The comparative effects of three Sedum species on green roof stormwater retention

Green roofs are typically dominated by Sedum species because they can tolerate hot, xeric environments. However, due to their high water use efficiency, some have questioned the selection of these species for stormwater management. We investigated (1) how three common Sedum species contribute to overall stormwater retention efficiency by green roofs in the mid-Atlantic region, and (2) whether species-specific differences in water use could be explained by morphological and physiological characteristics. Water use and CO2 exchange were continuously monitored in growth chamber studies under increasing drought stress for S. album, and S. kamtschaticum, two species known to variably cycle between CAM and C3 metabolisms. Under fall temperature conditions, S. kamtschaticum had gas exchange rates akin to C3 photosynthesis and used 35% more water compared to S. album. Interestingly, S. album conserved water and had malic acid accumulation confirming CAM metabolism for the duration of the experiment, even under well-watered conditions. In field studies, sixteen replicate green roof platforms (n=4 per species) were planted with S. album, S. kamtschaticum, S. sexangulare, or left unplanted during summer 2010. The platforms were monitored intensively for canopy growth, leaf area, root biomass, substrate moisture and runoff for two years (2011 and 2012). Plant treatment effects on stormwater runoff were significant, but most discernible for small and intermediate-sized rainfall events less than 62.5mm. The two species with the greatest stormwater retention efficiencies, S. kamtschaticumand S. sexangulare, also had the highest rates of evapotranspiration (ET), and higher ET rates resulted in less total runoff. Because evapotranspiration was identified as important for predicting performance by plants in the field study, I investigated how ET data from this study, combined with environmental data collected from a weather station at the study site, could be used to improve the application of the FAO56 Penman-Monteith evapotranspiration equations to green roofs. The incorporation of specific seasonal crop coefficients were found to improve correlations between predicted and measured rates of ET and these coefficients were related to plant characteristics. The refinement of ET equations can lead to more accurate hydrologic models of green roofs and design and management tools

Mapping the Design Process for Urban Ecology Researchers

The integration of research into the design process is an opportunity to build ecologically informed urban design solutions. To date, designers have traditionally relied on environmental consultants to provide the best available science; however, serious gaps in our understanding of urban ecosystems remain. To evaluate ecosystem processes and services for sustainable urban design and to further advance our understanding of social-ecological processes within the urban context, we need to integrate primary research into the urban design process. In this article, we develop a road map for such a synthesis. Supporting our proposals by case studies, we identify strategic entry points at which urban ecology researchers can integrate their work into the design process

A Pilot Study Considering Ecoroofs as Therapeutic Landscapes

The potential for urban open spaces to convey therapeutic benefits is increasingly substantiated. More work is needed to specifically consider how low impact designs to manage stormwater such as ecoroofs perform in this context. Here, we report on a pilot study addressing: (1) factors determining whether a hospital has an ecoroof, and (2) how ecoroofs might convey therapeutic benefits. We utilized a mixed methods approach which encompassed phone interviews of hospital ecoroof managers as well as analysis of national hospital databases. We also conducted a local case study which compared cortisol samples and stress indicators from patients, staff, and caregivers visiting an ecoroof to those waiting indoors at the Oregon Health and Sciences University in Portland OR. Behavioral observations took place at this same location. In 2017, we identified 105 hospitals with ecoroofs in the contiguous United States. Our analysis of a national hospital database found two factors that significantly increased the likelihood of a hospital having an ecoroof: Medicaid discharges per year; and non-profit status. Interviews with practitioners nationally revealed a wide range of motivations but that therapy was a consideration for a majority, but notably not all, of the hospitals surveyed. They similarly noted variation in roof design, maintenance, and programming around horticultural therapy; we highlight some best practices here. Our physiological case study was limited in sample size. Preliminary findings showed that salivary cortisol levels varied by ecoroof visitor type, ranging on average from 0.09 μg/ml for caregivers to 0.30 μg/ml for patients. We did not observe any significant changes in visitor cortisol. This could be explained by low replication or the short treatment duration. Alternatively, these pilot data may indicate a gap in horticultural therapy theory vs. practice. Behavioral observations demonstrated a wide array of different uses of the ecoroof space such as cell phone use and passing by. Though preliminary, our findings suggest that therapeutic effects may vary by user type and activity and depend on roof design and goals. This study offers both information on the therapeutic potential of hospital ecoroofs as well as lessons learned regarding different approaches to researching this somewhat new topic

