Data from: Fire and non-native grass invasion interact to suppress tree regeneration in temperate deciduous forests

1. While many ecosystems depend on fire to maintain biodiversity,
non-native plant invasions can enhance fire intensity, suppressing native
species and generating a fire–invasion feedback. These dynamics have been
observed in arid and semi-arid ecosystems, but fire–invasion interactions
in temperate deciduous forests, where prescribed fires are often used as
management tools to enhance native diversity, have rarely been
investigated. 2. Here we evaluated the effects of a widespread invasive
grass on fire behaviour in eastern deciduous forests in the USA and the
potential effects of fire and invasions on tree regeneration. We planted
native trees into invaded and uninvaded forests, quantified fuel loads,
then applied landscape-scale prescribed fires and no-burn controls, and
measured fire behaviour and tree seedling and invasive plant performance.
3. Our results show that fires in invaded habitats were significantly more
intense, including higher fire temperatures, longer duration and higher
flame heights, even though invasions did not alter total fuel loads. The
invasion plus fire treatment suppressed native tree seedling survival by
54% compared to invasions without fire, and invasions reduced natural tree
recruitment by 66%. 4. We also show that invasive plant biomass did not
change from one season to the next in plots where fire was applied, but
invader biomass declined significantly in unburned reference plots,
suggesting a positive invasive grass–fire feedback. 5. Synthesis and
applications. These findings demonstrate that fire–invasion interactions
can have significant consequences for invaded temperate forest ecosystems
by increasing fire intensity and reducing tree establishment while
promoting invasive plant persistence. To encourage tree regeneration and
slow invasive spread, we recommend that forest managers remove invasions
prior to applying prescribed fires or avoid the use of fire in habitats
invaded by non-native grasses.