Horticulture Meets Plant Ecology: Extensive Green Roofs Modeled from a Shortgrass Prairie Ecosystem

摘要

It has been suggested that the shortgrass prairie (aka, shortgrass steppe) of the western Great Plains be examined for native plant species suitable for cultivating on North American green roofs and also as a model for an extensive green roof ecosystem. To help explain this unique ecosystem more fully, this poster reviews the autecology of the dominant shortgrass prairie species, blue grama (Bouteloua gracilis) and the synecology of shortgrass communities. Next it discusses aspects congruent with extensive green roofs, and then proposes a different way of thinking about both above and below annual net productivity in the context of minimal maintenance inputs that is radically different from both strictly ecological and horticultural approaches. Shortgrass prairie has six key climatic characteristics resulting in a precipitation and temperate regime with the negative yearly water balance also found on green roofs: 1) high winds, 2) high insulation 3) high summer temperatures, 4) low winter temperature, 5) diurnal and seasonal temperature fluctuations, and 6) seasonal and long-term drought cycles. Other pertinent characteristics must be added to the mix and deal with soil (functional depth, fertility, organic matter, micro-organisms, texture and structure) and ecosystem factors (grazing, fire, competition and facilitation). Most of the preceding characteristics also guide plant selection in all types of roofgreening. A shortgrass prairie model for extensive green roof plantings might be applied over a large geographical area from Calgary and Winnipeg to Chicago, to St Louis and Dallas, and Kansas City, to Omaha and Minneapolis. After an establishment phase of 3-5 years, annual biomass production on extensive green roofs should not be an aim. Since the past approaches of both ecology and horticulture focus on biomass production, they have been blind to the possibilities of a system of living plants managed to produce homeostasis with balanced, yet low inputs and outputs of water, nutrients, and energy.