Effects of recycled aggregate growth substrate on green roof vegetation development: A six year experiment

Abstract

15Green roofs can potentially be used to tackle a variety of environmental problems, and 16 can be used as development mitigation for the loss of ground-based habitats. Brown 17(biodiversity) roofs are a type of green roof designed to imitate brownfield habitat, but 18 the best way of engineering these habitats requires more research. We tested the effects with larger plant coverage and diversity before the occurrence of a sequence of drought 31 disturbances, but was more strongly negatively affected by the disturbances than the 32 two less productive treatments. We suggest that this was due to the over-production of 33 plant biomass in the more productive treatment, which made the plants more vulnerable 34 to the effects of drought disturbance, leading to a kind of 'boom-bust' assemblage 35 dynamic. The 'ideal' amount of added organic matter for these green roof systems was 36 very low, but other types of green roof that have a larger water holding capacity, and/or 37 more drought resistant plant floras, will likely require more organic matter or fertiliser. 38Nonetheless, nutrient-supported productivity in green roof systems should be kept low 39 in order to avoid boom-bust plant assemblage dynamics. Research into the best way of 40 engineering green roof habitats should take place over a long enough multi-year time 41 period to include the effects of temporally infrequent disturbances. 42Keywords brown roof; development mitigation; drought disturbance; productivity 56 57 58 59 60 61 62 63 64 65 66 67 68 69

Plant Colonization of Green Roofs Is Affected by Composition of Established Native Plant Communities

“…The seasonal variation partly may have been an artifact of our sampling protocol, which involved repeated destructive sampling of colonists. Repeated disturbances (hand-pulling of colonists) may have favored disturbance-adapted species (Grime, 1979;Myers et al, 2015); however, colonist management is common on green roofs, especially during early establishment, and green roofs are subject to repeated drought disturbances that can drive changes in plant composition (Bates et al, 2013(Bates et al, , 2015Brown and Lundholm, 2015). Accordingly, different patterns of disturbance, or the absence of disturbance, could result in different patterns in colonist composition than those observed in the current study.…”

Biodiversity Impact of Green Roofs and Constructed Wetlands as Progressive Eco-Technologies in Urban Areas

“…With regard to temporal trends in plant abundance, these essentially resemble successional patterns known from ground-level habitats, with annual therophytes often dominating initial stages but declining afterwards, perennial species increasing [90][91][92], and shrubs or meadows developing in the long-term, depending on environmental constraints such as moisture [92]. Also, with increasing roof age, plant species spontaneously colonize roofs [42,45] and overall plant abundance tends to increase ( [43,89,93,94] but see [41,69]).…”

Urban Stormwater Characterization, Control, and Treatment

“…The challenge to maintain vegetation in thin, nutrient-poor greenroof media has driven research to promote vegetation persistence. Bates et al (2015) found plant recovery from drought was facilitated by media characteristics, with media high in crushed brick performing the best from a group of recycled aggregate materials tested. Additives for increasing the water holding capacity of media such as polyacrylamide gel have been shown to significantly increase plant recovery following a drought period (Young et al, 2015), while others have shown biologically based additives such as seaweed hold promise to improve both water and nutrient holding capacity of greenroof media (Vijayaraghavan and Joshi, 2015).…”