ArticlePDF Available

Abstract

1. Tropical savannas are known for the fire-prone ecosystems, yet, riparian evergreen forests are another important landscape feature. These forests usually remain safe from wildfires in the wet riparian zones. With global changes, large wildfires are now more frequent in savanna landscapes, exposing riparian forests to unprecedented impact. 2. In 2017, a large wildfire spread across the Chapada dos Veadeiros National Park, an iconic UNESCO site in central Brazil, raising concerns about its impact on the fire-sensitive ecosystems. By combining remote sensing analysis of Google Earth images (2003-2019) with detailed field information from 36 sites, we assessed wildfire impacts on riparian forests. For this, we measured the structure of trees, saplings and herbaceous plants, as well as topsoil variables. 3. Since 2003, all riparian forests had canopy cover above 90%, but after 2017, canopy cover dropped to 20% in some forests, indicating large variation in wildfire damage. A closer look in the field revealed that, on average, the wild-fire killed 52% of adult trees and 87% of tree saplings in flooded forests. In non-flooded forests, impacts on adult trees were negligible, but fire killed 75% of tree saplings. Opportunistic vines and the invasive grass Melinis minutiflora were already present in severely disturbed flooded forests. In all forests, impacts on many ecosystem variables were related to canopy damage, a variable measurable from satellite. Overall, seasonally flooded riparian forests were the most severely impacted, possibly due to the relatively thinner barks of their trees.
J Appl Ecol. 2020;00:1–12. wileyonlinelibrary.com/journal/jpe
|
  1© 2020 British Ecological Society
Received: 24 July 2020 
|
  Accepted: 23 October 2020
DOI: 10.1111/1365-2664.13794
RESEARCH ARTICLE
Tropical riparian forests in danger from large savanna wildfires
Bernardo M. Flores1,2 | Michele de Sá Dechoum2,3 | Isabel B. Schmidt4|
Marina Hirota1,2,5| Anna Abrahão1,6 | Larissa Verona1| Luísa L. F. Pecoral1|
Marcio B. Cure2| André L. Giles1,7 | Patrícia de Britto Costa1,8,9|
Matheus B. Pamplona10| Guilherme G. Mazzochini1| Peter Groenendijk1|
Géssica L. Minski2| Gabriel Wolfsdorf1,7| Alexandre B. Sampaio11| Fernanda Piccolo1|
Lorena Melo1| Renato Fiacador de Lima3| Rafael S. Oliveira1,8
1Depar tment of Plant Biology, Universit y of Campinas, C ampinas, Brazil; 2Gra duate Program in Ecology, Federal Un iversity of Santa Cat arina , Floria nópolis,
Brazil; 3D epar tment of Ecology and Zoology, Feder al Unive rsity of Santa C atar ina, Florianó polis, Brazil; 4D epar tment of Ecology, University of Brasília,
Brasí lia, Br azil; 5Department of Physics, Federal University of Santa Cat arina , Florianópolis, Bra zil; 6Institute of S oil Scie nce and L and Evalu ation, University
of Hohenheim, Stuttgart, G ermany; 7Grad uate Program in Ecology, Universit y of Campinas, C ampinas, Brazil; 8Scho ol of Biological Sciences, Universit y
of Western Australia, Per th, WA, Australia; 9Gra duate Program in P lant Biology, Universit y of Camp inas, C ampinas, Brazil; 10De part ment of Mat hematics,
University of E xeter, Exete r, UK and 11National Centre for Biodiver sity A ssess ment and Research and Conserv ation of the Brazi lian Cer rado, C hico Men des
Instit ute for Biologic al Conservat ion, Br asilia , Brazil
Correspondence
Bernardo M. Flo res
Email: mflores.bernardo@gmail.com
Funding information
Coordenação de Aperfeiçoamento de
Pessoal de Nível Superio r; Instituto
Serrapilheira, Grant/Award Number:
Serra-1709–18983; Fun dação Grupo
Boticá rio de Proteção à Naturez a, Gra nt/
Award Number: 1114-20181; Fundação de
Amparo à Pesquis a do Est ado de São Paulo,
Grant /Award Number: 18/01847-0 and
2016/25086-3
Handling Editor: Cécile Remy
Abstract
1. Tropical savannas are known for the fire-prone ecosystems, yet, riparian ever-
green forests are another important landscape feature. These forests usually
remain safe from wildfires in the wet riparian zones. With global changes, large
wildfires are now more frequent in savanna landscapes, exposing riparian forests
to unprecedented impact.
2. In 2017, a large wildfire spread across the Chapada dos Veadeiros National Park,
an iconic UNESCO site in central Brazil, raising concerns about its impact on the
fire-sensitive ecosystems. By combining remote sensing analysis of Google Earth
images (2003–2019) with detailed field information from 36 sites, we assessed
wildfire impacts on riparian forests. For this, we measured the structure of trees,
saplings and herbaceous plants, as well as topsoil variables.
3. Since 2003, all riparian forests had canopy cover above 90%, but after 2017,
canopy cover dropped to 20% in some forests, indicating large variation in
wildfire damage. A closer look in the field revealed that, on average, the wild-
fire killed 52% of adult trees and 87% of tree saplings in flooded forests. In
non-flooded forests, impacts on adult trees were negligible, but fire killed 75%
of tree saplings. Opportunistic vines and the invasive grass Melinis minutiflora
were already present in severely disturbed flooded forests. In all forests, im-
pacts on many ecosystem variables were related to canopy damage, a variable
measurable from satellite. Overall, seasonally flooded riparian forests were the
most severely impacted, possibly due to the relatively thinner barks of their
trees.
2 
|
  
Journal of Applied Ecology
FLORES E t aL.
