人工濕地干擾效應、生物多樣性及生態系功能之研究：以亞熱帶臺灣為例

Abstract

都市濕地因受到持續的人為干擾，易被外來物種拓殖，因此完全移除外來物種對都市濕地而言，是不切實際的。雖然外來種普遍被視為危害，部分外來種卻可為遭受劇烈人為干擾的生態系統提供效益(如原生物種食物的提供、棲地環境改良)。然而，外來種對都市濕地提供的潛在效益卻鮮少探討。因此，本研究探討外來種對都市濕地的生態系統服務能否提供效益，使用生態系統服務方法進行外來種影響定性評估，探討外來種對都市濕地生態系統服務造成的危害與效益。三個研究濕地皆被外來魚種嚴重拓殖(>35%)，外來鳥種則只占鳥類群聚的<3%。研究發現外來種可為魚食性的留鳥與候鳥提供重要的食物來源，並可提升都市濕地休閒旅遊與美學感受之價值，因此證實外來種可為都市濕地之生態系統服務提供效益。 因人為干擾持續增加，自然濕地已遭受大量的破壞。建立表面流人工濕地(FWSs)為目前常用的濕地異地復育方法。然而，探討有關優化FWSs於生物多樣性加強的潛能之研究卻相對缺乏。因此，調查限制FWSs優勢動物類群(如水生大型無脊椎動物群聚)的因子(如魚類掠食、水鳥掠食、溶氧和營養階層)是必須的。本研究選擇北臺灣兩座FWSs進行掠食者隔絕實驗，調查魚類與水鳥的存在對FWSs水生大型無脊椎動物群聚結構的影響，並比較不同因子對於FWSs水生大型無脊椎動物豐度與多樣性的相對重要性。在魚類隔絕的實驗組中，水生大型無脊椎動物的豐度明顯較魚類存在的組別高。水生大型無脊椎動物的多樣性以及各優勢類群(雙翅目、寡毛綱)的豐度也明顯於魚類隔絕的實驗組中較魚類存在的組別高。本研究的結果證實溶氧與魚類存在為限制FWSs水生大型無脊椎動物群聚結構最重要的兩個因子。然而，在不同實驗組(魚類出現與隔絕)中，水生大型無脊椎動物群聚的組成卻無明顯差異。由於較少掠食性水鳥出現於研究FWSs，且研究FWSs具有較深且波動的水位，水鳥的存在並不會對水生大型無脊椎動物群聚結構造成明顯的影響。 本研究結論為對都市濕地有益的外來種可予以保留，使其繼續對生態系統服務提供生態效益以協助都市濕地的復育，主張使用生態系統服務方法評估外來種造成的影響，以協助訂定都市濕地外來種之管理優先順序。本研究結果同時證實溶氧與魚類存在為限制FWSs水生大型無脊椎動物群聚結構最重要的兩個因子。本研究可為FWSs的設計與管理在生物多樣性加強方面提供重要的資料。

Complete eradication of non-native species has been unpractical in urban wetlands which commonly colonized by these species due to continuous anthropogenic disturbances. Despite non-native species have long been regarded as damages, some could provide ecological benefits to the intensively human-disturbed ecosystems (e.g. food provision for native species, and habitat modification). However, potential benefits caused by non-native species to urban wetlands have not been well documented. Therefore, we investigated if non-native species could provide good benefits to the ESs of urban wetlands. The qualitative non-native species effect assessment based on ES-approach was conducted to link the benefits and damages of non-native species to the ESs of urban wetlands. Results showed that three study wetlands were seriously colonized by non-native fishes (> 35%), but non-native birds comprised only < 3% in our study sites. Our results showed that the non-native species from our study sites could provide essential trophic support to the important native and migratory birds with predatory habit, and enhance the recreational and aesthetic values of urban wetlands. Natural wetlands have been extensively impaired due to increasing human activities. Free water surface constructed wetlands (FWSs) have been commonly established as a common method of off-site wetland restoration. But, research focusing on optimizing the biodiversity enhancement potential of FWSs is relatively limited. Therefore, it would be essential to investigate the factors, including fish and waterbird predation, dissolved oxygen (DO) and nutrient levels, constraining the dominant inhabitants of FWSs, i.e. macroinvertebrate community. A predator exclusion experiment was conducted in two FWSs from northern Taiwan to investigate the influence of fish and waterbird presence on the macroinvertebrate community structure of FWSs. Relative importance of different factors on macroinvertebrate abundance and diversity was also compared. Total macroinvertebrate abundance of fish-absence treatment was obviously higher than fish-presence treatment in our study FWSs during both study seasons. Taxon richness and abundance of dominant macroinvertebrate taxa (Diptera and Oligochaeta) were also higher in fish-absence treatment than fish-presence treatment. Our results confirmed that DO and fish presence were the two most important constraining factors for the macroinvertebrate community structure of FWSs. However, no obvious difference was found in macroinvertebrate community composition of our study FWSs between different treatments. Because of the low waterbird abundance and the relatively deep and fluctuated water depth of our study FWSs, there was no clear effect of waterbird presence on macroinvertebrate community structure. We concluded that the beneficial non-native species could be retained to provide good ecological benefits to the ESs for facilitating the restoration of urban wetlands. A framework for the non-native species effect assessment based on ES-approach is also proposed to facilitate developing the management priority of non-native species in the degraded urban wetland ecosystems. Our results also confirmed that DO and fish presence were the two most important constrains for the macroinvertebrate community structure of FWSs. Our results could provide important information for the design and management of FWSs with respect to biodiversity enhancement.