農村地區不同土地利用方式之水資源涵養效益評估 The evaluation of different land use of water resourse conservation performance in rural area

本年度計畫係以蓮華池研究中心周圍之農村地區為試驗區域，選取3種不同土地利用方式，分別為廢耕地（經土壤改良，混合溪砂）、桂竹林及油茶園等3種，並針對上述地區蒐集及分析土壤物理環境資料，包括乾總體密度及各種孔隙率分析等。土壤孔隙大小之分析方式為應用竹下（1985）之理論，將土壤孔隙區分為大、中、小及細孔隙等4種，而中、小孔隙又合稱為粗孔隙。粗孔隙因同時具有貯留及傳導水分的功用，故可採用土壤粗孔隙率評估土壤之最大有效貯水容量，乃以靜態的方式評估土壤涵養水源之能力，且粗孔隙率亦可用來表示不同地況之間的差異。本研究以土壤取樣深度30cm為計算基礎，將平均粗孔隙率乘以土壤深度30cm，計算單位面積1ha的水分貯留量，用以表示試驗區之單場降雨的最大貯留量，評估土壤水分貯留量的差異。
土壤物理環境分析部分，3個試驗區分析結果：(1)廢耕地（經土壤改良，混合溪砂）試驗區：平均大孔隙率0.59%、平均粗孔隙率14.84%、涵養水量445.2(m3/ha)。(2)桂竹林試驗區：平均大孔隙率1.73%、平均粗孔隙率11.32%、涵養水量339.6(m3/ha)。(3)油茶園試驗區：平均大孔隙率0.60%、平均粗孔隙率6.29%、涵養水量188.7(m3/ha)。上述分析結果顯示3種不同土地利用型態可涵養水源量大小順序為廢耕地（經土壤改良，混合溪砂）>桂竹林>油茶園。
水文環境分析部分，於油茶園試驗區表層進行土壤入滲試驗結果，飽和水力傳導度平均為3.13x10- 4cm/sec，相較於103年之草生地試驗區平均為2.11x10- 4cm/sec及104年度果園試驗區之平均為8.83x10-1cm/sec，顯示地表滲透速度緩慢，與草生地情形相近。
綜合分析本計畫目前研究成果，總計10種不同土地利用型態之土壤涵養水源能力優劣順序，依序為廢耕地（經土壤改良，混合溪砂）>天然林>桂竹林>人工林>檳榔及果樹園>廢棄果園>坡地檳榔園>人工草地>果園>油茶園。
針對農村地區水資源涵養保育策略如下：1.就整體農村環境而言，以營造類似林地之利用方式的農業使用方式為最佳。2.以個別土地利用型態而言：（1）可調整作物類型，避免單一作物，且以非勤耕作物為主，配合農地水土保持，即可增加水資源涵養能力。（2）在土壤條件不佳之地區，耕作前可先進行適當的土壤改良。
The study areas of this annual study were located in rural areas around Lienhuachih research center. A total of three different land-use types were investigated this year, including cultivation abandoned land(soil improvement, mixed river sand), bamboo and camellia plantation,and for the collection and analysis of information on the physical environment of soil in these areas, which included and various porosity. It used theory of Takeshita (1985) to analysis of soil pores and soil pores were divided into macropore, mesopore, minipore, micropore and containing mesopore and minipore collectively known as coarse pores. coarse pores having a function of storing and water conduction, so use the coarse porosity to assess the maximum effective water storage capacity, are based on a static way to assess soil ability to conserve water sources, and the coarse porosity may also be used to indicate the difference between the
land situation differently. In this study, soil sampling depth of 30 cm is calculated on the basis, the average coarse porosity multiplied soil
depth 30 cm, calculation of the water storage capacity per unit area of 1 ha, it shows that maximum storage capacity of single rainfall,valuation difference of water storage capacity in soil.
For the Soil physical environment data, the results of 3 experimental areas show that (1) cultivation abandoned land(soil improvement, mixed river sand): The average macroporosity was 0.59%, the average coarse porosity was 14.84%,water storage amount was 445.2 m3/ha. (2)bamboo: The average macroporosity was 1.73%, the average coarse porosity was 11.32%, water storage amount was 339.6 m3/ha. (3)camellia plantation: The average macroporosity was 0.60%, the average coarse porosity was 6.29%, water storage amount was 188.7 m3/ha. The results showed that the trend of water storage capacity in three different land-use types was: cultivation
abandoned land(soil improvement, mixed river sand) > bamboo> camellia plantation.
The strategies for water resources conservation in rural areas are as follows: 1. For the rural environment as a whole, agricultural use is the best way to create similar forest land-use types. 2. To individual land-use types: (1) adjustable crop types, to avoid a single crop, and nonground cultivation of crops, with soil and water conservation, can increase water storage capacity. (2) In areas with poor soil conditions, appropriate soil improvement can be carried out before planting.