Primary production and seasonal dynamics of the flora and fauna of the field stratum in a reserved field in Middle Finland

The underground biomass of a reserved field which had not been cultivated for three years, exceeded that of the aboveground living vegetation throughout the year. The mean amount of the aboveground detritus, including both loose litter and rooted nonliving parts of the vegetation, was in dry weight 300 g/m2. It was at its minimum end of June and early July. The aboveground net primary production measured by the harvesting method was 405—415 g/m2. year depending on the way of calculation, and the underground production was 343 g/m2. year. Seasonal dynamics of the green biomasses of 56 taxa could be studied and five groups were formed on the basis of the time and duration of the biomass maxima. Using Renkonen’s and Sorensen’s indices three seasonal aspects of the vegetation could be distinguished. The leafhoppers were divided into three phenological groups, and three seasonal aspects were formed. The vertebrate fauna was scarce in the study area. Shrews were the most abundant species and e.g. five Sorex isodon were trapped. During the period of maximum standing crops the herbivores amounted to 0.3 % of the green biomass. The higher the trophic level the later it reached the maximum