Edaphologia

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Sites polluted with oil are increasing in various places of Japan and therefore, development of techniques to remediate oil pollution is required. In this study, an attempt to remediate a polluted soil with oil (oil content=14g kg^<-1> soil, a mixture of light and heavy oil) was made using earthworms and organic wastes. When the polluted soil was added with earthworms, their commercial names King^R and Kumataro^R, belonging to Eisenia fetida (Savigny 1826), significantly decreased oil content measured by the soxhlet extraction method compared to the control without earthworms, while some kinds of earthworms did not affect the degradation rate of oil. When the polluted soil was added with King or Kumataro and different kinds of organic matters, oil content in soil was significantly lower in the soil added with the earthworms and tea extraction residue than in the control soil. Addition of pork manure, cow manure, chicken manure, rice husk and tofu residue together with earthworms did not increase the degradation of oil like tea extraction residue. Oil-degrading bacteria were more frequently isolated from the polluted soil added with the earthworms and tea extraction residue than from the control soil. These results suggested that a combined addition of earthworms and tea extraction residue to oil-contaminated soil may enhance biodegradation of oil.

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Adult emergence of Sciaridae and the other Diptera were studied by using newly designed emergence trap (40cm×40cm square). From April 2002 to April 2003, six emergence traps were settled on the ground of the mixed forest dominated by Castanopsis cuspidata (35°28′N 139°35′E, 60m alt.) in Yokohama during 20 days per month, and the pterygote insects emerged from soil were captured. Total catch of pterygote insects was 3,787 individuals, of these, 3,315 (88%) was Diptera, and 1,497 (40% of pterygota, 45% of Diptera) was Sciaridae. Estimated number of annual emergence abundance of Diptera was 4,781m^<-2> year^<-1>, that of Sciaridae was 2,159m^<-2> year^<-1>. Among the sciarid flies, most dominant species was Ctenosciara japonica, which was collected 910 individuals by emergence traps, showing the peak of abundance in early summer.

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Proturans (Acerentulus omoi Imadate and Yamatetomon yamato Imadate et Yosii) were collected from the ectomycorrhizal mat of Sarcodon scabrosus and Tricholoma matsutake and adjacent non-mat soil in a Japanese red pine forest. A small number of proturans was collected from the mat of S. scabrosus formed in the Ao layer, and the number differed significantly from that collected from adjacent non-mat soil. The numbers of proturans collected from the mat of T. matsutake and the Ao layer above the mat did not differ from those collected from the adjacent non-mat soil in most cases. These facts suggested that an ectomycorrhizal mat does not always provide a suitable habitat for proturans in the field.

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