Soil Diptera of a beech stand and an arable field: A comparison of dipteran emergence in neighbouring sites

The soil dipteran fauna emerging in a beech stand and a neighbouring arable field in Denmark was compared based on multi-year data. The species richness of the beech stand was higher than that of the field, with 248 vs. 184 species and the species diversity of the former site was distinctly higher. Of the total 387 dipteran species collected from the two sites, only about 12% overlapped, thus the similarity in species composition of the sites was low (quotient of similarity (QS) 0.17). The species abundance relationships of the two sites differed. In the beech stand, very few common species with large numbers of individuals and many rare species with few individuals were observed (e.g., more than half of the species were singletons or doubletons). In the field, a higher frequency of very abundant species was found, and only about a third were singletons or doubletons. The dipteran emergence abundance and biomass (dw) were higher in the field than in the beech stand, viz. 1197–1981 ind. m −2 yr −1 (247–301 mg m −2 yr −1) and 474–532 ind. m −2 yr −1 (96–124 mg m −2 yr −1), respectively. The total annual emergence abundance of soil Diptera in the Danish beech stand and arable field is apparently much lower than the average values reported from comparable European sites. The discrepancy is discussed. Phyto- and zoosaprophages were predominant in the soil dipteran assemblages of the sites.