Abstracts | Green Infrastructure Research Symposium

Academic Research Track

Haven Kiers, Aaron Guerra, and Hunter Ottman, University of California Davis 

As urbanization expands and continues to displace natural habitats, elevated ecosystems, particularly green roofs, offer a way to restore biodiversity. Designing green roofs to mimic local native habitats can extend the area available for native species to colonize in urban areas and promote gains in biodiversity. The UC Davis Green Roof Research project trials California native grassland plants for their adaptability to this novel ecosystem and investigates the potential to mimic local native habitats with green infrastructure. Data collected on plant growth, vigor, and floral display will ultimately contribute to a better understanding of the ecological value of grassland plants in the urban environment and their relationship to pollinators such as bees, hummingbirds, and butterflies. Since California grassland species have rarely been incorporated into green roofs, this trial develops a diverse list of recommended native grassland plants for green roof culture. General research questions included the following: 1) Are California native grassland plants suitable for green roofs?  and, 2) How does the green roof environment influence the growth and aesthetics of grassland plants? Two demonstration modular green roofs planted with a mixture of grassland species were constructed at the SmartLandscape site at the University of California, Davis. Plant species were monitored for water usage, survival, phenology, floral display, and overall aesthetics. Although much has been learned about the application of green roof vegetation in North America (Dvorak and Volder 2010), and despite an abundance of research on the use of both succulent vegetation and herbaceous plants on green roofs, the majority of these studies have been regionally based, focusing primarily on plant selection for the climates of the Northeast/Mid Atlantic, Midwest, and Pacific Northwest, where green roofs are more prevalent. Native prairie and grassland species have been studied for their ability to adapt to green roof conditions (Sutton et al 2012), but again the research was limited to specific geographic regions. As a result, plant selection for green roofs in California is poorly understood and typically reliant on biogeographical data irrelevant to our location and climate. Given the importance of native plantings for the maintenance of biodiversity, studies documenting how California grassland species perform on green roofs are essential.

References

Dvorak, B., and Volder, A. 2010. “Green Roof Vegetation for North American Ecoregions: A Literature Review.” Landscape and Urban Planning, 96(4): 197-213.

Sutton, R.K., Harrington, J.A., Skabelund, L., MacDonagh, P., Coffman, R.R., and Koch, G. 2012. Prairie-Based Green Roofs: Literature, Templates, and Analogs. Journal of Green Building, 7(1): 143-172.

Leigh Whittinghill, Christine Jackson, and Pradip Poudel, Connecticut Agricultural Experiment Station

While the use of green roof technology to produce food in urban areas has increased in the last decade, there are still significant research gaps around this practice. One area where research is still lacking is in nutrient management practices for vegetable production using green roof media. Studies on ornamental green roofs have shown that increasing the amount of organic matter in the media or using fertilizers (water soluble or controlled release) can increase the nutrient content of runoff water (Buffam. Mitchell, and Durtsche 2016; Clark and Zheng 2013, 2014; Czemiel Berndtsson 2010; Hathaway, Hunt, and Jennings 2008; Ntoulas et al. 2015; Rowe 2011). This has also been demonstrated on some agricultural green roofs (Harada et al. 2017; Harada et al. 2018a; Whittinghill et al. 2016). A long-term research study was designed to examine the impacts of annual additions of 0.33, 0.66, and 1 kg/m2 of compost. This practice is being used on agricultural rooftops to reduce the need for fertilizers (Almaaitah and Joksimovic 2022; Harada et al. 2018b; Whittinghill et al. 2016). A 0 kg/m2 compost control with green roof media and a no compost topsoil control were used. Lettuce was grown using cut and come again harvesting practices for two years, during the third and fourth years of this experiment. Lettuce was planted three times throughout the growing season and harvested up to 5 times for each planting when leaves reached approximately 12-15 cm in length. Compost was applied in the spring before the first planting, and organic fertilizers were applied at each planting to supplement the plant nutrients supplied by the compost. There were no significant differences among compost treatments for the number of days from planting to the first harvest, number of harvests achieved for each planting, or total yield. The topsoil control had significantly lower days from planting to harvest for the second planting than any green roof treatment. There were a few differences between lettuce yield from the topsoil control and the green roof treatments. In the second planting of the first harvest, the topsoil control had a higher yield than the 0 kg/m2 green roof media treatment but was not significantly different from any green roof media treatment that received compost. There were significant differences in yield among the harvests for each of the three plantings, with total yield decreasing significantly after the second or third harvest. This was consistent across compost treatments and the topsoil control, indicating a need for further research in nutrient management in cut-and-come again production to promote higher yields in later harvests. 

