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The role of Lumbricus rubellus Hoffm. in determining biotic and abiotic properties of peat soils

Makulec G.

Polish Journal of Ecology

2002

Vol. 50, nr 3

301-339

The field study was conducted on fifteen peat meadows located in the Biebrza river valley, north-eastern Poland, to estimate the range of changes in Lumbricidae communities with time after drainage. In a field experiment, the effects of L. rubellus were examined on the composition and abundance of microflora, Nematoda, Collembola, and Enchytraeidae, and on resources of exchangeable nutrients in drained peat soils. The occurrence of 2-6 earthworm species was noted in soils of drained peats. L. rubellus appeared already 3-5 years after drainage and rapidly reached high densities and biomass. It showed preference for moderately or heavily moorshed soils, with high contents of total nitrogen and phosphorus, low C/N, moderate porosity, and moderate moisture. Casts of this species contained more fungi and cellulolytic microorganisms, while less bacteria and actinomycetes, as compared with their contents in the soil. Also urease activity, content of fulvic acids and concentrations of exchangeable phosphorus, magnesium, and potassium were higher in casts. In a 4-month field experiment, different densities of L. rubellus were used: 2,4, and 6 individuals in 1.5 L isolators inserted to soil. The control variant was without earthworms. It was found that high L. rubellus densities in peat moorsh enhanced bacteria, ammonifying microorganisms, microorganisms utilising mineral nitrogen, and seasonally also actinomycetes and cellulolytic microbes. Also total microbial biomass, dehydrogenase activity, and the rate of cellulose decomposition were higher. The abundance of soil fungi noticeably decreased. Moreover, L. rubellus significantly influenced nemathode composition and abundance. Within a short time, their total numbers declined, especially numbers of bacterial-feeding nematodes. Also numbers an proportions of fungivorous nematodes slightly declined. Plat-feeding nematodes were least affected by this species, and in some periods their numbers were higher in the presence of earthworms than in the control. In the field experiment, no noticeable effect of earthworms was found on total enchytraeid numbers. In the period of autumn peak of Collembola, high numbers of L. rubellus reduced their densities. By modifying the composition and abundance of microflora, nemathodes and mesofauna high L. rubellus densities (above 200 individuals m^-2) can increase the rate of organic matter mineralization, intensify competition for nutrients, and indirectly they contribute to the biological decomposition of moorsh in soils of drained peat meadows.