Introduction
Globally, the distribution, seasonality, frequency and intensity of
fires has changed in recent decades due to anthropogenic global change
drivers including climate change, land-use change (with fire often used
to clear vegetation to facilitate land-use change) and, in some cases,
invasion by more flammable species (McLauchlan et al., 2020, Kelly et
al., 2020). These changes are predicted to accelerate over the next few
decades (Sheehan et al., 2019; Enright et al., 2015; Aragão et al.,
2008). There is particular concern regarding the impacts on
fire-sensitive tropical ecosystems, many of which are being rapidly lost
and degraded (Alroy, 2017; Busch & Ferretti-Gallon, 2017), making the
tropics the epicentre of current and future extinction risk (Edwards et
al., 2019). Given these changing fire regimes, it is crucial to
understand how fire influences biodiversity, and the rate of recovery
following fire events (Kelly et al., 2020). This need is widely
recognised, for example, by the Intergovernmental Science-Policy
Platform on Biodiversity and Ecosystem Services (IPBES, 2019) and the
UNFCC REDD+ program (UNFCC, 2019).
The impacts of fire on biodiversity are, however, complex and
incompletely understood (Gill et al., 2013; McLauchlan et al., 2020;
Tingley et al., 2016), with positive and negative impacts reported
(Kelly et al., 2020; Giorgis et al., 2021). Some tropical biomes, such
as woody savannas and grasslands, are frequently exposed to fire, and
several species that are characteristic of these biomes require fires to
persist (Simon & Pennington, 2012). In such biomes, fire positively
influences the diversity of photophilic floras and faunas (Pausas &
Keeley, 2019), with a landscape mosaic of vegetation patches that vary
in the time since they were burnt typically maximising biodiversity
(Driscoll et al., 2010). Long-term suppression of fire in these systems
typically generates more homogenous vegetation patches that support
fewer species (Giorgis et al., 2021; Abreu et al., 2017), promotes woody
species and gradual shifts from grasslands to woody savannas, and then
shrublands and forests (Probert et al., 2019).
In other biomes, such as tropical moist forests, fire is historically
extremely rare and most plant species are highly sensitive to fire
(Cochrane & Schulze, 1999, Giorgis et al., 2021). Consequently, recent
increases in the number of fires are a primary driver of tropical moist
forest degradation and biodiversity loss (Barlow et al., 2019; Lewis et
al., 2015), including tree (Galvao de Melo & Durigan, 2010, Cochrane &
Schulze, 1999) and forb communities (Gordijn et al., 2018). Increased
exposure to fire can also eventually convert moist tropical forest
ecosystems into open habitat and savannas (Flores & Holmgren, 2021).
Biodiversity will gradually recover following a fire event, and should
increasingly resemble the pre-fire community as time increases (Machida
et al., 2021). Frequent fire events can, however, prevent full recovery
by driving fire sensitive species to regional extinction (Gallagher et
al., 2021), and species recovery following fire can be much slower in
fire sensitive biomes than those that traditionally experience fire
(Nelson et al., 2014). Understanding of how biodiversity recovers
following fire events is, however, still insufficiently developed. In
part, this is because many studies of biodiversity responses to fire
focus exclusively on species richness, even though fires have strong
impacts on community composition and generate considerable turnover,
i.e. beta diversity (Gordijn et al., 2018; Durigan et al., 2020,
Peterson & Reich, 2008). The influence of landscape context on
biodiversity recovery following fire is also insufficiently understood.
Recovery rates are likely to be faster within relatively intact
ecosystems (i.e. effectively protected from anthropogenic stressors) in
which a greater abundance of natural vegetation increases the
availability of propagules that can recolonise burnt sites. Well managed
protected areas may thus facilitate faster recovery from fires, although
tropical protected areas vary greatly in their effectiveness, including
at reducing fire risk (Laurance et al., 2012).
Most studies assessing fire impacts on plant biodiversity focus on
single study locations. Meta-analyses are scarce but have assessed the
relative fire sensitivity of native and exotic plant species (Jauni et
al., 2015; Alba et al., 2014; Aslan & Dickson, 2020). Here, we build
upon a systematic compilation of data from published studies of tropical
and sub-tropical plant community responses to fire. We work on plants as
they comprise a wide range of life forms and life history strategies and
provide the habitat structure and resources that are exploited by other
taxonomic groups. We assess post-fire recovery of plant species richness
and composition following fire events. Specifically, we test whether
species richness and beta diversity (i.e., species turnover) between
burnt and unburnt plots respond differently to time since fire and fire
type (prescribed burns versus non-prescribed burns). We also assess if
protected area status (protected vs unprotected) moderates’ responses of
species richness and species turnover to fire events. Our analyses take
biome identity into account and distinguishes between prescribed and
non-prescribed burns. We do so as prescribed burns are often used in
management programmes to reduce the amount of flammable material and
thus the size and intensity of subsequent fires. The practice has,
however, been criticised (Ryan et al., 2013), with some studies
suggesting that prescribed burns can alter plant communities in a manner
similar to non-prescribed burns (Ffolliott et al., 2012; Pastro et al.,
2011).