1 | INTRODUCTION
Globally, interactions between climate change and human activi-
ties are exposing tropical ecosystems to new stressing conditions
(Barlow et al., 2018). Arguably, tropical savanna landscapes are
among the most threatened, in part because of misinformed land
management. Agribusiness expansion over savannas is often asso-
ciated with habitat loss and the introduction of non-native grasses
(Strassburg et al., 2017; Veldman et al., 2015). These grasses disperse
from planted pastures and become invasive in well-preser ved sites,
where they often outcompete native species, altering ecosystem
functioning (Damasceno et al., 2018; Zenni et al., 2019). They pro-
duce more fuel biomass than native grasses, increasing the risk of
large wildfires (Damasceno et al., 2018; D'Antonio & Vitousek, 1992;
Fusco et al., 2019). In addition, fire exclusion practices are also in-
creasing landscape flammability (Schmidt et al., 2018; Veldman
et al., 2015). As a result, tropical savannas are losing resilience to
withstand climatic changes, with potentially negative ecological and
societal consequences (Bengtsson et al., 2019).
Tropical savannas are well-known for their biodiverse open
habitats dominated by fire-resistant plant species. However,
fire-sensitive evergreen forests are another important feature of
these landscapes, often restricted to wet riparian zones (Bueno
et al., 2018; Kellman & Meave, 1997; Natta et al., 2002; Pettit &
Naiman, 2007; Ribeiro & Walter, 2008). Combined, these ecosys-
tem mosaics provide numerous services for societies. Grasslands
and savannas provide forage for herbivores, medicine and wild food
for local peoples, and contribute to the recharge of underground
water reservoirs (Bengtsson et al., 2019). Riparian forests reduce
soil erosion, enhancing water quality and water security (Wantzen
et al., 2006). They may act as fire breaks, reducing the spread of
wildfires (van Nes et al., 2018). Vertebrate species also benefit from
the water and shelter provided by riparian forests, including top
predators (Redford & Fonseca, 1986). Therefore, by connecting for-
es t ha bit at s and pr ov iding vita l re sou rc es for keys to ne sp ec ies , ri par-
ian forests contribute to stabilize trophic networks, and enhance the
overall resilience of tropical savanna landscapes (Estes et al., 2011).
Although riparian forests are surrounded by fire-prone ecosystems,
their humid microclimate and wet soils usually suppress wildfires
(Hoffmann et al., 2012). As a result, most tree species are fire-
sensitive, with relatively thin barks, compared to trees in the open
savanna (Dantas & Pausas, 2013). However, when rare large wild-
fires spread during extreme drought events, they are more likely to
penetrate riparian forests with potentially negative impacts (Pet tit
& Naiman, 2007).
In recent decades, tropical savannas world-wide have been
experiencing a lengthening of the fire weather season (Jolly
et al., 2015). In tropical South America, the season is now 33 days
longer than 35 years ago, which implies a higher wildfire risk (Jolly
et al., 2015). In 2017, a delayed onset of the rainy season, coupled
with land conflicts, resulted in numerous wildfires throughout Brazil
(Fidelis et al., 2018). A particularly large one spread across the
iconic Chapada dos Veadeiros National Park (CVNP), burning not
only savannas but also the fire-sensitive riparian forests (Figure 1;
Figures S1 and S2; Text S1). Here, we combine satellite image anal-
ysis with detailed field assessments, to quantify the impact caused
by this large wildfire to riparian forests of the CVNP. First, to con-
firm the actual timing of the wildfire and assess its damage to for-
est cover, we used ver y high spatial resolution Google Earth images
(2003 through 2019, ~0.5 m), and produced a time series of canopy
cover change for 16 riparian forest fragments. We then tested if
wildfire damage to the canopy, measured from satellite, was a good
predictor of impac ts on other ecosystem variables. Using field data
from 36 sites randomly spread across the study area (Figure 1), we
measured the structure of adult trees and saplings, the cover of her-
baceous plants, and several topsoil variables. We expected to find
that canopy damage was related to tree size and bark thickness dis-
tributions; traits previously shown to influence tree mortality (Balch
et al., 2011; Cochrane, 2003). Moreover, we hypothesized that in the
open burnt sites, invasive grasses and opportunistic plants would be
expanding, and that topsoils would be changing due to ash deposi-
tion and erosion processes.
4. Synthesis and applications. Our findings reveal how riparian forests embedded in
tropical savanna landscapes are in danger from large wildfires. The destruction of
some forests has opened space for new plant species that may propel a shift to
an alternative ecosystem state. Riparian forests are habitat of large savanna ani-
mals and their loss could affect entire trophic networks. Managing wildfires and
invasive grasses locally is probably the best strategy to maintain riparian forests
resilient. As wildfire regimes intensify in tropical savanna landscapes, our findings
stress the need for an integrated management that considers riparian forests as a
vulnerable element of the system.
KEYWORDS
Cerrado, climate change, drought, global change, invasive grasses, resilience, resistance,
tropical ecosystems
  
|
 3
Journal of Applied Ecolog
y
FLORES E t aL.
2 | MATERIALS AND METHODS
2.1 | Study area
We studied flooded and non-flooded riparian forest ecosystems
at the CVNP, Br azil (Figure 1). The la nd sc ape is formed by mos aics
of different vegetation types (Ribeiro & Walter, 2008). Wet and
dry grasslands and savannas occur in between streams, covering
most of the landscape. At the northwest edge of the park, dry
deciduous forests are found, whereas at the southwest edge, ri-
parian evergreen forests are most common (Figure 1a). Riparian
forests are closed-canopy ecosystems, which largely contrast to
the open palm swamp savannas, locally known as veredas. Along
riparian zones, the vegetation alters abruptly between closed-
canopy flooded forest and open palm swamp savannas, where na-
tive grasses coexist with the large monodominant palm Mauritia
flexuosa. Some riparian forests in our study area can be season-
ally flooded by streams in the wet season, whereas others remain
above the water level throughout the year (hereafter flooded and
non-flooded forests). The region receives a mean annual rainfall
of 1,500 mm, has a mean dry season of 130 days, and a mean
temperature of 21°C (Oliveira & Marquis, 2002). The park is sur-
rounded by rural areas with pastures as the main activity, and
small touristic towns.
FIGURE 1 The 2017 wildfire at the Chapada dos Veadeiros National Park. (a) Map of the study region, in Central Brazil, showing
in green forested areas, in grey the area affected by the wildfire, and in light green circles, our field study sites. (b) Photos show: (left)
savanna landscape with riparian forests and palm swamp savannas along streams; (centre) fires at night, burning riparian ecosystems; (right)
landscape burnt by wildfire, except for a fire break. Photo credits to B.M. Flores (lef t) and F. Tatagiba (ICMBio) (centre and right)
(a)
Alto
Paraiso
(b)
4 
|
  
Journal of Applied Ecology
FLORES E t aL.
