| Summary: | 碩士 === 國立中興大學 === 森林學系所 === 96 === In order to achieves the sustainable management of Swietenia macrophylla. It is necessary to collect and predict the status, functions and changes which in the forest level, stand level and tree level. The growth and yield are indispensable data in stand level and tree level. Therefore this study discussed the changes of three levels, in particular in thinning effect on the stand structure development and regeneration of Swietenia macrophylla plantation.
1. In the forest level, this study concerned about the landscape change of land-use in the Shin-Hua Forest Experimental Station in the year of 1993-2002. FRAGSTATS formula was used to analyze landscape structure index of land-use map in year 1993 and year 2002. We selected landscape index such as the general area index, the shape index and the landscape diversity index and landscape changes were discussed. The results showed that: 64.3ha (12.73%) of the Shin-Hua Forest Experimental Station was occupied by pure forest of Swietenia macrophylla, and 167.76ha (33.22%) occupied by Swietenia macrophylla mixed forest landscape area under the boundary of 505ha in the Shin-Hua Forest Experimental Station (there is 62.05% under the NCHU ownership of 374ha in the Shin-Hua Forest Experimental Station). From the results, we found that the 1993-2002 change of mean shape index (MSI) different forest type in Shin-Hua. The results showed Swietenia macrophylla related mixed forest types have expanded. The information revealed the increasing tendency of Swietenia macrophylla by the landscape diversity index. We could explain the forest types were more diverse in year 2002 than year 1993. It’s showed that the Swietenia macrophylla be adaptive to regenerate and grow in that area. Swietenia macrophylla is growing well. Because the pure forests of bamboo, Tectona grandis and Acacia confusa were substituted by Swietenia macrophylla mixed forests.
2. In the stand level, we established the thinning treatment of 10%, 20%, 30% thinning degree and control site by the parameter diameter basal area of Swietenia macrophylla which located at 2nd forest compartment of Shin-Hua Forest Experimental Station and planting in year 1978 and thinning in year 1999. Each thinning treatment has three duplicates and has 12 thinning plots which was 20m×25m. We carried out plots inventory after thinning separately in year 1999, 2001 and 2008. Finally, we used the parameter b and c value of Weibull probability density function to describe the diameter distribution. K-S goodness of fit test were used to test the observation data and predictvalue. We also inventoried and analysis the number of seedlings, age, height and ground- diameter. The thinning effect on the development of stand structure and regeneration of Swietenia macrophylla were discussed in the paper. The results showed that: Weibull parameter b value has increase along with age. The b value from 27.46-29.75 in age 21 to 32.12-37.23 in age 30 of 10% thinning degree. The b value from 26.61-34.90 in age 21 to 31.81-42.10 in age 30 of 20% thinning degree. The b value from 23.49-33.61 in age 21 to 34.78-43.75 in age 30 of 30% thinning degree. The thinning treatments were useful to diameter growth in stand. Weibull parameter c value was bigger than 3.6 after thinning and present negatively skewed. From the inventory in year 2001 and year 2008, we knew that the ingrowth number in 10% and 20% thinning degree was better. In consider of ingrowth, the c value in 10% and 20% thinning stand were 1.87 and 1.76.The regeneration inventory of seedling in the thinning plot, it was high relationship in power low in seedling’s age, height and place- diameter. The number of seedlings in 10% thinning degree is 9,300stems/ha. It was high than 4,200stems/ha of control, 6,000stems/ha of 20% thinning degree and 5,300stems/ha of 30% thinning degree. In this study, the 10% thinning treatment seemed useful to regeneration and growth in seedling of Swietenia macrophylla.
3. In the tree level, we investigated the tree core of percentile Xp.24, Xp.63 and Xp.93 sampling tree in each thinning plots and got the tree ring data. We used Schnute growth model to estimate the 3 percentiles in different time. Finally, we used percentile estimators to got Weibull parameter in different time. The changes of stand structure after thinning were detected. The results showed that: the absolute DBH growth of each percentile shared the same tendency, and the 30% thinning degree was the most. We used Schnute growth model and percentile estimators to calculate Weibull parameter b and c value. The result showed that Weibull parameter b value increased with age, and also increased with thinning degree. The c value was between 0.58-2.62 and present positively skewed.
Above all, Swietenia macrophylla was adaptive to regenerate and grow in Shin-Hua Forest Experimental Station. If we could give some tending operations, it will promote the seedling regeneration and stand growth. Therefore, if we want to apply thinning on the Swietenia macrophylla, it is necessary to decide the thinning intensity and consider the tree position, choose standard and environment factor, also.
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