碩士 / 國立屏東科技大學 / 熱帶農業研究所 / 87 / Physiological and Growth Responses to Different Elevations
and Light Environments in Seedlings of Six Species of
Nanjenshan Forest
Shu-Jen Lee and Yau-Lun Kuo
Graduate Institute of Tropical Agriculture,
National Pingtung University of Science and Technology
Abstract
Nanjenshan is an ecological reserve of Kenting National Park. Within the short range of 200m to 400m in elevation, its forest composes varieites of tropical, subtropical, and temperate species, indicating a phenomenon of vegetation compression. In this study, seedlings of six species, Ficus benjamina, Bischofia javanica, and Aglaia elliptifolia, representing tropical species in lower elevation, Osmanthus marginatus, and Aucuba chinensis, representing temperate species in higher elevation, as well as a widely distributed species, Ardisia sieboldii, were planted in two experimental sites. These two sites were set up at 260m and 460m in elevation. Each site had four canopy-gap plots and four understory plots. Thus, there were a total of 16 plots. Environmental factors included light intensity, light quality, temperature, and soil water potential were investigated during summer and winter seasons. Growth performance, survival rates, chlorophyll fluorescence, photosynthetic light responses, photosynthetic temperature responses, and biomass were measured. The objectives of this study were to understand the possible mechanisms of plant adaptation, and the reasons for plants not being able to established at different elevations.
Relative light intensity was 28-36% in gap plots, while only1-6% in understory plots of both sites. There was only once in July 1998 that the soil water potential dropped to -0.5 MPa. Otherwise, soil water was always sufficient. In winter, the daily mean temperature at gap plots of 460m site was 2.2oC lower than that of 260m site. The lowest temperature in 460m site was as low as 10.8oC. This is a possible factor for restraining the low elevation tropical species from distributing into high elevations.
For growth performance, no significant differences were found among the four treatments in A. chinensis. Seedlings of O. marginantus grew better in the aspects of height, biomass, and survival rates in gap plots than in understory plots. Seedlings of B. javanica, F. benjamina, and A. elliptifolia grew significantly higher in gap plots of 260m site than in the other three treatments. However, due to insect infestation and runoff disturbance, seedlings of B. javanica and F. benjamina had lower survival rates in gap plots of 260m site than those of 460m site. Biomass of O. marginatus and A. sieboldii at both sites, as well as biomass of B. javanica at 260m site, showed significantly positive correlation with light intensity.
The optimal temperatures for photosynthesis were 26oC and 20oC for O. marginatus and A. chinensis, respectively. B. javanica, F. benjamina, A. elliptifolia, and A. sieboldii had optimal temperatures in the range of 28oC to 31oC. In O. marginatus, B. javanica, F. benjamina, and A. sieboldii, their photosynthesis increased significantly as light intensity increased, with light saturation point at about 1200mmol m-2s-1 and maximum photosynthetic rates between 8 to 13 mmol m-2s-1. The light saturation points of A. chinensis and A. elliptifolia were between 300 to 400 mmol m-2s-1, indicating that they had low photosynthetic potential, and that their photosynthesis could be inhibited by high light intensity. The chlorophyll fluorescence(Fv/Fm) of A. elliptifolia in gap plots was lower than 0.75 in both winter and summer seasons. Along with the facts that its leaves became chlorotic in winter, A. elliptifolia clearly suffered from both excessive light intensity and low temperature. The chlorophyll fluorescence of A. chinensis in gap plots was also lower than 0.75 in summer seasons, but it recovered in winter. Obviously, A. chinensis could not tolerate high light intensity and high temperature in summer.
Although all six species could survive and grow in both the lower and the higher elevation sites, B. javanica, F. benjamina, and A. elliptifolia, the three low elevation tropical species, showed better growth performances in their original habitats. O. marginatus and A. sieboldii grew well in both elevations. Factors which restrain species from distribution into other habitats included light, temperature and possibly seed dispersal and competition.
Keyword: temperature, photosynthetic light responses, photosynthetic
temperature responses, chlorophyll fluorescence
| Identifer | oai:union.ndltd.org:TW/087NPUST643005 |
| Date | January 1999 |
| Creators | ShuJenLee, 李淑貞 |
| Contributors | Yau Lun Kuo, 郭耀綸 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 84 |
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