2.2 | Google Earth image analyses
To obtain a first overview of the actual damage caused by the 2017
wildfire on riparian forests of the CVNP, we analysed time series
of canopy cover produced with Google Earth images (Image data:
©2020 CNES/Airbus & Maxar Technologies) of ver y high spatial res-
olution (~0.5 m), freely available for different years in Google Earth
Pro software v 7.3.3.7699. Images prior to 2013 had 1.5 m spatial
resolution. We included images from 2003, 2014, 2015, 2016, 2017
and 2019, which had good quality (few clouds) for visual inspection
and detection of canopy cover. To quantify canopy cover, we first
used the image from 2014 to create polygons delimiting the contours
of 16 riparian forest fragments within the study area (Figure 1). We
classified each fragment as flooded or non-flooded, according to the
micro-she d to which they belonged (Table S1). Among all riparian for-
ests in the study area, 54% is seasonally flooded, whereas the other
46% does not flood in the wet season. We then added a spatial grid
of points, spaced by 0.0001 degrees (~11 m), totalling 7,425 sample
points within 90 ha of riparian forest (Figure S3). For each sample
point, in each year, we visually classified as covered by forest (1) or
non-forest (0), from a viewpoint of 1.5 km in height. We classified
areas with bare ground, shrub or herbaceous vegetation as non-
forest. For each year, we calculated canopy cover as the proportion of
points inside eac h fra gm ent that were covered by fo re st. This met ho d
has proven effective for detecting disturbances in the Amazon forest
(Flores et al., 2014), which was confirmed at the CVNP. We analysed
ca no py cover cha ng e over the 16-y ea r per io d us in g a ‘l oe ss’ smoot he r
with the ‘ggplot2’ package (Wickham, 2016), in R software (R Core
Team, 2019).
2.3 | Field sampling
Six months after the wildfire, in April 2018, we sampled 36 field
plots of 20 m × 10 m (0.02 ha) in riparian forests spread across
five micro-sheds (streams) within the CVNP burnt area (Figure 1;
Table S1; Figure S3a). With Landsat 8 (OLI) imagery from 29
January 2017, scene 221-070, using false colour composites
with the bands 7 (SWIR-2), 5 (NIR) e 4 (red) and the channels red,
green and blue, we first identified 82 micro-sheds that could be
used in the study. Among those possibilities, we chose five mi-
cro-sheds based on two criteria: (a) that they were embedded in
the landscape affected by the wildfire and (b) their accessibility
(Figure 1a). The plots were spaced by at least 30 m within for-
est fragments in each micro-shed, avoiding stream channels and
edges. Riparian forests in four of the five streams are seasonally
flooded (flooded forests). In contrast, forests along one stream
are not flooded because the river channel is at least 2 m deep,
keepin g the fore st soil we ll-dr ai ned even in th e rainy season (n on-
flooded forests). Among the 36 study sites, six were located in
unburnt forests, including one in the non-flooded area and five in
flooded areas. These sites were considered our ground reference
for the pre-fire st ate. The other 30 study sites were located in
forests burnt by the 2017 wildfire, including eight in non-flooded
forests, and 22 in flooded forests. We classified forests as burnt
or unburnt in the field using fire signs, such as charred trees and
ashes in the super ficial soil. We also confirmed our classification
with Google Earth , using three sampl e point s for each field si te , to
analyse their canopy cover change in time series.
In each 20 m × 10 m field plot, we measured the diameter at
breast height (1.3 m, DBH) of all trees ≥10 cm. We also measured
tree bark thickness using a bark corer. Because bark thickness in-
creases with tree age, we worked with relative thickness, calcu-
lated as 100 × (thickness/DBH), according to Lawes et al. (2013).
Moreover, in three evenly spaced positions along the 20 m central
line of each plot, we dug trenches to measure root mat depth, in-
cluding fine roots and hummus. In these same trenches, beneath
the root mat, we collected superficial soil samples (0–20 cm) that
formed one single compound sample per plot. These soil samples
were analysed for tex ture and available (exchangeable) nutrients at
the Soil Dep ar tment Lab oratory at the Fed eral Un ive rsity of Viçosa,
Brazil (see Text S2 for details).
For each 20 m × 10 m field plot, we fixed four subplots of
1 m × 1 m in each corner, in which we sampled tree saplings, na-
tive herbaceous cover, native vine cover, non-native (exotic) grass
cover, bare soil cover and canopy cover. All measures taken from
the four subplots were averaged to produce a single value per plot.
In each subplot, we measured the density of woody saplings with
DBH between 1 and 5 cm. We visually estimated the cover of her-
baceous plants, vines and non-native grasses within one of seven
classes; class-0 for 0% cover, class-1 for cover 0%–5%, class-2 for
cover 5%–25%, class-3 for cover 25%–50%, class-4 for cover 50%–
75%, class-5 for cover 75%–95% and class-6 for cover 95%–100%.
We also visually estimated bare soil cover from 0% to 100% in each
subplot, considering bare soil as the absence of root mat, litter or
living plants. We estimated canopy cover using a Lemmon Spherical
Concave Densiometer, taking measures to the north, south, east and
west from each subplot, at 1.2 m above the ground. We obtained a
total of 16 canopy cover measures per 20 m × 10 m field plot, which
we averaged to obtain a single estimate.
2.4 | Field data analyses
Our analyses involved three main steps: (a) detect canopy cover
changes over 16 fragments (~90 ha) of riparian forest; (b) test if fire
damage to the canopy, measured with satellite and in the field, was
a good predictor of other impacts on vegetation and soil variables
measured in the field; (c) test if fire damage could be explained by
tree diameter and bark thickness.
