COS 169-2 - Speed in which communities recover function and composition after disturbance varies across latitude and community age

Background/Question/Methods

Rates at which communities recover after disturbance, or its resilience, can be accelerated by increased net primary productivity and recolonization dynamics such as recruitment. These mechanisms can vary across broad-scale gradients, such as latitude, suggesting that biogeography is likely important to understanding and predicting resilience. To test whether community resilience, informed by functional and compositional recovery, changes with latitude, we employed a standardized replicated experiment on marine invertebrate communities across four regions from the tropics to the subarctic zone. We hypothesized that resilience varies with latitude and is faster towards the tropics, and that recruitment is an important mechanism accelerating rates of functional recovery. We further examined two alternative trajectories: 1) compositional recovery coincides with functional recovery; or 2) disturbance initiates a compositional shift regardless of the degree to which functions are restored. Communities naturally assembled on standardized substrate (PVC panels) while experiencing levels of repeated disturbance (zero, low, and high biomass removal) that opened space for new colonizers, thereby providing pulses of a limited resource to these communities. We then quantified functional (space occupancy and biomass) and compositional recovery across early and late community assembly stages (three and 12 months, respectively).

Results/Conclusions

Combining functional and compositional recovery, two important aspects of community resilience, we documented latitudinal variation in resilience across 47 degrees of latitude. Speed of functional recovery was higher towards lower latitudes, yet incomplete at late assembly in the tropics and subtropics. Further, high disturbance significantly reduced biomass and space occupation in subarctic communities, particularly during late assembly. Contrary to our expectations, mechanisms other than recruitment might contribute more strongly to functional recovery in these communities. In addition, the degree of functional recovery did not coincide with compositional recovery, and biomass removals shifted compositional trajectories of recovery in all regions at both assembly stages. Together, our results support the hypothesis of biogeographic variation in resilience, with community age and disturbance intensity largely defining the speed and degree of recovery. While biogeographic variation in community resilience has been theorized, our results are among the first to examine functional and compositional recovery to disturbance in a single large-scale standardized experiment. Physical disturbances have increased in frequency and severity in response to changing climate, modifying the distribution of living biomass globally. It is therefore critical to understand recovery dynamics of natural systems across broad geographic scales and their potential for resilience.