Abstract:

Abstract: This paper reviewed past research works and current research progress regarding disturbance regime,degradation and restoration status,and analyzed the following key issues on restoration and reconstruction of the degraded natural forests on the upper reaches of Yangtze River. By integrating the classical and basic ecological theoretical rules into restoration and reconstruction practice,the Chinese traditional concept of "closing hills for forest conservation" was replenished with some new meanings. The restoration and reconstruction strategies of degraded natural forests were as follows: based on the law of natural succession imitating the species composition and community structure of the old-growth,making full use of the natural driving force of spontaneous succession,and taking rational assistant measures timely to introduce appropriate key species at a critical successional stage. As a result,the degradation process can be reversed,or a given succession stage can skip or shorten,and therefore,the restoration process and reestablishing sound structure and function of the degraded natural forests can be accelerated. Indigenous species are encouraged to be used for species introduction when appropriate as assistant measure. The following four rehabilitation and restoration models were proposed. 1) Protecting the old growth,primitive natural forest strictly for conserving gene bank and biodiversity and model stands; 2) For badly degraded sites where natural forest are totally lost,human-assisted measures must be taken to restore the habitat environments in terms of soil functions and re-establishing pioneer population; 3) For moderate degraded secondary naturally regenerated forest,appropriate human-assisted measures are needed to facilitate its natural succession process and to enhance its ecosystem services by regulating the species composition and community structure at the early successional stage; 4) For pure plantations,in particular,pure conifer plantation,dense canopy coverage and simplified structure should be changed in order to switch on natural regeneration mechanism and adjust species composition toward to close to nature reference stands. It is strongly suggested that the landscape pattern and heterogeneity should be taken into consideration of degraded natural forests,i.e.,optimal land use pattern and land cover configuration by forest landscape planning.

Key words: Key words: degraded natural forest, landscape restoration, closing hills for forest conservation, ecological restoration strategies, upper reaches of Yangtze River