Studies On The Canopy Structure Of Plant Communities In Some Beijing Greenbelt

This study intends to provide some basic theory about the corresponding relations of plant communities-canopy structure-environment under trees-human comfort and some guide about how to choose the varieties of trees when building the ecological landscape in Beijing.The results show that:The actual leaf area index of community constituted with different kinds of trees is higher than that of community constituted with one kind of tree. Other factors of community have little effect on the actual leaf area index of community.There is no correlation between the actual leaf area index and the effective leaf area index measured by canopy analyzer of communities. The effective leaf area index of communities and the leaf area are significantly correlation. The actual leaf area index of community and single tree are significantly correlated.Most of the effective leaf area index of community in the autumn decreased over the summer, reduced to varying degrees. But the effective leaf area index is slightly higher than the summer after leaves falling in two communities. Therefor, the effective leaf area index measured by canopy analyzer can't reflect the density of leaves. The actual leaf area index can reflect the actual density of the leaves better, so it's more suitable for the study on the ecological benefit of community.In this experiment, the actual leaf area index of the species is between 1.0and4.0 except for Koelreuteria paniculata in one community whose actual leaf area index is 6.33. Salix matsudana 'Pendula'(1.07,1.64), Robin ia pseudoacacia(1.43), Malus spectabilis(1.48), Sophora japonica(1.53,2.52), Fraxinus pennsylvanica (1.74,2.36,2.88), Syringa pekinensis(1.84), Populus tomenlosa(2.05,3.24), Catalpa bungei(2.09), Paulownia tomentosa(2.19), Ginkgo biloba(2.24), Liriodendron tulipifera X L. chinense (2.30), Prunus persica'Duplex'(2.35), Acer truncatum(2.44), Juglans regia(2.92), Eucommia ulmoides(3.11), Populus canadensis(3.28), Platanus occidentalis(3.45), Koelreuteria paniculata(3.47,6.33), Tilia mongolica(3.49), Morus alba(3.96).By comparing the actual leaf area index of the same species in different communities, we can know that the actual leaf area index of trees pruned will be significantly reduced. At the same time, the environment and the configuration of trees is also important for the actual leaf area index.We have established the regression equations between some data of canopy structure and the total number of leaves for 15 kinds of trees:Sophora japonica(P=560.401D+3095.587), Populus tomentosa(P=630.503D-6518.890), Koelreuteria paniculata(P=941.645D-13633.205), P.canadensis(P=4640.573W-6729.255), Paulownia tomentosa(P=159.318D-549.390), Salix matsudana 'Pendula'(P=7730.742W-16590.727), Acer truncatum(P=2785.835D+5948.424), Syringa pekinensis(P=352.850D+1687.621), Eucommia ulmoides(P=1030.322D-9905.954), Tilia mongolica(P=2967.18D-10404.927), Robinia pseudoacacia(P=1858.508m-17227.592), Prunus persica'Duplex'(P=1952.404D-3609.789), Fraxinus pennsylvanica(P=1734.008W-5374.993), Malus spectabilis(P=1386.316D-608.955), Catalpa bungei(P=1068.199W-3122.831). By measuring the data can be obtained easily such as diameter(D), crown width(W), the height of tree(H), etc, we can get the total number of leaves(P). And then we can get the actual leaf area index through the total number of leaves, leaf area and crown width.There is certain correlation between the actual leaf area index of communities and the light and UV radiation shielding efficiency. The actual leaf area index of communities is greater, the light and UV radiation shielding efficiency is higher. And there is no correlation between the actual leaf area index and the cooling and humidification rate of communities.