Research Of Plant Mixtures And Substrate Depths On Extensive Green Roofs In Beijing Area

Vegetated green roofs is an increasingly popular method for mitigating the negative environmental impacts of urbanization. Considering that climate and precipitation characteristics, building conditions and the capital functions of Beijing, extensive green roofs which main features are light, low maintenance and less irrigation are more suitable be widely used. However, Extensive green roofs have some defects, such as few plant species and monotonous visual appearance. Few papers that experimentally manipulated diversity and the influence of substrate depths on green roofs. This paper describes an experiment investigating the effects of plant mixtures and substrate depths on extensive green roofs.7 plant mixtures were tested on substrates of 3 different depths (7cm,10cm,15cm), there had no irrigation except the first 3 mouth during this study.It was concluded that (1) In terms of all data, NO.5 (S. reflexum, S. spurium ’Coccineum’ and S.spurium’Splendens’) were the best plant mixture in this study.(2) Deeper substrate promoted higher plant survival and coverage, better appearance and growth vigor, as well as higher substrate moisture content. Plants on 15cm substrate showed higher tolerance response to environmental stress. There were 5,6 and 10 species performed well on 7cm,10cm and 15cm substrate depth.(3) Sedum lineare, S. album cv. ’Coral Carpet’, S. reflexum and S. reflexum were the best plants on rooftop. In contrast, Androsace incan and Phlox subulata showed poor performance in this study. In addition, there were some species grow well on different substrate depths, including Iris ’Music box’ (7cm,15cm), S. sexangulare (10cm,15cm), S. Spurium ’Coccineum’ (10cm), S. acre, Allium senescens and S. sarmentosum Bunge (15cm).(4) It was more difficulty for most species to survive during the drought summer. Most species were safe through the winter apart from Thymus hybrid, Saponaria officinalis, Phlox subulata and Chrysanthemum morifolium.(5) The plants in NO.2 and NO.5 plant mixtures had a symbiosis. S. album cv.’Coral Carpet’ suppressed another 2 species growth, especially S. acre in NO.1 plant mixture. Thymus hybrid and S. Sarmentosum Bunge performed well during 2014, but S. Sarmentosum Bung showed strong competitive power in 2015 in NO.3. In NO.4 and NO.6, Chrysanthemum morifolium was competitive.