References

Almaaitah, T. and D. Joksimovic. 2022. “Hydrologic and Thermal Performance of a Full-Scale Farmed Blue-Green Roof.” Water, 14: 1700. https://doi.org/10.3390/w14111700.

Buffam, I., M.E. Mitchell, and R.D. Durtsche. 2016. “Environmental Drivers of Seasonal Variation in Green Roof Runoff Water Quality.” Ecological Engineering, 91: 506-514. https://doi.org/10.1016/j.ecoleng.2016.02.044.

Clark, M. J., and Y. Zheng. 2013. “Plant Nutrition Requirements for an Installed Sedum-Vegetated Green Roof Module System : Effects of Fertilizer Rate and Type on Plant Growth and Leachate Nutrient Content.” HortScience 48(9): 1173-1180.

Clark, M. J., and Y. Zheng. 2014. “Fertilizer Rate and Type Affect Sedum-Vegetate Green Roof Mat Plat Performance and Leachate Nutrient Content.” HortScience, 49(3): 328-335.

Czemiel Berndtsson, J., 2010. “Green Roof Performance Towards Management of Runoff Water Quantity and Quality: A Review.” Ecological Engineering, 36: 351-360. doi:10.1016/j.ecoleng.2009.12.014. 

Harada, Y., T.H. Whitlow, N.L. Bassuk, and J. Russell-Anelli. 2017. “Biogeochemistry of Rooftop Farms”. 275-294. In Urban Soils. Eds. R. Lal and B.A. Stewart. CRC Press. Boca Raton.

Harada, Y., T.H. Whitlow, M.T Walter, N.L Bassuk, J. Russel-Anell, and R.R. Schindelbeck, R.R. 2018b. Hydrology of the Brooklyn Grante, and urban rooftop farm. Urban Ecosystems, 21: 673-689. https://doi.org/10.1007/s11252-018-0749-7. 

Harada, Y., T.H. Whitlow, P.H. Templer, R.W. Howarth, M.T. Walter, N.L. Bassuk, and J. Russell-Anelli. 2018a. “Nitrogen Biogeochemistry of an Urban Rooftop Farm.” Frontiers in Ecology and Evolution, 6: 153. doi:0.3389/fevo.2018.00153.

Hathaway, A.M., W.F. Hunt, and G.D. Jennings. 2008. “A Field Study of Green Roof Hydrologic and Water Quality Performance.” Transactions of ASABE, 51: 37-44.

Ntoulas N, P.A. Nektarios, T.-E. Kapsali, M.-P. Kaltsidi, L. Han and S. Yin. 2015. “Determination of the Physical, Chemical, and Hydraulic Characteristics of Locally Available Materials for Formulating Extensive Green Roof Substrates”. HortTechnology, 25(6): 774-748.

Rowe, D.B., 2011. “Green Roofs as a Means of Pollution Abatement.” Environmental Pollution, 159: 2100–10. doi:10.1016/j.envpol.2010.10.029.

Whittinghill, L.J., D. Hsueh, P.  Culligan, R. Plunz. 2016. “Stormwater Performance of a Full Scale Rooftop Farm: Runoff Water Quality”. Ecological Engineering, 91: 195–206. doi:10.1016/j.ecoleng.2016.01.047. 

G. Picca, C. Gomez-Ruano, M. Veliu, A. Goñi-Urtiaga, C. Plaza, M. Panettieri, Instituto de Ciencias Agrarias and Université Gustave Eiffel

Rapid urbanization – i.e. net rural to urban migration -  will lead cities to host nearly 70% of the world's population by 2050, contributing to food insecurity and malnutrition (FAO, Rikolto 2022). Rooftop agriculture (RA) is getting wider recognition as a critical factor for cities' resilience. The spread of RA underlines the need for inert-lightweight substrates that guarantee ideal conditions for plant development and production [2]. Composting urban biowaste represents a viable strategy to recycle nutrient-rich byproducts as agricultural substrates, addressing the circular economy paradigm (European Commission, 2020). The present study aimed to investigate the agronomic performance of different substrates made of organic wastes (spent coffee grounds, coffee silverskin and algae) composted with and without biochar and blended with peat-based substrate at a proportion of 50% (v/v) on a rooftop in Madrid (Spain). The cultivation system consisted of a crop rotation of three years with a succession of a local variety of tomato (Solanum lycopersicum L., cv. Moruno) and a consociation of lettuce (Lactuca sativa L., cv. Romana) and chard (Beta vulgaris var. Cicla). In the first year, the yield of tomato plants grown on the compost-based substrates was up to 20.56 kg/m2, exceeding that on a peat-based substrate, used as a control, by 101.86 %. Even though a general decrease in crop yield was registered, the difference between the agronomic performance of the compost-based substrates and that of peat was even higher in the second year, reaching 169%. The data proves that co-composted urban wastes are promising growing media for planning productive green roofs.

