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RESEARCH PRODUCT

Growth increase of birch seedlings under the influence of earthworms—a laboratory study

subject

description

The effects of the earthworm Lumbricus rubellus (Hoffm.) on net production and nitrogen content of birch seedlings were studied in laboratory microcosms. Coniferous forest floors with litter, humus and mineral horizons were simulated in transparent plastic cylinders. The materials were partially sterilized by microwaving, and re-inoculated with microflora and -fauna. A young (9 cm) birch seedling (Betula pendula Roth) was planted in each container. Earthworms were added to half of the replicates. The microcosms, through which a constant air flow was maintained, were incubated in a climate chamber. After two growth periods, leaf and stem biomasses of birch in treatments with earthworms increased by 33 and 24%, respectively, compared with controls, while the root biomass was slightly lower. The N contents of leaves were almost twice as high in the earthworm treatments as in the controls. The nitrogen contributed by dead earthworm biomass could only partly explain this difference. The plants absorbed virtually all net mineralized nitrogen and phosphorus from the soil.