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Title: Investigation of the potential of calcareous grassland vegetation for green roof application in the UK
Author: Choi, Min-Sung
ISNI:       0000 0004 2728 8497
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2012
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For the last few decades, the interest in green roofs has been developing quickly because of the benefits they have on the modern urban environment situation. Recently, of the range of native habitats in the UK appropriate for green roof application, calcareous grassland plant communities have been given much attention for use on green roofs because of the similarity that these habitats have to green roof conditions. However, there has been very little or no research into how locally-characteristic habitats can be recreated on green roofs, and this has led to a lack of specific recommendations for native plant communities or assemblages on green roofs in the UK. Thus, this thesis investigates the feasibility of calcareous grassland vegetation for green roof application in the UK. This study is comprised of four sections; (i) A review of calcareous grassland types, ecology and characteristics, (ii) A discussion of the restoration ecology of calcareous grasslands, (iii) An investigation into substrates for supporting calcareous grasslands on green roofs, (iv) Experimental investigation of plant selections and communities for calcareous grasslands on green roofs. The substrates investigation consisted of testing mixtures containing Limestone, LECA (Light Expanded Clay Aggregate), Brick rubbles with organic matter and loam in five composition rates. Leucanthemum vulgare, Briza media, and Prunella vulgaris were selected as indicator species. All the substrates met the minimum requirements that conform to FLL standards (the German guidelines for green roofs, Society of Landscape Development and Landscape Design), except for LECA and Limestone substrate types that tended not to meet the minimum moisture content (20%). Most of the substrates supported high seedling survival. In general, Limestone substrate types and a 60:20:20 (mineral material: loam: organic matter) composition rate tended to produce high seedling emergence and growth across all of the species, while LECA and Brick rubble substrate types, and 100:0:0 composition rate did in the opposite. The most successful substrate was a Limestone substrate type with 60:20:20 composition rate that had relatively good balance of moisture content and air filled porosity, and supported high seedling emergence, survival and growth across all of the species. To investigate plant selection and plant communities for calcareous grasslands on green roofs, seventeen forb species were planted to investigate the environmental tolerances of a range of species and to explore patterns of plant growth and flowering performance at the community and individual species level. Deeper substrate depth, the Limestone-based substrate, supplementary watering, and fertiliser addition tended to support significantly higher plant abundance, growth, structural characteristics, and flowering performance of the plant community. Some of individual species, however, showed different responses. Watering was an important factor regarding plant establishment and growth, especially with substrates of shallower depth. A 50 mm deep substrate is not suitable for satisfactory plant growth without additional watering; Supplemental watering produced statistically similar plant growth in the shallower substrate to that of the deeper substrate without it. The minimum substrate depth should be at least 100 mm to support good growth of the species on a green roof. Most species did not show significant difference in plant growth and performance between 100 mm and 200 mm depth. All the species in the Limestone-based substrate had a higher abundance rate, and the Limestone-based substrate produced significantly greater plant growth than the Zinco substrate. Additional fertiliser resulted in greater plant abundance and growth but there was a tendency for plant growth to be very vigorous. Hypochaeris radicata and Leucanthemum vulgare showed the greatest abundance under drought conditions in the shallow substrate depth. Overall, C. glomerata and H. nummularium across all treatments in a standard commercial green roof substrate without fertiliser addition, and P. officinarum and P. veris across all treatments including the additional fertiliser treatment were not effective green roof plants under the given conditions of the experiment. Across all experimental treatments except for the additional fertiliser treatment, the one legume in the experiment (Lotus corniculatus) tended to dominate over the 2-year period.
Supervisor: Dunnett, Nigel Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available