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.


Recently burned longleaf pine savanna showing resprouting bunchgrasses in understory

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.

Burned longleaf saplings (on the right) - despite how they look, these survived the fire

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.

Bunchgrass plot in early April, pre-fireSame plot in May, immediately after fireThree weeks post-fireIn September, same year