As one of China’s major cities, Shanghai’s natural sub-ecosystem has suffered drastic damage due to human activities and urbanization. Although urban re-naturalization has gained attention from city leaders, urban tree planting has largely consisted of two methods with limited ecological potential. One favors fast-growing monocultures to produce timber products and other benefits, while the other approach is to plant non-native species for decorative purposes. The authors believe the restoration progress of the natural sub-ecosystem could be further improved by adopting the “near-natural” method based on the concepts of potential natural vegetation and ecological succession.
The near-natural forest uses all native species and aims to create a complex structure with high biodiversity, high biomass and multiplayer canopies. It was adopted successfully in many countries, but the authors thought long-term studies of these forests were lacking. Therefore, they conducted a 10-year study at a near-natural forest established in 2000 in Pudong New Area of Shanghai to investigate the effectiveness of the forest in providing ecological benefits.
Results showed that the near-natural forest had higher sustainability value than artificial (“even-aged, managed”) forest in Shanghai based on its ecological and economic benefits. The high tree density and multiple vertical structures of the forest improved the air quality and soil fertility and decreased the concentrations of air bacteria and dust. It also had a much lower planting and maintenance cost than artificial traditional methods. Although the near-natural forest could not transcend the benefits of the natural forest, the study successfully proved its important role in urban re-naturalization by bridging the difference between the artificial and natural forests.
Results showed that the near-natural forest had higher sustainability value than artificial (“even-aged, managed”) forest in Shanghai based on its ecological and economic benefits
Over the course of the study, authors discovered a potential limitation of the approach, at least in its application in Shanghai. They observed high evergreen seedlings mortality, attributable to over-exposure to sunlight. Therefore, in subsequent plantings in 2003 and 2004, the authors modified the approach to optimize it to local conditions:
The key to the new method is to create a mixed deciduous–evergreen community by simultaneously planting shade-tolerant evergreen broad-leaved species and light-demanding deciduous broad-leaved species, but using smaller individuals for the former and larger individuals for the latter to form a multilayer vegetation structure. The shade-tolerant evergreen species benefit from the rapid growth of the light-demanding deciduous species, which offer shade and nutrients in the form of litter layer-based fertilizer, improving the soil for the evergreen species [Guo 2015: 5].
Overall, they suggest that the near-natural forest is a very sustainable method to be applied in Shanghai.
Guo, Xue Yan, Wei Li Li & Liang Jun Da, 2015, Near-Natural Silviculture: Sustainable Approach for Urban Re-naturalization Assessment Based on 10 Years Recovering Dynamics and Eco-Benefits in Shanghai, J. Urban Plann. Dev. 141(3), https://ascelibrary.org/doi/abs/10.1061/%28ASCE%29UP.1943-5444.0000276
 “Sub-ecosystem” here refers to the interdependent social, economic, and natural systems operating within an urban ecosystem.
 The vegetation that would be growing in the absence of human intervention.