Fire and bunchgrass dynamics in pine savannas
It is well known that ecological disturbance regimes affect plants;
it is less commonly appreciated how plants, in turn, affect those
disturbance regimes. For example, plant fuels often play an important
role in determining natural fire regimes. Fire is a powerful
evolutionary filter with the potential to radically change plant
populations and communities in a matter of minutes or hours. Changing
fire regimes are expected under climate change theory, with unknown
implications for plant populations and communities.
To explore the interactions between fire regime and plants, I have
investigated the relative importance of different fire characteristics
on diverse pine savanna understory vegetation. Results from this study
have demonstrated how fire severity drives large-statured bunchgrass
dynamics (Gagnon et al. 2012), with important
implications for community assembly in this species-rich ecosystem.
This same work has led me to develop a new evolutionary hypothesis to
explain why so many plants in fire-prone ecosystems produce highly
flammable fuels and burn with great intensity; the hypothesis also
informs burning prescriptions by managers of natural areas (Gagnon et
al. 2010). I next plan to experimentally test different facets of this
new hypothesis of plant flammability by manipulating composition and
architecture of plant fuels.
A related avenue involves global change phenomena viewed through the lens of disturbance ecology. Rising sea and CO2 levels, altered rainfall-, drought-, fire- and hurricane-regimes all have the potential to disrupt ecosystems and therefore, conservation plans. The perspective that plant populations and communities are dynamic assemblages provides a natural fit for global change-related investigations, and I am planning to establish a research program that explores how intensifying disturbance regimes are likely to affect plant populations.