不同農法對北台灣水稻田在耕作與休耕期間動物群聚結構的影響
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2020
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近年來持續有慣行農法與有機農法如何影響台灣無脊椎動物群聚結構的相關研究，但目前尚缺乏對於北台灣農業生態系的深入了解，且過去研究多著重於作物種植時期，對於休耕期間的群聚結構，會如何受到耕作期間施行農法所遺留影響所知甚少。然而休耕的農地能提供許多野生動物棲息和覓食的環境，如宜蘭的水稻田一年僅耕作一次，每年的八月至隔年二月為休耕時期，其湛水的休耕農田常能見到鷸鴴科等候鳥停佇並取食於田間。也因此探討耕作期間不同農法是否會接續影響休耕期間的動物組成和數量，例如能提供候鳥食物來源的無脊椎動物，即變得相當重要。本研究於宜蘭縣員山鄉和三星鄉各選三塊有機與慣行水稻田，共計12塊，採集稻作植株上以及稻田水面下的無脊椎動物，並配合目視記錄如蜻蜓、兩棲類、爬蟲類、鳥類等生物。同時調查各項環境因子，包括水質(水深、水溫、酸鹼值、溶氧量及導電度)、植株高度及田埂植被型態，之後鑑定物種進行動物群聚結構的比較分析，藉此了解不同農法在耕作與休耕期間的影響。
2019年三月至隔年三月共進行9次採樣，共採集無脊椎動物12綱30目144科共32,880隻個體，及記錄脊椎動物4綱9目15科381隻個體。結果顯示整體上有機農田的無脊椎動物物種數(以科的層級表示)及個體數顯著高於慣行農田，其中陸域無脊椎物種數及水生無脊椎個體數同樣以有機農田顯著較高，而農法之間多樣性指數則無顯著差異。陸域物種數及個體數自耕作初期至後期逐漸上升，且以有機農法的上升幅度較大，兩種農法水中無脊椎動物的個體數，則是在耕作後期和休耕初期差異最大，之後的差距隨著休耕時間而變小。群聚組成部分，不同農法並無顯著差異。而農田中的物種數及個體數除與農法相關外，環境中的氣溫、稻株高度、田埂型態、水質以及樣區所在的鄉鎮也各有顯著的影響。結果顯示耕作期間的農法差異對休耕期間無脊椎動物的影響並不特別顯著，兩種農法在冬季的休耕時期均能提供候鳥合適的棲地。
In recent years, several researches have focused on how organic and conventional farming practices differ in affecting invertebrate communities in Taiwan. However, agricultural ecosystems, including rice paddies, in northern Taiwan has rarely been studied; moreover, whether animal communities during the periodic fallow periods also differ between paddies with organic vs. conventional farming practices during the preceding cultivating periods is unclear. In Yilan of northern Taiwan, paddies are left fallow during the winter but are still flooded to prevent colonization of agricultural pests. Such temporary wetlands provide animals, particularly migratory Scolopacidae and Charadriidae shorebirds, foraging habitats; therefore, it is important to study whether abundance and composition of invertebrates differ with legacy of agricultural practices. In this study, three organic and three conventional farmlands were each studied in Yuanshan and Sanxing township of northern Taiwan six times from March 2019 to March 2020, with invertebrates collected from both rice plants and flooded water with sweep nets, and bird and amphibian species identified and number recorded. Environmental factors recorded included ambient temperature, water quality (water depth, water temperature, pH, dissolved oxygen and conductivity), paddy height as well as plant structure of field banks. Invertebrate specimens were identified to family level and biodiversity indices calculated. A total of 32,880 invertebrates belonging to 12 classes, 30 orders, and 144 families, as well as 381 vertebrates of four classes, nine orders, and 15 families were recorded. In total, significantly higher family richness and abundance of invertebrates were found in organic than conventional fields. Family richness of terrestrial invertebrates and abundance of aquatic invertebrates were also significantly higher in organic than conventional fields. Shannon index and community composition did not show significant differences. Family richness and abundance of terrestrial invertebrates increased with progression of rice cultivation, but with organic fields exhibiting higher increase than conventional fields. Difference in abundance of aquatic invertebrates between farming practices were higher in the late stage of cultivation and early stage of fallowing. Expect for agricultural practices, environmental factors such as temperature, water quality, paddy height and the vegetation of field bank also had significant effect on abundance and richness of invertebrates. Abundance and richness of predators and parasitoids were higher in organic than conventional fields. During the fallow period, abundance and composition of invertebrates did not differ between agricultural practices. Flooded fallow fields with either organic or conventional practices can provide ideal foraging habitats for migratory shorebirds.
In recent years, several researches have focused on how organic and conventional farming practices differ in affecting invertebrate communities in Taiwan. However, agricultural ecosystems, including rice paddies, in northern Taiwan has rarely been studied; moreover, whether animal communities during the periodic fallow periods also differ between paddies with organic vs. conventional farming practices during the preceding cultivating periods is unclear. In Yilan of northern Taiwan, paddies are left fallow during the winter but are still flooded to prevent colonization of agricultural pests. Such temporary wetlands provide animals, particularly migratory Scolopacidae and Charadriidae shorebirds, foraging habitats; therefore, it is important to study whether abundance and composition of invertebrates differ with legacy of agricultural practices. In this study, three organic and three conventional farmlands were each studied in Yuanshan and Sanxing township of northern Taiwan six times from March 2019 to March 2020, with invertebrates collected from both rice plants and flooded water with sweep nets, and bird and amphibian species identified and number recorded. Environmental factors recorded included ambient temperature, water quality (water depth, water temperature, pH, dissolved oxygen and conductivity), paddy height as well as plant structure of field banks. Invertebrate specimens were identified to family level and biodiversity indices calculated. A total of 32,880 invertebrates belonging to 12 classes, 30 orders, and 144 families, as well as 381 vertebrates of four classes, nine orders, and 15 families were recorded. In total, significantly higher family richness and abundance of invertebrates were found in organic than conventional fields. Family richness of terrestrial invertebrates and abundance of aquatic invertebrates were also significantly higher in organic than conventional fields. Shannon index and community composition did not show significant differences. Family richness and abundance of terrestrial invertebrates increased with progression of rice cultivation, but with organic fields exhibiting higher increase than conventional fields. Difference in abundance of aquatic invertebrates between farming practices were higher in the late stage of cultivation and early stage of fallowing. Expect for agricultural practices, environmental factors such as temperature, water quality, paddy height and the vegetation of field bank also had significant effect on abundance and richness of invertebrates. Abundance and richness of predators and parasitoids were higher in organic than conventional fields. During the fallow period, abundance and composition of invertebrates did not differ between agricultural practices. Flooded fallow fields with either organic or conventional practices can provide ideal foraging habitats for migratory shorebirds.
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農業生態系, 有機農法, 休耕, 水稻田, agroecosystem, organic agriculture, fallow, paddy field