References

FAO, Rikolto and RUAF. 2022. “Urban and Peri-Urban Agriculture Sourcebook – From Production to Food Systems.” Rome, FAO and Rikolto. https://doi.org/10.4060/cb9722en.

Grard, B.J., Manouchehri, N., Aubry, C., Frascaria-Lacoste, N. and Chenu, C., 2020. “Potential of Technosols Created With Urban By-Products for Rooftop Edible Production.” International Journal of Environmental Research and Public Health, 17(9): 3210. https://www.mdpi.com/1660-4601/17/9/3210/pdf. 

European Commission. 2020. “European Commission Circular Economy Action Plan.” 28, doi:10.2775/855540. 

Lee R. Skabelund, Kansas State University

Designers, contractors, and managers can create low input living roofs that support native species in the Central Great Plains (USA) but essential drivers of plant health and survival must be understood and addressed (Rowe, 2015; Skabelund et al., 2015; Dvorak and Skabelund, 2021). Well-drained full-sun green roofs in the Flint Hills Ecoregion (north-central Kansas) typically require supplemental irrigation for consistent native plant cover, however, they do not need daily irrigation even during very hot, dry periods. At Kansas State University we have observed that planted and seeded 6-24-cm-deep green roofs in Manhattan, Kansas – directly seeded, or from plants producing and spreading seed on planted and/or seeded green roofs – tend to be resilient during dry periods (Skabelund et al., 2014; Decker and Skabelund, 2021). However, design and context matter! Mixed species seem to fare better. Full sun green roofs without adequate rainfall or supplemental irrigation, coupled with too little afternoon and evening shade, are prone to brown-out and/or die-back, especially for tallgrass prairie species and less drought and heat tolerant Sedum species. Subsurface moisture helps support living plants, while too much sunlight creates great vegetative stress (Decker et al., 2022). Exploring how seeded native plants fare in different conditions is deemed very important to the process of learning about what species can thrive on green roof ranging in substrate depths of 6.5-23.5 cm. This presentation discusses new plants—including 12 Opuntia humifusa pads and seeds added to the KSU-APD Balcony Green Roof, and 11 different native species added to the three KSU-APD Experimental Green Roof beds in early June 2023. Lessons learned from ongoing monitoring and management activities are noted. As of late June 2023 only a few of the seeded species were visible (and only in an area regularly being hand watered on the KSU-APD Balcony Green Roof) while the Opuntia humifusa pads were stressed but living on this shallow 6-10-cm-deep green roof that regularly experiences surface temperatures between 50-75° C. 

References

Decker, A. and Skabelund, L.R.. 2021. “Investigating the Effect of Substrate Type and Species Mix on Plant Cover on a Manhattan, Kansas Green Roof.” Cities Alive 2021 Virtual Conference.

Decker, A., Skabelund, L.R., Gao, Y. and Shrestha, P. 2022. “Investigating Extensive Green Roof Native Plant Growth Over a Four-Year Period in the Central Great Plains (USA).” Cities Alive 2022 Conference. Philadelphia, PA.

Dvorak, B. and Skabelund, L.R. 2021. “Green Roofs in Tallgrass Prairie Ecoregions.” Ecoregional Green Roofs: Theory and Application in the Western USA and Canada. Springer Nature. https://doi.org/10.1007/978-3-030-58395-8_3. 

Rowe, B. 2015. “Long-Term Rooftop Communities.” Green Roof Ecosystems (R. Sutton, editor). Springer Science. www.springer.com/life+sciences/ecology/book/978-3-319-14982-0. 

Skabelund, L.R., Blocksome, C., Brokesh, D., Kim, H. Knapp, M., and M. Hamehkasi, M. 2014. “Semi-Arid Green Roof Research 2009-2014: Resilience of Native Species.” 12th Annual Cities Alive Green Roof and Wall Conference. Nashville, TN. 

Skabelund, L.R., DiGiovanni, K., and Starry, O. 2015. “Monitoring Abiotic Inputs and Outputs.” Green Roof Ecosystems (R. Sutton, editor). Springer Science. www.springer.com/life+sciences/ecology/book/978-3-319-14982-0. 

