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Although development of low (extensive) and high (intensive) maintenance green roof systems has progressed significantly, studies on the function of the growing substrate as a living constituent are lacking. The objective of this review paper is to summarize current scientific knowledge on the components, composition, and characteristics of green roof substrates and to identify future research needs. Due to variations in climate and desired plant types, there is no universal growing substrate. An appropriate substrate is expected to provide permanent physical support for plants and possess a fine balance between free drainage and adequate plant available water and nutrient retention. Typical substrate components include minerals in natural or modified forms such as sand, lava rock, or expanded shale, clay and slate; recycled waste materials like crushed bricks or tiles, crushed or aerated concrete and subsoil; stabilized organic matter such as composts; and plastic materials and slow release fertilizers. Proportions of components vary among substrates based on target vegetation, green roof type, and other considerations. Better green roof management for maximum benefits will require characterizing, quantifying and understanding the impacts of plant species and building attributes such as aspect, slope, height and heating on substrate performance, and should be considered for future research.
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... These green roof system types are defined by the arrangement and depth of their components (i.e., substrate, drainage, design) which have an intended hydrologic function. Conventionally engineered green roof systems, which are designed to be lightweight, well-drained, and composed of substrate low in organic matter (Ampim et al., 2010;Young et al., 2014), are favored over natural systems with unknown characteristics. Natural soils and their analogs are often more complex and require alterations to use on green roofs to ensure they are lightweight and do not clog drainage systems or inhibit water movement due to ultrafine particles (Best et al., 2015). ...
... We saw these trade-offs particularly when comparing the CGR and QTR, but they were not as strong for the BGR, which completely stopped stormwater and nutrient runoff and also performed well in terms of aesthetics and pollination potential. The QTR substrate contained more clay (Supplementary Table 1) and more organic matter (in the form of dried reeds), which would result in higher nutrient and water retention capacity (Ampim et al., 2010;Olszewski and Young, 2011;Bunt, 2012;Speak et al., 2013). This could lead to potential benefits in stormwater and nutrient runoff retention but result in possible issues from finer particles causing clogs in the drainage (Ampim et al., 2010). ...
... The QTR substrate contained more clay (Supplementary Table 1) and more organic matter (in the form of dried reeds), which would result in higher nutrient and water retention capacity (Ampim et al., 2010;Olszewski and Young, 2011;Bunt, 2012;Speak et al., 2013). This could lead to potential benefits in stormwater and nutrient runoff retention but result in possible issues from finer particles causing clogs in the drainage (Ampim et al., 2010). Lack of drainage in the QTR substrate likely led to pooling of water that then quickly evaporated due to the shallow substrate depth. ...
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... Since roofs cover approximately 20-25% of the total urban surface area the utilization of green roofs provide less energy consumption and thermal comfort to urban dwellers than other greening techniques (Cascone, 2019). Beyond everything, roof greening can mitigate the UHI effect through International Research Symposium -2021 University of Vocational Technology evapotranspiration, improve storm water management and air quality by absorbing dust, smog and other pollutants, reduce energy consumption and add ecological value to the urban environments (Ampim et al., 2010). Intensive and extensive green roofs are the main two categories of green roofs. ...
... Since roofs cover approximately 20-25% of the total urban surface area the utilization of green roofs provide less energy consumption and thermal comfort to urban dwellers than other greening techniques (Cascone, 2019). Beyond everything, roof greening can mitigate the UHI effect through International Research Symposium -2021 University of Vocational Technology evapotranspiration, improve storm water management and air quality by absorbing dust, smog and other pollutants, reduce energy consumption and add ecological value to the urban environments (Ampim et al., 2010). Intensive and extensive green roofs are the main two categories of green roofs. ...
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Assessment the availability of suitable non-metalize different packing materials of the Sri Lankan biscuit industry with respect to evaluate quality factors of the packing materials
... Since roofs cover approximately 20-25% of the total urban surface area the utilization of green roofs provide less energy consumption and thermal comfort to urban dwellers than other greening techniques (Cascone, 2019). Beyond everything, roof greening can mitigate the UHI effect through International Research Symposium -2021 University of Vocational Technology evapotranspiration, improve storm water management and air quality by absorbing dust, smog and other pollutants, reduce energy consumption and add ecological value to the urban environments (Ampim et al., 2010). Intensive and extensive green roofs are the main two categories of green roofs. ...
