Green Roof Plant Responses to Different Substrate Types and Depths under Various Drought Conditions

2010 ◽  
Vol 20 (2) ◽  
pp. 395-401 ◽  
Author(s):  
Christine E. Thuring ◽  
Robert D. Berghage ◽  
David J. Beattie
Keyword(s):  
Green Roof ◽  
Green Roofs ◽  
Plant Responses ◽  
Ice Plant ◽  
Herbaceous Perennials ◽  
Central Pennsylvania ◽  
Drought Conditions ◽  
Expanded Shale ◽  
Influence Of Substrate ◽  
Substrate Depth

Plants suitable for extensive green roofs must tolerate extreme rooftop conditions, and the substrates in which they grow must fulfill horticultural and structural requirements. Deeper substrates may retain more water for plants during dry periods, but will also weigh more, especially when near saturation. A study in central Pennsylvania was conducted to evaluate the influence of substrate type and depth on establishment of five green roof plants. Two stonecrops [white stonecrop (Sedum album) and tasteless stonecrop (Sedum sexangulare)], one ice plant (Delosperma nubigenum), and two herbaceous perennials [maiden pink (Dianthus deltoides) and saxifrage pink (Petrorhagia saxifraga)] were planted in three depths (30, 60, and 120 mm) of two commercially available green roof substrates (expanded shale and expanded clay). Study flats inside a plasticulture tunnel received three drought treatments (no drought, 2 weeks early drought, and 2 weeks late drought). The two stonecrops performed well under most conditions, although tasteless stonecrop was stunted by early drought. Ice plant only grew well when provided with water. When subjected to any drought, the herbaceous perennials had the fewest survivors in the expanded shale. Saxifrage pink flowered profusely wherever it survived. The study plants were most affected by substrate depth, except for maiden pink, which responded solely to drought. When subjected to early drought conditions, the herbaceous perennials did not survive in 30 mm of either substrate, or in 60 mm of expanded shale. Although the stonecrops performed well in 60 mm of substrate when subjected to drought, their performance was superior in the expanded clay compared with shale.

scholarly journals Legislative requirements related to substrate depth as a barrier to the construction of green roofs in Bulgaria

2020 ◽  
Vol 21 (2) ◽  
pp. 99-104
Author(s):  
Mariam Bozhilova ◽  
Miglena Zhiyanski ◽  
Plamen Glogov
Keyword(s):  
Layer Thickness ◽  
Green Roof ◽  
Green Roofs ◽  
Future Research ◽  
National Legislation ◽  
Green Area ◽  
Substrate Layer ◽  
Green System ◽  
Substrate Depth ◽  
Existing Data

There are 265 municipalities in Bulgaria. According to the national legislation, each Municipal Coun-cil adopts an Ordinance for the construction and protection of the green system. Most of the mu-nicipalities have such ordinances, however, only 75 of them stipulate regulative requirements, under which a green roof can be considered a green area. These requirements refer to the substrate depth and are unreasonably high. While positive impacts are reported in green roofs with a substrate layer thickness of 4 – 5 cm, green roofs with substrate depth under 10 cm are not considered a green area in any of the reviewed ordinances. One municipality considers green roofs with substrate 10-30 cm as a green area, under specific conditions. This paper provides a review of the stipulations of the Bulgarian local legislation against the existing data for the effects of green roofs with different substrate depths and outlines the need for amendment of the legislation and future research. 

scholarly journals Physical Characteristics of and Seed Germination in Commercial Green Roof Substrates

2015 ◽  
Vol 25 (2) ◽  
pp. 221-227 ◽  
Author(s):  
Derald A. Harp ◽  
Cheng Chen ◽  
Curtis Jones
Keyword(s):  
Seed Germination ◽  
Block Design ◽  
Green Roof ◽  
Chemical Properties ◽  
Green Roofs ◽  
Economic Benefits ◽  
Physical Characteristics ◽  
Internal Cooling ◽  
Pinto Bean ◽  
Expanded Shale

