Effects of light environment on the growth and establishment of the seedlings of two Chamaecyparis species in the subtropical cloud forest in Chi-lan-shan area, Taiwan
Date Issued
2006
Date
2006
Author(s)
Lai, I-Ling
DOI
zh-TW
Abstract
Chamaecyparis obtusa Sieb. & Zucc. var. formosana (Hayata) Rehder (CO) and C. formosensis Matsum. (CF), are two endemic tree species distributed exclusively in the mountainous cloud forests of Taiwan. The majority of CO seedlings is found under the canopy of mature forests or in small gaps, while those of CF predominantly under more open conditions in disturbed field. Such a differential distribution pattern was considered to be attributable to their difference in shade-tolerance. To test the hypothesis, the survival, growth, chlorophyll content, morphological and photosynthetic traits of young seedlings of either species were compared in Chi-lan-shan area of northeastern Taiwan. Data such as canopy openness, the micrometeorological conditions including fog occurrence and light intensity above and under the canopy of Chamaecyparis forest were collected and then were simulated in the controlled environment conducted in the growth chamber as well as in the green house to test the performance of seedlings under optimal water and nutrient conditions. The results showed that distinct seasonality, perhumid and dim light conditions were the most distinguished characteristics of the climate in Chi-lan-shan area. Fog occurrence reduced 88% of the light intensity reached the canopy and also reduced the frequency and duration of sunflecks under the canopy of Chamaecyparis forest. The frequency of fog occurrence has been as high as 40% of annual time and has reduced ca. 70% of the accumulated photosynthetically active radiation. The distribution pattern of the seedlings in Chi-lan-shan area shows that CO established in habitats with lower light regime than CF. Both species display a plasticity to the various light environments, either in the natural or controlled environments, but in different ways. Under low light condition, there was no significant difference between these two species in photosynthetic traits. Nevertheless, to acclimate to shade condition, seedlings of CO increase the leaf mass ratio under sufficient supplies of nutrients or reduce the leaf mass per area under poor nutrient supply. In contrast to CO, seedlings of CF increase the stem length. Under higher light condition such as in forest gaps, CF displays higher survival rate, photosynthetic capacity, relative growth rate of leaves, and, as a result, higher plant biomass. Hence, CF is considered to be superior to CO under higher light environment. However, continued high light reduces the photosynthesis and leaf growth of either species significantly. The seedlings of either two species are not extremely sun-acclimated. Results from this study suggest that the reduction of light intensity due to fog occurrence in the studied area provides a more favorable condition for CO than for CF. This study also provides evidence that the light environment has played an important role not only in affecting the growth of Chamaecyparis seedlings at early stage, but also in the subsequent survival, regeneration, and distribution of either species in the natural environment.
Subjects
扁柏
紅檜
小苗建立
光環境
耐陰性
雲霧林
霧
棲蘭山區
Chamaecyparis obtusa var. formosana
Chamaecyparis formosensis
establishment of seedlings
light environment
shade tolerance
cloud forest
fog
SDGs
Type
other
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