|論文名稱||Developing relative stand density index for structurally complex mixed species cypress and pine forests|
|期刊名稱||Forest Ecology and Management|
|摘要||Stand Density Index (SDI) is a numerical value that captures intensity of competition within a forest stand. It is a tool for managing spatial arrangement of trees, controlling crown development and maintaining degree of forest health through decisions made on initial planting density and thinning schedules. However, classical Reineke’s SDI (Reineke 1939. J Agric Res 46: 627-638) has been found to be unsuitable for mixed species and structurally complex forest stands. Alternative measures of SDI are being explored. Natural forests in Taiwan cover an area of approximately 1.5 million ha with 75% of them classified as mixed species forests. Current SDI research in Taiwan focuses on single species
natural and plantation forests such as Chamaecyparis formosensis and Cryptomeria japonica forests. No study has investigated and developed SDI for mixed species natural forests in Taiwan. Because management of these forests is crucial for conservation and protection against soil erosion, it is necessary to develop SDI for these forests to establish management guidelines. Therefore, based on the approach by Ducey and Knapp (2010, For. Ecol. Manag 260: 1613-1622), relative SDI was developed for cypress- and pine-dominated forests using data from the 4th Taiwan National Forest Inventory. Plots with at least 30% of basal area per hectare of target species were used for model fitting. During model fitting, it was discovered that specific gravity played an important role on model convergence. Lastly, three different relative SDI models for each forest type were produced that predicted minimum, mean and
maximum relative SDI for a forest stand. The major result from this study was that relative SDI could now be calculated and graphically presented for the mixed-species and structurally complex cypress and pine forests that allows a manager to design silvicultural strategies to meet forest management objectives.