Step 1 involved a landscape-scale analysis to understand the
magnitude of the 2017 wildfire. This approach also allowed us to
extrapolate our field observations. We validated our remote sens-
ing analysis by comparing canopy openness measured with Google
Ear th (image of 2019) with canopy ope nne ss measured in th e field
(in 2018), in both cases af ter the wildfire. Satellite estimates were
  
|
 5
Journal of Applied Ecolog
y
FLORES E t aL.
based on observations from the three sample points nearest to
each field plot (see Figure S3). Field estimates of canopy open-
ness were based on 16 observations per plot. We used a Pearson
correlation analysis to compare both estimates of mean canopy
openness.
For step 2, first we quantified mean fire impacts on the vegeta-
tion and topsoil in field sites. For this, we first divided values found
in burnt forests, by the mean value of unburnt reference forests:
(1 − ‘burnt-site’/‘reference-mean’) × 100; (in the cas e of non -flooded
forests, we used the values from the single reference site). For each
variable, based on the impact observed in burnt sites, we estimated
means and 95% confidence intervals. We then assessed in detail
whether canopy openness could be used as proxy for other eco-
system impacts. This hypothesis is consistent with previous stud-
ies, showing that severe fires cause high tree mortality in tropical
forests, increasing canopy openness and consequently the risk of
reburning, grass invasion and topsoil erosion (Brando et al., 2014;
Cochrane, 2003; Flores, Staal, et al., 2020). We related ‘canopy
openness’ with tree basal area, sapling density, native and non-na-
tive herbaceous cover, vine cover, bare soil cover, root mat depth,
as well as soil texture and nutrient availability. We analysed our
data using linear mixed models (LMMs) with the r package lme4’,
function ‘lmer’ (Bates et al., 2015). For each response variable, we
used ‘canopy openness’ as a fixed factor, and ‘micro-shed’ as a ran-
dom factor, to control for landscape heterogeneity (Table S1). As
a complementary analysis, we compared fire impacts between
burnt and unburnt flooded and non-flooded fores ts, again using the
function ‘lmer’ (Bates et al., 2015), with ‘forest type’ as fixed factor
and ‘micro-shed’ as a random factor. We visually analysed the re-
sidual-plots from each model to check for normality, and log-trans-
formed the variables: ‘sapling density’, ‘native vine cover’ and ‘P
concentration’, to approach normal distribution. For all analyses, we
tested for spa ti al autocorrel at io n us in g the fun ction ‘cor re log’, in the
r package ‘ncf’ (Bjornst ad, 2020), with distance classes of 0.005 de-
grees (~550 m). We did not find any spatial autocorrelation among
our field study sites in any of the analyses (Figures S4 and S5), and
thus assumed that all field sites were independent replicates. Due
to an imbalance in the number of replicates for flooded and non-
flooded forests (Table S1), we compared burnt forests of the single
non-flood ed micro-she d, with bur nt fore st s gr ouped in fo ur floode d
micro-sheds. For this group comparison, we used the nonparametric
Mann–Whitney (Wilcoxon) test, with the function ‘wilcox.test’ in R
software (R Core Team, 2019), which uses ranked data and hence is
rather robust to imbalanced sample sizes.
To understand whether tree diameter and bark thickness
could explain differences in wildfire damage between flooded
and non-flooded forests, we analysed the density distributions
of DBH and relative bark thickness for all trees in each forest
type, using data from unburnt forest reference sites only. We
compared both forest types using a Mann–Whitney test with
the function ‘wilcox.test’ in the R sof tware. Both traits have
been shown to influence fire resistance (Balch et al., 2011;
Cochrane, 2003).
3 | RESULTS
3.1 | Wildfire damage to the canopy from satellite
Our analysis of canopy cover change in riparian forests at the CVNP,
using Google Earth imagery, suggest s that at least since 2003, can-
opy cover in all 16 fores t fragment s remain ed high above 90%. After
2017, however, canopy cover decreased in many forests, reaching
20% in some cases, and showing that wildfire impac ts varied from
mild to highly destructive. Wildfire damage to the canopy varied ac-
cording to the micro-shed where forests are located (Figure S6), and
also to the local flooding conditions (Figure 2). We found a striking
difference between flooded and non-flooded forests, with the first
appearing to be more fire-sensitive (Figure 2). We validated our sat-
ellite estimates in the field, and found that post-fire canopy openness
measured with Google Earth and in field plots were strongly corre-
lated (r = 0.80; Figure 2). Moreover, the analysis of canopy cover in
the 16 forest fragments, before and after the wildfire, demonstrated
how the damage was unrelated with pre-wildfire levels (Figure S7).
3.2 | Wildfire impacts assessed in the field
Field assessments show that (Table 1), on average, in flooded for-
ests, the wildfire decreased canopy cover by 38 (±13)%, killed 52
FIGURE 2 Temporal changes in canopy cover on 16 forest
fragments in the study area (~90 ha), from 2003 through 2019,
derived from Google Earth images. Before 2017, canopy cover was
generally high, above 90%, but after the 2017 wildfire (vertical
grey dashed line), canopy cover became variable, revealing a
gradient of fire damage. We applied a small jitter to the horizontal
(year) axis to reduce data overlap. Inner plot shows the correlation
between canopy cover measured in the field in 2018 and canopy
cover measured with Google Earth in 2019. For details on sampling
method, see Figure S3. Satellite image credits to Google Earth
(Image data: ©2020 CNES/Airbus & Maxar Technologies)
0.00
0.25
0.50
0.75
1.00
2005 2010 2015 2020
Canopy cover
Forest type
Flooded
Non−flooded
Sample points (n)
0
500
1,000
1,500
2,000
03366 100
020406080 100
r = 0.80
Canop
y
openness in field
(
%
)
Canopy openness
in Google Earth (%)
– Fire damage +
2017
Field vs. Google Earth (after fire)
Year
6 
|
  
Journal of Applied Ecology
FLORES E t aL.
