Extreme climate events: They happen, but how often do they matter?

Projected increases in climate extremes have raised questions about how plant composition will respond – will communities remain stable, change linearly, or exhibit threshold dynamics? Using long-term records from nine US grasslands, we first identified extreme climate values and assessed compositional response, and secondly identified extreme compositional changes and related these to potential climate drivers. Communities were often highly dynamic, but large shifts in composition were not associated with identifiable climate extremes. This suggests either extreme climate-extreme response relationships are based on difficult-to-capture drivers (such sequences of climate variables), or that species composition may be buffered to most climate extremes.