Landscape disturbances influence local plant diversity beyond stand-scale effects in a North American boreal forest

Natural and anthropogenic disturbances are major threats to biodiversity worldwide, with important consequences for forest ecosystems. Landscape characteristics play a central role in shaping diversity–disturbance relationships by capturing ecological processes that operate beyond the local stand scale. However, when disturbances co-occur across multiple spatial scales, their combined effects are difficult to predict, and interactions among scales may either mitigate or amplify their impacts on biodiversity. Here, we tested how spatiotemporal characteristics of disturbances measured at the landscape-level interact with stand-level disturbances to shape plant alpha and beta diversity across one quarter-hectare plots in the boreal forest of Alberta, Canada. Using a multi-scale approach, we evaluated how time since disturbance, weighted by the proportion of area affected by fire, forest harvesting, and seismic lines, explained variation in plant diversity beyond the stand-level effects typically associated with succession after wildfires. We found that species richness was primarily shaped by a dominant negative effect of seismic lines. Specifically, plots with more recent and extensive seismic line networks within a 1-km radius exhibited lower local species richness. Species turnover between randomly paired plots was largely explained by stand-level effects of recent fire moderated by the effect of the surrounding disturbance mosaic, although no single disturbance type emerged as a relevant predictor. Finally, multivariate analyses indicated that nearly all species responding significantly to seismic lines were negatively affected by this disturbance. In the context of accelerating forest cover change driven by human activities, understanding how interacting disturbances across scales shape local biodiversity is essential for informing forest management and conservation. Our results indicate that in boreal forests, a system subject to ongoing natural resource extraction, anthropogenic disturbances associated with oil and gas development can outweigh natural disturbances, resulting in a dominant negative effect on plant diversity. This highlights that landscape-scale patterns of disturbance can be as important as, or more important than, local stand-scale disturbances in structuring plant diversity in a stand. Together, these findings underscore the need to adopt a landscape-level perspective when managing and restoring ecosystems exposed to multiple, interacting disturbances.自然与人为干扰（natural and anthropogenic disturbances）是全球生物多样性（biodiversity）面临的主要威胁，对森林生态系统（forest ecosystems）造成深远影响。景观特征（landscape characteristics）在塑造多样性-干扰关系中发挥核心作用，其通过捕捉超出局部林分尺度（stand scale）的生态过程实现调控功能。然而，当干扰在多个空间尺度（spatial scale）上同时发生时，其综合效应难以预测，且不同尺度间的交互作用可能缓解或加剧其对生物多样性的影响。本研究以加拿大阿尔伯塔省（Alberta）北方针叶林（boreal forest）内的0.25公顷样地为研究对象，检验了景观尺度（landscape-level）下测得的干扰时空特征（spatiotemporal characteristics）与林分尺度干扰的交互作用，如何调控植物α多样性（alpha diversity）与β多样性（beta diversity）的分布格局。研究采用多尺度方法（multi-scale approach），评估了以野火、森林采伐与地震勘探线（seismic lines）影响面积占比加权的干扰后时间，在通常与野火后群落演替（succession）相关的林分尺度效应之外，如何解释植物多样性的变异。研究发现，物种丰富度（species richness）主要受地震勘探线的显著负向效应调控。具体而言，1千米半径范围内拥有更近期且更广泛的地震勘探线网络的样地，其本地物种丰富度更低。随机配对样地间的物种周转（species turnover），主要由近期野火的林分尺度效应所解释，且受周围干扰镶嵌体（disturbance mosaic）的效应调节，但并未发现单一干扰类型可作为有效的预测因子（predictor）。最后，多变量分析（multivariate analyses）显示，几乎所有对地震勘探线产生显著响应的物种，均受到该干扰的负面影响。在人类活动驱动森林覆盖加速变化的背景下，理解跨尺度交互干扰如何塑造本地生物多样性，可为森林管理与保护（forest management and conservation）提供关键依据。本研究结果表明，在持续开展自然资源开采（natural resource extraction）的北方针叶林生态系统中，与油气开发（oil and gas development）相关的人为干扰，其影响可超过自然干扰，进而对植物多样性产生主导性的负向效应。这一结果凸显出，在林分水平构建植物多样性格局时，景观尺度的干扰模式可与局部林分尺度干扰同等重要，甚至更为关键。综上，本研究结果强调，在管理与修复受到多重交互干扰影响的生态系统时，需采用景观尺度的研究视角。