(±15)% of the adult trees and 87 (±9)% of tree saplings, causing a
47 (±13)% decrease in tree basal area, while native herbaceous and
vine cover had increased by 20%–25% and <5% respec tively. On
average, invasive grasses increased <5%, but were already present
in t wo severely burnt flooded forest s. Bare soil cover increased by
39 (±14)%, and root mat depth decreased by 65 (±18)% . Soil clay
decreased by 25 (±9)%, and phosphorus availability increased by
18-fold. In contrast, in non-flooded forests, the wildfire did not sig-
nificantly alter canopy cover, tree density, invasive grass cover, root
mat depth, bare soil cover and soil clay. However, it killed 75 (±26)%
of tree saplings, increased native herbaceous and vine covers by
20%–25%, and slightly decreased phosphorus concentration. Burnt
non-flooded forests also had more tree basal area than the single
reference forest. These patterns and the values obser ved in refer-
ence forests also show how, for most ecosystem variables, wildfire
impacts were severer on flooded forests, compared to non-flooded
forests (Figure S8), regardless of which micro-shed they belonged
to (Table S2).
When then related ‘canopy openness’ to other ecosystem vari-
ables (Figure 3), and found that wildfire damage to the canopy sig-
nificantly predicted reductions in tree basal area (Figure 3a) and
root mat depth (Figure 3f), as well as increases in bare soil cover
(Figure 3e) and soil available phosphorus (Figure 3h). Damage to
the canopy was also significantly related to an increase in soil pH
and decrease in soil aluminium (Figure S9). We found a near-signifi-
cant (p = 0.06) reduction of sapling density (Figure 3b). Native vine
cover, non-native grass cover and clay fraction did not change with
fire damage (Figure 3). We could not estimate changes in non-na-
tive grass cover because most sites had zero cover, although we
found that two burnt sites were already colonized by the African
grass species Melinis minutiflora (<5% cover in Figure 3d). In gen-
eral, we found the strongest wildfire damages in flooded forests,
TABLE 1 Fire impacts on vegetation and topsoil variables
of flooded and non-flooded riparian forests. We show per cent
changes (mean ± CI), relative to reference sites. Red downward
facing triangles indicate reduction. Blue upward facing triangles
indicate increase
Ecosystem variable
Change (%) af ter the wildfire
Flooded forests
Non-flooded
forests
Vegetation
Canopy cover −38 ± 13 −4 ± 2
Tree density −52 ± 15 +4 ± 17
Tree basal area −47 ± 13 +83 ± 53
Sapling density −87 ± 9 −75 ± 26
Native herbaceous cover +20–25 +20–45
Native vine cover +0–5 +20 –25
Non-native grass cover +0–5 0
Topsoil
Root mat depth −65 ± 18 +4 ± 11
Bare soil cover +39 ± 14 0
Clay fraction −25 ± 9 −17 ± 16
Silt fraction +63 ± 19 −17 ± 20
Sand fraction −10 ± 22 +45 ± 45
P concentration +1,808 ± 473 +36 ± 20
Ca2+ concentration −6 ± 40 −59 ± 30
pH +8 ± 6 −4 ± 4
Sum of bases −2 ± 34 −54 ± 27
Note: Fire impacts were estimated by dividing each burnt forest value
(N = 22 for flooded and N = 8 for non-flooded) by the forest reference
mean (N = 5 for flooded and N = 1 for non-flooded). Confidence
Intervals (CI) are based on alpha = 0.05. The cover of herbaceous, vines
and grasses changed between classes on a sc ale from 0 to 6, with 0 as
0% cover, 1 as 0%–5% cover, 2 as 5%–25% cover, 3 as 25%–50% cover,
4 as 50%–75% cover, 5 as 75%–95% cover and 6 as 95%–100% cover.
FIGURE 3 Wildfire impacts on riparian forests of the Chapada
dos Veadeiros National Park. We used data on canopy openness
as a proxy for fire damage. We then related canopy openness to
vegetation and soil variables: (a) tree basal area, (b) tree sapling
density, (c) native vine cover, (d) non-native grass cover, (e) bare soil
cover, (f) root mat depth, (g) clay fraction and (h) topsoil phosphorus
concentration. Field data were collected 6 months after the
wildfire. The vertical grey dashed line indicates the mean canopy
openness of reference sites. Statistically significant effects (based
on LMM) are shown above each plot. The cover of plants in (c) and
(d) varied on a scale from 0 to 6, with 0 as 0% cover, 1 as 0%–5%
cover, 2 as 5%–25% cover, 3 as 25%–50% cover, 4 as 50%–75%
cover, 5 as 75%–95% cover and 6 as 95%–10 0% cover
020406080
0
10
20
30
40
50
60
Tree basal area (m2/ha)
p = 0.005
020406
08
0
Tree saplings per m2
p = 0.06
0123
020406080
0
1
2
3
4
5
6
Native vine cover
p = 0.81
020406
08
0
0.0
0.2
0.4
0.6
0.8
Non−native grass cover
●●
p not estimated
020406080
0
20
40
60
80
Bare soil cover (%)
●●
p < 0.001
020406
08
0
0
5
10
15
Root mat depth (cm)
p < 0.001
020406080
20
30
40
50
Clay fraction (%)
p = 0.58
020406
08
0
0
20
40
60
80
100
P available (mg/kg)
p < 0.001
Flooded burnt
Non−flooded burnt
Flooded reference
Non−flooded reference
Canopy openness (%)
Fire damage
(a) (b)
(c) (d)
(e) (f)
(g) (h)
  
|
 7
Journal of Applied Ecolog
y
FLORES E t aL.
whereas non-flooded forests suffered mild damages to most eco-
system variables (Figure 3). Further analyses indicated that the cover
of native vines and non-native (exotic) grasses did not change with
topsoil phosphorus (P) concentration, neither with bare soil cover
(Figure S10). Both sites where non-native grasses were present,
however, had high P concentration.
Our analyses of density distributions of tree DBH and relative
bark thickness indicated that, although trees in both forest types
have similar DBH values (Figure 4a; p = 0.53), trees in the non-
flooded forests have relatively thicker barks, compared to trees in
flooded forest s (Figure 4b; p = 0.002).
4 | DISCUSSION
4.1 | Wildfire impacts on riparian forests
Our result s reveal how large wildfires can be destructive for ripar-
ian forests embedded in tropical savanna landscapes. In riparian
forests of the CVNP, the 2017 wildfire killed on average half of all
adult trees and 88% of tree saplings. It consumed half of topsoil root
mats, exposing 28% of bare soils, which boosted phosphorus avail-
ability, probably as a result of ash deposition. These impacts were
stronger on seasonally flooded forests than on non-flooded forests,
with some sites suffering complete mortality and topsoil combustion
(Figures 3 and 5a,b). In severely burnt forests, favourable light and
nutrient conditions may have facilitated the expansion of opportun-
istic plants, such as vines and ferns, which already covered par ts of
our field plots only 6 months after the wildfire (Figure 5d,e). In two
of these sites, invasive grasses were already present at low covers.
