Exploration And Evaluation Of Ecological Benefits Of Urban Near-natural Forest

Since rapid urbanization resulted in worsening human habitat and increasing threat to physical health,Urban Greening has evolved its function from mere aesthetic landscaping to improving city environment and thus minimizing health threats. Near-natural forest is a new vegetation restoration concept that applies a simulated natural approach to create an artificial forest close to regional Climax Community on species composition and community structure.In year 2000,an Near-natural forest area of 3000 m~2 was constructed in Shanghai for the first time.This paper uses this sample plot as the research object,and contrasts it with the evergreen broad-leaf forest in TianTong National Park and with green landscapes commonly seen in urban cities.Several indexes were selected in the investigation,including concentration of air positive and negative ions,air temperature and humidity,air microorganisms and soil microorganisms.We will explore and evaluate the ecological benefits of the near-natural forest.We get the following result.1.The field effect of the air negative ions in near-natural forest is not significant.Air negative ion concentration in the center of forest differs little from that near the edge. It does,however,drop sharply outside of the forest.At the six sample plots located in ECNU campus,the first peak in air negative ion concentration values occurs during April-May,while the second peak occurs during August-September.It shows that air negative ion concentration is related to metabolism of plants.The more complete the Community's structure is,the higher air negative ions will be.The correlation between air negative icons and air humidity is strong.2.The air negative ions in near-natural forest are much higher compare to those typical urban green landscapes.But it's biomass is quite limit still can't compare to TianTong National Park,and not very helpful with the urban environment.3.The air microbe sampler can put air microorganisms onto six stages by their size. The results proved that the distribution of air bacteria,air fungi,and air actinomycete are definitely different.The total air bacteria concentrations of urban near-natural forest in four seasons are lower than Pudong and Campus sample plots.This tells us that near-natural forest can decrease the amount of air bacteria.On the other hand,the total concentration of air fungi and actinomycete of near-natural forest in four seasons is higher than Pudong and Campus sample plots.We observed that near-natural forest has integrated deadwood fallen nuts with abundant soil fungi and actinomycete.4.Soil bacteria,actinomycete and azotobacter do not have notable differences between 0-10cm and 10-20cm among the sample plots,but epiphyte does.Using linear transformation method,we normalized the amount of soil bacteria,fungi and actinomycetes into numbers between 0 and 1.The result shows that near-natural forest is approaching natural forest better than contrasted man-made urban greening. This paper shows that near-natural forest can effectively improve the concentration of air negative ions,decrease temperature,and enhance humidity to some extent.Also,it can reduce the amount of air bacteria and increase biodiversity. But because of the area and the biomass we can't tell its benefit to the environment. But we can believe in the few year.They will contribute a lot the cities.For all of this, we suggest popularizing the planting of near-natural forest in urban areas,especially along road or around factory.