Study On Physiological And Ecological Characteristics Of Several Virescence Trees In Beijing

The urban trees play a very vital role in the protection of ecological enviroment as an important component in the forest ecosystems of city. But at same time these trees have so many problems, such as excessive water consumption, water conservation and the urban water resources use, and the contradictions are difficult to reconcile.5 kinds of virescence trees have been choosed for study in this paper in order to deal with these issues. Compred with the photosynthesis ability and water use efficiency of different trees, the theory basis for choice of Beijing ornamental plant and the cultivation management is provided. The results as follows,1. By the research on the daily change of the net photosynthetic rate and relation of Pn and its influencing factors, the conclusion was elicited. During the whole growth seasons, the daily change of Pn on Ginkgo biloba, Salix matsudana cv. Pendula and Prunus persica was bimodal curve mainly and midday rest depression appears. The turns were Salix matsudana cv. Pendula > Prunus persica > Gingko biloba > Cedrusde odara > Lonicera maackii from positive to negative by the analysis of compensation and saturation and the situation when suppressed by glare. The photosynthetic compensation points were 49.90μmol?m-2?s-1, 43.50μmol?m-2?s-1, 29.182μmol?m-2?s-1, 23.09μmol?m-2?s-1, 12.497μmol?m-2?s-1 in order. But in some special months, these trees are unimodal curve. Cedrusde odara and Lonicera maackii assume the unimodal curve. As a eutropic plant, Prunus persica is most positive, but the shade tolerance of Cedrusde odar is strongest. The main factors of affecting daily change of Pn on 5 trees are PAR, Ta, RH, Gs and Ls.2. Carried the analysis of daily change on Tr and relation on Tr and its influencing factors, the results are followed. During the growth season, the daily change of Tr is same with daily change of Pn. The average transpiration rate was Prunus persica (4.83μmolH2O?m-2?s-1) > Gingko biloba (3.20μmolH2O?m-2?s-1) > Lonicera maackii (2.74μmolH2O?m-2?s-1) > Cedrusde odara(2.57μmolH2O?m-2?s-1) > Salix matsudana cv. Pendula (2.24μmolH2O?m-2?s-1). This shows that Tr related with the change of Pn.3. In may, the WUE was Salix matsudana cv. Pendula(3.41μmolCO2?mol-1H2O)> Prunus persica( 2.07μmolCO2?mol-1H2O ) >Cedrusde odara ( 2.06μmolCO2?mol-1H2O ) >Ginkgo biloba(2.02μmolCO2?mol-1H2O)> Lonicera maackii(1.55μmolCO2?mol-1H2O). In June, Salix matsudana cv. Pendula(2.06μmolCO2?mol-1H2O)> Lonicera maackii(1.83μmolCO2?mol-1H2O)> Cedrusde odara(1.76μmolCO2?mol-1H2O)>Ginkgo biloba(1.46μmolCO2?mol-1H2O)>Prunus persica(1.01μmolCO2?mol-1H2O). In July, Cedrusde odara(1.80μmolCO2?mol-1H2O)>Salix matsudana cv. Pendula(1.64μmolCO2?mol-1H2O)>Ginkgo biloba(1.36μmolCO2?mol-1H2O)> Lonicera maacki(i1.20μmolCO2?mol-1H2O)>Prunus persica(1.15μmolCO2?mol-1H2O). In August, Lonicera maackii(1.82μmolCO2?mol-1H2O)>Prunus persica(1.65μmolCO2?mol-1H2O)> Salix matsudana cv. Pendula(1.61μmolCO2?mol-1H2O)>Ginkgo biloba(1.34μmolCO2?mol-1H2O)> Cedrusde odara ( 1.13μmolCO2?mol-1H2O ) . In September, Salix matsudana cv. Pendula(2.57μmolCO2?mol-1H2O)>Cedrusde odara(2.22μmolCO2?mol-1H2O)> Lonicera maackii( 2.08μmolCO2?mol-1H2O ) > Ginkgo biloba ( 1.48μmolCO2?mol-1H2O ) >Prunus persica(1.29μmolCO2?mol-1H2O). In October, Salix matsudana cv. Pendula(3.26μmolCO2?mol-1H2O)>Ginkgo biloba(1.96μmolCO2?mol-1H2O)>Prunus persica(1.81μmolCO2?mol-1H2O)>Cedrusde odara(1.45μmolCO2?mol-1H2O)> Lonicera maackii(1.38μmolCO2?mol-1H2O).Carries on the comparison of average water use efficiency on 5 trees, the results are followed. WUE of Salix matsudana cv. Pendula is highest, so it absorbs the most soil water and suits for cultured in north area. The WUE daily changes of other trees are different among all months. Appropriate cultured trees should be choosed according to the environmental condition. As a result, Prunus persica and Salix matsudana cv. Pendula are the most appropriate trees which are fit to Beijing because of the high Pn and WUE. The ability of Gingko biloba is weaker. The Pn and WUE of Lonicera maackii and Cedrusde odara are lower than others, so they would not be choosed as landscaping trees in north.