Overall, our findings confirm our hypothesis that riparian forests are
fire-sensitive ecosystems, and indicate that seasonally flooded for-
ests, which represent 54% of all riparian forests in this landscape,
are the most vulnerable to wildfires. Although our field assessments
are imbalanced with relatively more sites representing flooded for-
ests, our analyses were robust in suggesting their higher sensitivit y,
compared to non-flooded forests (Table S2).
A similar pattern has been obser ved in the Amazon, where sea-
sonally flooded forests are more sensitive to wildfires than non-
flooded forests (Flores et al., 2014; Nogueira et al., 2019; Resende
et al., 2014). Flooding conditions are known to cause hypoxia, and
trees often invest in above-ground root systems to overcome this
stress (Parolin et al., 2004). Slow litter decomposition in these sys-
tems also causes humus to accumulate in the topsoil (dos Santos
& Nelson, 2013). Root mats retain soil humus, reducing nutrient
leaching and erosion (Stark & Jordan, 1978), while enhancing oxy-
gen acquisition under water (Parolin et al., 2004). Yet, during the dry
season of extremely dry years, root mats may act as fuel for deadly
smouldering wildfires (Flores et al., 2014; Resende et al., 2014). In
most tropical forests, a single wildfire usually kills between 23% and
44% of the trees (Cochrane, 20 03). In floodplain forests, however,
one single wildfire event can kill 60%–10 0% of all adult trees, which
places them among the most fire-sensitive tropical forests (Flores
et al., 2014, 2016; Resende et al., 2014). Our findings at the CVNP
reveal that, while the non-flooded forests suffered negligible tree
mortality, flooded forests suffered on average 52% tree mor tality
from a single wildfire event.
Root mats may have contributed to increase forest flammabilit y
during the 2017 drought. However, non-flooded forests also have
root mats (Figure 3f), which raises the question of why they only
suffered mild damage. Tree size and bark thickness are traits known
to enhance internal protection from fire damage in tropical forest
trees (Balch et al., 2011; Cochrane, 2003). We found that, while both
forest types had similar DBH distributions, trees in the non-flooded
forest had higher bark thickness, compared to trees in the flooded
forest (Figure 4). This pattern suggests that both forest types may
FIGURE 4 Comparing (a) DBH and (b) relative bark thickness of individual trees in unburnt flooded and non-flooded forest s. The Mann–
Whitney test confirmed that both forests did not differ in terms of DBH (p = 0.53), but were significantly dif ferent in terms of relative bark
thickness (p = 0.0 02). In flooded forests, we show 166 individual trees from five distinct reference sites, whereas in non-flooded forests, we
show 12 trees from the single non-flooded forest site. Trees in non-flooded forests have higher relative bark thickness than trees in flooded
forests, which may help explain the differences in wildfire severity
0.00
0.01
0.02
0.03
0.04
0.05
20 40 60
Diameter at breast height (cm)
Density
FOREST TYPE
Flooded unburnt (n = 166)
Non−flooded unburnt (n = 12)
0.00
0.03
0.06
0.09
01020
Relative bark thickness
(a) (b)
8 
|
  
Journal of Applied Ecology
FLORES E t aL.
FIGURE 5 Riparian forests of the Chapada dos Veadeiros National Park af ter the 2017 wildfire. (a, b) Two burnt flooded forest s with
forest structure and organic soils severely disturbed. (c) Burnt flooded forest with low tree mortalit y. (d) Severely burnt flooded forest
dominated by the opportunistic fern Pteridium arachnoideum. (e) Severely burnt flooded forest dominated by vines. (f–h) Three unburnt
flooded forest s
  
|
 9
Journal of Applied Ecolog
y
FLORES E t aL.
have experienced different fire regimes in the past (Pellegrini
et al., 2017). Another possibilit y is that the thicker barks of trees in
non-flooded forests are an adaptation to reduce water loss during
the dry season (Loram-Lourenco et al., 2020), which contributed to
increase their wildfire resistance.
4.2 | Post-wildfire ecosystem response
An emerging question is whether severely disturbed riparian for-
ests will recover back to their original state or remain arrested
by self-perpetuating vines, ferns and invasive grasses. In a similar
tropical savanna landscape of Belize, riparian forests were shown
to recover well from small wildfires (Kellman & Meave, 1997). At
the CVNP, however, the 2017 wildfire was a rare event that killed
most trees and saplings, and consumed most of the organic soil in
some forests (Figure 3), potentially destroying tree seed banks.
Remnant trees of ten contribute to attract animal dispersers and
fac ilitate forest recover y af te r di st urbance s, yet , wh en mos t tree s
have been killed, dispersal may be limited. Even if seeds are able
to arrive in burnt forests, they will have to overcome multiple re-
cruitment limitations, such as competition with herbaceous plants
(Figure 5d ,e). In bur nt for est s, in cr ea se in soil pho sp horus con ce n-
tration, as well as reduction in soil acidity and toxicity may now
boost the growth of opportunistic and invasive plants. In fact,
6 months after the fire, the non-native C4 grass Melinis minuti-
flora was already present in two severely burnt flooded forests
(Figure 3d), pro ba bly be nefiting from the impro ved soil cond itions
(Bustamante et al., 2012). Because of its high biomass and flam-
mable compounds, the expansion of M. minutiflora may reduce
tree s ee dl in g su rvi va l (H of fmann & Har id as an, 2008) an d enhance
overall ecosystem flammability (Hoffmann et al., 2004). Hence,
the spread of M. minutiflora and other opportunistic plants in
disturbed riparian forests may contribute to arrest forest succes-
sion, as previously shown in forests of the Cerrado and Amazonia
(Flores et al., 2016; Hoffmann & Haridasan, 2008; Veldman &
Putz, 2011).
