Consistent physiological, ecological and evolutionary effects of fire regime on conservative leaf economics strategies in plant communities

The functional response of plant communities to disturbance is hypothesised to be controlled by changes in environmental conditions and evolutionary history of species within the community. However, separating these influences using direct manipulations of repeated disturbances within ecosystems is rare. We evaluated how 41 years of manipulated fire affected plant leaf economics by sampling 89 plant species across a savanna-forest ecotone. Greater fire frequencies created a high-light and low-nitrogen environment, with more diverse communities that contained denser leaves and lower foliar nitrogen content. Strong trait-fire coupling resulted from the combination of significant intraspecific trait-fire correlations being in the same direction as interspecific trait differences arising through the turnover in functional composition along the fire-frequency gradient. Turnover among specific clades helped explain trait-fire trends, but traits were relatively labile. Overall, repeated burning led to reinforcing selective pressures that produced diverse plant communities dominated by conservative resource-use strategies and slow soil nitrogen cycling.