Green Roofs in Arid and Semi-arid Climates

A special issue of Land (ISSN 2073-445X). This special issue belongs to the section "Land Planning and Landscape Architecture".

Deadline for manuscript submissions: 30 June 2024 | Viewed by 6336

Special Issue Editors


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Guest Editor
Laboratory of Floriculture and Landscape Architecture, Department of Agriculture, School of Agricultural Sciences, Hellenic Mediterranean University, Heraklion, 71410 Crete, Greece
Interests: landscape architecture, design and restoration; green roof establishment in semi-arid climates; vertical green walls; turfgrass science, culture and management; urban agriculture and food production; selection of native species for establishing sustainable green roofs; substrate selection for horticulture and green roof systems; environmental protection from agrochemical leaching; plant communities and plant interaction, allelopathy; water stress plant physiology; landscape design and restoration; stabilization and restoration of inclined surfaces
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Laboratory of Floriculture and Landscape Architecture, Department of Crop Science, Agricultural University of Athens, Iera Odos 75, 11855 Athens, Greece
Interests: urban horticulture; green roofs; living walls; turfgrass science and management; inorganic and organic amendments

Special Issue Information

Dear Colleagues,

During the last two centuries, uncontrolled urbanization has resulted in contemporary cities being characterized by dense buildings and constructions, sealing of surfaces and a lack of open and green spaces. The rapid intervention of humans in the natural surroundings has caused irreversible damage to the urban landscape and climate, which has led to deterioration in several aspects of the urban environment, landscape and quality of life.

Based on the continuously expanding growth of cities and severe reduction in urban open spaces, it has become obvious that buildings and constructions could serve as a matrix element for establishing new flora within cities. More specifically, green roofs have the potential to serve as elements for re-introducing the lost flora and fauna within cities. Their advantages include environmental and esthetic aspects, such as building energy savings, mitigation of the urban heat island effect, noise and dust abatement, stormwater management and improvement of inhabitant life quality. Their numerous environmental and esthetic advantages have turned them into the most widely used technical solution by architects worldwide, while stakeholders and public bodies are gradually providing innovative initiatives to promote their application.

Green roofs used to be more applicable to northern climates, but in the course of the last 20 years, an increasing number of studies have evaluated their establishment and management in arid and semi-arid climatic zones. Research has provided most of the necessary elements for studying, establishing and managing green roofs in semi-arid and arid climates, including building energy savings, runoff retention, substrate type and depth selection, environmental impacts, plant selection and their drought and salinity tolerance, urban food production, water and irrigation requirements, and flora and fauna biodiversity contribution.

We cordially invite the submission of original contributions on green roof research and technology. This Special Issue, “Green Roofs in Arid and Semi-arid Climates”, of MDPI’s Land journal (impact factor: 3.905) is considered a boost to this ongoing research as well as a highlight of new sectors of green roofing that are currently being investigated.

A wide range of reviews or research topics on green roofing in arid and semi-arid climates will be published in this Special Issue. Some indicative subject areas include: substrate and drainage layer selection, quantification of environmental benefits, leaching of pollutants, runoff and flood abatement, flora and fauna biodiversity and pollinators, plant species selection and irrigation requirements, recycled water irrigation, plant species’ tolerance of drought and salinity, plant stress physiology, biotic and abiotic stresses, fertilization, establishment and management, thermal savings and comfort, urban agriculture and food production, economics and depreciation, and sensors and monitoring.

Dr. Panayiotis Nektarios
Dr. Nikolaos Ntoulas
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • green roofs
  • arid and semi-arid climates
  • urban landscape and environment
  • drought/heat resistance and tolerance
  • biodiversity

Published Papers (6 papers)

