Microenvironment Variations under Canopy Gaps and Responses of Broad-leaved Tree Seedlings

• Main Authors: Hsio-Wen Yao, 姚曉文
• Other Authors: Shing-Rong Kuo
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/36779739304527833990

碩士 === 臺灣大學 === 森林環境暨資源學研究所 === 98 === Gaps of various sizes were made in Japanese Sugi (Cryptomeria japonica) plantation at Chi-tou, Central Taiwan after removed Ma Bamboo (Dendrocalamus latiflorus) 2002. Canopy openness was measured on 45 gaps, and the irradiation, temperature of air and soil, diurnal air temperature fluctuation, relative air moisture, and soil water potential were measured on 10 of the 45 gaps during the period of 2005 to 2009. The average openness ranged from 13.2 to 30.6%, and the gap size ranged from 0.1 to 1.6, and the irradiation intensity ranged from 1.5 to 10.4 mol m-2 day-1 in the growing season(from March to September). Two additional gaps were observed during Apirl 2006 to September 2008. In which the average openness ranged from 35.3 to 38.1%, and the irradiation intensity ranged from 12.3 to 18.8 mol m-2 day-1. The maximum absolute difference of average openness between all gaps was 17.3 mol m-2 day-1 in the growing season, 15.5 mol m-2 day-1 in the non-growing season, and it was 16.5 mol m-2 day-1 in the whole year. We found that it appeared to be a linear relationship between gap size and canopy openness. We also found that the irradiation intensity and soil water potential were directly determined by the canopy openness. However, the variations of other microenvironmental conditions were indirectly determined by openness and affected by seasonal changes at the same time. 6 species of 1 year old seedlings, Beilschmiedia erythrophloia, Lindera megaphylla, Cyclobalanopsis stenophylloides, Cyclobalanopsis glauca, Pasania hancei var. ternaticupula and Quercus variabilis were planted and growing well in 45 gaps from 2005 to 2009. The growth of height and basal diameter, crown width, number of lateral stems, growth of height/diameter ratio, SLA (specific leaf area) of 45 gaps and leaf physiological activities of 10 gaps were measured from April to August 2009. The results showed that the growth of height and basal diameter of L. megaphylla, C. stenophylloides, C. glauca and P. hancei var. ternaticupula were proportional to the increase of canopy openness, which suggested that they would be more suitable to planted in larger gaps. The growth of C. stenophylloides, C. glauca and P. hancei var. ternaticupula were due to the increase in accumulation of irradiation. Nevertheless, the growth of L. megaphylla was mainly determined by soil moisture. As a result, it would be appropriate to plant in moisture habitats. The physiological activities of Q. variabilis had been limited, which implied that it would be more appropriate to plant in larger gaps with canopy openness being >30%. In B. erythrophloia, there was no significant effect on the growth of height on canopy openness, but on the growth of basal diameter was. The crown width of 4 Fagaceae species, C. stenophylloides, C. glauca, P. hancei var. ternaticupula and Q. variabilis increased as the canopy openness increased. The number of lateral stems of C. stenophylloides and C. glauca also grew in the same pattern. A longer period of survey would be more useful for silviculture strategies.