Bruce Dvorak and Thomas Woodfin, Texas A&M University

When green roofs are planted to maximize biodiversity, specifying local or regional native vegetation can be an efficacious approach to establishing biodiverse green roofs (Cook-Patten 2012, Madre et al. 2013). In the southern plains, there is little research to support the effectiveness of establishing green roof vegetation through seeding as most of the research is outside the ecoregion (Dunnett, Nagase et al. 2008, Sutton 2013, Skabelund, Decker et al. 2017, Saraeian, Farrell et al. 2022). This study observes the establishment of vegetation on green roofs through seeding. Four green roof plots in south-central Texas were subject to four substrate and seed mix arrangements, at depths ranging from 11.3 cm to 30 cm. Three seed mixes were purchased from a regional provider of native prairie seeds and were sown onto an FLL-compliant growing media at the recommended rate per seed mix on May 19, 2022, and October 2022. The green roofs were watered daily from May through November 2022. Thirty-three (33) of forty-eight (48) species were annual or perennial wildflowers. Thirteen (13) species of wildflowers were observed during the second week of June 2023. Greater plant height was present in 17.7 cm-deep substrates (R2 0.98) for nine species compared to 11.3 cm-deep substrates. Additionally, green roofs with substrate depths ranging from 17.7 cm to 30 cm deep supported greater mean vegetation height compared to 11.3-deep substrates (R2 0.78) for eleven species. Grass species were present but not included. This study establishes baseline data for the ecoregion.

References

Cook-Patten, S. and Bauerle, T. 2012. “Potential Benefits of Plant Diversity on Vegetated Roofs: A Literature Review.” Journal of Environmental Management, 6: 85-92.

Dunnett, N., A. Nagase and A. Hallam. 2008. "The Dynamics of Planted and Colonising Species on a Green Roof Over Six Growing Seasons 2001–2006: Influence of Substrate Depth." Urban Ecosystems, 11: 373-384.

Madre, F., A. Vergnes, N. Machon, P. Clergeau. 2013.. "A Comparison of 3 Types of Green Roof as Habitats for Arthropods." Ecological Engineering, 57: 109-117.

Saraeian, Z., C. Farrell and N.S. Williams. 2022. "Green Roofs Sown With an Annual Plant Mix Attain High Cover and Functional Diversity Regardless of Irrigation Frequency." Urban Forestry and Urban Greening, 73: 127594.

Skabelund, L.R., A. Decker, T. Moore, P. Shrestha, and J.L. Bruce. 2017. "Monitoring Two Large-Scale Prairie-Like Green Roofs in Manhattan, Kansas." CitiesAlive: 15th Annual Green Roof and Wall Conference 2017 Conference Proceedings, Seattle, WA.

Sutton, R.K. 2013. "Seeding Green Roofs with Native Grasses."

Eliza Gross, Maria Chavez PhD., Jennifer Bousselot PhD. 

Rates of food insecurity and population growth are simultaneously increasing in urban areas (Food Security, n.d.). Therefore, reevaluating food production and land management is vital for agriculture. Rooftop agrivoltaics (AV), growing crops under rooftop solar panels, is an efficient way to produce clean energy and high yields of specialty crops in underutilized spaces (Uchanski et al., 2023). The Colorado State University Spur Campus is located in Denver, Colorado where chile peppers are a high value crop and well adapted to the arid climate. They hold economic and cultural significance to the southwest (Hawkes et al., 2008). This study is on the Hydro building rooftop agrivoltaics system. It will incorporate four varieties of chile peppers: Hatch, ‘Pueblo Primrose’, ‘Pueblo Mosco’, and an unnamed CSU experimental. Individuals of each variety were planted under two treatment plots (opaque and bifacial silicon solar panels), and in one full sun control plot. Plants will be evaluated by yield (fruit production), water efficiency (stomatal conductance), and vegetative biomass (dry weight and plant height). Studies show chile peppers perform better under 35% shade than in full sun due to heat stress reduction (Valiente-Banuet and Gutiérrez-Ochoa, 2016). Other varieties of horticultural crops, such as leafy greens, demonstrated improvements in yield in AV systems (Marrou et al., 2013). We expect greater fruit production from chile peppers grown under solar panels than in full sun. Additionally, we will collaborate with other researchers to understand the microbiome of chile peppers and their nutritional quality. Utilizing rooftop agrivoltaics to produce high value crops, like chile peppers, will be vital to reducing food insecurity in urban areas. 

References 

Food Security. USDA. (n.d.). https://www.usda.gov/topics/food-and-nutrition/food-security. 

Hawkes, J., Libbin, J.D., and Jones, B.A. 2008. “Chile Production in New Mexico and Northern Mexico.” Journal of American Society of Farm Managers and Rural Appraisers, 83-92. http://www.jstor.org/stable/jasfmra.2008.83. 

