Faunal communities of the field stratum and their succession in reserved fields

[摘要] The arthropod of the field stratum and small mammal fauna of 51 reserved fields were studied in Central Finland in 1974. In high summer the arthropod density was on the average 210 individuals/m2, of which Auchenorrhyncha formed 42 %, Hymenoptera 18 %, Coleoptera 14 %, and others 26 %. Arthropods were more abundant in fields that had been reserved after leys than in fields after open cultivations. The abundance of most arthropod taxa increased as the time in reservation increased. However, the abundance of most pests of any significance decreased with years. Sorex araneus L. and Microtus agrestis L. formed almost 90 % of the small mammal fauna of the fields. Their abundance was on the average much less than in the Scots pine seed orchards nearby. The leafhopper faunas were divided into three communities. One appeared in young (1st —3rd year) fields, and the other two in older (2nd—6th year) fields, one in dry and one in moist fields. The Apion fauna was divided into four communities. The dependence of the described arthropod communities on the vegetational communities of the fields was weak, although some relationships were observable.