The location and vegetation physiognomy of ecological infrastructures determine bat activity in Mediterranean floodplain landscapes

Ecological infrastructures (EI), defined as natural or semi-natural structural elements, are important to support biodiversity and could play a crucial role in counteracting the well-known impacts of intensive agriculture. Yet, the importance of EI remains largely unexplored in Mediterranean agricultural landscapes and for species providing essential ecosystem services such as bats. Here, we evaluated the role of different EI types – in terms of location (riparian vs terrestrial) and vegetation physiognomy (woody vs non-woody) – in shaping bat guild activity in crop fields located in the floodplains of the Iberian Peninsula. We recorded 60,732 bat sequences in 96 crop fields and characterized 106 EI patches via an adaptation of the Biodiversity Potential Index (BPI). We found that the activity of mid-range echolocators (MRE) and long-range echolocators (LRE) was twofold higher when the nearest EI patch was riparian (i.e., contiguous to a watercourse) than when it was terrestrial. When assessing changes in bat activity in crop fields in relation to a gradient distance from EI types, our results revealed both distinct and similar effects of the location and vegetation physiognomy of the EI on bat guilds. For instance, while only the LRE guild positively responded to the proximity of woody EI, both MRE and LRE showed a marked increase of activity when increasing distances to non-woody EI, thus suggesting low bat activity levels near these features. Our habitat quality assessment also revealed that woody EI and riparian EI had higher biodiversity potential and related habitat quality, thus contributing to our understanding of bat responses to EI type in crop fields. As riparian areas are rarely targeted in biodiversity-friendly measures in farmland, we strongly recommend including riparian EI (especially the woody type) in conservation planning as they are crucial for both biodiversity conservation and ecosystem functioning.生态基础设施（Ecological infrastructures, EI）被定义为自然或半自然结构单元，对维持生物多样性具有重要意义，且可在抵消广为人知的集约化农业负面影响方面发挥关键作用。然而，在地中海农业景观中，针对蝙蝠这类提供关键生态系统服务的物种而言，生态基础设施的重要性在很大程度上仍未得到探明。本研究以伊比利亚半岛泛滥平原内的农田为研究对象，评估了不同类型生态基础设施——按区位（河岸型与陆地型）和植被外貌（木本与非木本）划分——对蝙蝠类群活动度的调控作用。研究团队在96块农田中共记录到60732条蝙蝠序列，并通过改良的生物多样性潜力指数（Biodiversity Potential Index, BPI）对106个生态基础设施斑块进行了特征表征。研究发现，当最近的生态基础设施斑块为河岸型（即与水道相连）时，中距离回声定位者（MRE）和长距离回声定位者（LRE）的活动度是陆地型生态基础设施附近的两倍。在分析农田内蝙蝠活动度随与不同类型生态基础设施的距离梯度变化的规律时，结果显示生态基础设施的区位与植被外貌对不同蝙蝠类群的影响既有差异也存在共性。例如，仅长距离回声定位者类群会对木本生态基础设施的临近产生正向响应；而当中距离回声定位者与长距离回声定位者的活动度随与非木本生态基础设施的距离增加而显著提升时，表明此类设施附近的蝙蝠活动水平较低。本研究的栖息地质量评估还显示，木本生态基础设施和河岸型生态基础设施具有更高的生物多样性潜力与相关栖息地质量，这有助于深化我们对农田中蝙蝠响应不同类型生态基础设施机制的理解。鉴于河岸区域极少被纳入农田生物多样性友好型保护举措，我们强烈建议将河岸型生态基础设施（尤其是木本类型）纳入保护规划，因其对生物多样性保护与生态系统功能均具有关键意义。