Marrou, H., Wery, J., Dufour, L., and Dupraz, C. 2013. “Productivity and Radiation Use Efficiency of Lettuces Grown in the Partial Shade of Photovoltaic Panels.” European Journal of Agronomy, 44: 54-66. https://doi.org/10.1016/j.eja.2012.08.003. 

Uchanski, M., Hickey, T., Bousselot, J., and Barth, K.L. 2023. “Characterization of Agrivoltaic Crop Environment Conditions Using Opaque and Thin-Film Semi-Transparent Modules.” Energies, 16(7): 3012. https://doi.org/10.3390/en16073012. 

Valiente-Banuet, J.I., and Gutiérrez-Ochoa, A. 2016. “Effect of Irrigation Frequency and Shade Levels on Vegetative Growth, Yield, and Fruit Quality of Piquin Pepper (Capsicum annuum L. var. glabriusculum).” HortScience, 51(5): 573-579. https://doi.org/10.21273/HORTSCI.51.5.573. 

Emerging Professional/Student Track

Ariel Zhu, Zahra Jandaghian, and Hitesh Doshi, Toronto Metropolitan University

In dense urban canopy, the rooftops cover more than 23% of the areas.[1] Vegetated roof assemblies where used have been a successful stormwater management strategy. Blue roofs can be installed on roofs where vegetated assemblies may not be possible providing a more cost-effective nature-based alternative. These assemblies on low-sloped roofs (<2%), can effectively help alleviate the pressure on stormwater infrastructure. This research aims to provide a guideline for the installation of blue roofs, on whether existing or new rooftops, while clearly outlining each type of system’s risk management, advantages, and disadvantages. The types of blue roof constructions are categorized by how the water is detained, into Roof-Integrated Design (RID) or Modular Tray Design (MTD), whereas the RID uses the roof itself as a ponding medium, and the MTD collects the water in trays, while the roof perform as a conventional roof. RIDs can be further categorized by how the system functions into passive and active Modified Drainage Inlet (MDI), where passive MDI installs a weir on the roof drain, and the active install an operable valve on the drainpipe. Design considerations of a Stormwater Detention Assembly (SDA) on the roof in the Canadian climate includes structural, contaminants, temperature, wind, and membrane integrity concerns (Jandaghian et al., 2022). From simulating detention performances, backed suggestions can be made of what are the design parameters of the systems. Preliminary results of the simulations shows that the MTD system can be affected by independent variables such as orifice size, absorptive material used, and roof coverage percentage. Comparing the different variables, roof coverage percentage has the most effect on flattening the curve. The passive MDI’s parameters, on the other hand, includes the number of drains, and the size of orifice on the weir. This presentation aims to provide the most current and adaptable future possibilities that can be implemented using a blue roof approach vis-a-vis current regulatory requirements and taking into account risk considerations related to the main function of the roof. 

References

Akbari, H., Rose, L.S. and Taha, H. 2003. “Analyzing the Land Cover of an Urban Environment Using High-Resolution Orthophotos.” Landscape and Urban Planning, 63(1): 1-14.

Jandaghian, Z., Zhu, Y., Saragosa, J., Doshi, H. and Baskaran, B. 2022. “Low-Sloped Rooftop Storm-Water Detention Assembly to Mitigate Urban Flooding.” Buildings, 13(1): 8.

Armando Villa-Ignacio and Jennifer Bousselot, Colorado State University

As the world continues to urbanize, food and energy becomes increasingly difficult to acquire. By 2050, 68% of the world’s population will reside within urban areas (Ritchie and Roser 2018). It is also projected that the overall population would grow by 2 billion, or by 20%. Food production would need to more than double that, about 50% more, to feed the growing population (Deutsch et al., 2013). Rooftop agrivoltaics combines effective land management, food security, and energy production. This study evaluates the growth of high value leafy greens in two sites. The first site contains silicon polycrystalline framed solar panels, opaque CdTe frameless panels, 40% semi-transparent CdTe frameless panels, and in full sun as a control treatment in a simulated rooftop agrivoltaic site at grade in Fort Collins, Colorado, at the Foothills Campus of Colorado State University. The second site contains silicon opaque panels, silicon bifacial panels, and a full sun treatment the CSU Spur campus on the Hydro Building. Biomass accumulation, growth rate, stomatal conductance, and environmental conditions were evaluated through multiple growth cycles for five leafy greens. Upon preliminary analysis, leafy greens grown under semi-transparent panels accumulated the largest fresh weights comparative to the other panel types and full sun treatments. It was also found that the plants have a lower stomatal compared to the full sun treatment, and the shade from the opaque and frameless panels resulted in lower stomatal conductance across species, except kale. There is greater biomass accumulation under solar panel treatments than in full sun. The mean substrate temperature is shown to have decreased under solar panels comparative to the full sun treatment, which is similar to the mean air temperature. The minimum air temperature across all treatments is relatively similar, however, the minimum substrate temperature through the growing season is shown to have been warmer than the full sun treatment. Similarly, the max air temperature found was also similar to the full sun treatment while the substrate max temperature was lower. Plants growing in an agrivoltaic setting under solar panels receive less light, but this has now been shown to be associated with positive tradeoffs in terms of reduced evaporative loss of soil moisture in a dryland area (Barron-Gafford et al., 2019) understanding the growth characteristics and growing environment of high value crops under these treatments will increase understanding of how these crops will grow in a green roof system under solar panels. These systems can be used to ease food, energy, and land needs within urban centers and supplement the population’s basic needs.