An alternative possibility is that Mauritia flexuosa palms, as
well as native grass species may colonize burnt riparian forests,
as these sites are connected to palm swamp savannas along
streams (Figures 1b and 5). Mauritia flexuosa palms often survive
from wildfires and increase their seed production, potentially
leading to mass recruitment in burnt sites ( Arneaud et al., 2017).
Transitions from riparian forest to Mauritia swamp savanna have
been shown across the Neotropics by palaeoecological evidence
(Rull & Montoya, 2014). For instance, at the Venezuelan Gran
Sabana region, riparian forests were replaced by Mauritia swamp
savannas following an increase in fire activit y 2000 years ago
(Montoya et al., 2011). Fires initially arrested the ecosystem in a
state dominated by ferns for 200 years, until palm swamp savan-
nas expanded permanently (Rull et al., 2013). Interestingly, some
of the burnt forests we studied are also dominated by the oppor-
tunistic fern Pteridium arachnoideum (Figure 5d), a species known
to outcompete tree seedlings and arrest forest succession (Pivello
et al., 2018).
Our findings imply that, as large wildfires become more fre-
quent in tropical savannas, riparian forests will be increasingly
exposed to the risk of collapse (Scheffer et al., 2001; van Nes
et al., 2018). The complete destruction of some forests (Figure 5)
may open space for new plant species with contrasting functions
th at pr op el the ecos yst em to an alt ern at ive veg eta tio n sta te, whic h
could potentially be: (a) a degraded state with invasive grasses and
opportunistic plants or (b) a palm swamp savanna state with M.
flexuosa and native grasses. To reduce such risk, it is necessary
to manage landscape flammability. Some protected areas of the
Brazilian Cerrado, for instance, have already started implement-
ing an Integrated Fire Management program, with the use of pre-
scribed controlled fires (Schmidt et al., 2018). Small prescribed
fires act as micro-disturbances that help restore landscape hetero-
geneity, reducing wildfire spread (Mistry et al., 2005). The CVNP
only adopted this strategy at a larger scale after the 2017 event.
Additionally, the persistent control of non-native grasses is fun-
damental to reduce their invasion in disturbed sites. Managing
wildfires and invasive grasses at the landscape scale is challenging,
yet probably the best strategy to maintain riparian forests resil-
ient. These forests are an important habitat for large animals that
move across the savanna landscape (Redford & Fonseca, 1986),
implying that they contribute to stabilize trophic networks (Estes
et al., 2011).
In summary, our findings reveal how riparian forests embed-
ded in tropical savanna landscapes are in danger from large wild-
fires. Seasonally flooded forests were the most impacted by the
2017 wildfire at the CVNP, raising concerns about whether they
will recover or shift into an alternative ecosystem state. In our study
area, long fire-free periods allowed grass fuel to build-up, causing
wildfires to be intense and uncontrollable. In addition, a synergis-
tic combination of climate change (Jolly et al., 2015) and environ-
mental governance loss (Levis et al., 2020) is causing large wildfires
to happen more often in savannas landscapes of the Cerrado and
Pantanal, in Brazil (Mega, 2020). The most promising solution to re-
duce such risk probably lies in combining the ancient indigenous fire
management knowledge with recent scientific discoveries (Durigan
& Ratter, 2016; Mistry et al., 2005). New forms of management using
prescribed fires are already being applied in many fire-prone eco-
systems, restoring landscape heterogeneity and reducing the risk of
large wildfires (Buisson et al., 2019; Schmidt et al., 2018). Evidence
we present here contribute to these initiatives by stressing the need
to consider riparian forests as a vulnerable element of tropic al sa-
vanna systems.
ACKNOWLEDGEMENTS
The work was supported by the Fundação Grupo Boticário de
Pr ote çã o à Natur eza , grant 1114 -2 018 1. B. M . F. is fu n d e d by São Pa ulo
Research Foundation FAPESP grant 2016/25086-3. P.G. acknowl-
edges FAPESP grant 18/01847-0. B.M.F., M.H., P.G. and R.S.O. ac-
knowledge the grant from Instituto Serrapilheira/Serra-1709–18983.
10 
|
  
Journal of Applied Ecology
FLORES E t aL.
A.A., A.L.G., P.d.B.C. and G.W. acknowledge the Coordenação de
Aperfeiçoamento de Pessoal de Nível Superior (CAPES, Brazil) Code
001. We thank the CVNP and ICMBio for logistics. B.M.F. and A.A.
acknowledge Sisbio for licences 6 4171-1 and 43511.
AUTHORS' CONTRIBUTIONS
B.M.F., M.H., M.d.S.D., I.B.S., A.A., M.B.P., A.B.S. and R.S.O.
conceived and designed the study; B.M.F., M. S.D., M.B.C., A.A .,
A.L.G., P.d.B.C., M.B.P., P.G., G.L.M., G.W., L.V., L.L.F.P., F.P. and
R.S.O. collected the field data; B.M.F. and G.G.M. analysed the
field data; L.V. and L.L.F.P. collected satellite data, and together
with B.M.F., analysed the data. All authors contributed to result
interpretation. B.M.F. led the writing and all authors contributed
substantially.
DATA AVAILAB ILITY STATE MEN T
Data available via the Dryad Digital Repository https://doi.org/
10.5061/dryad.rr4xg xd72 (Flores, de Sá Dechoum, et al., 2020;
Flores, Staal, et al., 2020). Satellite data are freely available from
Google Earth.
ORCID
Bernardo M. Flores https://orcid.org/0000-0003-4555-5598
Michele de Sá Dechoum https://orcid.org/0000-0002-3484-2498
Isabel B. Schmidt https://orcid.org/0000-0001-9420-6509
Anna Abrahão https://orcid.org/0000-0001-9295-2292
André L. Giles https://orcid.org/0000-0002-1973-400X
Peter Groenendijk https://orcid.org/0000-0003-2752-6195
REFERENCES
Arneaud, L . L ., Farrell, A. D., & Oatham, M. P. (2017). Mar ked reproduc-
tive plasticity in response to contras ting fire regimes in a neotropical
palm. Tropical Ecology, 58(4), 693–703.
Balch, J. K., Nepstad, D. C., Curran, L. M., Brando, P. M., Portela, O.,
Guilherme, P., Reuning-Scherer, J. D., & de Car valho, O. (2011).
