Serotiny and resilience to fire in the context of a warming climate and altered disturbance regimes: Who are the winners and losers?

Background/Question/Methods

Climate change is already altering disturbance regimes around the world.  Fire regimes are directly affected; as the climate warms and precipitation is redistributed, many areas will see large increases or decreases in fire likelihood, intensity, severity, and extent.  Serotiny, the retention of seeds in the canopy of vegetation, is a common plant adaptation to fire, and many species considered “fire adapted” are serotinous, or semi-serotinous.  The expectation may be that increases in fire will result in near-universal increases in these species because of this highly adapted response strategy, and some studies have found large increases in serotinous systems due to more frequent fires.  However, despite this specialized resilience mechanism, many studies are finding surprising lack of resilience to increased frequency of fires in some ecosystems, and observing landscape-scale switches to alternate regimes.  We present a conceptual framework to describe when and where alterations to the fire regime, including frequency and variability in return interval, should increase or decrease a given landscapes resilience to fire. 

Results/Conclusions

Through four specific case studies (the mountains of Oregon, the mountains of BC and the boreal, and the Rocky Mountains), and with examples from Australia, we illustrate the point that serotiny does not necessarily mean resilience to future fire regimes.  Rather, there are complex interactions between life history traits, physiographic differences, and community composition which govern resilience to future fire regimes.  Some ecosystems will see dramatic increases in serotinous species, while others may surprisingly change to non-serotinous alternative vegetation types.   This has important implications for land management.  Management practices often select for species with different fire resilience strategies.  For example, initiation of low severity/high frequency fire regimes often favors species that endure fires, rather than serotinous species.  This leads to the question:  What attributes of a landscape will make it more or less resilient to future disturbance regimes?  How do we plan for landscape resilience to future disturbance conditions?  Should land managers prioritize species resilient to future conditions or appropriate to current conditions?  While individual responses will be shaped by local needs and policies, the conceptual framework links knowledge of current ecosystem state and disturbances to future regimes, highlighting areas likely to be sensitive to changes in disturbance frequency, and thereby informing researchers and managers of potential "low-resilience" situations before they occur.