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The Grassland Fragmentation Experiment in the Swiss Jura Mountains: A Synthesis
Journal
Diversity
Volume
15
Number
2
Pages / Article-Number
130
Keywords
biodiversity, calcareous grasslands, environmental change, functional dispersion, habitat fragmentation, invertebrates, population dynamics, time lags
Abstract
We synthesize findings from a 7-year fragmentation experiment in species-rich, nutrientpoor, dry calcareous grasslands in the north-western Jura mountains, Switzerland. We used a standardized approach with 48 fragments (0.25-20.25 m 2 ) and corresponding control plots in three sites. The 5-m-wide isolation area around the fragments was maintained by frequent mowing. Fragments experienced various ecological changes, e.g., plant biomass increased along fragment edges. We examined fragmentation effects on species richness and composition, abundance, genetic diversity, functional diversity, species traits and species interactions (pollination, herbivory, parasitism, disease) in a wide array of invertebrate (gastropods, spiders, woodlice, various insect groups) and plant taxa. Responses to fragmentation differed between taxonomical groups and species. While species richness and individual density were lower in fragments in some groups, the opposite was true for other groups. Fragmentation effects were most pronounced on species interactions; however, some effects only occurred with a delay. For example, fragmentation influenced foraging patterns of bumblebees, affecting pollination, which in turn resulted in a decreased outcrossing frequency and reduced genetic diversity in a focal plant species. We highlight key findings of the experiment and emphasize their implications for grassland conservation.
