Collembolan preferences for soil and microclimate in forest and pasture communities

The goal of the present study was to determine whether the habitat preference of collembolan species is more influenced by soil properties or by microclimate and whether the preference for a given soil matches the preference for the corresponding microclimate. To answer these questions, we set up a soil core transfer experiment between a forest and an adjacent pasture. We first eliminated the entire soil fauna from forest and pasture soil cores and inoculated them with a new community originated from forest or pasture. After enclosing them, in order to prevent exchanges of soil animals between treated soil and surrounding environment, soil cores were transplanted back to the field for four months and a half. The experimental design comprises every combination of three factors (community origin, soil nature and microclimate) for a total of 8 treatments. Twenty-two species were present in the experiment, 16 of which were present in more than 10% of the experimental soil cores. We determined habitat preference for these 16 species using a large dataset comprised of field observations in the same region. Results showed that most forest species did not withstand pasture microclimate, although some of them preferred pasture soil. Likewise several pasture species were favoured by the forest microclimate, some of them also preferring forest soil. We concluded that forest species were absent (or less abundant) in pastures because they are not resistant enough to drought, while pasture species were absent (or less abundant) in forests because of food requirements, and/or soil physicochemical properties such as soil pH and organic carbon content, and/or were less competitive. Moreover, when selecting their habitat, some species are submitted to a trade-off between preferences for different habitat features.