The Resistance Of Greening Woody Plants

Roof greening as a major highlight of the urban greening is more and more popular. Currently roof greening plant material is unitary in most of the cities, mainly in Sedum plants and a few grass locally plants and even ground greening plants are taken to roof directly in some projects. Roof, especially the high-rise building roof, has different temperature, wind, solar radiation and other characteristics with ground, and which caused higher cost or worse landscape effect. The choice of green space special materials has become the bottleneck of such greening. Currently roof greening woody plants'resistance is lack of study, especially in northern China under natural conditions, which has not been reported.In the paper, based on the climate conditions of Shijiazhuang City, combined with field observations of meteorological factors, 8 species of woody plants'resistance sucb as Salix matsudana, Ulmus pumila, Broussonetia papyrifera, Periploca sepium, Populus simonii, Ulmus pumila cv.jinye, Sorbaria sorbifolia, Lonicera maackii were studied to explore these plants'adaptability under natural conditions of drought, high and low temperature and provide reference for the screening of woody species in the roof greening. The results showed that:1. Temperature, humidity, wind speed change during the growing season were observed. The results showed that the roof had lower temperature, greater speed wind and lower humidity and smaller temperature difference than the grand in Shijiazhuang, the temperature of the roof surface was 4.9℃higher than that of the soil surface in summer, that was not conducive to plant growth and dry matter accumulation. The rhizosphere temperatures were higher, and ranged from large and that would accelerate root system aging. These environmental characteristics determined that the screening plants must have stronger drought resistance, heat resistance, barren resistance, etc.2. Through the test of growth morphology index, leaf water content, cell membrane permeability, osmolyte of 8 plants, the results were that the Salix matsudana Koidz, Ulmus pumila L. and Periploca sepium Bunge. heat resistance were best, Populus simonii Carr, Lonicera maackii (Rupr.) Maxim. and Sorbaria kirilowii (Reqel) Maxim. heat resistance were better, Broussonetia papyrifera and Ulmus pumila cv.jinye heat resistance were worst. 3. Under heat stress, the leaf heat treatment and the rate of cell injury of 8 woody plants showed "S" curve, passed the test of significance and meet Logistic equation. Based on semi-lethal temperature LT50, 8 plants heat resistance in order were: Periploca sepium Bunge. 65.30℃, Lonicera maackii (Rupr.) Maxim. 63.80℃, Populus simonii Carr. 57.85℃, Salix matsudana Koidz. 56.84℃, Ulmus pumila L. 55.87℃, Sorbaria kirilowii (Reqel) Maxim. 49.94℃, Broussonetia papyrifera 44.81℃, Ulmus pumila cv.jinye 43.98℃.4. Under natural conditions in winter, roof had lower temperature, greater speed wind and lower humidity than the grand, and had different injury with membrane of branches in different periods. The cold resistance of Populus simonii Carr. and Ulmus pumila cv.jinye were best, and which of Ulmus pumila L. was better, and the cold resistance of Salix matsudana Koidz, Broussonetia papyrifera, Periploca sepium Bunge, Lonicera maackii (Rupr.) Maxim were common, Sorbaria kirilowii (Reqel) Maxim. had worst cold resistance.Using conductivity for evaluation of the cold hardiness of roof greening woody plants is a reliable, and that can provide a reference for rapid screening strong cold resistance woody plants.Through determination for the resisance of 8 kinds woody plants and a comprehensive evaluation, it is concluded that the resistantce of the Ulmus pumila L, Salix matsudana Koidz. and Periploca sepium Bunge. were best, and which of the Populus simonii Carr, Lonicera maackii(Rupr.) Maxim, and Sorbaria kirilowii (Reqel) Maxim. were better, and which of the Broussonetia papyrifera and Ulmus pumila cv.jinye were worst. The study can provide theoretical and practical basis for roof greening plants selection and application.