Qingyuan Forest CERN was founded in 2003 in montane regions of eastern Liaoning Province, Northeast China (124º54'E, 41º51'N, 500-1100 m a.s.l.). The climate is continental monsoon type with a strong monsoon windy spring, a warm and humid summer, and a dry and cold winter. There is 1350 ha of experimental forests, 80% of which is mixed broadleaved secondary forests and 20% is Korean pine plantations and Larch plantations. In the study area, natural secondary forests dominated by Fraxinus rhynchophylla Hance, Acer mono Maxim., and Quercus mongolica Fisch., etc. have gradually regenerated from the primary mixed broad-leaf Korean pine forests in the early 1950s, and patches of larch plantations have partially replaced secondary forests in the 1960s to meet the increasing timber demands in Northeast China. This typical secondary forest ecosystem is therefore a result of both the secondary forests and the plantations and plays a critical role in carbon sink, conservations of biodiversity and water resource, and protection for Northeast plains & cities and so on. However, the functions of secondary forest ecosystems are quite different from the ones of primary forests. So, we do the basic researches for restoration or improvement of the secondary forest ecosystems by comparing with primary forests. Three research topics are focused on 1) structure, function and regulation of secondary forest ecosystems, 2) main ecological processes under disturbances in secondary forest ecosystems, and 3) degradation and restoration mechanisms of secondary forest ecosystems. Especially we are now interested in the quantifying the forest gap and stand structure with LiDAR, determining the relationships between stand structure and function, and indicating the restoration mechanisms of water conservation functions for secondary forest ecosystems. Furthermore, there is long-term monitoring of water, soil, atmosphere and biology in strict accordance with the request of the Chinese Ecosystem Research Network (CERN).