烏心石間作作物之效益探討

森林的多方面效益日受重視，但臺灣近年來推動「私有地造林」面臨林農參與度低之困境，能否於造林之同時，提昇農民所得，使經濟獲益與環境保育達到平衡，為當前重要議題。混農林業可解決小農經濟之不定性，亦可能加強農業與環境、生態之連結，是維繫農業發展及因應氣候變遷之重要調適策略。作物與林木間作對作物產量與品質、林木生長及總體經濟效益之影響，依施作地區、林木作物組合與栽培方式而不同。系統之種間互動關係為影響系統生產力之關鍵，與實施當地之環境條件有關，故需實地評估。本研究於國立臺灣大學生物資源暨農學院實驗林管理處 (以下簡稱：實驗林) 及國立臺灣大學生物資源暨農學院附設農業試驗場 (以下簡稱：農業試驗場) 進行，探討於烏心石 (Michelia compressa) 造林初期，以作物與之間作，影響林木與作物之程度，包括各作物之產量與經濟效益，以及烏心石生長情形。於實驗林以作物間作烏心石，其底土氧化鎂濃度下降幅度高於烏心石純林，明日葉 (Angelica keiskei) 及糯米團 (Gonostegia hirta) 可增加總體淨利，而山蘇 (Asplenium nidus)、過溝菜蕨 (Anisogonium esculentum) 及糯米團可長期栽培，作物更新頻率較小；實驗林各作物之品質與營養價值較農業試驗場高，作物栽培期間烏心石生長未受影響。於農業試驗場，作物與烏心石間作與否不影響作物產量及品質，亦不影響烏心石生長，顯示於造林初期，物種間互動關係不影響林木生長及作物生產，其中以甘藷葉 (Ipomoea batatas)、白鶴靈芝 (Rhinacanthus nasutus) 產量較高，甘藷葉、白鶴靈芝及糯米團之產值較高，除過溝菜蕨，其餘作物可有正收益。以上結果顯示，於造林初期以適當作物與烏心石間作有提昇獲益之可能，惟於山坡地執行農作有其相當之困難度。

關鍵字

混農林業；林木生長；作物品質；經濟價值

並列摘要

The multi-benefits of forest are more and more emphasized. However, afforestation on private lands in Taiwan has recently faced the difficulty of low participation of forest farmers. At present, how to enhance farmers’ income during afforestation to balance the economic benefit and the environmental conservation is an important issue. Appling agroforestry not only resolves the uncertainty of small scale farmers’ economy, but also strengthens links of environment, agriculture and ecology. It may be an important adaptive strategy to protect agricultural development and respond to the climate change. The effect of intercropping crops with forest trees on the yield and quality of crops, trees growth and overall income are different in various regions, intercropping combinations and planting methods. Interspecific interaction in the system is the key point to affect the productivity, also relates with the environmental condition of the implemented sites. Thus, the on-site assessment is necessary. This research was executed in the Experimental Forest and Experimental Farm, National Taiwan University, and was aimed on the effect of intercropping crops with Michelia compressa on the crop production, tree growth, and economic benefit during the early period of afforestation. The results in the Experimental Forest showed that intercropping enhanced the decrease of magnesium oxide concentration. The intercropping of Angelica keiskei and Gonostegia hirta with Michelia compressa increased the overall net income. The renewal frequency of Anisogonium esculentum, Asplenium nidus and Gonostegia hirta was low for long-period intercropping. All crops had better quality and higher nutritional contents than those grown in the Experimental Farm. Furthermore, the growth of Michelia compressa was not affected by intercropping. The results in Experimental Farm showed that the yield and quality of crops and the growth of Michelia compressa were not affected by intercropping. Interspecific interactions did not affect tree growth and crop production in the initial stage of afforestation. During intercropping, the productivities of Ipomoea batatas and Rhinacanthus nasutus were higher, and output values of Ipomoea batatas, Rhinacanthus nasutus and Gonostegia hirta were higher. Except Anisogonium esculentum, the rest of crops could yield positive overall income. It was feasible to increase benefit via intercropping Michelia compressa with crops in the initial period of afforestation. However, some difficulties do exist for conducting the agricultural practices on highlands.