| Secondary forest has become the main body of forest resource in China. Forest resource shortage were caused by unreasonable management and utilization, how to manage secondary forest scientifically is an important theory and practical problem. The paper is a part of the public welfare and forestry:Research on forest thinning and efficicent utilization of southern collective forest (Number:201004032). Based on the summary of the structure, growth law and management technology of secondary forest, Schima superba secondary forest had been taken as the study object in State-owned Forest Farm of Qingshigang. Data of sample plot, sample tree and soil testing were collected, and diameter distribution, competitive growth process, management technical system and effect were studied. In order to solve the problem of thinning object selection, the intermediate cutting index was built. The results solved these problems about beginning time of intermediate cutting, thinning intensity and selection of thinning object, then it formed the management technical system of Schima superba secondary forest. The result and main conclusion have been studied as following:(1) Study on stand structure in Schima superba secondary forest.①The quantity was accounted for94.81%of Schima superba which aged between10and24years. Unimodal curve with a peak was formed at14years. The quantity of trees which aged around14years decreased gradually. The quantity was accounted for80.25%of Pinus massoniana which aged between10and24years too. Other trees which aged mainly between5and12years were very few.②Weibull function was used to fitting the diameter distribution of Schima superba secondary forest, and significant difference of the actual value and theoretical fitting value of diameter distribution was verified with method of test for Coriolis. Through comparison between theoretical and practical about skew degree, kurtosis degree of DBH distribution, the applicability of the distribution function was confirmed. The result showed that Weibull function can satisfactorily fit the Schima superba secondary forest.(2) Study on growth model in Schima superba secondary forest.In order to confirm the best competitive radius of the Schima superba secondary stand, Hegyi competition index was used to analyze the competitive relationship. According to individual tree basal area accounted for the total stand basal area ratio, species were divided into Schima superb, Pinus massoniana and other tree. According to the standard deviation, competition index was divided into3levels. According to the average competition index, each species was divided into superior tree, mediocre tree and inferior tree, then diameter, height and volume increment process of the superior tree, mediocre tree and inferior tree were imitated separately, The fitting results were as following:①Fitting effective of Johnson Schumacher equation presented the most optimal to diameter growth of all species;②Logistic equation presented the most optimal fitting effective to hight growth of Schima superb superior tree, mediocre tree and Pinus massoniana inferior tree, Gompertz equation presented the most optimal fitting effective to hight growth of Schima superb inferior tree and Pinus massoniana superior tree, while Johnson Schumacher presented the most optimal fitting effective to hight growth of other superior tree, mediocre tree and inferior tree;③Bertalanffy equation presented the most optimal fitting effective to volume growth of all Schima superb and Pinus massoniana. Johnson Schumacher equation presented the most optimal fitting effective to volume growth of other superior tree and mediocre tree, while Richards equation presented the most optimal fitting effective to volume growth of other inferior tree.(3) Study on competitive growth law in Schima superba secondary forest.①The First competition pattern:Competition index of Schima superba objective tree which aged between8and15years increased slowly and increased more fast than the former after15years.②The Second competition pattern:Competition index of Schima superba objective tree which aged between4and6years decreased obviously and decreased slowly after6years.③The Third competition pattern:Competition index of Schima superba objective tree which aged between4and6years decreased quickly and which aged between6and8years decreased slowly, while competition index increased continuously and slowly after8years.④The Fourth competition pattern:Competition index of Schima superba objective tree which aged between5and8years showed dramatic decline downtrend and decreased slowly. Competition index was kept between0.2and0.28after9years, but it decreased slowly.(4) Study on thinning beginning time.Forstat2.1was used to fit the relationship between competition index and age of objective tree in four competition patterns. The fitting results showed that were the most optimal to competition index of objective tree of all competition patterns with the model (CI=c+b*A+d*A2+e*A3). Competition index is more greater, competition is more intensely. Through calculating, the age was respectively15.8,14.1,15.2,13.9years of the four competition patterns when competition index reached the maximum value. It is consistent to the average age of four competition patterns when the competition strength reached the maximum value, so the thinning beginning time was determined at14-15years of Schima superba secondary forest.(5) Study on competitive structural unit and the maximum area of competitive structural unit.One tree which is the nearest to objective tree is chosen as competitive tree in each quadrant, objective tree and four competitive trees form a competitive structural unit, when the objective tree is selected and taken as the center. Area of competitive structural unit is defined that four competitive trees form a quadrilateral. By proof, area of competitive structural unit has a maximum value, but the area has no minimum value.(6) Study on technology of density control in Schima super ba secondary forest.Total biomass is taken as the dependent variable, canopy density is taken as the independent variable. Relationship between biomass and canopy density of Schima superba secondary forest was simulated. Fitting result was W总=-18.4531+101.8078P-74.2689P2. The biomass reaches the maximum value when canopy density is0.6854. Canopy density is a function of the average crown width and stand density, average crown width and stand density was used to estimate canopy density. If the canopy density is controlled at0.68, the area of competitive structural unit is more larger, the number of competitive structural unit is less, While each competitive structural unit has five trees, then the least reserved density equal to the number of competitive structural unit multiplied by five. Sample plot No.19had been taken as an example to calculate thinning intensity of Schima superba secondary forest.(7) Build the intermediate cutting index.The Brainstorming, Delphi and Meetings was used to filter these indexes that were consisted of intermediate cutting index, then six indexes (degree of freedom, mingling, open comparison, health index, spatial density index and aim index) were selected to build intermediate cutting index. The AHP was used to get weight coefficients of the six indexes. An experiment sample plot had been taken as an example, the value of every index and intermediate cutting index of each tree were calculated. According to the relationship between actual stand density and the least reserved density, thinning intensity and thinning object were determined with intermediate cutting index. It theoretically solved the problem of thinning object selection.(8) Study on management pattern and effect in Schima superba secondary forest.According to the management target, six management patterns were designed for Schima superba&Taxus mairei mixed forest. Reasonable technological standard of each management pattern was explored. Contrastive study of management effect in different management pattern was researched.①Among the six management patterns:Soil bulk density, capillary porosity, maximum water-holding capacity and field capacity were without obviously difference, while the total porosity and non-capillary porosity were with significant difference. Soil organic matter content was relatively high, total N, available P and total P content were relatively low. Species composition exists significant difference in tree layer, species were the most in rare tree introduction pattern, while species were the least in thinning pattern. Species were the most of closure pattern in shrub layer and were the least in cutting and planting combination pattern and thinning pattern. Change trend in herbaceous layer was in agreement of shrub layer. Height class and diameter class were different, closure pattern had five height classes, after-culture pattern had four height classes, cutting and planting combination pattern only had three height classes. The distribution of Ⅰ, Ⅱ, Ⅲ height class were balanced in thinning pattern.②In the same management pattern:Chemical properties of different soil layers was with variation. The pH increased with the depth of soil layer, while other indexes decreased. |
PDF Full Text Request