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This study was aimed at investigating the effects of students’ attitudes towards online learning during the Covid19 Pandemic and focused on students in the University of Vocational Technology (UoVT). The study reveals insights on students’ attitudes towards online learning during the Covid19 pandemic with the objectives intended on giving an understanding of how students' attitude towards online learning depends on the online learning experience. The study exerted a quantitative approach with descriptive statistics and regression analysis utilizing Management undergraduates in the University of Vocational Technology as respondents. The results of the study denote that the independent variables correlate with the depicted dependent variable, demonstrating that the model is statistically significant. The outcome derived from the study was that the students’ experience of their attitude towards online learning at the UoVT is favorable in the essential education and environment experience and technological availability and accessibility, though there is a refusal toward the psychological and emotional attitudes of the students towards online learning. This study emphasizes its importance in serving as an interpreter of prospective students’ attitudes toward e-learning and evidence for educationalists, investigators, policymakers, academics, decision-makers, stakeholders, or anybody interested in the
... University of Vocational Technology evapotranspiration, improve storm water management and air quality by absorbing dust, smog and other pollutants, reduce energy consumption and add ecological value to the urban environments (Ampim et al., 2010). Intensive and extensive green roofs are the main two categories of green roofs. ...
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The interest towards green roof implementation has highly boosted in tropical cities as a means of mitigating high daytime temperatures and thermal discomforts experienced by urban dwellers. This scientific review plans to evaluate the impact of plant species and growing substrates to enhance the thermal comfort of roof greening through a comprehensive overview of the existing literature. Accounting for plant species selection, height, morphology, thickness of leaves, size of leaves, and color of leaves were identified as the decisive factors in mitigating thermal stress. Sedum, Ipomea pescaprae, Nephrolepis spp and Euphorbiaceae family plants were identified as suitable species for integrating into tropical rooftops. The impact of the substrate media is another significant factor that determines the heat mitigation potentials of rooftop greeneries. Depth and composition of the substrate, water holding capacity and porosity properties were the key factors that determine the thermal performance of a specific substrate. Burned sludge, perlite and peat mixture were revealed as ideal substrates to rooftops of urban landscapes owing to their high thermal performance indices. Hence, the appropriate plant species and substrate selection are vital to optimize the thermal benefits associated with roof greening in the tropical context.
... Increasing organic matter content through greater addition of peat or compost also increases substrate water retention (Graceson et al., 2014;Hill et al., 2016;Nagase and Dunnett, 2011). However, organic matter decomposition reduces substrate depth (Emilsson and Rolf, 2005;Handreck and Black, 2002;Nagase and Dunnett, 2011), infiltration capacity and rootzone gas exchange and, increases waterlogging (Ampim et al., 2010;De-Ville et al., 2017;Friedrich, 2005). ...
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... Growing media are used for a variety of purposes such as soilless cultivation of vegetables in greenhouses (Asaduzzaman et al. 2015), the production of substrate mixtures for the hobby and professional market (Schmilewski 2008) and substrates for green roof systems (Ampim et al. 2010). The broad field of application of growing media is based on the formulation of different mixtures using constituents with diverse physical properties, including both organic and inorganic materials (Carlile et al. 2015). ...
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The provision of raw material is an important ecosystem service provided by peatlands. Using materials produced on re-established peatland sites can help to increase the interest of stakeholders in expediting further restoration measures. Promising possibilities include paludiculture and Sphagnum farming, which offer new perspectives for exploring renewable alternatives to peat as constituents of growing media. Therefore, gaining knowledge about processing and physical properties of the material becomes increasingly necessary. The hydro-physical properties of harvested and processed Sphagnum palustre L. biomass can compete with those of peat and coir, which are materials traditionally used in the horticultural industry. Even a partial substitution of peat with Sphagnum biomass increased maximum water-holding capacities and plant available water contents of mixtures while increasing wettability and hydration efficiency.
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Green roof substrates provide water, nutrients, and physical support to vegetation development, as well as being a key element in the hydrological performance of the system. In this regard, the use of aggregate components that improve physicochemical properties of the substrates optimises the ecosystem services provided by green roofs. This study demonstrates the effects of using rice husk as an aggregate material in engineered substrates for extensive green roofs. Sixteen different substrates compositions were tested with different proportions of natural (NRH) and carbonized (CRH) rice husk incorporated into a base mixture with fixed proportions of vermicompost, vermiculite, and construction waste. The study consists of two phases: i) laboratory analyses to assess the substrates' physicochemical properties, and ii) a pilot-scale field experiment to evaluate hydrological performance under real subtropical climate conditions and vegetation development using a monoculture planting of Sedum rupestre. The findings showed that CRH has the potential to improve some physicochemical properties, such as water holding capacity, bulk density, and porosity. Additionally, CRH substrates presented a slightly increased average retention rate (up to 7%) comparing to local topsoil. The average stormwater retention rate for all engineered substrates was 77.73%. Multiple linear regression models were satisfactorily fitted to observed data from the open field experiment allowing an estimation of potential substrates’ retention rates. Moreover, vegetation development was positively affected by adding CRH comparing to the NRH. Carbonized rice husk presents as a useful material for improving green roof substrates properties and could be a sustainable alternative for local agriculture waste management.
