Study On Growth Model Of Schima Superb. And Pinus Massoniana Secondary Forest

Secondary forest is not only a principal part but a significant base of forest resources in China, of which faced with a dilemma state between continuous undermining and ineffective management. Therefore, more and more attention was paid in today's forestry research on secondary forest growth succession process to achieve the aims of establishing reasonable management plans. On the basis of previous studies of secondary forest, Pinus massoniana and Schima superb communities in natural secondary forest on state-owned forest farm of Qingshigang, Yanling County, were analyzed and classified according to the investigation data from the surveyed sample plots and analytic trees, in combination with the method of Hegyi's simple competition index for individual tree by calculating the average competition index for each species. In addition, individual tree growth (diameter, height and volume) models and height curve models of different types in the species were established. Besides, the short-term total stand basal area and volume changes were also stimulated by individual tree growth models in this thesis. This article's content is a part of the public welfare industry of the state forestry administration research projects:"Southern collective secondary forest tending and thinning and efficient use of technology research (The Item Number:201004032)." Results are as follows:1. The competitive relationship between species in the stand was analyzed according to Hegyi's simple competition index, and the optimal competitive radius of the objective species in the stand was5meters by using gradual area expansion method. The average competition indexes of Schima superb, Pinus massoniana and other species in the sample plots was10.6,10.5,8.3, respectively. And based on which, tree species were divided into two types, namely competitive superior trees (individual competition index did not exceed the average competition index in the species) and competitive inferior trees (individual competition index was greater than the average competition index in the species), indicating a more accurate expression of tree growth state.2. Based on the proportion of the total basal area of the species to that of the stand, species in the sample plots were divided into three classes, namely Schima superb, Pinus massoniana and other species. In terms of model selection, Johnson Schumacher model presented the most optimal fitting degree to diameter growth, being over0.9; the fitting degree of the tree height growth models was more than0.8, in which the Logistic regression model fitted the height growth best in Schima superb superiors and that in Pinus massoniana inferiors, with Gompertz model showing a fairly well fitting degree to their corresponding inferiors or superiors of the two species. Besides, Johnson Schumacher model also had a best fitness for height growth in other species of the stand. For volume growth part, Bertalanffy model expressed the best fitness to Schima superb and Pinus massoniana, while Johnson Schumacher model was the best for the superiors of other species with Richards model best for the inferiors. Growth models of diameter, height and volume inclined to show "S" shaped curves. During the same period, the total increment (diameter, height and volume) in superior trees of the same species was consistently greater than that in the inferior ones, yet the total increment between superior and inferior trees among species was different, with volume growth between which following the order:Schima superb's> Pinus massoniana's>other species's, respectively.3. Surveyed sample stands were mainly small and medium diameter-class young forest. Based on individual tree growth model, short-term predictions of average age, stand volume and current annual increment of tree volume were made in this thesis. Results indicated that current annual increment of tree volume in the curve continued to grow with the increasing average age of the stand, rapidly at the early stage, then became slowly when the average age varied from38to40.