This thesis evaluates the impact of land-use practices (management) on phytodiversity of mesic grasslands in a Central European sub-mountainous region (Lahn-Dill Highlands, Hesse, Germany). Evaluation of suitable management types is of crucial importance for the maintenance of species rich grasslands. The overall aim of the studies is to assess the relative impact of current management types (low-intensity grazing and mowing regimes) on three components of phytodiversity: the aboveground vegetation, the soil seed bank and the population structure of selected plant species. Furthermore, site conditions such as edaphic parameters and topography are considered.
In the first study the relative impact of management, site conditions, grassland age and regional scale geomorphology on aboveground vegetation of grasslands is quantified. The current management has relatively low impact on floristic composition. In contrast, soil chemical variables, together with topography, explain almost twice as much variation in floristic composition as does the current management. There is no evidence that the different management types exert a large impact on species richness.
The second study of soil seed banks in grasslands shows that the type of management has no significant impact on species richness and seed density of the seed bank, but significantly influences the floristic composition and functional characteristics. Irrespective of management type only a limited proportion of characteristic grassland species is likely to re-establish from the seed bank after disappearance from aboveground vegetation.
In the third study we investigated the population stage structure of three model species (Pimpinella saxifraga, Leontodon autumnalis and Sanguisorba officinalis) of grasslands with respect to management, site conditions and vegetation structure. The results show that viable populations of all three species may occur in all of the studied management types. The species respond differently to site conditions and vegetation structure and significant effects are stage-specific. The main variables of influence are soil moisture, nutrient availability and litter coverage.
The variability of site conditions, due to the heterogeneity of the region, and moderate variation in intensity of current grassland management are most likely responsible for the observed relationships. Finally, in accordance with other studies, our analyses show that there is a wide variety of low-intensity management options to contribute to the maintenance of phytodiversity in European mesic grasslands.
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