(University of South Bohemia and Biological Research Centre, Academy of Sciences of the Czech Republic, Ceske Budejovice, Czech Republic)
Species coexistence and community stability in an oligotrophic grassland
Most of the grasslands in Central Europe are human made communities, dependent on regular human intervention. This is particularly true for wet oligotrophic meadows. In one such locality, we started a series of experiments 20 years ago, with the aim to reveal the mechanisms maintaining high species diversity (about 40 spp. per m2), and to ascertain the effects of external drivers and biological properties of constituent species on the community stability.
The main experiment comprises factorial combination of mowing, fertilization and dominant removal. The long term data show that regular mowing is crucial for maintenance of species diversity, whereas fertilization has detrimental effect on species coexistence. This is because fertilization causes shift from competition for nutrients to competition for light, which is more asymmetric, and leads to exclusion of weaker competitors. However, the competitive exclusion can take rather long time. The negative effect of the dominant species (Molinia caerulea) on diversity of the rest of the community is rather minute, with exception of the unfertilized unmown plots, where Molinia prevails and leads to strong suppression of rest of the community. The mowing and fertilization affects significantly the composition of species traits.
The stability (defined here as temporal fluctuation of biomass of the whole community and of its constituent species) is determined by both, the external drivers, and by the traits of the species. In particular, the total biomass fluctuates more in the fertilized plots, but also the same species fluctuate more in the fertilized conditions. The species with conservative resource use strategy (characterized by high Leaf Dry Matter Content) fluctuate less than species with low LDMC. The fluctuation of the whole community biomass is lower than that of individual species due to asynchrony in temporal fluctuations, nevertheless, on average, the biomass of species is positively correlated over the years. The asynchrony is more pronounced in the fertilized plots, nevertheless, it is not sufficient to stabilize the biomass there.
Recently published results from the experiment:
Lepš, J. (2014). Scale‐and time‐dependent effects of fertilization, mowing and dominant removal on a grassland community during a 15‐year experiment. Journal of Applied Ecology 51, 978-987.
Májeková, M., de Bello, F., Dolezal, J., & Lepš, J. (2014). Plant functional traits as determinants of population stability. Ecology, 95, 2369-2374.