THE ORIBATID MITE COMMUNITY (ACARINA) OF PURE AND MIXED STANDS OF BEECH (FAGUS-SYLVATICA) AND SPRUCE (PICEA-ABIES) OF DIFFERENT AGE

In November 1994, the density of oribatid mite species was determined in litter and soil of pure and mixed stands of beech (Fagus sylvatica) and spruce (Picea abies) of an age of ca. 30 and 120 years. The study sites were located in the Selling, a plateau of red sandstone in nort hern Germany. The stands grow on acidic brown-earth with a moder humus form. The average oribatid mite density was 160 000 ind m(-2) and a t otal of 68 species was present. The diversity and density of the two a ge classes did not differ significantly indicating little effect of st and age on the structure of oribatid mite communities. The diversity a nd density did not differ significantly between beech, spruce and mixe d stands. However, more 'endemic' species (species which only occurred in one of the three stands within one age class) occurred in the mixe d stands presumably due to a more heterogeneous and patchy habitat str ucture. Some species of oribatid mites had higher densities in beech t han in spruce (Hypochthonius rufulus C.L. Koch, Nanhermannia coronata Berlese) while others (Tectocepheus velatus (Michael), Adoristes ovatu s/poppei C.L. Koch) were more common in spruce. Parallel to the distin ct stratification of organic layers a strong decline of oribatid mite densities occurred from the L/F to the H/Ah and By horizon. Small-size d oribatid species like the Brachychthonioidea dominated in the deeper horizons (H/Ah; and By). (C) 1998 Elsevier Science B,V.