Management recommendations for maintaining grassland biodiversity

How do local and landscape management plans affect biodiversity?  In their upcoming article in Diversity and Distributions, Kormann et al. examine small fragmented patches of calcareous grasslands in central Germany, which in their study are interspersed between agricultural lands.  The grasslands are managed through mowing, grazing, or abandonment.  They aimed to look at how landscape complexity, habitat connectivity, and different management regimes affect species abundance and richness within grassland fragments, in particular the responses of species according to body size and threatened (red list) status.  Focusing on 30 small (<1 ha) grassland fragments, they sampled nine taxa of plants and invertebrates, including butterflies, bees, grasshoppers, leafhoppers, spiders, hoverflies, true bugs, and rove beetles.  They recorded over 600 species from almost 20,000 individuals through transect sampling, pitfall traps, and numerous other methods.  Their results highlight how management strategy and connectivity can affect biodiversity:

1. Landscape simplification – in this case, increasing arable land in the surrounding matrix – had a consistent negative effect on species richness across all taxa. Pollinators in particular greatly decreased in abundance in highly simplified landscapes.

2. Increasing habitat connectivity generally increased species richness, especially for butterflies, grasshoppers and rove beetles. Species richness of large-bodied species increased with increasing connectivity, while richness of small-bodied species did not, presumably due to relative dispersal abilities.

3. Local management strategy strongly affected species richness, abundance and community composition, with the highest richness and abundance measures found in mown patches.  In contrast to traditional management ideas about grazing being useful in keeping grasslands open, grazing was the least effective management strategy to support species richness, with red-listed species negatively affected most strongly.

The authors recommend managing for biodiversity in fragmented landscapes by adopting an intermediate management strategy: mowing or lenient grazing and short-term abandonment, combined with a complex landscape in the surrounding matrix and high connectivity between fragments.  Their study provides a good example of universal, trait-mediated effects of management, landscape complexity and connectivity on local biodiversity in fragmented communities across multiple taxa.