References

Barron-Gafford, G., M. Pavao-Zuckerman, R. Minor, L. Sutter, I. Barnett-Moreno, D. Blackett, M. Thompson, Y. Dimond, A. Gerlak, G. Nabhan, and J. Macknick. 2019."Agrivoltaics Provide Mutual Benefits Across the Food–Energy–Water Nexus in Drylands." Nature Sustainability, 2: 1-8. https://doi.org/10.1038/s41893-019-0364-5.

Deutsch, L., Dyball, R., and Steffen, W. (2013). “Feeding Cities: Food Security and Ecosystem Support in an Urbanizing World.” In:, et al. Urbanization, Biodiversity and Ecosystem Services: Challenges and Opportunities. Springer, Dordrecht. https://doi.org/10.1007/978-94-007-7088-1_26. 

Ritchie, H., and M. Roser. 2018. “Urbanization.” Our World in Data.org

Fatima and Hitesh Doshi, Toronto Metropolitan University 

This presentation explores the shading that can be accomplished by using elevated vegetative systems on a rooftop. Elevated vegetative systems, such as pergolas, arbors or trellises are frequently used as shading devices in ground-based systems (Kraus et al., n.d). Using vegetation to provide shade reduces surface temperature and provides benefits related to evapotranspiration. Green roofs are the most common means of providing vegetation on rooftops. They have faced some challenges related to structural loading. A paper was presented at the 23rd Conference on Passive and Low Energy Architecture to discuss the use of conventional cooling techniques to lower temperatures around buildings which can be achieved through heat absorption or via transpiring mechanism, in different climatic conditions. The above study was carried out in three different regions namely Riyadh, Saudi Arabia; Athens, Greece; and Mumbai, India; having different climate zone. Six types of cooling techniques namely concrete roof, pond roof, white roof, old white roof, green roof and green sky were studied. Green sky referred to elevated vegetative system (Jones et al., 2006). Even though all cooling techniques lower temperature but green sky works best as it creates a buffer space between roof and vegetative layer (Jones et al., 2006). In a review article on vertical green systems shows that decrease in temperature up to 0.5 oC to 17.62 oC can be achieved depending on the type and scale of installation systems, the geographic location in which Horizontal System applied and the shading extents of the chosen plants (Wang Y. et al., 2022). This presentation explores the use of elevated vegetative systems in such situations. It can lower UHI by providing shade on the roof surface. The study outlines the development of mild steel elevated horizontal and vertical vegetative systems and uses simulation to determine the amount of shading that can be achieved with this approach. Three plants were selected for this work based on their fast growth and foliage cover. The plants selected were Virginia Creeper, Dutchman’s Pipe and Trumpet Vine. This study uses computer simulations via Sketchup and AutoCAD to evaluate the amount of shading observed through various plants on a building in downtown Toronto. Shadow study was simulated for a period from May to September. The simulation indicated the amount of roof area that could be shaded. The results show that there is a possibility of using this elevated vegetative system to provide shading on roofs to reduce urban heat island. Moreover, results also indicated that the horizontal system provided the most vegetative cover thus leading to more shade i.e. 60% of the roof will remain under shade during summer months. A systemic review of data was explored and analysed through IBM SPSS 2022 and it concluded that the reduction in surface temperatures ranging from 6.24 to 12.80C (with SD +/- 4.2 and +/- 6.37) respectively can be achieved. Vertical system was unable to provide significant shading due to lack of surface area from plant growth. Many variables contribute in the disparity seen in temperature reductions like the geographic location of cities, urban landscapes, (Zhaowu Yu et al., 2018), size of canopy, height and density of canopy; and the surface area of leaf layers and vegetation species (Ennos et al, 2013). 

References

Armson, D., Rahman, M.A. and Ennos, A.R. 2013. A Comparison of the Shading Effectiveness of Five Different Street Tree Species in Manchester, UK. Arboriculture & Urban Forestry, 39(4): 157-164.

