人工林行列疏伐對地表及地下水文環境之影響

Effects of Row Thinning on the Surface and Underground Hydrological Environments

呂宗烜(Tsung-Hsuan Lu) ； 梁偉立(Wei-Li Liang) ； 周坤宇(Kun-Yu Chou) ； 李勝倫(Sheng-Lun Li) ； 詹孟浚(Meng-Chun Chan)

《台灣林業科學》 30卷3期 (2015/09) Pp. 185-199

https://doi.org/10.7075/TJFS.201509_30(3).0004

摘要

臺灣就疏伐或皆伐對於水土資源的相關研究相當缺乏，本研究於新竹縣五峰鄉新竹林區管理處竹東事業區87、88林班之行列疏伐地（包含皆伐帶及下層疏伐帶）及未伐採地設置觀測樣區，對其環境基本特性及水文反應進行多項目調查，並探討皆伐帶、下層疏伐帶以及未伐採樣區間環境基本特性及水文反應差異。觀測結果可歸納為地表環境及深層地下環境之兩部分：就地表環境而言，皆伐帶及下層疏伐帶的地表植生覆蓋率皆很高且無明顯差異。皆伐帶、下層疏伐帶、未伐採樣區三者的土壤孔隙率平均值接近，但伐採作業等人為干擾程度會影響土壤孔隙率分布。皆伐帶的表層土壤呈現高含水率，其主要原因為雨水直接到達地表，進而產生較大的漫地流量。就較深層地下環境而言，伐採所造成的地表環境改變不足以影響較深層地中水流的分布，反而是地質分界、不連續介面等地質條件對地下水脈分布有較大的影響。藉由以上的結果可以得知，皆伐或疏伐的影響主要集中在近地表的水土環境，特別是皆伐帶為一水土反應變動較高的區域，在進行行列疏伐時，除了應避免於坡地凹處設置皆伐帶，同時需參考地質結構，避免地表環境的改變影響到深層水文反應的變化。

關鍵字

地下水 ； 行列疏伐 ； 土壤孔隙率 ； 土壤含水率 ； 地表植生覆蓋率

並列摘要

Previous studies on the relationship between logging operations and soil and water conservation are rare in Taiwan. This study attempted to measure environmental characteristics and hydrological responses in a non-logged plot and row-thinned plots including clear-cut and low-thinned areas in forest compartments nos. 87 and 88 in the Zhudong working circle, Hsinchu Forest District. For observed results in the near-surface environment, coverage of the understory showed no differences between the clear-cut and low-thinned areas. Soil porosity in the near-surface layer was similar among the clear-cut, low-thinned, and non-logged areas. However, logging operations enlarged the variability of soil porosity. We found a higher surface soil water content in clear-cut areas than in low-thinning areas. This was due to the larger amount of rainwater reaching the surface in the clear-cut areas, where the amount of overland flow was greater than that in low-thinned areas. For the underground environment, the spatial distribution of groundwater was little related to logging operations, but was mainly controlled by geological conditions, such as a separation interface of bedrock. We concluded that clear-cut and low-thinned operations would greatly affect interactions of soil and water processes in the region near the surface but not in the region of the bedrock layer. To reduce potential influences of disturbances in the near-surface environment on the underground hydrological responses, it is unsuitable to set up clear-cut areas in valleys or geologically sensitive areas.

並列關鍵字

Groundwater ； row thinning ； soil porosity ； soil water content ； understory coverage