Green roofs provide multiple environmental and economic benefits, such as roof surface temperature reduction, reduced internal cooling needs, storm water management, and extended life span of roofing materials. However, green roof substrates must be relatively lightweight, so it is typically coarse with limited water holding capacity. We hypothesize the physical characteristics that make the substrates successful on a roof are likely to reduce seed germination. For this study, we tested the germination of three perennial species and one annual: shasta daisy (Leucanthemum ×superbum), yarrow (Achillea millefolium), and indian blanket (Gaillardia pulchella), and pinto bean (Phaseolus vulgaris) (as a control) across five different substrates: peat/perlite/large expanded shale, compost/sand/expanded shale, compost/black dirt/expanded shale, compost/expanded shale, and peat/perlite (control). Substrate physical and chemical properties were analyzed, and a germination test conducted using a randomized complete block design, with each species/substrate combination appearing once per block. Germination was defined as seedling emergence, and monitored every 7 days for 28 days. Pinto bean had the highest germination (76.2%) across all substrates, compared with 43.4% for indian blanket, 40.4% for yarrow, and 23.0% for shasta daisy. Seed germination, across all species, was lower in green roof substrates. Germination success was very strongly correlated with seed length, seed width, and seed area, while no relationship was found between seed germination and substrate pH or electrical conductivity (EC). Therefore, it is likely that the physical characteristics of green roof substrates create poor conditions for seed germination.

EFFECT OF SUBSTRATE DEPTH AND TYPE ON PLANT GROWTH FOR EXTENSIVE GREEN ROOFS IN A MEDITERRANEAN CLIMATE

2019 ◽  
Vol 14 (2) ◽  
pp. 29-44 ◽  
Author(s):  
Mert Eksi ◽  
D. Bradley Rowe
Keyword(s):  
Green Roof ◽  
Green Roofs ◽  
Municipal Compost ◽  
Sedum Acre ◽  
Armeria Maritima ◽  
Survival And Growth ◽  
Roof Design ◽  
Substrate Depth ◽  
Extensive Green Roofs ◽  
Better Than

Although numerous examples of green roofs can be found in Turkey, limited research has been conducted on plant material and substrate type in this climate. Both plants and substrate are very important components in green roof design, it is essential to determine the proper substrates and plants in green roof systems for domestic green roof design. Two types of growing substrates: a commercial substrate consisting of crushed brick and clay (45%), pumice (45%), and organic matter (10%), and a recycled substrate including 90% coarse pumice (10–20 mm) and municipal compost (10%), were tested in three depths of 4, 7 and 10 cm. Tested plant species included Achillea millefolium , Armeria maritima , Sedum acre and Sedum album . Overall, the commercial substrate performed better than the recycled pumice. In addition, deeper substrates promoted greater survival and growth for nearly all species tested. Either A. maritima or A. millefolium survived in the recycled pumice at any depth, whereas they did survive when grown in the commercial substrate in greater than 7 cm and 10 cm, respectively. They both likely would require supplemental irrigation to be acceptable for green roofs in Istanbul or locations with a similar climate. Both Sedum species survived in all substrate types and depths. Information gained can be utilized by green roof professionals in the Istanbul region and in other parts of the world with a similar climate.

Effect of substrate depth on 18 non-succulent herbaceous perennials for extensive green roofs in a region with a dry spring

2014 ◽  
Vol 71 ◽  
pp. 490-500 ◽  
Author(s):  
Hui Zhang ◽  
Shanshan Lu ◽  
Jian Wu ◽  
Yi Jiang ◽  
Yingmin Lu ◽  
...  
Keyword(s):  
Green Roofs ◽  
Herbaceous Perennials ◽  
Substrate Depth ◽  
Extensive Green Roofs

scholarly journals Substrate Depth Influences Sedum Plant Community on a Green Roof

HortScience ◽  
2009 ◽  
Vol 44 (2) ◽  
pp. 401-407 ◽  
Author(s):  
Kristin L. Getter ◽  
D. Bradley Rowe
Keyword(s):  
Plant Community ◽  
Plant Stress ◽  
Green Roof ◽  
Green Roofs ◽  
Plant Performance ◽  
Blue Spruce ◽  
Waterproofing Membrane ◽  
Substrate Moisture ◽  
Substrate Depth