Comparing Heavy Metal Content Found in Spinach (Spinacia Oleracea) Grown on the Roof And Ground Sites At Portland State University

As a result of urbanization, fresh, healthy food can be expensive and easily contaminated but space for local farming is limited. Roofs can be underutilized in densely populated cities and can offer a space for local fresh farming. The purpose of this study is to find if growing leafy vegetables on the roof can limit heavy metal exposure from air pollutants. By growing Spinach on five roofs and five ground locations around the Portland State University campus, at varying heights, we can extract the heavy metals found in these greens and compare them to each other. The expected results show that growing leafy greens on the roof will have fewer heavy metals and grow faster, stronger and with fewer growing variables than the ground sites. Evidence that growing vegetables on the roof results in less contaminants can lead to larger-scale local gardens and fresher, healthy vegetables

Effects of Substrate Depth and Precipitation Characteristics on Stormwater Retention by Two Green Roofs in Portland OR

Study Region: This study took place in Portland Oregon, a city of over 600,000 residents located in the Willamette Valley in the state of Oregon in the Pacific Northwest region of the United States. Portland experiences a temperate climate with Mediterranean features. Study Focus: Runoff patterns from two extensive green roofs with substrate depths of 75 and 125 mm, situated on a 5000 square meter retail store, were compared over a one year period. Precipitation, irrigation, and storm water discharge were continuously monitored and the performance of the green roofs for storm water control was investigated in detail. New Hydrological Insights for the Region: Over the study period, the 125mm and 75mm green roofs retained 32.9% and 23.2% of all precipitation by volume, respectively. The hydrologic response of the green roofs during individual storm events was found to depend strongly on the total depth of the storm event as well as the length of the antecedent dry weather period. Differences in performance between the two substrate depths were most pronounced for small storms with long antecedent dry weather periods. Both green roofs showed strong seasonal dependence in storm water retention, with higher percent retention in the relatively dry summer months compared to lower retention in the wetter winter months. These findings have important implications for the effective installation of green roofs for stormwater management in our region. Because of the increased frequency of storm events during the Pacific Northwest winters, it is imperative that efforts to increase storage capacity through increased substrate depth be paired with efforts to ensure rapid removal. If deeper substrates are to be utilized effectively; more research is needed to identify ways to increase evapotranspiration, for example via more informed plant selection, during wet winter months

Population Density of Free-Roaming Cats in Relation to Feeding Stations on Hayden Island

Free-roaming cats have a devastating impact on wildlife populations with stray/feral cats being the most problematic. In some areas, community members provide these cats with food, water, and shelter often in conjunction with a trap, neuter, return (TNR) program. Regardless of TNR, some studies suggest that feeding stray cats allows them to live longer which increases their impact on local wildlife populations. In contrast, we documented that a constantly available food source correlated to a higher density of cats in urban areas with less wildlife value and where they can be integrated into a TNR program. The Hayden Island Cat Project has utilized TNR, cat adoption, and outreach to humanely reduce the free-roaming cat population since 2014. Many residents on the island provide feeding stations for the cats and actively participate in the TNR program. To determine how feeding might affect cat spatial distribution, camera traps were placed at 20 different stations in urban and natural areas on Hayden island. Additional data from the annual road cat count was used to compare cat density relative to feeding stations utilizing ArcGIS. Coordinates of feeding stations based on a resident survey were overlaid onto the cat location coordinates and a clear density correlation appeared. Camera traps reinforced these findings whereby only a single cat was photographed in the natural area. These results demonstrate that feeding free-roaming cats combined with management actions aimed at humanely reducing cat populations, may lessen the impact on wildlife and be ethically acceptable to local residents

