Diversity of soil mites (Acari: Mesostigmata) in streamside mountain forests

Habitat loss and fragmentation are among the most influential factors responsible for recent biodiversity decline. The key to understanding the changes in ecosystem functioning is the analysis of the relationship between species diversity and environmental gradients such as those found near streamside forests. We used soil mites (Mesostigmata) as model species as they are predators in soil ecosystems, they occur in high relative abundance, their communities are species-rich and are robust toward sampling and extraction methods. The main goals of this study were to (1) check how the plant community and associated environmental variables (light conditions, litter accumulation, and soil acidity) along mountain streams affect soil Mesostigmata abundance and diversity, and (2) to analyze the distance from mountain streams to which the ecosystem functions (Mesostigmata diversity) are affected, based on a distance gradient. We systematically established 31 study plots (500 m(2)) every 200 m along the watercourses, representing three habitat types along the stand composition gradient (ash-sycamore [Fraxinus excelsior-Acer pseudoplatanus], European beech [Fagus sylvatica], and Norway spruce [Picea abies] forests) for measurements of soil litter thickness, soil acidity, and light conditions. We extracted soil Mesostigmata mites from samples in Tullgren funnels and identified them to the species level. We found that Mesostigmata abundance in forests decreased in the following order: Norway spruce forest > European beech forest > ash-sycamore forest. Additionally, changes in Shannon diversity were associated with light conditions. In conclusion, streamside mountain forests maintained abundant, diverse and species-rich Mesostigmata communities, which were associated with a plant community-light condition gradient. Additionally, more abundant mite communities occurred in forests with higher soil pH values, and under higher light conditions.