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.