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Research

18 pages, 8360 KiB  
Article
Earlier Flowering Phenology and Pollinator Visitation on Urban Green Roofs Compared to Ground-Level Gardens
by Michael Guidi and Jennifer Bousselot
Land 2024, 13(2), 178; https://doi.org/10.3390/land13020178 - 02 Feb 2024
Viewed by 629
Abstract
Urban green space, green infrastructure, and horticultural installations are gaining recognition for their potential to foster biodiversity. Green roofs are challenging growing environments for plants, characterized by extreme substrate temperatures, high light intensity, limited moisture availability, and limited substrate depth. Plants have a [...] Read more.
Urban green space, green infrastructure, and horticultural installations are gaining recognition for their potential to foster biodiversity. Green roofs are challenging growing environments for plants, characterized by extreme substrate temperatures, high light intensity, limited moisture availability, and limited substrate depth. Plants have a variety of physiological responses to these unique conditions, but little is known about how green roof growing conditions affect ecological characteristics like plant flowering phenology. Meanwhile, studies are only just uncovering the degree to which green roofs can provide habitat and support urban pollinator biodiversity. We evaluated the flowering phenology and made in situ pollinator observations of 15 plant taxa growing both on green roof systems and at ground level in Denver, Colorado, over two growing seasons. We found that flowering phenology occurs substantially earlier on green roofs compared to ground level among the observed plant taxa and observed a greater number of pollinators on green roofs early in the season, compared to ground level, presumably due to the availability of floral resources among the observed plant taxa. We observed significantly higher substrate temperatures along with wider diurnal temperature amplitude during the growing season that may contribute to the observed phenological patterns. Divergence in flowering phenology between individual plants of the same species on green roofs and plants at ground-level may have implications for organisms that rely on floral resources in urban environments. Earlier flower initiation on green roofs may provide pollinators with unique foraging opportunities and aid targeted conservation where early-season floral resources are limited. Full article
(This article belongs to the Special Issue Green Roofs in Arid and Semi-arid Climates)
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14 pages, 1942 KiB  
Article
Tolerance of Tall Fescue (Festuca arundinacea Schreb.) Growing in Extensive Green Roof Systems to Saline Water Irrigation with Varying Leaching Fractions
by Nikolaos Ntoulas, Georgios Papaioannou, Konstantinos Bertsouklis and Panayiotis A. Nektarios
Land 2024, 13(2), 167; https://doi.org/10.3390/land13020167 - 31 Jan 2024
Viewed by 556
Abstract
As urbanization intensifies environmental challenges in contemporary cities, widespread green roof installations emerge as a potential solution. This study explores irrigating tall fescue (Festuca arundinacea Schreb.) turfgrass with saline water in extensive green roof systems, aiming to conserve freshwater resources. The objectives [...] Read more.
As urbanization intensifies environmental challenges in contemporary cities, widespread green roof installations emerge as a potential solution. This study explores irrigating tall fescue (Festuca arundinacea Schreb.) turfgrass with saline water in extensive green roof systems, aiming to conserve freshwater resources. The objectives include determining the period of saline water tolerance and identifying the leachate electrical conductivity threshold affecting tall fescue’s green coverage. This greenhouse study comprised 24 lysimeters equipped with extensive green roof layering. Treatments included three NaCl irrigation solutions with an electrical conductivity of 3 dS m−1, 6 dS m−1, and 9 dS m−1, while tap water served as the control. Additionally, irrigation treatments were applied at two different regimes, resulting in an average leaching fraction of 0.3 for the low irrigation regime and 0.5 for the high irrigation regime. Tall fescue’s tolerance to saline water was evaluated through the determination of green turf cover (GTC) as well as the clipping dry weight and the leachate electrical conductivity (ECL) draining from the lysimeters. It was found that tall fescue turfgrass growing in extensive green roof systems can tolerate irrigation with water of electrical conductivity up to 9 dS m−1 for extended periods, approximating three months, without GTC declining below 90%, provided that a minimum leaching of 30% is maintained. Furthermore, irrigating with water at 9 dS m−1 resulted in a 24.5% reduction in cumulative clipping dry weight over the four-month study period. The regression analysis between GTC and ECL highlighted a substantial decline in GTC when ECL surpassed the critical threshold of 12.5 dS m−1. Full article
