Effects of fire type
Previous studies reported that non-prescribed burns, specifically
wildfires, and prescribed burns have equivalent effects on plant
communities (Ffolliott et al., 2012; Pastro et al., 2011) and survival
(Nesmith et al., 2011). Our analyses provide rare evidence that
prescribed and non-prescribed fires can have divergent impacts on plant
communities.
Prescribed burns increased climber species richness, whilst
non-prescribed burns tended to reduce climber species richness. These
results extend previous work suggesting reduced species richness of
climbers in burnt compared to unburnt plots, irrespective of the fire
type (e.g., Addo-Fordjour et al., 2020; Balch et al., 2011). Climbers
can play a key role in vegetation dynamics; for example, fire-resilient
lianas can protect trees from further fire (Uhl et al., 1988);
conversely, lianas are often associated with reduced tree growth rates
and higher subsequent mortality (Becknell et al., 2022; Finlayson et
al., 2022). Given these roles of climbers in vegetation dynamics, and
the use of prescribed burns as a conservation tool to reduce the
probability of larger, more intense fires, it is important to understand
the mechanisms driving the difference in impacts of prescribed and
non-prescribed burns. Climbers proliferate in tropical habitats when
disturbance events increase light levels or soil nutrients (Magnago et
al., 2017), which will happen following a fire. It is plausible that
prescribed burns enable this proliferation to occur, increasing climber
richness, but the greater intensity of non-prescribed fires (Marshall et
al., 2020) limits such proliferation. We also found evidence that in
moist broad-leaved forest, prescribed burns increased forb species
richness whilst non-prescribed burns had negligible impact on it. Such
patterns may also be driven by prescribed burns beneficially altering
abiotic conditions for forbs, but greater intensity of non-prescribed
burns preventing forb communities from benefitting from these
conditions. It is unclear why the opposite pattern, increased forb
richness following non-prescribed burns and negligible impact of
prescribed burns, occurs in flooded grasslands and savannas - although
it may be linked to such biomes having greater historical exposure to
fire.