Fire Eases Imbalances of Nitrogen and Phosphorus in Woody Plants

Fires are widespread and can result in large nutrient losses from ecosystems simultaneous with pulses in nitrogen (N) and phosphorus (P) that can increase their availability to plants. Plant growth is frequently limited by N and P, and fire has the potential to enhance or moderate the magnitude of N and P limitation in plants with important consequences for long-term net primary productivity and global carbon cycling. We used meta-analysis to explore fire effects on N and P concentrations in aboveground plant biomass among a variety of plants and plant communities worldwide. We show that across all observations, fire enhanced N concentration in plants when N/P ratios in biomass were low, and enhanced P concentration in plants when biomass N/P ratios were high. P concentration increased particularly in woody plants. Furthermore, responses of the N/P ratio in woody plants were more flexible than in herbaceous plants so that fire eased N and P imbalances only in woody plants. Our results suggest that these changes in plant N and P in response to fire may help sustain net primary productivity and persistence of woody plants in fire-affected ecosystems worldwide.