Pilot Study on the Impact of Green Roofs on Ozone Levels Near Building Ventilation Air Supply

Outdoor air is often introduced into commercial buildings from ventilation intakes sited on rooftops where vegetation (a green roof) is increasingly present. Little is known about the impact of green roofs on the quality of building outdoor ventilation air supply. In this study, we investigated the potential for green roofs to impact ozone (O3) levels in ventilation air by parameterizing O3 dry deposition to vegetation and substrate typical of extensive green roofs in field and laboratory studies. Values obtained constrain a 2-D advection-diffusion model of O3 transport and reaction at the rooftop scale. The 10th, 50th, and 90th percentiles for O3 surface resistances measured using flux-gradient methods in field studies were 46 s/m, 155 s/m, and 1700 s/m. Surface resistances measured in laboratory chambers for substrate and green roof samples ranged from 360 s/m to 435 s/m, in the 60th-70th percentile of field measurements. The modeled impact of a green roof on O3 levels in building outdoor ventilation air intake was a reduction ranging from 0.25 to 1.8 μg/m3 for short fetch lengths (1 m) and low vertical mixing to larger fetch lengths (5 m) and stronger vertical mixing, respectively, from ambient O3 levels of 144 μg/m3. Vegetation fetch and vegetation height had the largest impact on modeled O3 reductions, suggesting large, continuous, intensive green roof designs may enhance O3 reductions in building ventilation air

Identifying Synergies and Gaps in the Portland-Vancouver Regional Conservation Strategy Under Climate Change

Our understanding of the benefits from urban nature has expanded considerably in the last decade, including the benefits of green infrastructure for managing stormwater and air pollution and for physical and mental health. However, an already difficult environment for natural systems is likely to be exacerbated by climate change. A lunch discussion at the 2017 Portland-Vancouver Urban Ecosystem Research Consortium symposium showed considerable interest in the topic from diverse stakeholders. In this poster, we describe our survey which aims to determine to what extent both the regional conservation strategy and concerns about climate change are influencing local organizational activities and decisions. We further aim to identify gaps and overlapping areas of interest on this topic as well as innovative practices which we plan to share along with our overall findings at a stakeholder meeting later this year

Preliminary Acoustic Surveys of Bats in Portland’s Urban Parks

Bats are a diverse group of animals that serve important roles in the ecosystem; they contribute to pollination and seed dispersal, and are the principal predators of night-flying insects. Certain bat species are sensitive to habitat changes and are used as indicators of ecosystem integrity, but others are highly adaptable, and frequently observed in urban environments. Several bat species and populations in North America are under threat from White Nose Syndrome (WNS), which has been characterized as the largest wildlife epidemic in the past century. WNS was detected in Western states for the first time in 2016, highlighting the need for studies on bat populations in this region. We conducted preliminary acoustic surveys of bats in parks around Portland, OR during late summer 2017. We surveyed many of the sites described in a report by the City of Portland’s Bureau of Environmental Services in 2008, which had the following parameters: within 0.25 miles of water, with some forest structure, and easily accessible. We used a Pettersson’s M500 microphone to detect ultrasonic bat calls, and then ran three of the surveys through Sonobat’s automatic classification. Sonobat identified three bat species with high confidence: Eptesicus fuscus (big brown bats) at Laurelhurst Park and Kelly Point Park, Lasionycteris noctivigans (silver-haired bat) at Kelly Point Park, and Myotis lucifigus (little brown bat) at Pier Park. These represent significant differences in species found in the 2008 report. Future work will focus on surveying bats at more locations, to determine ecological constraints on species occurrences