The Wog Wog experiment after 29 years: The value of a long-term, large scale fragmentation experiment

Background/Question/Methods

Experiments provide the strongest inferential framework to understand the dynamics of communities and species in response to habitat fragmentation – one of the greatest global threats to diversity. Experiments of large spatial scale and long temporal scale, like the Wog Wog experiment in Australia, allow us to disentangle the different factors contributing to the response of species and communities to fragmentation. More fundamentally, such experiments allow understanding of how community assembly changes when the spatial context and environmental conditions of communities are altered, and can provide insights into community assembly and species coexistence. The fragmentation experiments are now at the height of their importance.

Wog Wog is a controlled replicated experiment in temperate Eucalyptus forest, in southeastern Australia, now in its 29th year. A focus has been the very speciose beetle fauna (~700 species) while new work also includes investigation of the soil microbial community, skink, ant and plant communities, and microclimate.

Results/Conclusions

In the first five years post fragmentation, we saw dramatic declines in a core group of beetle species in fragments but no extinction -- what became of these species? Do the transient dynamics of beetle species through five years post fragmentation predict their long term dynamics? Yes and no. While some species that showed dramatic declines in the short term eventually went extinct in fragments, other species that showed dramatic initial declines still persist in fragments 27 years after fragmentation. Traits of species that predicted short term responses to fragmentation also predict long term dynamics.

At an ecosystem level, fragmentation altered key soil nutrients via changes to nutrient cycling. Soil carbon declined in fragments versus controls, while soil nitrogen increased. Similarly, the biomass of the soil microbial community declined in fragments, and native plant richness and density increased. These changes link to changes in beetle community structure.

Insights into community assembly: experimental alteration of the spatial context of beetle communities increased richness on fragment edges via a mass effect, increasing the role of niches vs. stochastic assembly in fragment communities compared to control communities, providing unique experimental evidence of a mass effect outside of mesocosm systems.