Quantifying the diversifying potential of conservation management systems: An evidence-based conceptual model for managing species-rich grasslands

The differential effect of main grassland management types (primarily grazing and mowing) on plant species richness has been discussed in many papers. In-depth investigations, focusing on the effects of particular management attributes (herbage removal intensity, timing, etc.) are less frequent. We propose a new, evidence-based conceptual model for quantifying the specific effects of particular management attributes on the richness and diversity of plant species. The applicability of the model was tested in Central-Hungarian species-rich meadow-steppe grasslands, characterised by different management regimes. Two management attributes involved in this study (herbage removal intensity and spatio-temporal complexity of management regime) significantly affected both the diversity and the plant species richness at a 1 m2 spatial scale, whereas management type had a significant effect on species richness only. With regard to the overall variance in species richness, none of the single attributes (without combining with other ones) had considerable explanatory power; for making precise predictions, all the management attributes must have been considered. The “dichotomous effect” of grazing (i.e. both the highest and the lowest levels of plant species richness were observed at pastures) could be quantitatively explained by the model. Grazing at low or medium intensity (less than 0.5 animal unit/ha), with an annually varying rotation sequence of pasture units, led to a much higher, whereas permanent overgrazing resulted in a much lower, level of plant species richness than traditional mowing (conducted once a year during midsummer). Generalisation of the proposed model can be used to predict the potential overall effect of particular management systems on the plant species richness of other grassland types. For the potential overall effect of management, a new term has been introduced: the diversifying potential.