COS 89-5 - Community synchrony, stability, and biodiversity responses to global change: Evaluating short-term versus multi-decadal responses

Background/Question/Methods

Anthropogenic influences have been increasingly altering ecosystems, leading to a need to understand how community stability, diversity, and synchrony respond to these changes in both the short and long term. In particular, stability not only depends on species diversity, but can also be strongly influenced by synchrony, a widespread phenomenon where species’ abundances fluctuate in a positively correlated (synchronous) or negatively correlated (compensatory) manner across time. Therefore, the objective of this research was to evaluate shifting responses of multiple community properties, including stability, synchrony, and metrics of biodiversity, to anthropogenic environmental change. We tested this by analyzing a long term (22 year) grasslands dataset from Cedar Creek, MN (USA) where plots were treated with two common agricultural impacts: soil disturbance crossed with a gradient of nutrient deposition in a factorial experiment. To tease apart the effects of these impacts on community dynamics, we used a linear regression model with a moving window approach to see how stability and synchrony change through time. Additionally, we integrated structural equation models with a moving window to examine the strength of ecosystem relationships, and compared how these relationships changed over time.

Results/Conclusions

We found that over 200 of 252 plots displayed predominantly compensatory dynamics. Unexpectedly, disturbance and nutrients decreased both synchrony and stability. Our moving window revealed that synchrony values of disturbed and undisturbed plots converged on independent fluctuations at the end of the timeseries, with neither synchronous nor compensatory dynamics dominating. Stability was shown to gradually increase over time, but increased more quickly in communities with low nutrient additions. These results were supported by the findings of the structural equation models, which revealed moderate to strong negative effects of nutrient addition and disturbance on stability, synchrony, and species richness and evenness. The relationship between synchrony and stability was strongest, with a large path coefficient of -0.64 denoting the effect of synchrony on stability, but nutrients also negatively influenced species richness and evenness. In examining community dynamics through time, we found that disturbance had a decreasing effect on synchrony and stability, whereas the effects of nutrients remained relatively static and strong. These results highlight how synchrony is influenced by global change and in turn strongly influences community stability, and yields insight into how synchrony, stability, and biodiversity are projected to shift after anthropogenic change.