| Summary: | 碩士 === 國立臺灣大學 === 森林學研究所 === 92 === Canopy gaps play an important role in forest regeneration cycle. Many researches were performed to understand the effects of gap size and form on tree regeneration. The study was aimed to understand the Microenvironment conditions and their effects on seedling growth in two gaps in a natural broad-leaved forest at Shen-Mu area, Centeral Taiwan. Gaps sizes were 550m2 and 250m2 each. Solar radiation, air temperature, soil temperature, and soil moisture in both gaps were monitored. 1-year-old seedlings of seven different species were planted within gaps and their growths were monitored. The results showed that formation of gap would increase the solar radiation, especially from March to September. Light intensity under both large and small gap was 10 times higher than that in the understory. Meanwhile, the solar radiation was different among plots in gaps because of the effects of latitude. The average solar radiation in northern plots inside of the gap is higher than the average of those of southern ones. The changing ranges of air temperature and soil temperature were higher in gaps than those under the canopy. Also, the lost of heat in gaps was faster than those under canopy. In March to September when solar radiation was higher, the air and soil temperature were higher in the gaps. The results varied and were different between two gaps in the rest of the year. In general, soil moisture in the gaps was higher than that under canopy. Based on the results, we found that the closer the plots were to the canopy, the lower the moisture and the drier the soil. In season with higher radzation, direct sun light in the gaps increase the evaporation of surfice soil and decrease the soil water potential. The seedlings grew better in gaps than under canopy, which shows that the formation of gaps is beneficial to the growth of seedlings, and this study also showed that the internal environmental conditions provide the screening factors on seedlings of different species that affect of growth rate of those seedlings.
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