Objective It is an important premise to clarify the timber assortment structure of Cunninghamia lanceolata plantations and build a reasonable outturn model, aiming to increase the wood yield, improve the forest management techniques and optimize the management plan for Cunninghamia lanceolata plantations.
Method Based on the 492 felling areas of Cunninghamia lanceolata plantations from 6 state-owned forest farms in Fujian Province of eastern China in the past 15 years, the response of 6 timber assortment outturn (i.e., dimension timber, non-dimension timber, commercial timber, fuel wood, merchantable timber, refuse wood) to each factor, including average DBH, average height, stand age, stand volume, stand density and site quality, was investigated. On this basis, the main stand factors affecting the yield of timber species were screened, the timber outturn model for final felling stands of Cunninghamia lanceolata was constructed and the applicability of the model was evaluated.
Result Among the stand factors of Cunninghamia lanceolata final felling stands, average DBH and average height showed much larger influence than other stand factors on the outturn of each timber assortment, followed by stand volume, age and density, and the influence of site quality was relatively small. The dimension timber, commercial timber and fuel wood timber assortment outturn model system using average DBH and average height as predictive variables showed good fitting and validating results. Based on this, the timber assortment outturn model of non-dimension timber, merchantable timber and refuse wood timber assortment outturn model was constructed. The prediction errors of the timber assortment outturn for different diameter classes were small and stable.
Conclusion This study reveals the timber assortment structure rule, as well as its influencing factors for Cunninghamia lanceolata final felling stands. The model system can be used to calculate the timber assortment yield of Cunninghamia lanceolata final felling stands, and provide support for the formulation of rational production plan of Cunninghamia lanceolata plantations.