Open-top warming chambers were installed across a burn severity gradient within nine months of a mixed-severity fire in order to assess the combined effects of burn severity, time since fire, and experimental warming on plant community recovery. Composition differed significantly according to burn severity, time since fire, and their interaction, while experimental warming did not significantly influence composition. Species richness significantly increased in burned areas compared to unburned control within two years of fire.
Abstract
Questions
Anthropogenic climate change is causing increases in the severity of wildland fire in many parts of the world. At the same time, post-fire succession is occurring under new, warmer temperatures that are projected to continue increasing. Despite this, the combined effects of uncharacteristically high burn severity and increased ambient temperature on post-fire community composition remain poorly understood. We ask how post-fire forest understorey community composition and species richness are influenced by (1) burn severity, (2) experimental warming, and (3) years since fire.
Location
Museum Fire Scar, Pinus ponderosa forest, Arizona, United States.
Methods
We established 120 1-m2 quadrats in unburned, low- and high-severity locations nine months after a mixed-severity fire. Half of the plots were subject to experimental warming via open-top warming chambers that elevated daytime temperatures by 1.079°C, simulating near-term anthropogenic warming. Plant composition data were collected annually for three years. Relationships between community composition, burn severity, and experimental warming were analyzed using repeated-measures PERMANOVA and linear mixed-effects models.
Results
Composition differed significantly according to burn severity, time since fire, and their interaction, while experimental warming did not significantly influence composition. Species richness significantly increased in burned areas compared to unburned control within two years of fire.
Conclusions
Our results suggest that near-term temperature increases, driven by anthropogenic climate change, will have little effect on community composition relative to fire severity. High-severity fire drove large, rapid changes in plant composition compared to unburned controls, favoring exotic annuals in a historically perennial-dominated plant community.