Local and landscape management drive trait-mediated biodiversity of nine taxa on small grassland fragments

Abstract

Aim Biodiversity across the globe is heavily eroded by intensified management at local and landscape scales. Species communities of calcareous grasslands, which are among Europe's most diverse habitats, are severely threatened by the cessation of appropriate traditional management, loss of habitat connectivity and simplification of the surrounding landscape. However, our understanding of these often interrelated factors remains limited, in particular for trait-mediated responses across taxa. Here, we test the independent effects of local management (grazing, mowing and abandonment), habitat connectivity (measured by a connectivity index) and landscape complexity (indicated by the percentage of arable land) on nine taxa: plants, butterflies, bees, grasshoppers, hoverflies, spiders, true bugs, rove beetles and leafhoppers on small semi-natural calcareous grassland remnants (< 1 ha).Location Central Germany. Methods We use a joint analysis across taxa to identify general and trait-mediated responses (body size and Red List status) in species richness, abundance and community composition. Results We identified three key drivers of local diversity patterns: First, an increasing proportion of arable land from 10% to 80% led to a 29% loss of overall species richness. Second, despite differences between taxa, increasing habitat connectivity generally enhanced species richness. Connectivity effects were more accentuated in the large species per taxon, which can be expected to be good dispersers. Finally, grazing reduced species richness and abundance much more than annual mowing or short-term abandonment (5-15 years), in particular for red-listed species. We attribute this to plant resource removal through overgrazing and trampling.Main conclusions For the conservation management of small calcareous grasslands, we advocate an alternating strategy of mowing or lenient grazing and short-term abandonment, prioritizing connected fragments surrounded by diverse landscapes. Despite taxon-specific responses, our study across nine taxa demonstrates universal, trait-mediated effects of management, landscape complexity and connectivity on local biodiversity in fragmented communities.

Biodiversity conservation across taxa and landscapes requires many small as well as single large habitat fragments

“…Krauss et al 2003;Schüepp et al 2011), whereas the use of taxa with small body sizes and therefore restricted mobility like leafhoppers, true bugs and snails is far less common (but see Boschi and Baur 2007;Kőrösi et al 2012;Kormann et al 2015). Due to their restricted mobility, the latter are likely to be much more affected by fragment size, connectivity and landscape complexity (Greenleaf et al 2007;Stoll et al 2009;Marini et al 2012).…”

Trait‐matching and mass effect determine the functional response of herbivore communities to land‐use intensification

“…; Kormann et al . ) because of: (i) the direct destruction of their habitat leading to its increasing scarcity at the landscape level, e.g. due to their conversion to arable land (Kormann et al .…”

“…due to their conversion to arable land (Kormann et al . ); (ii) and the low quality of the remaining habitats due to the replacement of traditional extensively managed grasslands by low plant species richness, highly productive sown grasslands (Wesche et al . ).…”

How are biodiversity and dispersal of species affected by the management of roadsides? A systematic map

“…While there is an increasing literature on how roadsides act as corridors for species' movement [11,12,35,54], little attention has been paid as to how management might enhance or diminish this role. This lack indicates an important research priority, and studies might build on recent work [55,56] considering how management can enhance connectivity among grassland fragments. Livestock grazing and movement are often invoked as enhancing grassland connectivity through their dispersal of seeds, but grazing on roadsides is uncommon, as we found in this systematic map.…”