Acari and Collembola are the dominant groups within the mycophagous arthropods linked to fungal-based food webs in undisturbed soils. Studies on soil microarthropod communities in old, traditional, multifunctional farmland, and studies on secondary succession following marginalization and abandonment of traditional farmland are lacking in Europe. Thus, we studied patterns of microarthropod communities related to different land use regimes in a traditional farm in Western Norway. Soil mesofauna communities were analysed at four sites: site OM – old, herb rich, open hay meadow in traditional use; site F1 – abandoned hay meadow with pollarded trees (first fallow); site F2 – deciduous woodland (abandoned hay meadow with old pollards, heavily overgrown, second fallow); and site RM – restored hay meadow with scattered, newly pollarded trees. The abundance of the taxa varied considerably between habitats (for instance: total microarthropods – from 112.4 ±11.4 to 29.2±3.4, Acari – from 83.9±10.2 to 15.6±1.8 and Oribatida – from 68.6±9.5 to 8.2±1.3 × 10³ m⁻², for OM and RM sites respectively). The abundance of total Acari, total Oribatida, Oribatida adults and juveniles differed significantly between OM-F1, OM-RM, OM-F2 and RM-F2 sites and it was significantly correlated with continuity of land use and/or tree cover. Oribatida was the group with the highest densities and percentage dominance (except RM site). The percent contribution of total Oribatida in Acari abundance was negatively correlated with the percentage of Actinedida. Nine Ptyctimina species, six Nothroidea species and four Uropodina species were detected, but most of them occurred as single individuals. Abundance of three Ptyctimina [Atropacarus (Atropacarus) striculus (C.L. Koch), Phthiracarus ferrugineus (C.L. Koch), P. globosus (C.L. Koch)], and two Uropodina [Trachytes pauperior Berlese and Dinychus perforatus Kramer] species differed significantly between some sites. The percentage similarity (Renkonen index) has a high indicative value for measuring the distance between ecosystems with apparently similar communities of Uropodina. The OM and RM sites differed most and site pairs – F1-F2 and F1-RM were the most similar. The densities of some taxa were about twoor three-fold greater for the F1site than the RM site. Ratios of Acari to Collembola, total Oribatida to Collembola and total Oribatida to Actinedida were highest on OM site (3.2, 2.6, 11.8 respectively) and decreased in the following order: F2>F1>RM (as an example, total Oribatida to Actinedida ratios were 9.8 on F2 site, 6.2 on F1 and 3.1 on RM). These ratios differed significantly between the OM and RM sites. The lowest ratios on RM site are probably an effect of recent disturbance (change of land use) of this site. Our results suggest that soil in OM site, despite constant disturbance during long time (scything, hay raking and sheep grazing), has probably a stable mesofauna community with the highest abundance of Oribatida. Our results have provided new knowledge about ecosystems in traditional farmland and can be used in monitoring programmes of post-arable land.
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