Because the waterproofing membrane beneath green roofs is estimated to last at least 45 years, long-term plant performance beyond initial establishment is critical. Plants that survive initially on a green roof may not exist in the long term because of variability in climate and other factors. This study evaluated the effect of green roof substrate depth on substrate moisture, plant stress as measured by chlorophyll fluorescence, and plant community development and survival of 12 Sedum species over 4 years in a midwestern U.S. climate during 4 years of growth. Plugs of 12 species of Sedum were planted on 8 June 2005 and evaluated biweekly for absolute cover (AC). Most species exhibited greater growth and coverage at a substrate depth of 7.0 cm and 10.0 cm relative to 4.0 cm. For the species evaluated, substrate depths of at least 7.0 cm are highly recommended. AC of Sedum was significantly greater at this substrate depth than at 4.0 cm. Mean volumetric moisture content of the three substrate depths followed the same pattern as AC. When averaged over time, the 4.0-cm substrate depth held less moisture than depths of 7.0 or 10.0 cm, whereas the 7.0- and 10.0-cm substrate depths were statistically the same. Species exhibiting the greatest AC at all substrate depths were S. floriferum, S. sexangulare, S. spurium ‘John Creech’, and S. stefco. In general, species that are less suitable at these substrate depths are S. ‘Angelina’, S. cauticola ‘Lidakense’, S. ewersii, S. ochroleucum, and S. reflexum ‘Blue Spruce’.

scholarly journals Monitoring and Modeling the Long-Term Rainfall-Runoff Response of the Jacob K. Javits Center Green Roof

Water ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1494 ◽  
Author(s):  
Noura Abualfaraj ◽  
Joseph Cataldo ◽  
Yara Elborolosy ◽  
Daniel Fagan ◽  
Sloane Woerdeman ◽  
...  
Keyword(s):  
New York ◽  
Environmental Protection Agency ◽  
Green Roof ◽  
Substantial Reduction ◽  
Cost Effective ◽  
Green Roofs ◽  
The United States ◽  
Rainfall Runoff ◽  
Substrate Depth

Drainage from the 27,316-m2 Jacob K. Javits Convention Center (JJCC) green roof was investigated in the field to quantify the system’s long-term rainfall-runoff response. The JJCC hosts one of the largest extensive green roofs in the United States. Utilizing four years of rooftop monitoring data collected using a weather station, custom designed and built drainage systems, three Parshall flumes equipped with pressure transducers, and weighing lysimeters, this study quantified the 25.4-mm-deep green roof’s ability to decrease the volume and peak rate of runoff. With parameters derived from the site, the Environmental Protection Agency Stormwater Management Model (EPA-SWMM) predicted event total runoff volume and event peak runoff rates to within +10% to −20% and +25% to −15% of the observations, respectively. The analysis further indicated that approximately 55% of the cumulative precipitation that fell on the JJCC extensive green roof during the monitoring period (warm weather months, June 2014–November 2017) was captured and retained. The average percent retained on an event-basis was 77%, and average event runoff coefficient was 0.7, implying a substantial reduction in the volume and rate of runoff generated from the roof compared to the pre-green roof condition, when most, if not all, of the precipitated water would have immediately resulted in runoff. Our research suggests that, on average, 96% of rainfall events 6.35 mm or less were retained within the green roof, whereas 27% of the total event volume was retained for events greater than 12.7 mm in depth. A sensitivity analysis suggests if the substrate depth were increased, better stormwater capture performance would be achieved, but only up 127 mm, whereas increased precipitation coupled with warmer temperatures as a result of climate change could decrease the performance by up to 5%, regardless of substrate depth. An equivalency analysis suggested that even shallow green roofs can significantly reduce the required stormwater detention volume that New York City requires on new development. This particular green roof appears to be more than 18 times as cost-effective as a subsurface cistern would be for managing an equivalent volume of stormwater in Midtown Manhattan.

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