Abstract:The secondary forest or second-growth forest, originated from natural regeneration after the destructive disturbances of original forests induced by human beings (e.g., long-term and large-scale logging) or by natural extreme events, has become the major forest resource worldwide. Since the flood disasters happened in the Yangtze River and Nen River in 1998, the Chinese government began to realize the importance of natural forests and started to implement the Natural Forest Conservation Project. A more rigorous protection measure of comprehensive ban on commercial logging in natural forests was implemented in 2016. As a result, the forest farmers, whose main business was timber harvesting, are facing unemployment. In such context, the new requirements for scientific research work have been put forward to indicate how to protect and restore the existing secondary forest ecosystem, and how to make rational use of existing forest resources and promote the economic transformation in forest regions. Since its establishment in 2003, Qingyuan Forest CERN (Qingyuan Forest) of Chinese Academy of Sciences has been conducting the long-term monitoring of the ecological elements (including water, soil, atmosphere, and biotic factors), the basic researches on forest ecology and silviculture, as well as the applied researches on the conservation and restoration of the temperate secondary forest ecosystem and efficient utilization of non-wood resources by experimental demonstration and technology promotion. All of these important progresses have provided scientific and technological support for the ecological conservation, restoration, and sustainable development of forests in Northeast China. Significant research achievements include the precision quantification technology/method of forest stand/gap structure, and the development of the technologies for the restoration of secondary forests and the cultivation of Panax ginseng under forest canopy based on the regulation principle of vertically stratified structure of forest stands, the clarification of the natural disturbance processes and its ecological significance, and the development of the techniques for promoting the restoration of secondary forest ecosystems and cultivation and utilization of Chinese herbal medicine under forest canopy by simulating natural disturbance (e.g., forming forest gaps). The researchers in Qingyuan Forest also revealed the coexistence mechanism of dominant tree species in secondary forests and applied it to the techniques of promoting forest gap regeneration and cultivation of wild vegetables under forest canopy. They also indicated the mechanism of forest litter for maintaining productivity of larch plantations in the secondary forest ecosystem, and developed measures for improving water conservation function of the forest ecosystem, and increased the survival rate of Rana chensinensis breeding under the forest canopy. The above progresses have provided the basic theory and technical support for ecological security construction and protection, restoration of resource capacity and efficient utilization of resources in temperate forests. These research and extension activities have made Qingyuan Forest an important platform to carry out the cooperative researches at home and abroad and a center for generating and transferring scientific knowledge for forest restoration and sustainable management in temperate forest ecosystems.