Kraus, F. and Anschober, J. (n.d.). Green4Cities. [Pdf] On Buildings and Structures - Vegetated Pergola. 

Yu, Z., Guo, X., Zeng, Y., Koga, M. and Vejre, H., 2018. “Variations in Land Surface Temperature and Cooling Efficiency of Green Space in Rapid Urbanization: The Case of Fuzhou City, China.” Urban Forestry and Urban Greening, 29: 113-121.

Jones, P. and Alexandri, E. 2006). Ponds, Green Roofs, Pergolas, and High Albedo Materials; Which Cooling Technique for Urban Spaces?: In proceedings of the 23rd Conference of Passive and Low Energy Architecture, Geneva, Switzerland.

Wang, Y., Berardi, U. and Akbari, H., 2016. “Comparing the Effects of Urban Heat Island Mitigation Strategies for Toronto, Canada.” Energy and Buildings, 114: 2-19.

Kevin Duerfeldt, Iowa State University 

In urban environments there are increasing pressures to create multifunctional areas for people and ecosystem services. Geographic information Systems and Remote Sensing can analyze and apply spatial data to urban planning issues.  The area of interest was Porto, Portugal, and questions were: 

1) Which classification method best suits the region? 

2) How was land cover classified in 2017 and 2022, and how has it changed? 

3) How does Normalized Difference Vegetation Index (NDVI) compare to classification? 

4) Are there spatial trends in landcover?

5) Are there correlations between areas of lost vegetation and gained “other roof"?

Landcover was classified into seven categories for five Concelhos of Porto District Portugal using PlanetLabs PlanetScope satellite imagery (Institutio Nacional de Estatistica 2021; PlantetLabs 2023). Images were obtained for 4 July, 2017 and 1 July, 2022. Political boundaries were from the National Institute of Statistics. K-Nearest Neighbor was the most accurate supervised classification method with 2017 Kappa = .87 and 2022 Kappa = .98.  Vegetation decreased and other roofing material increased from 2017 to 2022 supported by change in NDVI, mean difference -0.043. Classification showed 32.68 million square meters were “other roofs”, commercial or industrial white surfaced roofs, which may be the most likely targets for vegetative interventions. Zonal statistics show changes in vegetated areas within neighborhoods are not randomly distributed, Moran’s I = .0249 or 0.402.  Additional socioeconomic data could help understand this distribution and make decisions addressing climate justice. LiDAR data would increase accuracy and allow for clearer selection of roofs and quantification of green roof benefits. 

References

Instituto Nacional de Estatistica. 2021.  2021 Census geopackage. https://mapas.ine.pt/download/index2021.phtml. 

PlanetLabs PBC. 2023. Planet Scope. https://api.planet.com.

Pam Blackmore and Lee R. Skabelund, Kansas State University

As many pollinators decrease across North America and other parts of the world (Potts et al., 2010; Janousek et al., 2023) it is vital to understand how to reverse this trend. Cities, which have frequently eliminated pollinator habitat, can utilize rooftops for the benefit of specific pollinators (Matteson and Langellotto, 2010; Benvenuti, 2014; Madre et al., 2014; Sutton, 2015; Dvorak, 2021; Jacobs et al., 2023; Schiller et al., 2023), but we should not oversell the potential green roofs have for biodiversity conservation for all species (Williams et al., 2014). The Memorial Stadium green roofs at Kansas State University were planted in native U.S. prairie vegetation in 2015 and 2016. Pam Blackmore (2019) evaluated the effectiveness of these green roofs as pollinator habitat in an urban context by comparing butterfly communities at an urban native prairie at Warner Park in Manhattan, Kansas, a protected tallgrass prairie at the Konza Prairie Biological Station (approximately 10 km south of Manhattan), and K-State’s Memorial Stadium during the warm-season months of 2017 and 2018. On-site vegetation composition was assessed and butterfly species richness, distribution, behavior, and abundance documented, with vegetation used by individual butterflies mapped. Findings suggest that urban green roofs can provide habitat for butterflies. In fact, butterfly abundance and mean species richness were greater at the Memorial Stadium than at either native prairie. However, while the green roofs support many species of butterflies, tallgrass prairie specialist species that were seen in the native prairie sites, such as the regal fritillary (Speyeria idalia), were not observed using the green roofs. Butterfly behavior also varied between sites: butterflies using the stadium green roofs were predominately foraging, whereas butterflies at much larger native prairies were flying through and not interacting with plants along the transects. This study suggests that green roofs can, to some degree, compensate for lost pollinator habitat in urban areas. However, further research is needed to understand habitat changes over time as well as green roof design and management implications. Per Blackmore (2019) the two Memorial Stadium green roofs provided habitat for a much higher abundance of late season butterflies than either native (Konza) or urban (Marlatt Park) prairie. The mean number of species of butterflies using Memorial Stadium was comparable to native and urban prairie, but the specialist butterflies present at the prairie sites were absent from Memorial Stadium. Forbs, floral resources, and aboveground biomass were important for butterfly communities, while plant or species evenness negatively impacted the butterfly community.

