Data from: Forest management intensity affects aquatic communities in artificial tree holes

Forest management could potentially affect organisms in all forest habitats. However, aquatic communities in water-filled tree-holes may be especially sensitive because of small population sizes, the risk of drought and potential dispersal limitation. We set up artificial tree holes in forest stands subject to different management intensities in two regions in Germany and assessed the influence of local environmental properties (tree-hole opening type, tree diameter, water volume and water temperature) as well as regional drivers (forest management intensity, tree-hole density) on tree-hole insect communities (not considering other organisms such as nematodes or rotifers), detritus content, oxygen and nutrient concentrations. In addition, we compared data from artificial tree holes with data from natural tree holes in the same area to evaluate the methodological approach of using tree-hole analogues. We found that forest management had strong effects on communities in artificial tree holes in both regions and across the season. Abundance and species richness declined, community composition shifted and detritus content declined with increasing forest management intensity. Environmental variables, such as tree-hole density and tree diameter partly explained these changes. However, dispersal limitation, indicated by effects of tree-hole density, generally showed rather weak impacts on communities. Artificial tree holes had higher water temperatures (on average 2°C higher) and oxygen concentrations (on average 25% higher) than natural tree holes. The abundance of organisms was higher but species richness was lower in artificial tree holes. Community composition differed between artificial and natural tree holes. Negative management effects were detectable in both tree-hole systems, despite their abiotic and biotic differences. Our results indicate that forest management has substantial and pervasive effects on tree-hole communities and may alter their structure and functioning. We furthermore conclude that artificial tree-hole analogues represent a useful experimental alternative to test effects of changes in forest management on natural communities.森林经营（Forest management）可能会对所有森林生境中的生物产生潜在影响。然而，积水树洞（water-filled tree-holes）中的水生群落可能尤为敏感，原因在于其种群规模较小、存在干旱风险且潜在扩散受限。我们在德国两个区域内经营强度各异的林分中设置了人工树洞（artificial tree holes），并评估了局部环境属性（树洞开口类型、树木胸径、水体体积与水温）以及区域驱动因子（森林经营强度、树洞密度）对树洞昆虫群落（不考虑线虫（nematodes）、轮虫（rotifers）等其他生物）、碎屑含量、氧气浓度与营养盐浓度的影响。此外，我们将同一区域内人工树洞与自然树洞的观测数据进行对比，以评估使用树洞替代物（tree-hole analogues）的实验方法可行性。研究发现，在两个区域及整个观测季中，森林经营对人工树洞中的群落均产生了显著影响。随着森林经营强度提升，群落个体丰度与物种丰富度均出现下降，群落组成发生偏移，且碎屑含量随之降低。树洞密度、树木胸径等环境变量可部分解释这些变化。不过，由树洞密度效应所体现的扩散限制，总体上对群落的影响相对较弱。与自然树洞相比，人工树洞的水温（平均高出2℃）与氧气浓度（平均高出25%）均更高。人工树洞内的生物个体丰度更高，但物种丰富度更低。人工树洞与自然树洞的群落组成存在差异。尽管两类树洞系统在非生物与生物特征上存在差异，但两者均能观测到森林经营带来的负面影响。研究结果表明，森林经营对树洞群落具有显著且广泛的影响，可能会改变其结构与功能。此外，我们认为人工树洞替代物可作为一种有效的实验替代方案，用于探究森林经营变化对自然群落的影响。