Composition of soil seed bank and the responses of growth and physiology in seedlings to light environment in broadleaf-coniferous forest of Dona

• Main Authors: Wen-Chin Lin, 林文智
• Other Authors: Yau-Lun Kuo
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/17357762102392221413

碩士 === 國立屏東科技大學 === 森林系 === 89 === Different regeneration strategies for forest plants will effect the future succession of forest community. It is helpful to understand the dynamics of the forest by investigating the various regeneration methods of plants. The soil seed bank is one of the important regeneration strategies. Through this research of 1 ha area of research site, we try to check the composition of the soil seed bank in the broadleaf-coniferous forest of Dona, and investigate the responses of growth and physiology in three different light environments using Litsea cubeba, Eurya nitida var. nitida and Cycolbalanopsis longinux as materials. The Dona forest were dominated by Castanopsis carlesii、Pseudotsuga wilsoniana、Illicium tashiroi、Cyclobalanopsis longinux and Machilus thunbergii. The J shape of diameter structure of Pseudotsuga wilsoniana reveals this specie can not regenerate in this forest. Another species of dominant species in Dona forest present opposite J shape of diameter structure and can regenerate continuously by forming a lot of seedlings. The soil seed band is dominated by pioneer species, including 15 species、716 seedlings of pioneers and 1 species、11 seedlings of late successional plants. Both shows outstanding different. The soil seed bank has a higher proportion of herbs and shrubs, being 7.4% and 81% of all germinated seeds respectively, including Litsea cubeba、Rubus linearifolius and Eurya nitida var. nitida. Eurya nitida var. nitida has 1129 germinated seeds, involves 52% of all germinated seeds and spreads from 0-30 cm of soil. Machilus thunbergii and Eurya nitida var. nitida of Dona forest were the only species appearing in the soil seeds bank. But Machilus thunbergii is produced in this year and may germinate soon to form seedling bank. So the regeneration strategy of the dominant plants of late successional forest is not from the soil seed bank. This research try to compare the difference of germinated soil numbers of soil seed bank between gap and understory environment of forest in man-made forest. It reveals the numbers of gap environment is 2.6 times to the ones of understory environment. So gap environment can advance the germination of seeds in soil seed bank. The various microenvironments in the forest, especially the light environment, have a severe impacts on the growth and survival of different successional seedlings.In the research environment of high light , gap and understory, the Amax and relative growth rate of tree height per month in Litsea cubeba is obvious higher than the other species in high light environment, being 8.7 μmol m-2s-1and 18.6%, respectively. It is obvious higher than Cyclobalanopsis longinux, being 6.6μmol m-2s-1 and 2.2%. It shows Litsea cubeba can grow well, and utilize light resources efficiently in a high light environment. However, the dark respiration, light saturation point, and maximum photosynthetic rate of Litsea cubeba and Cycolbalanopsis longinux has no conspicuous difference. The result reveals that Cycolbalanopsis longinux has no better physiological characteristics in understory of the forest, but could have other advantageous mechanisms for flourishing growth and development. The relative growth rate of Eurya nitida var. nitida in tree height is 18.8% in high light environment, and do not differs significantly from Litsea cubeba. In the understory of forest, the dark respiration and light saturation point of Eurya nitida var. nitida are lower than the other species, but the photosynthesis is higher significantly. These characteristics can enhance survival rate of Eurya nitida var. nitida. These representations indicate that Eurya nitida var. nitida can grow well in the understory of forest or in a full light environment. The outcome shows that changes in light from gap formation will be beneficial for the growth and survival of different successional species. Keyword: soil seed bank, photosynthesis, pioneer species, Shade tolerant species