References

Benvenuti, S. 2014. “Wildflower Green Roofs For Urban Landscaping, Ecological Sustainability And Biodiversity.” Landscape and Urban Planning, 124: 151-161. 

Blackmore, P. 2019. Butterflies, Tallgrass Prairie, and Green Roofs. Kansas State University Masters of Landscape Architecture Thesis. https://krex.k-state.edu/handle/2097/39694.

Dvorak, B. Editor. 2021. Ecoregional Green Roofs: Theory and Application in the Western USA and Canada. Springer: Cities and Nature. 

Jacobs, J., Beenaerts, N., and Artois, T. 2023. “Green Roofs and Pollinators, Useful Green Spots for Some Wild Bee Species (Hymenoptera: Anthophila), But Not So Much for Hoverflies (Diptera: Syrphidae).” NaturePortfolio, 13: 1449. https://doi.org/10.1038/s41598-023-28698-7. 

Janousek, W.M., Douglas, M.R., Cannings, S., Clément, M.A., Delphia, C.M., Everett, J.G., Hatfield, R.G., Keinath, D.A., Koch, J.B.U., McCabe, L.M. and Mola, J.M. 2023. “Recent and Future Declines of a Historically Widespread Pollinator Linked to Climate, Land Cover, and Pesticides. Proceedings of the National Academy of Sciences: Ecology, 120(5): e2211223120. https://doi.org/10.1073/pnas.2211223120.

Madre, F., Vergnes, A., Machon, N., and Clergeau, P. 2014. “Green Roofs as Habitats for Wild Plant Species in Urban Landscapes: First Insights From a Large-Scale Sampling.” Landscape and Urban Planning, 122: 100-107.

Matteson, K C. and Langellotto, G.A. 2010. “Determinates of Inner City Butterfly and Bee Species Richness. Urban Ecosystems, 13(3): 333-347.

Potts, S.G., Biesmeijer, J.C., Kremen, C., Neumann, P., Schweiger, O., and Kunin, W.E. 2010. “Global Pollinator Declines: Trends, Impacts and Drivers.” Trends in Ecology and Evolution, 25(6).

Schiller, J. Rayner, J.P., and Williams, N.S.G. 2023. Guidelines for biodiversity green roofs. Report for the City of Melbourne, Australia.

Sutton, R., Editor. 2015. Green Roof Ecosystems. Springer: Ecological Studies 223.

Williams, N.S.G., Lundholm, J., and MacIvor, S. 2014. Do Green Roofs Help Urban Biodiversity Conservation? Journal of Applied Ecology, 5: 1643-1649.

Madeline Shaub, Kent State University 

Increased demand for food has led to a subsequent decrease in resources such as land and water. Green walls, particularly those used in Vertical Farming (VF) practices, are of interest due to their surface area and potential for abundance in the urban environment (Abel, 2010). These VF systems are often modular in construction and take advantage of hydroponic or aeroponic methods of irrigation which are less intensive than traditional agricultural methods. This study aims to utilize 3D printing technology to establish a baseline for cultivating food crops in 3D printed substrate for possible implementation in a modular wall panel design. Test squares measuring 3” x 3” x ½” were fabricated using three different filament types: 100% pure PLA, PLA with 20% wood infill composite, and PLA with 30% wood infill composite. Each square was designed with a gyroid pattered infill at 20% density. These were then seeded with a mixture of broccoli, kale, kohlrabi, and cabbage microgreens, and left to grow in uncontrolled ambient conditions for one week. Our findings show that despite differences in watering methods, similar rates of germination were found among all three tests. This reinforces our hypothesis that the higher the percentage of organic material present within the composite filament, the higher the chance for wicking/moisture retention to occur. Future tests may be focused on exploring how edible plants that have short term growth cycles are harvested from the prints, as well as how expansion into the Z-axis will affect filament performance and plant growth.

References

Abel, C. 2010. “The Vertical Garden City: Towards a New Urban Topology.” Council on Tall Buildings and Urban Habitat, 2: 21-24. https://global.ctbuh.org/resources/papers/download/390-the-vertical-garden-city-towards-a-new-urban-topology.pdf.