| Abstract: | 隨著人類對環境變化影響的加劇，研究環境變化如何影響生態系統功能變
得越來越重要，該領域的研究始於研究單個生態系統功能如何受到生物多樣性
降低的影響，儘管研究表明生物多樣性的降低對生態系統功能產生負面影響，
但為何不同系統功能會對生物多樣性降低有著不同反應、以及如何預測生物多
樣性降低的影響仍不清楚。此外，生態系統因其能同時執行多個生態系統功能
的能力而受到重視，而生態多系統功能也可能被除了生物多樣性之外的因素影
響，但我們對驅動生態多系統功能性的機制尤其是在隨時間尺度上如何變化的
了解有限。另外，環境變化可能以非隨機方式調節物種喪失，然，我們對非隨
機喪失對生態系統功能的影響的理解仍不清楚。因此，本論文欲通過研究臺灣
翡翠水庫的原核生物群落相關之生態系統功能來探討生態系統功能如何對環境
變化作出反應。具體而言，我發現以促進功能的物種數量和運用基質之複雜度
的兩個特異性指標有助於預測生物多樣性損失對生態系統功能的影響(第 2
章)。我展示了生物因素(多樣性)、外源因素(氣候)和內源因素(營養
鹽)分別對有機碳原利用相關之生態多系統功能性在短期動態、季節和年際尺
度上的影響最為顯著(第 3 章)。我藉由提出環境變化會驅動不同有機碳源利
用之生態位寬度及功能潛力之關係的全新的假說，揭示了功能潛力實際上可能
會增加以緩解面對惡劣養分條件的影響(第 4 章)。總結而言，本論文從不同
的方面探討了翡翠水庫原核生物群落在環境變化下的生態系統功能反應並提供 了不同層面的理解。這對於制定有效的管理策略，以維護地球生物多樣性及其 對人類的服務至關重要。;Due to human impacts on Earth′s biological system, the study of how environmental change affects ecosystem functioning has become increasingly important. Research in this area began with examining how individual ecosystem functioning is affected by biodiversity loss. While research has shown that the loss of biodiversity negatively impacts ecosystem functions, the reasons for the different responses of functions to biodiversity loss and how to predict them are not yet fully understood. Moreover, the ecosystem is appreciated for its ability to perform multiple ecosystem functions simultaneously (i.e., ecosystem multifunctionality, EMF); moreover, factors other than diversity could impact ecosystem functioning. However, our current understanding of the underlying mechanisms that explain EMF, especially in terms of temporal variabilities, remains limited. In addition, environmental change could mediate the species loss in a non-random way. Yet, the understanding of the consequence of non-random loss on ecosystem functioning remains unclear. Therefore, the aim of this thesis is to comprehend how ecosystem functioning responds to environmental change, specifically through the prokaryotic community in Feitsui Reservoir, Taiwan. In particular, I demonstrated that the consequences of biodiversity loss on ecosystem functioning could be predicted by two specificity indices based on the number of species that promotes the functions and substrate complexity (Chapter 2). I identified primary factors influencing substrate-utilization based EMF at different temporal scales: biotic factor (diversity) for short-term dynamics, exogenous factor (temperature) for seasonal variations, and endogenous factor (dissolved organic carbon) for inter-annual patterns (Chapter 3). Additionally, I evaluated the potential influence of environmental change on ecosystem functioning by considering the non-random loss of species, which is influenced by their niche breadth in relation to resource utilization. By proposing a link to anticipate the relationship between niche breadth and functional potential under environmental change, I revealed that the functional potential could actually increase, thereby buffering the impact of harsh nutrient conditions (Chapter 4). In conclusion, this thesis provides a comprehensive understanding of how ecosystem functioning of prokaryotic community in Feitsui Reservoir responds to environmental change through different aspects, which is essential for developing effective management strategies to preserve the planet′s biodiversity and its services to humanity. |
