Soil organic matter distribution as influenced by enchytraeid and earthworm activity

Loam and sandy soils, and the earthworm casts produced with 14C-labelled plant material in both soils, were incubated in airtight glass vessels with and without enchytraeids to evaluate the effects of soil fauna on the distribution and fragmentation of organic matter. After 1, 3, and 6 weeks, the amount of C mineralised was determined in soils and earthworm casts, and the soil was fractionated into particulate organic matter (POM), the most active pool of soil organic matter, after complete physical dispersion in water. The percentage weight of fine fractions (0-50 ?m) was 67.4␒n the loam soil. Sand (coarse, i.e. 150-2,000 ?m and fine 50-150 ?m) represented 87.2␘f total weight in sandy soil, while the percentages of C (PC) were 23.2␒n coarse POM (2,000-150 ?m) and 11.9␒n fine POM (150-50 ?m). These percentages were higher than those in loam soil, i.e. 3.4øcoarse POM) and 5.4øfine POM). The PC in coarse POM (9.50€and fine POM (16.4€remained higher in casts from sandy soil than in casts from loam soil (4.7␒n coarse and 14.3␒n fine POM). The highest percentages of 14C-labelled leaves were found in fine fractions, 55.9␒n casts from loam soil and 48.8␒n casts from sandy soil. The C mineralisation of the added plant material was higher in casts from the sandy soil (20.3€than from the loam soil (13.5Ž Enchytraeids enhanced C mineralisation in the bulk sandy soil, but did not affect the mineralisation of added plant material in either soil. The main enchytraeid effect was enhancement of the humification process in the bulk sandy soil, the casts from this soil, and the bulk loam soil.