| Summary: | 碩士 === 國立宜蘭大學 === 森林暨自然資源學系碩士班 === 99 === The model in forest development and harvesting is needed to contain growth. Individual diameter growth models are presented to construct mixed effects models for Chamaecyparis formosensis, Taiwania cryptomerioides, Cryptomeria japonica, Calocedrus formosana, Acacia confusa and Fraxinus griffithii plantations using the first and the second survey data of permanent plots from Taiwan Forestry Bureau. The independent variables are diameter at breast height (DBH), site index (SI), crown ratio (CR), stand basal area (SBA) and stand basal area in trees larger than subject tree (BAL). The dependent variable is the diameter growth, using the SAS Proc Mixed for analysis, and the significant of regression coefficients, the VIF values, the adjusted R2 value and the AIC value are used for the independent variables selection.
The results of fitting fixed effects growth models show that only in Calocedrus formosana the relationship between D and diameter growth is with monotonic increasing curve, and the other models are with convex curve effect, therefore D is the major growth factor. SI is positive significantly effecting diameter increment of trees in Chamaecyparis formosensis, Cryptomeria japonica and Acacia confusa. CR in Taiwania cryptomerioides and Acacia confusa models are not significant, and the other models are positive significant. SBA in four conifer species are negative significant. BAL in Cryptomeria japonica and Acacia confusa models are not significant, and the other models are positive significant. We use plot as random effect to establish mixed effect models. The growth models with fixed effects compared to the growth models with mixed effects, the adjusted R2 from the original 0.23 ~ 0.35 increased to 0.36 ~ 0.51. These models are biologically and statistically reliable.
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