(This article belongs to the Special Issue Green Roofs in Arid and Semi-arid Climates)
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13 pages, 2250 KiB  
Article
Green Roofs Affect the Floral Abundance and Phenology of Four Flowering Plant Species in the Western United States
by Kyle Michael Ruszkowski and Jennifer McGuire Bousselot
Land 2024, 13(1), 115; https://doi.org/10.3390/land13010115 - 21 Jan 2024
Viewed by 1124
Abstract
This study investigates the potential for green roofs to support pollinator diversity and abundance in urban ecosystems through the altered floral phenology and floral abundance of plants. Floral phenology and the floral abundance of green roof plants are compared to plants grown at [...] Read more.
This study investigates the potential for green roofs to support pollinator diversity and abundance in urban ecosystems through the altered floral phenology and floral abundance of plants. Floral phenology and the floral abundance of green roof plants are compared to plants grown at grade on the Front Range in Fort Collins, Colorado, and how these changes may affect pollinator biodiversity in urban ecosystems. An independent block design is employed, within one green roof and one ground-level garden, approximately 120 m apart, with replicate plants of 4 species in each garden. Pollinator observations were made weekly during the bloom period for each species. Blue vane traps were used to passively measure pollinator diversity along a transect between the green roof sites and the sites at grade. The total number of flowers per plant is variable between site types, depending on the plant species. However, all species of plants tested bloomed earlier when grown on the green roof than when grown at grade. Pollinator abundance and diversity were low at both site locations. Green roofs may provide foraging opportunities earlier in the season in temperate regions, which can extend the duration of floral foraging opportunities when supported by green infrastructure at grade. Full article
(This article belongs to the Special Issue Green Roofs in Arid and Semi-arid Climates)
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19 pages, 11174 KiB  
Article
Simulation-Based Study on the Effect of Green Roofs on Summer Energy Performance in Melbourne
by Elmira Jamei, Gokul Thirunavukkarasu, Majed Abuseif, Mehdi Seyedmahmoudian, Saad Mekhilef, Alex Stojcevski and Hing-Wah Chau
Land 2023, 12(12), 2105; https://doi.org/10.3390/land12122105 - 25 Nov 2023
Viewed by 1136
Abstract
Green roofs are increasingly recognised as a crucial urban solution, addressing climate change, enhancing energy efficiency, and promoting sustainable architecture in densely populated areas. In this manuscript, the research study delves into the influence of green roofs on energy consumption, focusing on the [...] Read more.
Green roofs are increasingly recognised as a crucial urban solution, addressing climate change, enhancing energy efficiency, and promoting sustainable architecture in densely populated areas. In this manuscript, the research study delves into the influence of green roofs on energy consumption, focusing on the Treasury Place building in Melbourne, Australia. The utilisation of DesignBuilder and EnergyPlus simulations was explored. Various green roof parameters such as the Leaf Area Index (LAI), plant height, soil moisture, and tree coverage were optimised and compared against base case scenarios. The key findings indicate an optimal LAI of 1.08 for maximum energy savings, with diminishing returns beyond an LAI of 2.5. The soil moisture content was most effective, around 50%, while a plant height of approximately 0.33 m optimised energy reduction. The introduction of 50% canopy tree coverage provided temperature regulation, but increased soil moisture due to trees and their influence on wind flow had an adverse energy impact. These results emphasise the necessity for precise green roof representation and parameter optimisation for maximum energy efficiency. This research offers essential insights for those in urban planning and building design, endorsing green roofs as a pivotal solution for sustainable urban environments. Full article
(This article belongs to the Special Issue Green Roofs in Arid and Semi-arid Climates)
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19 pages, 2818 KiB  
Article
Coexistence and Succession of Spontaneous and Planted Vegetation on Extensive Mediterranean Green Roofs: Impacts on Soil, Seed Banks, and Mesofauna
by Christel Vidaller, Anaïs Jouet, Carmen Van Mechelen, Tania De Almeida, Jérôme Cortet, Lucie Rivière, Grégory Mahy, Martin Hermy and Thierry Dutoit
Land 2023, 12(9), 1726; https://doi.org/10.3390/land12091726 - 05 Sep 2023
Viewed by 1023
Abstract
Extensive green roofs are well known to improve the urban environment, but in the Mediterranean regions, dry climatic conditions pose the problem of their sustainability when no irrigation is applied. After planting or sowing in 2012, 18 local Mediterranean plant species on different [...] Read more.
