Individual growth simulation for natural secondary forest of Quercus variabilis in Qinling Area based on FVS.

Quercus variabilis is a precious economic and timber tree species with a broad range of uses. It is distributed in the whole country of China, and the area from Qinling Mountain to Dabieshan Mountain is one of its main distribution ranges. In this study we took natural secondary forest of Q. variabilis from both northern and southern slopes of Qinling Mountain as research object, set up temporary sample plots and took on investigations at Shanyang and Zhen’an counties of Shangluo City, Zhouzhi County of Xi’an City and Taibai County of Baoji City in Shaanxi Province, and used the data from totally 104 sample plots and 150 analytical trees to build five individual Q. variabilis core growth models based on Quercus FVS (forest vegetation simulator) system, including DBH-tree height model, crown width model, DBH growth model, tree height growth model, and volume model. Results were as follows: the equation of DBH-tree height model was determined as H=1.082esup>3.245-17.291DBH+1+3.56, the crown width model expression as CW=0.257+0.244DBH-0.002DBH2, the equation of DBH (5 years) growth model as ln(DDS)=-12.669-0.055A-0.004DBH2+0.117SI-39.181ln(DBH)+43.138ln(DBH+1)+0.013·sin(SL), the equation expression of tree height growth model as HTG=6.372+0.025AvgH+0.108DomtH+0.008DBH2-0.254SD+0.168SI+0.038 sin(SL)-3.613ln(DBH), and the equation of volume model as V=0.338+11.477DBH-11.582DBH0.997·H0.001+0.002DBH·H. The bark adjustment factor was calculated as 1.159 2, the upper limit of the crown competition factor was close to 450, and the maximum of stand density index was 923 plants/ha. Taking t-test and residual distribution test with each model, the results showed that the fitting is good. The models are expected to lay the foundation of FVS system localization research on cork oak forests in Qinling Region, and provide the basis for the management decision of local oak forest.