Structure and dynamics of reserved field ecosystem in central Finland

Abstract

This study deals with the plant community, decomposition activity, soil fauna and field-layer fauna of reserved fields in central Finland, with special attention to primary production, herbivory, succession, trophic structure and management of reserved fields. In addition, when five methods were evaluated experimentally, suction sampling was the most reliable for sampling most field-layer arthropods. After abandonment, reserved fields were colonized by weeds typical of open cultivations. The plant community gradually became meadow-like; and after ten years of secondary succession, the proportion of big forbs (Filipendula, Geum) increased rapidly in the relatively moist main study field. Generally, the species of early successional stages were more r-selected than were those of later successional stages. Dicotyledonous Achillea ptarmica decomposed faster than did graminid species. Decomposition rate was determined mainly by moisture. About one-third of the plant litter produced annually decomposed during the snow period. The biomass of consumers, especially that of herbivores, increased with successional age of the field. Leafhoppers were the most important aboveground herbivores. By biomass, earthworms were most important decomposer animals. The impact of herbivores on primary productivity was assessed. They obviously increased the rate of nutrient circulation and biomass turnover. The net aerial primary production was increased by mowing in early July. Ploughing (in late May) had no effect on the net primary production, but it created a weed dominated community. The ecosystem of a successional reserved field is compared to its initial state (cropland) and to stable climax grasslands (American prairies).