Study On Target Tree Management Of Natural Broad-leavead Timber Forest In Mid-subtropical Zone

It has widely distribution and aboundance of resource of natural broad-leavead forest inour mid-subtropical zone and the forest resources have important ecological, economic, socialvalue.The natural broad-leavead Castanopsis carlesii in Yong’an is taken as study objectiveaim to resolve realated problems of target management. Such as charictaristics of naturalbroad-leavead Castanopsis carlesii, basis of target management, target tree diameter, target treedensity, target tree management effect on single and stand. The study hopes to provide areference for sustaninable manangement of broad-levead forest in our mid-subtropical zone.The study made the following conclusions:(1) Basis on the different tree layers of natural broad-leaved Castanopsis carlesii, its standcharacteristics such as species composition, species diversity and importance value, diameterstructure, tree height structure, volume composition, spatial structure were studyed so as toprovide reference for target tree management. The main characteristics of natural broad-leavedCastanopsis carlesii were as follow. Natural broad-leaved Castanopsis carlesii had three treelayers obviously with height more than18meters for first tree layer, height between10.1-16.9meters for second tree layer, height less than10meters for third tree layer. The dominantspecies in the research stand were Castanopsis carlesii, Schima superba, Neolitsea sericea,Elaeocarpus sylvestris, Sloanea sinensis, Castanopsis fargesii.Normal distribution and Weibulldistribution were the best model for diameter structure of each tree layer of naturalbroad-leaved Castanopsis carlesii, Gamma distribution and negative exponential distributionwere best suitable model for the diameter structure of the natural broad-leaved Castanopsiscarlesii stand.Mingling degree of stand and main tree species were medium or intensive. Thedifferiatiation value and uniform angle value of natural broad-leaved Castanopsis carlesii standwere0.48,0.75.(2) Target tree management incorporating selecting a small number of outstandingindividual trees as management main objective and leaving most trees in the stand under natural regulation was ecologically reasonable and ecomomic effective. The number in firsttree layer of natural broad-leaved Castanopsis carlesii was only15%of the total stand trees,but the timber volume of first tree layer had more than70%of the total stand volume. Thecharacteristics of vertical structure distribution suggested that few large diameter trees were themain part providing timber volume. Different diameter classes growth model was establishedwith “average growth plus standard deviation” method. The results showed that the standgrowth process was mainly carried out by the dominat trees which grew faster than other trees.That was, larger diameter trees whose DBH was for vigorous growth period had faster growthtrend.(3) Through quantitative mehods to solve the target tree density problem of naturalCastanopsis carlesii when the stand was in current stage and in harvest stage. Base on Voronoidiagram to get competition index and dominance of target trees, in the current period theaverage density of target trees of natural broad-leaved Castanopsis carlesii stand was105stems per hectare. We finally set the range of100~110stems per hectare as reasonable targettree density. In final harvest period, with use of the unite nutrition area of target tree, We gotthe vaverage signle nutrition area, average unit nutrition area and average target tree densitywere143.05m2,155.49m2,68stems per hectare respectively. By stepwise regression method,the crown wide model was established to obtain the average target tree density of Castanopsiscarlesii stand was68~74stems per hectare when target trees reached the harvest period. In theend, we got the results that the last two method for final havest period target tree density wasreasonable and in the final harvest period the appropriate target tree density of Castanopsiscarlesii stand was63~73stems per hectare.Based on target tree nutrition area and community completion area, we got the suitabletarget tree density was69stems per hectare.(4) After thinning, research resulsts showed that the growth increment and growth rate oftarget tree was significantly higher than that of non-targert tree. The fact indicated that thinningcould increase target tree growth obviously. The consequence of annual increment, averageincrement of DBH and volulme was target treeT>non-target treeNTI>non-target treeNT>non-target treeNTII>non-target treeNTIII,target treeTdiffered siginificantly with non-targerttree. The order of basal area growth rate, volume growth rate of target tree and non-target treewas non-target treeNT>target treeT>non-target treeNTI. Growth rate of basal area and volumehad the maximum2years after thinning. The growth rates of2year thinning later were notsignificant with that of3.5years thinning later, but had significantly differentce with that of1year thinning later.(5) By analysis basal area and volume growth rate of different management models from2008to2011, the results showed that the order of basa area growth rate of stand and each treelayer was target tree management>traditional management>control. Stand basal area growthrate of control differed significantly with that of tradional management and target treemanagement, however, the stand basal area growth rate of two latter management models hadno significant difference. The consequence of volume growth rate of stand and each tree layerwas target tree management> traditional management>control. Stand volume growth rate ofcontrol differed significantly with that of traditional management and target tree management,however, the stand volume growth rate of the two latter management models had no significantdifference.(6) By analysis the importance value changes before and after cutting in differentmanagement models, results showed that Castanopsis carlesii, Schima superba were still the dominantspecies. In the control test belt, the importance value of Castanopsis carlesii, Schima superba, Sycopsisdunnii, Alnus trabeculosa, Nyssa sinensis was decreasing with small tendency, importance valueof Neolitsea aurata, Sloanea changii, Symplocos lancifolia increaed. In traditional management test belt,importance value of Castanopsis carlesii, Schima superba, Neolitsea aurata, Randia cochinchinensis,Alnus trabeculosa had increased. In the target tree managemt test belt, the important value ofCastanopsis carlesii, Schima superba, Machilus chekiangensis, Alniphyllum fortune,Elacocarpus japonicas, Cryptocarya chinensis showed decreasing trendecy, the importantvalues of Neolitsea aurata,Elaeocarpus chinensis, Liquidambar formosana, Daphniphyllumoldhami, Dendropanax dentiger, Nyssa sinensis had increasing trendency.