INFLUENCE OF MANAGEMENT ON THE SEED PRODUCTION AND SEED BANK OF CALCAREOUS FEN SPECIES

The dynamics of the seed production and seed bank of two dominant pere nnial species of calcareous fens were investigated in response to diff erent mowing frequency, fallow or pasture. The production of fertile s hoots responded strongly to management practices. On sites where mowin g alternated with fallow, autumn mowing led to an increase of fertile shoot density in Schoenus ferrugineus and a decrease in Molinia caerul ea in the subsequent season. Repeated annual mowing after long-term fa llow raised the density in Schoenus and inhibited initiation of flower ing shoots in Molinia. Seed set and viability were influenced mainly b y climatic or other factors. Variation of seed production between site s and in consecutive years at the same site could thus be large. The r elationship between total seed production and seed bank was weak, but it improved when germination rates were included in the calculation. A s the seed bank was generally smaller than the viable seed production, low survival and a high turnover of seeds in the upper soil layers is assumed for both species. Implications for recruitment strategies are discussed.