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Soilless container media have almost no capacity to retain PO4 or K. The nutrient retention of two calcined clays, attapulgite and arcillite, and brick chips, precharged with PO4 and K, was investigated. These could serve as an alternative slow-release fertilizer when incorporated into a soilless medium as a component of the mix. Sorption curves were developed at 25 °C for attapulgite of two particle sizes (0.8 to 1.6 mm and 1.6 to 3.2 mm), arcillite (1.1 to 3.2 mm), screened pieces of brick (1.0 to 3.6 mm), and a medium of 7 sphagnum peat : 3 perlite (v/v) using solutions of KH2PO4 (P at 0 to 20,000 mg·L-1). Curves indicated that PO4 and K sorption were similar for both particle sizes of attapulgite, so only the larger size [1.6 to 3.2 mm (8 to 16 mesh)] was used in greenhouse studies. Materials were evaluated in greenhouse studies by growing 'Sunny Mandalay' chrysanthemum [Dendranthema xgrandiflora Kitam. (syn. Chrysanthemum xmorifolium Ramat.)]. The precharged materials were tested at 10%, 20%, and 30% by volume of a peat : perlite root medium. Phosphate, K, and pH were determined on unaltered medium solutions collected throughout the cropping cycle and foliar analyses were determined on tissue collected at midcrop and end of the crop. Data indicated that precharged calcined clays retained and released PO4, and to some degree K, over time. Precharged clays did not provide K at levels which met plant needs during the latter half of the cropping cycle, but it was released and used at appreciable levels during the first month of crop production. Growth of plants receiving PO4 solely from precharged attapulgite and arcillite at 20% of the medium volume was not significantly different from that of a commercial control when the leaching fraction was maintained at 0.2. However, release of PO4 from the brick chips was not enough to match plant demand. Phosphate lost through leaching from the precharged clays was reduced by about two-thirds compared to control plants fertilized with P at 46.5 mg·L-1 from water-soluble fertilizer at each watering.
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On the roof of a building 90 shallow containers were filled with 10 cm substrate. This first year was characterized by annual plants. The living conditions on the north side (60 species, which produced 48.4 g/m² biomass May-September) are better than on the south side (38 species 18.3 g/m² biomass). -from Author
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Use of green roof technology is becoming increasingly widespread throughout the world because of its environmental, economic, and aesthetic benefits. The ability of a green roof to retain stormwater and limit the amount of fertilizer in the effluent flow are important characteristics of a properly installed green roof system. However, scientific research quantifying these characteristics is limited - particularly in the United States. Simulated rooftop platforms were constructed and runoff was analyzed from four commercially available green roof systems containing three distinct vegetation types. Quantity of rainfall retained ranged from 38.6% for Xeroflor to 58.1% for Siplast. Quantitatively, Xeroflor resulted in the greatest volume of runoff, but these volumes were only significant for the sections of Sedum plugs and seed during the fourth rainfall event. Differences in water retention can likely be attributed to substrate depth, rather than drainage system or vegetation type. Results demonstrate two important concepts that affect the amount of stormwater a green roof can retain - substrate thickness and substrate moisture content immediately prior to a rainfall event. Nitrate concentrations in the runoff varied from 0.22 ppm in the Sarnafil native plant sections 314 days following fertilizer application to 22.7 ppm in Xeroflor Sedum seed sections 314 days following fertilizer application. No significant differences were observed between any of the treatments with regard to phosphorus concentrations.
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Because of greater interest in green roofs in the United States, it is critical to increase the number and geographic range of proven plant resources for long-term survival on rooftops. Successful plant taxa for extensive green roofs must establish themselves quickly, provide high groundcover density, and tolerate extreme environmental conditions. Furthermore, dead load weight restrictions on many buildings may limit the substrate depth that can be applied. The objective of this study was to evaluate the effect of substrate depth on initial establishment and survival of 25 succulent plant taxa for green roof applications in the midwestern United States. Survival, initial growth, and rate of coverage were compared for plants grown in three substrate depths (2.5, 5.0, and 7.5 cm) on 24 roof platforms. Plant coverage was determined from image analysis of weekly digital photographs. Results indicate deeper substrates promote greater survival and growth; however, in the shallowest depth of 2.5 cm, several species continued to persist. Of the 25 species initially planted, only 47% survived in the deepest substrate of 7.5 cm. Recommended species at the depths tested for climates similar to southern Michigan include Phedimus spurious Raf. 'Leningrad White', Sedum acre L., S. album L. 'Bella d'Inverno', S. middendorffianum L., S. reflexum L., S. sediforme J., and S. spurium Bieb. 'Summer Glory'. Subsidiary species that are present at specific substrate depths but may not exhibit an ability to cover large areas include S. dasyphyllum L. 'Burnatii', S. dasyphyllum L. 'Lilac Mound', S. diffusum W., S. hispanicum L., and S. kamtschaticum Fisch. The primary deterrent for these subsidiary species was little to no survival at 2.5 cm. Deeper substrates promoted greater survival and growth for nearly all species tested.
