Temporal variation of soil microarthropods in different forest types and regions of Central Europe

Biodiversity and biomass of aboveground arthropods in Central European forests continuously declined during the last decade. However, whether belowground microarthropod communities follow similar patterns has not been investigated. In this study, we compared the abundance, diversity, community composition, stability and asynchrony of oribatid mites (Acari: Oribatida) sampled in four forest types of increasing management intensity (unmanaged beech, old managed beech, young managed beech, and coniferous) at three-year intervals from 2008 to 2020. Forest sites were replicated in three regions in southern, central and northern Germany, i.e. the Swabian Alb, Hainich-Dün and the Schorfheide Chorin, which differ in soil characteristics and climate. We found 25,152 individuals and 121 species of oribatid mites and detected no linear decline in abundance and diversity over the last decade, suggesting that microarthropods in forest soils are buffered against land-use effects. However, we observed that years with low winter precipitation in regions with soils that are prone to drought, resulted in significant decreases in oribatid mite densities. Community compositions remained similar across sampling years, but differed between regions and forest types, predominantly due to differences in the proportion of asexual individuals. The stability of oribatid mite communities did not decrease in managed forests and was highest in deep soils with high water-holding capacity, which may reduce temporal variation, suggesting that soil properties are more important for the stability of oribatid mite communities than forest management. However, stability patterns were not explained by asynchrony in species fluctuations, as all communities either showed a high degree of synchrony or were not different from random. Our study highlights that the temporal dynamics of belowground communities may differ from those aboveground, and that regional differences in precipitation and soil properties are more important than forest types.

Methods
Species abundance data for oribatid mites sampled with soil cores from unmanaged beech, managed beech and spruce forests in three regions of Germany at three-year intervals from 2008 to 2020. Excel spreadsheets also contain environmental data and traits used for the analysis (please see methods section and README).

近十年来，中欧森林地表节肢动物的生物多样性与生物量持续下降。然而，地下小型节肢动物群落是否遵循相似的变化模式，目前尚未得到研究。
本研究于2008年至2020年间，以三年为采样间隔，在德国南部、中部与北部的三个区域（施瓦本侏罗山、海尼希-敦恩、肖尔夫海德-措林）的四种经营强度递增的森林类型（未经营山毛榉林、成熟经营山毛榉林、幼龄经营山毛榉林与针叶林）中采集甲螨（Acari: Oribatida）样本，对比分析其丰度、多样性、群落组成、群落稳定性及物种波动异步性。上述三个区域的土壤特性与气候均存在显著差异。
本次研究共采集到25152只甲螨个体，隶属于121个物种；未发现近十年来甲螨的丰度与多样性存在线性下降趋势，这表明森林土壤中的小型节肢动物可缓冲土地利用活动带来的影响。不过，研究观察到，在土壤易发生干旱的区域，冬季降水量偏低的年份会导致甲螨种群密度显著降低。
甲螨群落组成在各采样年份间保持相对稳定，但在不同区域与森林类型间存在明显差异，这主要源于无性繁殖个体的占比不同。经营森林中的甲螨群落稳定性并未出现下降，且在持水能力较强的深层土壤中稳定性最高——这类生境可降低种群的时间波动，这表明土壤特性对甲螨群落稳定性的影响较森林经营更为关键。然而，群落稳定性的变化无法通过物种波动的异步性来解释，因为所有受试群落要么呈现高度同步的物种波动，要么与随机群落无显著差异。
本研究凸显出地下群落的时间动态可能与地表群落存在差异，且区域间降水与土壤特性的差异较森林类型对群落的影响更为重要。

方法
本数据集包含2008年至2020年间，以三年为间隔，从德国三个区域的未经营山毛榉林、经营山毛榉林与云杉林土壤钻芯样本中获取的甲螨物种丰度数据。Excel表格中同时收录了本次分析所用的环境数据与功能性状数据（详见方法章节与README文件）。