Data and R code from: Relics of beavers past: time and population density drive scale-dependent patterns of ecosystem engineering

Like many ecological processes, natural disturbances exhibit scale-dependent dynamics that are largely a function of the magnitude, frequency, and scale at which they are assessed. Ecosystem engineers create patch-scale disturbances that affect ecological processes, yet we know little about how these effects scale across space or vary through time. Here, we investigate how patch disturbances by beavers (Castor canadensis), ecosystem engineers renowned for their pond-creation behavior, affect ecological processes across space and time. We evaluated how beaver population recovery influenced surface water dynamics in relation to population density over 70 years across multiple spatial scales (pond, watershed, and regional) in northern Minnesota. Surface water area was positively related to population density at the watershed scale; however, despite variation in beaver densities (and therefore surface water area) at the watershed scale, regional-scale surface water area was stable through time. This stability appears to have been driven by asynchronous beaver density fluctuations among watersheds, combined with the increasing importance of abandoned ponds. Beavers initially created and occupied larger ponds with greater surface water area, but through time shifted towards occupying smaller ponds. As ponds accumulated on the landscape proportionally more surface water was stored within abandoned ponds, which offset the smaller size of occupied ponds. Beaver engineering—driven by density-dependent mechanisms and the legacy effects from abandoned ponds—not only follows general patterns of patch disturbance dynamics by creating a spatial mosaic of patches, but the organism-created mosaic also appears to generate ecological stability at greater spatial scales. We suggest restoring beavers to landscapes is a viable method for increasing surface water storage and will ultimately help advance numerous conservation and rewilding objectives. Our study demonstrates that ecosystem engineering effects can be scale-dependent, indicating researchers should evaluate the ecological impact of engineers across diverse spatiotemporal scales to fully understand their functional roles in ecosystems.

Methods
Refer to main text of the published manuscript for all methods related to this data set. All analyses were performed in program R.

与诸多生态过程类似，自然干扰呈现出尺度依赖的动态特征，其在很大程度上取决于被评估的干扰强度、发生频率与观测尺度。生态系统工程师（ecosystem engineers）会营造出影响生态过程的斑块尺度干扰，但目前我们对这些效应如何随空间尺度拓展或随时间变化仍知之甚少。本研究聚焦于以筑造池塘行为闻名的生态系统工程师——北美海狸（Castor canadensis）所营造的斑块干扰，探究其如何在不同时空尺度下影响生态过程。我们以明尼苏达州北部为研究区域，在70年的时间跨度内，于池塘、流域、区域多个空间尺度上，评估了海狸种群恢复如何通过种群密度影响地表水动态。在流域尺度上，地表水面积与海狸种群密度呈正相关关系；但尽管流域尺度下的海狸密度（及对应的地表水面积）存在波动，区域尺度的地表水面积却始终保持稳定。这种稳定性似乎源于不同流域间海狸密度波动的异步性，以及废弃池塘的重要性随时间不断提升。海狸最初会营造并占据水面面积更大的池塘，但随着时间推移，其栖息选择逐渐转向小型池塘。随着研究区域内池塘数量增多，废弃池塘储存的地表水占比逐渐提升，抵消了当前栖息池塘面积较小带来的影响。海狸的生态工程作用——由密度依赖机制与废弃池塘的遗留效应共同驱动——不仅通过营造空间斑块镶嵌格局契合了斑块干扰动态的一般规律，而且这种生物塑造的镶嵌结构还能在更大空间尺度上催生生态稳定性。我们认为，将海狸重新引入适宜生境是提升地表水储存量的可行方案，最终将助力实现多项保护与再野化目标。本研究证实，生态系统工程师的效应具有尺度依赖性，这提示研究者需在多样的时空尺度下评估工程师物种的生态影响，才能全面理解其在生态系统中的功能角色。

方法
本数据集相关的全部研究方法，请参见已发表论文的正文部分。所有分析均通过R语言程序完成。