Data from: Monitoring microarthropods assemblages along a pH gradient in a forest soil over a 60 years' time period

The goal of this study was to assess the development, over 60 years, of microarthropod communities over a pH gradient in forest soil. Site Description Hackfort is an oak coppice grove in the East-Southeast of the city of Zutphen in the province of Gelderland, the Netherlands, 52°06′09.7″ N, 6°15′56.0″ E (see Figure 1). The experimental area is about 1.5 ha and is divided in a 10 m × 10 m grid. Vegetation is dominated by common oak (<em>Quercus robur</em>), mixed with birch (<em>Betula pendula</em>), and had in 1959, an understory of wood sage plugs (<em>Teucrium scorodonia</em>), wood anemone (<em>Anemone nemorosa</em>), bracken (<em>Pteridium aquilinum</em>), and wavy-hair grass (<em>Deschampsia flexuosa</em>). In later years, the understory became more dominated by bramble species (<em>Rubus fruticosus </em>and<em> R. idaeus</em>) and common nettles (<em>Urtica dioica</em>) at the edges of the forest, due to increased N deposition from adjacent farmland. The forest is situated at the transition from western riverine deposits and eastern periglacial cover sands. The soil is a riverine deposit with a few elevation differences, making a number of gradients in clay and loam content, which results in many short-distance gradients in soil types, varying from typic haplaquolls with the largest loam contents, via psammaquentic haplorthods to humaqueptic spodic psammaquents, slightly elevated and low in loam contents. Microarthropod Sampling and pH Measurement In 1959, samples were taken at three subsequent dates: 11 September, 9 October, and 30 October. Samples in 1987 were taken on one date, 9 October, just as on 30 October 2019. Samples were taken following a standard procedure, developed at the Institute for Applied Biological Research in Nature, Wageningen, the Netherlands (later merged into the Research Institute for Nature management, Institute for Forestry and Nature Research and Alterra resp., now known as Wageningen Environmental Research); this procedure has been published by Siepel and van de Bund in 1988 (Siepel and van de Bund, 1988). Each mineral soil sample has 100 cc: a volume of 5 cm diameter and 5 cm depth plus litter on top. In 1959, two samples per date were taken on each plot, making a total of 6 samples (only pooled data are available); in 1987 and in 2019, 4 and 5 samples for each plot were taken on, respectively (data per sample available). Soil cores were put on a Tullgren funnel for 1 week, during which temperature was increased from 35 to 45 °C, and then, microarthropods were collected in 70% alcohol and later put into 20% lactic acid for clarification and identification (Siepel, 1990; Siepel and van de Bund, 1988). The Tullgren funnel used for extraction (Siepel, 1990) has been used ever since 1936 and efficiency has not changed as the tool and protocol was the same all over the years. Identification was done to the species level as much as possible using at present the keys for Oribatida(Weigmann and G., 2006), for Gamasina (Lehtinen, 1994), for Uropodina (Karg, 1989), and for Collembola (Hopkin, 2007). Material from the extractions of 1959 and 1987 was re-examined as far as possible to check the correct species identification. In the 1959 and 1987 samples, only oribatid mites were identified to the species level, whereas in 1959, all species of <em>Quadroppiidae, Oppiidae</em>, and <em>Suctobelbidae</em> were pooled. In 2019, all microarthropods were identified to the species level. Sorting and identification of the 1959 microarthropods was carried out by an experienced acarologist (J.G. de Gunst), in 1987, this was done by a student (C. Arnold) and completed and checked by the second author. For the 2019 samples, we decided to demonstrate the potential difference in picking out the microarthropods from the extraction fluid into the slides for identification as part of the