The Study On The Initial Effort Of Transforming Pinus Massoniana Plantation Into Close-to-nature Forest

Pinus massoniana is a main timber and afforestation tree species widely used in South China. It also played an important role in soil and water conservation, biodiversity protection and so on..However, these coniferous pure forest standshave many problems, such as poor species composition, simple stand structure, and large proportion of young and middle-aged stands, resulting in poor vulnerability tonature and human disturbance.Besides, the current Pinus massonianaplantation can not meet the multiple demands from the markets, especially the timber of large size.In2007, we employed4different models for transforming the pure Pinus massoniana plantation into close-to-nature forests, and reserve stand and control, which was reforested in1993on the clear-cutting sites in Tropical Forestry Research Center, Chinese Academy of Forestry. Our total objective was to convert the simple construction pure stands into uneven-aged mixed foreststands which are of rich species diversity, multiple functions and stable forest structure. In each transformation model, we installed4permanent circular plots with the size of400m2for continuous monitoring purposes. In this study, based on the montoring data that we abtained in2008,2010and2012, we evaluated the transformation effects in terms of species composition, stand structure, stand growth dynamics and soil chemical characteristics. The initial results suggested that the transformed stands have significant advantage over the pure stands. For example, the transformed stands have rich tree species, and the diameter distribution is approaching reverse J-shaped distribution, and the vertical structure was gradually developed and now the distinte canopy layeres were formed. In terms of spatial structure, the species mixture was greatly improved and the spatial point distribution is changing to random distribution or cluster distribution from the even distribution. In addition, the soil chemical property was greated enhanced. In addition, we analyzed the growth difference amongst dominate tree, intermediate tree, suppressed tree. The results of growth comparison indicated that the dominate trees have great advantage over the intermediate trees and suppressed trees. Given that the classical yield table which was developed for the pure plantation can not be efficiently used for prediction for the mixed irregular forest stands, we used step-wise regression to produce individual tree growth model for support the decision making process of making forest management regimes. In a word, transforming pure plantation into close-to-nature forest had greatly diversified species composition, opimazied stand structure and improved the soil quality and hence resulted in a sustainable and continuous cover forest ecosystem.As a result, we drewan initial conclusion that the close-to-natural transformation that transforming pure conifer plantation into mixed-species forests is a possible solution to multi-purpose forest management.