Data from: Fire season and drought influence fire effects on invasive grasses: A meta-analysis

Fire can shape plant communities when species respond differently to fire
characteristics like season and intensity. If invasive plants are more
vulnerable than native species to specific aspects of fire, managers could
use prescribed fires to control non-native species. We conducted
a meta-analysis of fire effects on six closely related Afro-Eurasian and
Australian grasses (Bothriochloa bladhii, B. ischaemum, B. pertusa,
Dichanthium annulatum, D. aristatum, and D. sericeum, collectively
“invasive bluestems”) that have invaded grasslands worldwide. Using data
from 31 studies (only 3 from their native range), we evaluated whether
these grasses (275 effect sizes) responded differently than native grasses
(184 effect sizes) to fire season, fuel load, and drought. Original data
included 15 different response variables (e.g., biomass, survival) that
were converted to standardized mean difference for
analysis. Fires in summer, fall, and early winter had negative
effects on invasive bluestems; no fire season had significant positive
effects. Most data were for B. ischaemum, but the other bluestems may also
be vulnerable to summer fire. Native grasses did not show significant
negative responses in any month. Drought (Keetch-Byram Drought
Index) in the month before fire increased the negative effects of fire on
invasive bluestems but not native grasses. Drought after fire led to
similar negative effects on both groups. Unexpectedly, fuel load
(which influences fire intensity) did not significantly influence fire
effects in any analysis. At the fuel loads examined (~600 – 10,000 kg/ha
dried herbaceous biomass), fire intensity may have been too low to cause
meristem mortality. Between-study heterogeneity was large in all
analyses (I2>80%), suggesting that additional factors beyond those
reported in the studies influence fire effects. These factors could
include plant phenology, fire behavior, weather conditions during the
fire, and soil characteristics. Synthesis and applications: Fires during
summer and fall, especially during dry conditions, could harm invasive
bluestems relative to native grasses, likely due to subtle differences in
heat sensitivity, phenology, and drought resistance. Other invasive
species may have similar vulnerabilities to specific fire seasons and
rainfall conditions that allow the use of fire as a control method.