experiment: the first author made a first series of slides including all distinguished animals (dataset 2019 a), while the second author made an extra set of slides with the animals missed by the first (dataset 2019 b). The first author did know since the beginning that the second author would check all samples after her sorting session. In this way, we intended to demonstrate the potential difference in this crucial part of the procedure by a starting and an experienced professional. In the analysis, we compare dataset (2019 a) with (2019 a + b), in order to highlight the difference between a starting and an experienced acarologist. Nomenclature adopted was updated according to current standards, following, e.g., the checklists for Oribatida (Siepel et al., 2009), for Astigmatina (Siepel et al., 2016), and for Mesostigmata (Siepel, 2018). Values of pH-KCl were measured in the core material after the extraction of the microarthropods, both in 1959, 1987, and 2019. We have four data files: 1959 hackfort microarthropods data.csv 1989 hackfort microarthropods data.csv 2019 hackfort microarthropods data.csv pH data Hackfort 1959-2019.csv. Explanation of the variables in the datasets: higher taxon: Oribatida, Astigmata, Mesostigmata, Prostigmata, Collembola or Protura Name in De Gunst 1959: taxonomic identification by De Gunst in 1959 Valid name: Henk Siepel re-checked these species names in 2019 Plot: plot 1, plot 2, plot 3, plot 4, plot 5 a: identified by Yuxi Guo b: re-checked by Henk Siepel from remaining soil microarthropods in slide pH(KCL) and pH(H2O): pH values based on indicated methods本研究旨在评估60余年来森林土壤中沿pH梯度分布的微型节肢动物群落（microarthropod communities）的演替动态。 样地概况 Hackfort样地位于荷兰海尔德兰省聚特芬市东南偏东方向，为栎类矮林，地理坐标为52°06′09.7″N，6°15′56.0″E（见图1）。实验区域面积约1.5公顷，划分为10m×10m的网格样方。植被以夏栎（*Quercus robur*）为优势种，混生白桦（*Betula pendula*）；1959年时林下植被包括药用石蚕（*Teucrium scorodonia*）、银莲花（*Anemone nemorosa*）、蕨菜（*Pteridium aquilinum*）和曲芒发草（*Deschampsia flexuosa*）。后续年份中，受周边农田氮沉降增加影响，林缘地带的林下植被逐渐以悬钩子属物种（*Rubus fruticosus*与*R. idaeus*）和异株荨麻（*Urtica dioica*）为主。该林分处于西部河流沉积与东部冰缘覆盖砂质沉积物的过渡地带，土壤为河流沉积型，存在少量地势起伏，形成黏土与壤土含量的梯度差异，进而造就了短距离范围内多样的土壤类型：从壤土含量最高的典型湿润冷凉淋溶土（typic haplaquolls），经砂质湿润冷凉硬磐淋溶土（psammaquentic haplorthods），过渡到地势稍高、壤土含量较低的腐殖质湿润冷凉砂质淋溶土（humaqueptic spodic psammaquents）。 微型节肢动物采样与pH测定 1959年分别于9月11日、10月9日、10月30日三个连续日期采集样品；1987年仅于10月9日采样，与2019年10月30日的采样时间一致。采样流程遵循荷兰瓦赫宁根应用生物自然研究所制定的标准方法，该机构后分别并入自然管理研究所、森林与自然研究所及Alterra，现更名为瓦赫宁根环境研究中心，相关流程由Siepel与van de Bund于1988年发表（Siepel & van de Bund, 1988）。每份矿质土壤样品体积为100cc，即直径5cm、深度5cm的土柱加上表层凋落物。1959年每个采样日期每个样方采集2份样品，总计6份（仅提供合并后数据）；1987年与2019年每个样方分别采集4份与5份样品（提供单份样品数据）。将土芯置于Tullgren漏斗（Tullgren funnel）中分离1周，期间温度从35℃升至45℃，微型节肢动物被收集于70%酒精中，随后移入20%乳酸溶液进行透明化与物种鉴定（Siepel, 1990; Siepel & van de Bund, 1988）。本次实验采用的Tullgren漏斗自1936年起沿用至今，由于工具与操作协议未发生变化，提取效率始终保持一致。 物种鉴定尽可能至种级水平，目前参考的分类检索表包括：甲螨亚目（Oribatida，Weigmann & G., 2006）、革螨亚目（Gamasina，Lehtinen, 1994）、尾足螨亚目（Uropodina，Karg, 1989）及弹尾纲（Collembola，Hopkin, 2007）。研究团队对1959年与1987年提取的标本尽可能进行了复检，以确认物种鉴定的准确性。1959年与1987年的样品中，仅甲螨类被鉴定至种级水平；1959年的*Quadroppiidae*、*Oppiidae*与*Suctobelbidae*科所有物种均合并统计。2019年所有微型节肢动物均鉴定至种级水平。 1959年微型节肢动物的分选与鉴定由资深蜱螨学家（acarologist）J.G. de Gunst完成；1987年的工作由学生C. Arnold完成，并由第二作者复核完善。针对2019年的样品，本研究设置了分选环节的对比实验：第一作者制作了包含所有检出动物的玻片标本（数据集2019 a），第二作者则对第一作者遗漏的动物另行制作玻片标本（数据集2019 b）。第一作者自实验初始便知晓第二作者将对所有样品进行复检，旨在通过新手与资深专业人员的操作对比，展示该关键实验环节的潜在误差。分析阶段将数据集2019 a与2019 a+b进行对比，以凸显新手与资深蜱螨学家在分选鉴定中的差异。 本研究采用的分类命名体系已根据现行标准更新，例如参考甲螨亚目（Siepel et al., 2009）、无气门亚目（Astigmatina，Siepel et al., 2016）及中气门亚目（Mesostigmata，Siepel, 2018）的分类名录。在微型节肢动物提取完成后，对土芯样品进行了pH-KCl值测定，采样年份涵盖1959年、1987年与2019年。 本数据集包含4个数据文件：1959 hackfort microarthropods data.csv、1989 hackfort microarthropods data.csv、2019 hackfort microarthropods data.csv及pH data Hackfort 1959-2019.csv。 数据集变量说明 higher taxon：高级分类单元，包括甲螨亚目、无气门亚目、中气门亚目、前气门亚目、弹尾纲或原尾纲 Name in De Gunst 1959：1959年由De Gunst完成的分类鉴定名称 Valid name：2019年由Henk Siepel复核修正的有效物种名称 Plot：样方1、样方2、样方3、样方4、样方5 a：由Yuxi Guo完成的物种鉴定 b：由Henk Siepel对玻片残留的微型节肢动物进行复核鉴定 pH(KCL)与pH(H2O)：基于对应方法测定的pH值