Slope Roof Turf Establishment Technology

With the urbanization process accelerating, green roof methods has received more and more attention for increasing more green areas in the limited urban landscape resources. Now green roofs have become one of the city's ecological construction components. Almost all greenroof researches are focused on the flat roofs. However, most of the urban buildings are constructed with the slope roofs. Few reports about green technical studies on the slope roofs can be found, which limits the development of green roof in China. Our studies were carried out on a simulated slope green roof of 37 degree. The main contents include the screening of plants for slope green roofs from the summer performance, the effects of sandy and loamy growth mediums on the plant growth on the slope roofs, the environmental difference in southern and northern slopes and their effects on plant growth, and the improvements of ladder-type structure in water and nutrients retention in the soil and plant performance. The results are showed as followings:(1) Among the four tested plant species, Sedum lineare performed steadily throughout the whole summer with no significant changes in plant coverage ratio and plant density, and showed the best heat tolerance in the summer months. However, the cooling effects of Sedum lineare was the lowest, showed the higher canopy and soil temperatures on the roofs, when compared to other three plant species. Seashore Paspalum showed the best cooling effects for the roofs among all tested plants, and could achieve the highest turf quality and quick recovery from the heat injury, but the plant coverage ratio and density declined significantly under the prolonged high temperature during the summer months. Bermuda, and zoysia also showed good cooling effects on green roofs, but their summer performance were no as good as Seashore Paspalum.(2) The water retention capacity of loamy growth medium (sand : clay = 2 : 1) was significantly higher than sandy growth medium (sand : peat = 10 :1). During the summer months, the water content of loamy growth medium was significantly higher than the sandy and still reached 14.53% and 12.97% in Seashore Paspalum and Sedum lineare roofs, respectively, compared to 10.43% and 8.15% in sandy growth medium. The growth of Seashore Paspalum was more impacted by medium water content. Plants showed severe water deficit stress with lower plant relative water content, palnt coverage ratio, density, and biomass in sandy growth medium than the loamy. The root activity of Sedum lineare in sandy growth medium was significantly higher than that in the loamy, but no significant difference was detected in the Seashore Paspalum roof.(3) There were significant environmental differences between the southern slope roof and the northern slope roof, with the higher light radiation intensity, medium temperature, and water evaporation in the south than the north. Such environmental differences impacted significantly on the growth of Seashore Paspalum. The plant coverage ratio, density, biomass, and relative water content of plants in the south with lower medium water content were significantly lower than that in the north with higher medium water content. Environmental differences impacted significantly on RWC and relative conductivity of Sedum lineare, while impacted little on growth. plant root activity was higher in the soutgh than the north of two grasses..(4) The ladder-structure roof had significant effects on the medium water content and achieved more uniform of medium water in the upper and the lower part of the roof when compared the common slope, resuling in higher leaf relative water content, plant coverage ratio, density, showed the significant improvement in water and nutrients retention capacity. The ladder-structure roof improved the growth environment of upper part of the roof, especially in the 25 cm of upper roofs in this study, thus achieved a uniform growth of plants in the slope roofs. These results showed that the potential application of the ladder-structure in slope green roof technology.Our results indicated that Sedum lineare could be a good candidate plant for slope green roofs because of its steady seasonal performance, but its disadvantage is inefficient cooling effect on green roofs. Seashore Paspalum had the best cooling effects on green roofs, but its disadvantage is quality decline during the summer months under prolonged heat stress. It could be also considered as a good candidate plant for slope green roofs because it can be soon recovered. The loamy growth medium with higher water retention capacity is more suitable for slope green roofs when compared to the sandy growth medium with lower poor water retention capacity. The plants grew better in the northern slope than that in southern slope in our study, which indicated that more water supply should be supplied to southern slope green roofs. The ladder-structure showed effective improvements for plants growth in the slope green roofs.