天然闊葉林冠層孔隙內微環境的變化與苗木之生長

Micro-Environmental Variation and Seedling Growth in Canopy Gaps of a Broad-Leaved Forest in Central Taiwan

林謙佑(Chien-Yu Lin) ； 郭幸榮(Shing-Rong Kuo) ； 劉興旺(Shing-Wang Liou) ； 楊正釧(Jeng-Chuann Yang) ； 沈介文(Chieh-Wen Shen)

《中華林學季刊》 41卷4期 (2008/12) Pp. 465-481

https://doi.org/10.30064/QJCF.200812.0003

摘要

本試驗目的為觀測位於台灣中部闊葉林內2個冠層孔隙20個樣點間之光合作用有效輻射、土壤水勢、氣溫及土溫的變化，並栽植7種原生闊葉樹苗木於各樣點，探討小苗在各樣點的生長表現。研究孔隙位於南投縣台大實驗林所轄神木溪天然闊葉樹保護林，北緯23°31'，東經120°51'，海拔高1490m，孔隙面積分別為550及250平方公尺，監測林內2個孔隙內及冠層下共20個樣點之4項微環境因子連續16個月的變化。結果顯示：樣區間光量差異在3至9月最顯著。孔隙所在緯度導致太陽軌道在1年當中大多時間偏南，使孔隙內北緣樣點平均日累積光量高於南緣樣點，且前者光量在1年當中會出現2次高峰，孔隙內東西兩側樣點的光量則差異不顯著。孔隙中心、孔隙邊緣樣點之氣溫及土溫日夜溫差幅度皆比冠層下方大。各樣點平均溫度並不因為孔隙邊緣冠層的效應而呈現固定的提升或降低趨勢，而是隨季節變化互有交替。各樣點土壤水勢在研究期間多在-50kPa以上，惟在冬季乾燥季節，水平位置越接近孔隙邊緣的樣點，土壤水勢越低，顯示冠層的蒸散作用使土壤水勢下降在乾季較為明顯。試驗所栽植的7種苗木，高生長及直徑生長皆受光量的顯著影響，但變化趨勢在樹種間不同，其它微環境因子對生長的效應則不顯著。

關鍵字

氣溫 ； 冠層孔隙 ； 光合作用有效輻射 ； 苗木 ； 土溫 ； 土壤水勢

並列摘要

This study was aimed to observe the variations of photosynthetically This study was aimed to observe the variations of photosynthetically active radiation, soil water potential, air temperature and soil temperature of 20 plots in two canopy gaps in a broad-leaved forest, and to assess the growth performances of planted seedlings of seven native broad-leaved trees of Taiwan. The two forest gaps were located at Shenmuhsi of the Experimental Forest of National Taiwan University, in Nantou County, Taiwan (N 23° 31', E 120° 51', elevation around 1490m). Areas of two gaps were 550 and 250 m^2. The variations of four micro-environmental parameters were monitored continuously at 20 measurement plots in the two gaps and under canopy for 16 months. The results showed that difference of light intensity among plots of each gap was mostly significant in March to September. Mean daily accumulative light intensity in plot NGE was higher than in SGE due to latitude effect, while the measurement in NGE had two peaks in a year. However, there was no significant difference in light intensity between the eastern and western plots in each gap. The difference between day and night soil temperature was higher in plot GA and GE than in UC, and was varied with season. Soil water potential was usually higher than -50kPa. However, in drier winter season, soil water potential decreased with the decreasing horizontal distance between measurement plots and nearby canopy. This result demonstrated that the decrease of soil water potential was more significant in dry season because of transpiration. Relationships between height and collar diameter growth of planted seedlings and light intensity in plots were significant in all species. The effects of other three micro-environmental parameters on growth of planted seedlings were not significant.

並列關鍵字

Air temperature ； Canopy gaps ； Photosynthetically active radiation ； Seedling ； Soil temperature ； Soil water potential