Study On Soil Improvement Benefit Of Coastal Protective Forest In Shanghai City

The study has compared with the seven main coastal protective forest models in shanghai through measuring forest biomass,soil physical and chemical properties and species diversity in grass.Based on these,this paper analyzed and compared with soil improvement benefit of coastal protective forest in shanghai.The results are described as follows:1.Total biomass of seven protective forests is:water fir>java bishopwood>pond cypress>poplar>swamp cypress>salix babyloncia>camphortree,it shows that camphortree's growth speed is most slowly,and pond cypress grow more rapidly.2.The plots can be divided three kinds by the available distance clustering analysis,the difference of the soil fertility conditions among the plots indicates that forests improve the soil condition and then enhance the growth of the trees.And the older forests make the better effect.3.Soil organic matter, total nitrogen, total porosity, noncapillary porosity, moist content of different layers of seven coastal protective forest models'plot are bigger than bottomland's, while soil moist content and pH of different layers of seven coastal protective forest models'plot are smaller than bottomland's. These indicate that each protective forest can improve coastal soil. Because of the different of tree species and time of afforesting, the benefits of improvement are different.4.Soil bulk density,pH,organic matter content,effective phosphorus,salt content and porosity had a good correlation coefficient with other nutrient activities, and they played an important role in main composition analysis,so under certain condition,they can be regarded as the major indicator to appraise soil fertility.5.Study on the relationship between soil fertility properties and species diversity in grass layer showed that the main factor affecting species diversity was soil pH,then was the soil total phosphorous.The soil salt content,bulk density and total nitrogen also affected the species diversity.6.Of all the kinds of tree species in second seawall of shanghai,Java bishopwood and pond cypress are better.The adaptability of the poplar is very strong too,and the growth speed is greater than other varieties of trees,the biomass is accumulated quickly.Now the protective forests such as water fir and swamp cypress were growing slowly,and most were pure models.They were easily harmed by illness and did no good to trees.Some of them might be cut,then we could plant poplar,Java bishopwood or pond cypress.Thus the forests could still prevent the wind when they were replaced,and also could remedy soil degradation,using the productive power of forest soil batter.