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Four substrates were investigated for their efficacy as roof garden vegetative layers. The substrates comprised a sandy loam soil (S), sandy loam soil amended with urea formaldehyde resin foam (S:F) in a proportion of 60-40 v/v, sandy loam soil amended with peat and perlite (S:P:Per) in a proportion of 50-30-20 v/v and peat amended with urea formaldehyde resin foam (P:F) in a proportion of 60-40 v/v. The substrates were evaluated for their physical and chemical properties and their capacity to sustain growth of Lantana camara L. Physical and chemical evaluation included weight determination at saturation and at field capacity, bulk density determination, water retention, air filled porosity at 40 cm, pH and EC. When compared to the control (S) a weight reduction of 16.8%, 23.9% and 70.3% was obtained at field capacity with S:F, S:P:Per and P:F substrates respectively. Bulk density was reduced by 46%, 43% and 95%, in substrates S:F, S:P:Per and P:F, respectively, compared to the control substrate S. Air-filled porosity at 40 cm was slightly increased for substrate S:F while it was substantially increased for substrate P:F. The pH response between the initiation and the termination of the study was similar for the four substrates. EC decreased in substrates S and S:P:Per but increased in substrates S:F and P:F. Plant growth was monitored as shoot length, shoot number, main shoot diameter and the number of buds and flowers. Substrates S and S:F resulted in similar plant growth, while substrate S:F promoted flowering. Substrate S:P:Per induced slow plant growth during the first 6 months which subsequently increased resulting in a final growth that was satisfactory and comparable to the S and S:F substrates. Substrate P:F did not support sufficient plant growth and its use should be considered only in special cases where reduced weight of the roof garden is imperative.
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Green roof technology in the United States is in the early development stage and several issues must be addressed before green roofs become more wide-spread in the U.S. Among these issues is the need to define growing substrates that are lightweight, permanent, and can sustain plant health without leaching nutrients that may harm the environment. High levels of substrate organic matter are not recommended because the organic matter will decompose, resulting in substrate shrinkage, and can leach nutrients such as nitrogen (N) and phosphorus (P) in the runoff. The same runoff problems can occur when fertilizer is applied. Also, in the midwestern U.S., there is a great deal of interest in utilizing native species and recreating natural prairies on rooftops. Since most of these native species are not succulents, it is not known if they can survive on shallow, extensive green roofs without irrigation. Five planting substrate compositions containing 60%, 70%, 80%, 90%, and 100% of heat-expanded slate (PermaTill) were used to evaluate the establishment, growth, and survival of two stonecrops (Sedum spp.) and six nonsucculent natives to the midwestern U.S. prairie over a period of 3 years. A second study evaluated these same plant types that were supplied with four levels of controlled-release fertilizer. Both studies were conducted at ground level in interlocking modular units (36 × 36 inches) designed for green roof applications containing 10 cm of substrate. Higher levels of heat-expanded slate in the substrate generally resulted hi slightly less growth and lower visual ratings across all species. By May 2004, all plants of smooth aster (Aster laevis), horsemint (Monarda punctata), black-eyed susan (Rudbeckiet hirta), and showy goldenrod (Solidago speciosa) were dead. To a lesser degree, half of the lanceleaf coreopsis (Coreopsis lanteolata) survived in 60% and 70% heat-expanded slate, but only a third of the plants survived in 80%, 90%, or 100%. Regardless of substrate composition, both 'Difrusum' stonecrop (S. middendorffianum) and 'Royal Pink' stonecrop (S. spurium) achieved 100% coverage by June 2002 and maintained this coverage into 2004. In the fertility study, plants that received low fertilizer rates generally produced the least amount of growth. However, water availability was a key factor. A greater number of smooth aster, junegrass (Koeleria macrantha), and showy goldenrod plants survived when they were not fertilized. Presumably, these plants could survive drought conditions for a longer period of time since they had less biomass to maintain. However, by the end of three growing seasons, all three nonsucculent natives also were dead. Overall results suggest that a moderately high level of heat-expanded slate (about 80%) and a relatively low level of controlled-release fertilizer (50 g·m-2 per year) can be utilized for green roof applications when growing succulents such as stonecrop. However, the nonsucculents used in this study require deeper substrates, additional organic matter, or supplemental irrigation. By reducing the amount of organic matter in the substrate and by applying the minimal amount of fertilizer to maintain plant health, potential contaminated discharge of N, P, and other nutrients from green roofs is likely to be reduced considerably while still maintaining plant health.