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

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.

THERMAL PERFORMANCE OF AN EXTENSIVE GREEN ROOF UNDER SEMI-ARID CONDITIONS IN CENTRAL ARGENTINA

Extensive green roofs improve the provision of ecosystem services in urban environ-ments,particularly in semiarid regions.The aim of this paper is to compare their thermal performance during six months between two rooms,one with a green roof and the other with a conventional roof,in Córdoba(Argentina).The room with a green(planting)roof showed a lower inside surface temperature since the begin-ning of the study than the control room(between 5-6°C of difference).During the selected period,the indicators such as temperature amplitude(the difference between the maximum and the average temperature)and the anti-interference characteristics of the layers to the outdoor air temperature are produced a better performance for the green roof compared to the conventional roof.The pattern of a better perfor-mance was consistent across the study for the green roof,characterized by a higher cooling and warming of the roof surface during the day and night,respectively.The green roof was more effective at blocking an upward heat flux during the day and suppressing heat loss during the night.Evaporation,conductive flux and climatic conditions seem to dominate the thermal performance of green roofs in areas with semiarid climate conditions.

Vegetation composition of old extensive green roofs(from 1980s Germany)

Introduction:Since their development in the late 1970s in Germany,extensive green roofs(EGR)have become increasingly popular as mitigation tools for urban environmental issues around the world.EGRs are planted with select species,which ensure consistent cover and performance over time.This research presented herein is part of a systematic re-evaluation of EGR technology since the German industry began.Methods:Given the opportunity to access a small sample of old EGRs installed over 20 years ago in south-west Germany,this research surveyed the vegetation and substrate with an interest in describing these parameters with time-through-space substitution.Results:Similar to previous studies,this preliminary work found correlations between roof age with vegetation(cover abundance and species diversity)and substrate properties(e.g.,depth,organic content,pH,and nutrients).Roof age had positive relationship with soil organic content(Corg),and negative relationships with substrate depth and soil pH.These soil variables are inter-related,as shallow acidic substrates create unfavourable conditions for decomposition and thereby the accumulation of duff.Substrate variables correlated with EGR vegetation,suggesting a trend of simplified species composition over time.Indeed,Corg had a negative relationship with cover and species diversity of most life forms;only Sedum species had positive associations with Corg.Conclusions:Considering the dynamics associated with shallow mineral substrates,and the greater floristic diversity of younger roofs,simple Sedum-based vegetation may represent a steady state for conventional EGRs.

Green roofs for storm water management:a review

The rapid urbanization and industrialization involve an unsustainable use of natural systems,leading to various problems in cities.The urban hydrological system experiences fluctuating amount of surface runoff water when it rains heavily.It has been suggested that green roofs significantly mitigate storm water runoff generation even in tropical climate.Green roofs have become popular due to its proven benefits by mitigating urban heat island effects and protecting biodiversity.The annual rainfall and runoff relationship for green roofs is determined by the depth of the substrate.Water retention capacity mostly depends on substrate's physical conditions such as dry or wetness.Generally 6 mm to 12 mm rainfall is required for dry substrate to initiate runoff whereas response of wet conditions is mostly straight.Besides,there are some other factors affecting runoff dynamics such as type of a green roof and its slope,age of green roof,type of vegetation,soil moisture characteristics,weather.The review indicates that there is not much research in green roofs performance over storm water runoff;hence there is a need for further research.This paper reviews and addresses the role of green roofs in urban storm water management.

MEDIA COMPOSITION INFLUENCES GREEN ROOF PLANT VIABILITY IN THE OZARK HIGHLANDS

Plant selection and establishment are critical components for green roof health and success. Plant palettes (sets of plant species selected for specific conditions) for green roofs vary in their ability to confer benefits depending on the species make-up and their adaptation to particular environments and climates. The response of various species to climatic factors on rooftops is unknown for the Ozark Highlands region. The objective of this study was to compare plant survival and spread in three growing medium treatments (course and fine texture with compost and fine texture with no compost) installed as part of a green roof system. The study was performed on a green roof system at the University of Arkansas in Fayetteville over 3 years. Data were collected on 13 species installed in September of 2006 and surveyed on three dates thereafter: April 30, 2007;May 19, 2009;September 10, 2009. The treatments with added compost had statistically greater vegetated cover (from 73 to 87%) compared to the fine medium without compost (36 to 43%). In most cases the spread of individual plants was not significantly different between treatments. Results indicated that rooting medium containing compost increased survival and overall vegetated roof coverage, and identified various potential green roof plant species for the Ozark Highland environment. Two species, Sedum middendorffianum var. diffusum and Sedum spurium ‘Roseum’, did particularly well in all treatments. One species, Sedum kamtschaticum, did well only in the treatments with compost.