本研究選擇臺大實驗林清水溝、水里及和社等三個營林區中三個混農林業試驗地，以評 估施行不同造林樹種與作物之混農林業對山區農地土壤性質之影響。研究結果顯示，三個混農林 業試驗地之土壤 pH 值高低依序為和社>水里>清水溝。清水溝試驗區之土壤，由於長期種植茶樹與 施用肥料的緣故，造成土壤 pH 值的下降 (pH 3.5–4.0)，而和社試驗區的土壤 pH 值則是受到土壤母 質的影響 (pH 5.4–7.3)。地勢相對平坦之清水溝試驗地和地形較陡峭和社試驗地，皆因地形因素而 影響土石沖刷或崩塌的程度，使得前者含石量較低，後者之含石量較高。水里及和社營兩試驗地 之坡度及地形可能影響土壤中磷之移動及分佈，且由於沖蝕作用與土壤表面逕流水之移動，使上 方種植肖楠土壤中之磷遷移下方土壤，而增加下方臍橙區土壤中的有效性磷 (11.7–208.6 mg kg-1)。 水里營林區及和社營林區試驗地之土壤總碳、氮含量之分佈趨勢大致與土壤有效性磷類似。在該 兩試驗區中，坡度對於土壤性質的影響較實施混農林業來的明顯。

Three study sites in Chingshueigou, Shuili, and Heshe tracts of the Experimental Forest, National Taiwan University, which have been practicing agroforestry, were selected for estimating effects of different agroforest systems on soil properties. The results showed that order of soil pH of the three studies was Heshe > Shuili > Chingshueigou. Low soil pH (3.5–4.0) in Chingshueigou tract was caused by long-term fertilization for tea trees. In Heshe tract, the higher soil pH (5.4–7.3) compared to those in Shuili and Chingshueigou tracts, might be affected by parent material. Low and high contents of stones in Chingshueigou and Heshe tracts were both affected by slope factor, which caused different degrees of soil erosion. The steep slope of Shuili and Heshe tracts might also affect movement and distribution of available phosphorous. Due to soil erosion and run-off of surface soil, available P could move and accumulate at lower hills planted with navel oranges (181.7–208.6 mg kg-1). Distribution of total nitrogen and carbon in Shuili and Heshe tracts were similar with distribution of available P. Topography might have greater effects on clay content, distribution of total nitrogen, total carbon and available P than agroforestry implementation in these two study sites