The Grassland Fragmentation Experiment in the Swiss Jura Mountains: A Synthesis

We synthesize findings from a 7-year fragmentation experiment in species-rich, nutrient-poor, 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.

Automated summary

We conducted a 7-year fragmentation experiment in nutrient-poor grasslands in Switzerland to examine the effects of fragmentation on species richness, composition, abundance, genetic diversity, functional diversity, species traits, and interactions. Our findings showed that the responses to fragmentation varied among taxonomical groups and species, with some groups experiencing lower species richness and individual density in fragments while others showed the opposite trend. Fragmentation had the most pronounced effects on species interactions, with some effects occurring after a delay. For example, fragmentation influenced the foraging patterns of bumblebees, which in turn affected pollination and resulted in decreased genetic diversity in a focal plant species. Our study highlights the implications of these findings for grassland conservation.