Extensive green roofs are well known to improve the urban environment, but in the Mediterranean regions, dry climatic conditions pose the problem of their sustainability when no irrigation is applied. After planting or sowing in 2012, 18 local Mediterranean plant species on different types of exposure and substrate in a non-irrigated extensive green roof in Avignon (South-Eastern France), the physico-chemical characteristics of the soil, winter and spring soil seed banks, soil mesofauna and initially sown, planted, or spontaneous vegetation expressed on the surface were studied from 2013 to 2020. In 2020, significant differences related to the exposure conditions (shade/sun) and, to a lesser extent, to the depth of substrate used (5 cm/5 cm or 10 cm with a water retention layer) were found. The deeper plots in the shade have significantly higher soil fertility, cover, and vegetation height. However, the plots in the sun have higher moss cover, planted or sowed vegetation abundance, and springtail abundance. By 2020, more than half of the initially sown species had disappeared, except for several planted perennials and short-cycle annual species. On the other hand, a significant increase in the species richness of spontaneously established species was measured over time. In the absence of a permanent and transient seed bank for the sowed and spontaneous species, the plant community is then mostly dependent on species flows via the local surrounding seed rain. Planting perennial species (Sedum spp., Iris lutescens), followed by spontaneous colonization of species present in the vicinity of the roof would then represent a more efficient strategy for the persistence of extensive non-irrigated green roofs in Mediterranean environments than sowing a species-rich local Mediterranean seed mixture dominated by annual species. Full article
(This article belongs to the Special Issue Green Roofs in Arid and Semi-arid Climates)
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16 pages, 5815 KiB  
Article
Response of Spontaneous Plant Communities to Sedum mexicanum Cover and Water Availability in Green Roof Microcosms
by Dean Schrieke, Nicholas S. G. Williams and Claire Farrell
Land 2023, 12(6), 1239; https://doi.org/10.3390/land12061239 - 16 Jun 2023
Cited by 1 | Viewed by 989
Abstract
Lack of maintenance can lead to ‘weedy’ spontaneous vegetation on green roofs. Aspects of green roof design, including substrate depth and roof height, have been shown to influence the composition of spontaneous vegetation. In drier climates, Sedum species are often planted on shallow [...] Read more.
Lack of maintenance can lead to ‘weedy’ spontaneous vegetation on green roofs. Aspects of green roof design, including substrate depth and roof height, have been shown to influence the composition of spontaneous vegetation. In drier climates, Sedum species are often planted on shallow substrate ‘extensive’ green roofs and irrigated during summer to maintain cover. However, the response of spontaneous vegetation to Sedum cover and water availability is unclear. Understanding this relationship could help minimise maintenance and maintain Sedum vegetation cover. We hypothesised that increasing Sedum (Sedum mexicanum) cover and reduced water availability would reduce the abundance, biomass, species and functional richness, and the community weighted mean specific leaf area (SLA; CWM by abundance) of spontaneous plant communities. We conducted a 10-month experiment in green roof microcosms planted with S. mexicanum (0%, 25%, 50%, 75% and 100% total cover), subjected to a well-watered or water-deficit irrigation treatment, and sown with a mix of 14 plant species that commonly occur as spontaneous on green roofs. We measured spontaneous species abundance, community biomass, and functional traits (specific leaf area, leaf dry matter content, and relative growth rate), and calculated species and functional richness. Increasing S. mexicanum cover reduced spontaneous species abundance and species and functional richness but did not affect community biomass. Species richness was affected by the interaction of S. mexicanum cover and watering treatment and was greatest in well-watered microcosms with 0% S. mexicanum cover. Increased water availability increased spontaneous plant biomass but did not affect functional richness. The SLA of spontaneous communities was affected by the interaction of S. mexicanum cover and watering and was significantly greater in well-watered treatments where S. mexicanum cover was <100%. Therefore, maximising Sedum cover and limiting water availability on green roofs will likely limit the abundance, biomass, and diversity of spontaneous vegetation. Conversely, for green roofs where substrate is left to be naturally colonised, increasing water availability could encourage establishment and increase functional richness of spontaneous vegetation. Full article
(This article belongs to the Special Issue Green Roofs in Arid and Semi-arid Climates)
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