緩坡地三種不同土地利用之土層水力性質與長期的水分分佈

The Hydraulic Properties and Long-Term Water Distributions of Soil Profiles under Three Different Land Use Types on Gentle Slope

蔡義誌(Yi-Zhih Tsai)

《工程環境會刊》 25期 (2010/07) Pp. 77-91

https://doi.org/10.6562/JEE.2010.25.6

摘要

坡地的大量開發導致了原有生態環境的改變，若沒有適當的防治措施及維護，將導致嚴重水土流失及環境資源惡化。本研究針對緩坡地上不同土地利用之土層水力性質及水分分佈進行探討，並於田間架設土壤水分觀測儀器長期監測土深5cm、30cm、60cm、90cm處之水分變化，以瞭解草生地、林地、工地的土壤水分在土層內部移動之過程與特性。三個試區的土壤水分特性曲線，在相同張力下林地比草生地、工地含有更多的水分，且草生地在高張力時，曲線位置比林地、工地還低，這些現象均與砂粒含量和粘粒含量多寡有關。在土壤飽和水力傳導度方面，則以林地最高；工地次之；草生地最小。工地的土層經過挖填，土壤的結構和分佈均改變，呈現較鬆散狀態，直接影響飽和水力傳導度、水分勢能及水分含量分佈，造成涵養水分能力低落，水分快速通過土層，無法保存住水分。然而，林地和草生地受根系影響，也會消耗土層中的水分，林地又比草生地更爲明顯，因此草生地的土壤水分變化幅度不如林地和工地試區。

關鍵字

坡地土壤 ； 土壤水分勢能 ； 水分特性曲線 ； 水力傳導度 ； 土壤水分移動

並列摘要

Hillside developments changed the original ecological environment. Serious soil loss and degradation of environmental resources will happen without protecting and maintaining on hillside. This study discussed about the hydraulic properties and water distributions of soil profiles under different land use types on gentle slope, and soil water sensors and a datalogger were set up in the field for long-term measuring soil moisture matric potential at 5cm, 30cm, 60cm, 90cm depth. The field experimental areas were under three different land use types on gentle slope, namely grass area, forest area and construction area. The results of soil water characteristic curve showed that the forest area had higher volumetric water content than the grass area and construction area at the same matric potential, and that the curve of grass area was below the forest and construction area, because of the impact of sand content and clay content. The results of soil saturated hydraulic conductivity showed that forest area has the highest value, followed by construction area, and grass area has the lowest value. Soil structure and particle distribution in the soil profile of construction area were changed by excavating and backfilling, and saturated hydraulic conductivity, water potential and water content distribution were affected directly, led to low water holding capacity, water quickly through the soil profile. However, soil moisture was also consumed by root system in the forest area and grass area, and the forest area was more obvious than the grass area. Therefore, the variations in the soil water content of grass area were less than the forest area and construction area.

並列關鍵字

hillside soil ； soil moisture matric potential ； water characteristic curve ； hydraulic conductivity ； soil moisture movement