Northwest Urban Roof Garden Construction, A Preliminary Study

With the rise of roof garden construction in cities gradually in the world, the requirements for the technology of roof garden in cities becomes higher increasingly. The present research provided scientific and rational methods for seeking for roof garden plants by means of experiments on the stress resistance of common roof garden plants. Moreover, cost-benefit analysis was conducted to determine the better patterns of constructing roof garden by comparing roof lawn with rosebush gardening. Based on the research, the thesis provides theoretical foundation for spreading technology of roof garden in cities and the new idea of city ecological protection, and for constructing solid virescence in cities in the future. Three conclusions can be drawn as following:(1) About 30 plant species suitable for roof garden from abundant wilding resources in Shaanxi province were selected. The consideration for selecting these plants mainly lies in the difference between the ecological conditions on the roof and on the ground. On the roof, sunlight is fiercer;temperature fluctuation is wider;humidity is lower and winds are stronger, therefore, all the plants selected are of such features as being able to bear dryness and coldness, resist winds, easy to grow and light and beautiful, longer green period, shallow roots and growing slower.(2) The stress resistance of common roof garden plants, e.g. Dahlia hybrida, Callistephus chinensis, Calendula officinalis and Chrysanthemum multicaule were determined by mensurating such index as chlorophyll content, electrolyte leakage, water content, Pro content, MDA content and dissoluble sugar content. The result indicates that Dahlia hybrida is the best, Callistephus chinensis next, Calendula officinalis and Chrysanthemum multicaule are weaker as to drought resistance;while in the experiment on coldness resistance, the ability to bear coldness ranks from the best to the worst is Poa annua, Festuca arundinacea and Trifolium.(3) Comparison between experiment on roof garden in small-scale in soft cultivation soil with two kinds of plants indicated that roof garden has strong impacton roof temperature. In the experiment, gardening plants can decrease temperature of roof surface at most by 20.6 °C. Dahlia hybrida (rosebush) garden can decrease roof temperature more than Festuca arundinacea (lawn) garden can. However, according to the cost-benefit analysis, Festuca arundinacea (lawn) garden can compensate the costs earlier and obtain benefit earlier.