Ecosystemic, climatic and temporal differences in oribatid communities (Acari: Oribatida) from forest soils.

Oribatid mite communities from 18 natural autochthonous forest soils in the Basque Country, belonging to five forest types, distributed along an ombrothermic gradient of five climatic regions were broadly studied. Forest type and climatic region together (45 % of the total variability) were important factors influencing the oribatid community. The local scale variable (forest type, 28 %) was about as determinant a factor as the regional scale (climatic region, 26 %), though together they accounted for just 9 %. By contrast, the influence of spatial distribution (geography) was not significant by itself but played an important role as a co-variable. Differences in community indices were detected only for species abundances, with holm oak showing the highest oribatid density and beech the lowest. The effect of the passage of time on oribatid communities was also analyzed by comparing recent communities to those of 19-26 years ago in the same forests. The community indices are influenced by the course of time when separate periods of time are compared. Although the recently studied forests apparently show the same conservational conditions as those studied in the past, they are less diverse.