Herbaceous vegetation responses to experimental fire in savannas and forests depend on biome and climate

Fire-vegetation feedbacks potentially maintain global savanna and forest distributions. Accordingly, vegetation in savanna and forest ecosystems should have differential responses to fire, but fire response data for herbaceous vegetation have yet to be synthesized across biomes. Here, we examined herbaceous vegetation responses to experimental fire at 30 sites spanning four continents. Across a variety of metrics, herbaceous vegetation increased in abundance where fire was applied, with larger responses to fire in wetter and in cooler and/or less seasonal systems. Compared to forests, savannas were associated with a 4.8 (+/- 0.4) times larger difference in herbaceous vegetation abundance for burned versus unburned plots. In particular, grass cover decreased with fire exclusion in savannas, largely via decreases in C-4 grass cover, whereas changes in fire frequency had a relatively weak effect on grass cover in forests. These differential responses underscore the importance of fire for maintaining the vegetation structure of savannas and forests.

Automated summary

Fire-vegetation feedbacks are crucial for maintaining global savanna and forest distributions. Through studying herbaceous vegetation responses to fire at 30 sites across four continents, we found that herbaceous vegetation increased in abundance after fire, with wetter and cooler ecosystems showing larger responses. Savannas had a significantly higher difference in herbaceous vegetation abundance between burned and unburned areas compared to forests, indicating the importance of fire in shaping the vegetation structure of these ecosystems.