柳杉人工林微環境特性與疏伐產生的效應

Characteristics of Microenvironment and Effects of Thinning Treatment in a Cryptomeria japonica Plantation

林奐慶(Huan-Ching Lin)

指導教授 ： 陳明杰

國立臺灣大學/生物資源暨農學院/森林環境暨資源學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.02470

摘要

本研究的目的在於探討柳杉人工林微環境特性與疏伐後對於微環境所造成的效應。試驗地位於林務局南投林區管理處巒大事業區74、75、76林班35年生柳杉人工林，在試驗地內設置12個1公頃的樣區，分別以0%、25%、50%三種不同強度的疏伐處理，四個重複。另外，於附近空曠處設置一個氣象站。收集2006年5 月至2008年4月之氣溫、相對溼度、光合作用有效輻射量（PAR）、土壤溫度等資料，比較疏伐前樣區與氣象站，以及樣區疏伐前後之微環境因子的差異。
疏伐前，比較12個樣區與氣象站的資料發現，樣區之PAR月總量約為氣象站的1/10~1/4 左右，月份變化幅度也較小。觀測期間樣區之年平均氣溫高於氣象站約0.35 °C。樹冠層阻擋輻射能量進出林內，且使樹冠至地面空間的能量交換延滯，使樣區之一日溫差較氣象站小，尤其在夏季期間的差異更為明顯。其次，森林有調節溼度的作用，日變化幅度要小於氣象站，樣區之相對溼度高於氣象站，尤其在冬季期間的差異更為明顯。5月至7月樣區之土壤能量屬於吸熱狀態，而氣象站則是3月至9月，氣象站之土壤吸熱狀態的時間較長。
樣區在2007年9月初完成疏伐作業之後，林地的各項微環境因子受到影響而改變。隨著疏伐度的增加，林地接收更多的太陽輻射，疏伐度50%的樣區PAR月總量約為疏伐度25%的兩倍，約為對照樣區的四倍。疏伐後增加太陽輻射近入林地的機會，造成氣溫和一日溫差隨疏伐度增加而提高，其中又以一日溫差的改變最為明顯。其次，相對溼度則隨疏伐度增加而降低。疏伐後對土壤溫度的影響主要在深度30 cm範圍內，疏伐度50%樣區之土壤溫度提升為較多。在土壤能量為放熱狀態的12月，接近地表的土壤溫度則有疏伐樣區低於對照樣區的情況發生。

關鍵字

柳杉人工林 ； 微環境 ； 氣象因子 ； 疏伐

並列摘要

This research is to investigate the microenvironment character of plantation and that under the influence of thinning. The experimental site of Cyptomeria Japonica plantation belonging to Nantou Forest District Office, Forestry Bureau was selected. 12 plots, each plot is one hectare, were taken in this experimental site that was treated by 0%, 25% and 50% thinning intensity with four duplications. Also, a weather station was set at open location near experimental site. Data include air temperature, relative humidity, photosynthetic active radiation (PAR), and soil temperature etc. of plots and weather station were collected from May 2006 to April 2008 that to compare the microenvironment difference between plots and weather station, and to compare that of plots before and after thinning.
Forest canopy can impede largely solar radiation incident upon forest land in daytime. Before thinning, from May 2006 to May 2007, observed data of 12 plots and weather station was compared that reveal monthly amount of PAR in plantation was about 1/10~1/4 as that of weather station and was less variation in month. Forest canopy can impede radiation energy input and output, which introduces energy exchange lagging in tree space. So, daily absolute temperature difference of plantation was lower than that of weather station, especially in summer. In observed period, yearly average air temperature of plots was higher 0.35 °C than weather station. Besides, relative humidity of plots changes smoothly in a day, which was usually higher than weather station, especially in winter. Others, Soil energy in plantation had longer exothermic state but at weather station had longer endothermic state.
After thinning, being completed on September 2007, microenvironment character of plot was affected and varied. When thinning intensity increases, more sunlight go through gap that introduces PAR increase obviously. Monthly amount of PAR in plots with 50% thinning intensity were about twice than that with 25% thinning intensity, and fourfold than that with control plot. Thinning also increase the chance of sunlight incident upon forest land directly. The result was that air temperature and daily absolute temperature difference increase but relative humidity decreases. Also, soil temperature of above 30 cm depth was change evidently after thinning, and increased more evidently in 50% thinning intensity plot. Besides, in December with soil energy at exothermic state, it revels that soil temperature near surface of thinning plot was lower than that of control plot.

並列關鍵字

Cyptomeria Japonica Plantation ； meteorological factor ； microenvironment ； thinning.

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