Vascular plant community data for Northwest Territories, Canada

Climate change is altering disturbance regimes outside of historical
norms, which can impact biodiversity by selecting for plants with
particular traits. The relative impact of disturbance characteristics on
plant traits and community structure may be mediated by environmental
gradients. We aimed to understand how wildfire impacted understory plant
communities and plant regeneration strategies along gradients of
environmental conditions and wildfire characteristics in boreal forests.
We established 207 plots (60m2) in recently burned stands and 133 plots in
mature stands with no recent fire history in comparable gradients of stand
type, site moisture (drainage), and soil organic layer (SOL) depth in two
ecozones in Canada’s Northwest Territories. At each plot, we recorded all
vascular plant taxa in the understory and measured the regeneration
strategy (seeder, resprouter, survivor) in burned plots, along with
seedbed conditions (mineral soil and bryophyte cover). Dispersal,
longevity, and growth form traits were determined for each taxon. Fire
characteristics measured included proportion pre-fire SOL combusted (fire
severity), date of burn (fire seasonality), and pre-fire stand age (time
following fire). Results showed understory community composition was
altered by fire. However, burned and mature stands had similar plant
communities in wet sites with deep SOL. In the burned plots, regeneration
strategies were determined by fire severity, drainage, and pre- and
post-fire SOL depth. Resprouters were more common in wet sites with deeper
SOL and lower fire severity, while seeders were associated with drier
sites with thinner SOL and greater fire severity. This led to drier burned
stands being compositionally different from their mature counterparts and
seedbed conditions were important. Our study highlights the importance of
environment-wildfire interactions in shaping plant regeneration strategies
and patterns of understory plant community structure across landscapes,
and the overriding importance of SOL depth and site drainage in mediating
fire severity, plant regeneration, and community structure.