The impacts of forest clear felling on the oribatid mite fauna inhabiting Formica aquilonia nest mounds

Abstract

The ubiquitous soil-dwelling oribatid mites have long been investigated as potential bioindicator agents for environmental changes, such as those resulting from forest management. However, the oribatid community composition often lacks detectable changes, mainly due to the difficulties of finding homogenous microhabitats from the landscape for investigation purposes. Red wood ant nest mounds in boreal forests, however, form uniform, moisture, and temperature regulated, microhabitats of which are also inhabited by a rather characteristic oribatid fauna. With this standardized microhabitat—the red wood ant Formica aquilonia nest mounds in Finland—we studied the impacts of forest clear felling on the oribatid mites inhabiting those nests. We compared the oribatid assemblages of altogether 41 ant mounds, located in three separate clear fell areas and in adjacent mature coniferous forest. A total of 16,499 specimens, representing 67 oribatid species, were observed. The ten most abundant species represented 90.9% of the total abundance. The oribatid species richness was significantly lower in clear fell mounds and was positively related to the surface moisture content of the mounds. Oribatid abundance or community composition did not markedly differ between clear fell and forest mounds. Despite the attempt to standardize the microhabitat of oribatid fauna, the use of oribatid mites as biological indicators of harvesting disturbance was limited with this study design due the lack of changes in community composition. Then again, the oribatid species richness of this characteristic microhabitat may provide useable quality measures about the harms of forest clear felling.