests. In urban relative to rural forests, we observed greater T. plicata growth, but no difference in seedling densities. However, seedling densities were lower in urban and rural forests than in old-growth forests. In all, our results suggest urban influences enhance adult T. plicata growth, but not seedling recruitment. Recruitment in urban and rural forests was reduced compared to old-growth forests, implying that fragmentation and logging reduce T. plicata seedling recruitment.     

Temporally stable and distinct fish assemblages between stream and earthen stormwater drain reaches in an urban watershed

Streams and rivers have essential roles in landscape connectivity; however, urban watersheds are frequently modified to drain stormwater from urban areas. To determine whether an earthen stormwater drain in an urban landscape provides fish habitat temporally, we compared the fish assemblage among three reaches of a contiguous urbanized watershed in Kanata, Ontario, Canada. Watts Creek is connected to an earthen municipal surface stormwater drain (herein Kizell Drain), before discharging into the Ottawa River. We delineated transects in three reaches of the system, in Watts, in the Drain, and below their confluence (Main) and assessed the fish community using single-pass electrofishing repeated across eight months covering all seasons. Fish community composition was compared among reaches using non-metric multidimensional scaling (NMDS) and permutated multivariate analyses of variance (perMANOVA). Sign association tests identified indicator species driving assemblage patterns among reaches. Redundancy analysis (RDA) was used to assess the influence of physical characteristics of the transects on fish assemblage structure. Finally, fish assemblage measures were separated by month and temporal comparisons of fish assemblage were performed with NMDS and perMANOVA. Over the year, fish assemblages were distinct among the three reaches, and appear to be significantly influenced by temperature, undercut banks, and riparian vegetation type. Biotic homogenization in the Drain can be attributed to degraded physical features associated with channel modification in stormwater drains. Despite management and jurisdictional differences between streams and stormwater drains, evidence that earthen stormwater drains can maintain fish assemblages temporally demonstrates their biological potential and need to be considered as interconnected fish habitat elements within the overall watershed.