The Research Of Growth And Yield Forecast Model For Pulp Eucalyptus Plantation

Stand growth and yield forecast model is the mathematical model to study the growth rule of forest, it can describe the growth process and predict the future state of stand, it is not only the basis of establish and revise all kinds of forestry tables, but also is main gist of taking measures in forest management and administration, at the same time it also play an important role in research of biomass model, carbon reserves model and forest economic maturity. As an important timber forest, pulp eucalyptus plantation is lack of systematic study on its stand growth and yield forecast model. Select pulp eucalyptus plantation that it is named Huaan No.1 which circulation period is five years form state-run Leizhou forestry bureau as the research object. We carry out field investigation between January and February in 2015, measure and calculate DBH(average diameter at breast height, average height), average top height, stem-number, basal area per hectare and volume per hectare of stand as the basic data to build the model. Apply mathematical statistics software such as SPSS19.0, EXCEL2010, For Stat2.2 and refer to the theory and technical methods of Forest Mensuration, Forest Management and Statistics, analyze and study SI(site index) model, SDI(stand density index) model, basal area model, volume yield model, basal area forecast model, volume model and so on. Systematic build stand growth and yield forecast model of pulp eucalyptus plantation. The research results which are helpful for the forest resource dynamic monitoring, scientific management, decision support, forest assessment, forestland evaluation of state-run Leizhou forestry bureau pulp eucalyptus plantation have an important practical guiding significance.(1)Build SI model. Using dummy variable of the guide curve method, analyze and compare nine theory growth equations, logistic equation that its accuracy is highest suitable for describe the relationship between average top height and age of stand. According to the guide curve equation, use the method of relative advantage height to calculate SI table. By inspection, this SI table can reflect site quality grades of state-run Leizhou forestry bureau pulp eucalyptus plantation very well and can evaluate site quality grades in actual production application. In the end, according to the method of relative advantage height backstepping SI model.(2)Build SDI model. According to the relationship between with stem-number and basal area per hectare, by using the method of eliminate multiply understocked land simulate the fully stocked state. Eventually the parameter b we calculate is close to constant 1.605 which is proved form Reineke. Take the parameter b into SDI equation, then get Reineke SDI equation. Observe the scatterplot of the relationship between with SDI and age and combine with previous research results, assuming that their relationship is S-shape curve. By using Korf equation simulate the relationship, take SI and SDI into the equation. Then calculate the parameter and get the answer.(3)Build basal area model. Take SI and SDI into the assimilation-alienation equation which is proved by Bertalanffy. The conversion between assimilation reaction parameter and potential growth rate is related to SDI. By separate and transform variable, derivate basal area model which contains SI, SDI and age of three independent variable. Then calculate the parameter and get the answer.(4) Volume model directly select Schumacher equation, the equation contains SDI, age of reciprocal and basal area of three independent variables. Because of the volume model contains independent variable density, so it can reflect volume growth rule under different density, it convenient for study volume change in the future when stand initial density is different. Then calculate the parameter and get the answer.(5)The general formula of forecast model is obtained by mathematical transformation, SDI forecast model and basal area forecast model is derived by the ratio of present and future, while volume forecast model is derived by subtraction between present and future. Based on the previous results, we studied yield change under different initial planting density and different status index, found that in initial planting density of 1750 plants/ha is suitable density. When the density is too small, it will not be able to fully play to soil fertility. However when the density is too large, its influence for the yield is very small. So consider the aspects of economic factors, we recommend planting spacing is 2.4*2.4 for pulp eucalyptus plantation in Leizhou forestry bureau.