Development And Application Of Density Management Diagram For Cunninghamia Lanceolata Plantation In Fujian Province

Cunninghamia lanceolata is one of the most important tree species for plantation insouth China. Therefore it is of great importance to sustainable forest management in SouthChina. Density management is a necessary silviculture measure for plantation asmaintaining suitable stand density is an important way of maximizing forest function andenhancing forest productivity. Therefore, the main objective of this study was to constructdensity management diagram for Cunninghamia lanceolata plantation. We synthetized31empirical height-diameter models based on which we conducted Cross-validation toindemnity the optimum model. Richard model (model23) was selected to be the optimummodel. We compared the soil physical characteristics among different age classed withspecial attention on soil water capacity which was a foundation for developing densitymanagement diagram for water. We developed different self-thinning model for differentsites to construct their own density management diagrams. Based on the above study, wedeveloped normal density management diagram as well diagram special for watermanagement. With the diagram, we modeled the scenario of different management optionsand finally dertermined the best management option. Finally, we developed the denstiywarning diagram for Jiangle County, Fujian Province.The main results were as follows:1) Comparing soil physical characteristics amongst different age classWe examined and compared soil bulk density, soil porosity and soil moisturecapacity of Cunninghamia lanceolata plantation of different age classes. The resultsindicated that from young forest to near mature forest, the soil physical characteristicsdeclined. However, it showed an improving tendency as the forest was getting mature. Weowed the decreasing of soil physical characteristics from young forest to near mature forestto intermediate cutting, whereas the improving of soil physical characteristics from nearmature forest to mature forest to improvement of stand structure, especially the enhancedspecies richness. Finally, we suggested that the traditional clearing-cutting managementsystems for plantation should be converted to the mixed-species management systemsfeatured by selective cutting.2)Indemnification of the optimum height-diameter modelHeight-diameter models are wildly used for diameter prediction as it is of lowefficiency, time-consuming, and difficult to measure diameter. This paper synthesized31height-diameter models that are normally used both nationally and internationally and thenwe employed the data of Cunninghamia lanceolata platation in Fujian Province to fit thesemodels. We used the indices for model efficiency, precision, and bias as well as theresidual plots to evaluate the31models and then select4best models. However, the above mentioned indices could not further identify the optimum model. Therefore we conductedleave-one-out Cross-validation analysis using the data of16stem analysis trees toinvestigate the optimum model. The results indicated that Richards model (model23)23showed the best performance and was selected to be the optimum model. The optimummodel could contribute the precise perdition of Cunninghamia lanceolata individuals inthe study area.3) Self-thinning model in different site conditionOur results demonstrated that in different site condition the slope of self-thinningmodel varied. Therefore, if we develop the density management diagram withoutconsideration of site condition, biased estimation would occurred, which of course misleadthe management practices.4) Construction and application of density management diagramWe selected the fully stocked stand for constructing density management diagram.With RMA regression, we developed the self-thinning line for Cunninghamia lanceolataplantation. In addition, we also determined the optimum growth interval line as well as thecanopy closure line. By applying the density management diagram, we model3differentsilviculture options for3stands of different density. The result will contribute to theindentificaiton of the optimum management option.5) Construction of warning diagram for stand density and management suggestionWe categorized the Cunninghamia lanceolata plantion into suitable density, lowdensity, high density. Based on GIS, we developed warning diagram for stand density andmanagement and hence realized the spatial description of density distribution. For highdensity stand, we proposed the methods of selecting the cutting tree based on forest spatialinformation.