| Summary: | 碩士 === 國立臺灣大學 === 森林學研究所 === 91 === This study was proceeded with three kinds of Taiwan native boreal tree, Camphor tree（Cinnamomum camphora）, Ring-coupled oak（Cyclobalanopsis glauca）and Formosan ash（Fraxinus formosana）, which had different ecological characters , and tried to investigate the nitrogen content in the leaves and the performance of seedling in morphorlogy and quality after 5-month different water regimes and fertilizer supplements. The 5-month old seedling were treated with three different levels of dry-wet cycles combined with three different amount of fertilizer supplements, which were 0 to —0.03MPa(WH), 0 to —0.08MPa(WM), 0 to —0.2MPa(WL), 150kg/ha(NL), 300kg/ha(NM), 450kg/ha(NH), respectively. After 5 months, we harvested the trees and observed the total biomass and nitrogen concentrations in the leaves. The results showed that the pre-dawn branch water potential of all the three species were influenced by the soil water potential. The growth and nitrogen concentration of the three species had different effects under different water regimes and fertilizer supplements. The dry weights of the three species were greater in the WH treatment than in the WL. The biomass of Camphor tree was increased with the enhanced fertilizer supplements but that of Ring-coupled oak was not different singnifcantly. Only the dry weights of leaves and roots in Formosan ash were different obviously. The S/R ratio of Camphor tree and Ring-coupled oak were different in sundry water and nutrient treatment , and that of Formosan ash was increased with enhanced and that of Formosan ash was greater and greater with declined water and fertilizer supplements. The nitrogen concentration was higher in WL and NH treatment because the growth dilution effect. To sum up, Camphor tree could grow well in plenary water and nutrition supplies , on the other hand , it would grow misfitly in drought and barren. Ring-coupled oak grew well in plenty of water, but there was no manifest effect with different fertilizer supplements. Formosan ash was similar to Ring-coupled oak but the former is easier affected by the fertilizer suppliment than the later.
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