Size, species, and fire behavior predic t tree and liana mor tality from
experimental burns in the Brazilian Amazon. Forest Ecology and
Management, 261(1), 68–77. https://doi.or g/10.1016/j.for eco.2010.
09. 0 29
Barlow, J., Franca, F., Gardner, T. A., Hicks, C. C., Lennox, G. D., Berenguer,
E., Castello, L., Economo, E. P., Ferreira, J., Guénard, B., Leal, C . G.,
Isaac, V., Lees, A. C., Parr, C. L., Wilson, S . K., Young, P. J., & Graham,
N. A. J. (2018). The future of hyp erdiverse tropical ecosystems.
Nature, 559(7715), 517–526.
Bates, D., Maechler, M., Bolker, B., & Walker, S. (2015). Fitting linear
mixed-effects models using lme4. Journal of Statistical Soft ware, 67,
1–4 8 .
Bengt sson, J., Bullock, J. M., Egoh, B., Everson, C., Everson, T., O'Connor,
T., O' Farrell, P. J., Smith, H. G., & Lindborg, R. (2019). Grasslands—
More important for ecosystem services than you might think.
Ecosphere, 10(2), e02582. https://doi.org/10.1002/ecs2.2582
Bjornstad, O. N . (2020). ncf: Spatial covariance functions. R package ver-
sion 1.2-9. Retrieved from https://CRA N.R-proj e ct.org/pack a ge=ncf
Brando, P. M., Balch, J. K., Nepstad, D. C ., Morton, D. C., Putz, F. E.,
Coe, M. T., Silverio, D., Macedo, M. N., Davidson, E. A., Nobrega,
C. C., Alencar, A., & Soares-Filho, B. S. (2014). Abrupt increases
in Amazonian tree mortality due to drought–fire interactions.
Proceedi ngs of the National Academy of Sciences of the United States of
America, 111(17), 6347–6352 . ht tp s://doi .or g/10.1073/pna s.13 05 4
99111
Bueno, M. L., Dexter, K. G., Penning ton, R . T., Pontara, V., Neves,
D. M., Ratter, J. A., & de Oliveira-Filho, A. T. (2018). The envi-
ronment al triangle of the Cerrado Domain: Ecological fac tors
driving shif ts in tree species composition between forests and
savannas. Jou rnal of Ecology, 106(5), 2109–2120. ht tps://doi.
org /10.1111/1365-2745 .12969
Buisson , E., Le Stradic, S., Silveira, F. A., Durigan, G., Overbeck, G. E.,
Fidelis, A., Fernandes, G. W., Bond, W. J., Hermann, J.-M., Mahy, G.,
Alvarado, S. T., Zaloumis, N. P., & Veldman, J. W. (2019). Resilience
and restoration of tropic al and subtropical grasslands, savannas, and
grassy woodlands. Biological Reviews, 94(2), 590–609.
Bustamante, M. M., de Brito, D. Q., Kozovit s, A. R., Luedemann, G., de
Mello, T. R., de Siqueira Pinto, A., Munhoz, C. B., & Takahashi, F. S.
(2012). Effec ts of nutrient additions on plant biomass and diversity
of the herbaceous-subshrub layer of a Brazilian savanna (Cerr ado).
Plant Ecology, 213(5), 795–808. ht tps://doi.org/10.1007/s1125
8-012- 0 042-4
Cochrane, M. A. (20 03). Fire science for rainforests. Nature, 421(6926),
913–919.
Damasceno, G., Souza, L., Pivello, V. R., Gorgone-Barbosa, E., Giroldo, P.
Z., & Fidelis, A. (2018). Impac t of invasive grasse s on Cerrado under
natural regeneration. Biological Invasions, 20(12), 3621–3629. https://
doi.org/10.10 07/s1053 0- 018-1800 -6
Dantas, V. D. L., & Pausas, J. G. (2013). The lanky and the corky: Fire-
escape strategies in savanna woody species. Journal of Ecology,
101(5), 1265–1272. https://doi.org/10.1111/1365-2745.12118
D'Antonio, C. M., & Vitousek , P. M. (1992). Biological invasions by ex-
otic grasses, the grass/fire cycle, and global change. Annual Review of
Ecology and Systematic, 23(1), 63–87. https://doi.org/10.1146/annur
ev.es.23.110192.000431
dos Santos, A . R., & Nelson, B. W. (2013). Leaf decomposition and fine
fuels in floodplain forests of the Rio Negro in the Brazilian Amazon.
Journal of Tropical Ecology, 29(5), 455–458. ht tps://doi.org/10.1017/
S 0 2 6 6 4 6 7 4 1 3 0 0 0 4 8 5
Durigan, G., & Ratter, J. A . (2016). The need for a consistent fire policy
for Cerrado conservation. Journal of Applied Ecology, 53(1), 11–15.
https ://doi.or g/10.1111/1365 -266 4.1 2559
Estes, J. A., Terborgh, J., Brashares, J. S., Power, M . E., Berger, J., Bond,
W. J., Carpenter, S. R., Essington, T. E., Holt, R. D., Jackson, J. B. C.,
Marquis, R. J., Oksanen, L., Oksanen, T., Paine, R. T., Pikitch, E. K.,
Ripple, W. J., Sandin, S. A., Schef fer, M., Schoener, T. W., … Wardle, D.
A. (2011). Trophic downgrading of planet Earth. Science, 333 (6040),
301–306.
Fidelis, A ., Alvarado, S., Barradas, A., & Pivello, V. (2018). The year 2017:
Megafires and management in the Cerrado. Fire, 1(3), 49. https://doi.
org /10.3 390/fire1 030049
Flores, B. M., de Sá Dechoum, M., S chmidt , I. B., Hirota, M., Abr ahão, A .,
Verona, L., Pecoral, L., Cure, M., Giles, A., Costa, P., Pamplona, M.,
Mazzochini, G., Groenendijk, P., Minski, G., Wolfsdorf, G., Sampaio,
A., Piccolo, F., Melo, L., Fiacador, R., & Oliveira, R . (2020). Data from:
Tropical riparian forests in danger from large savanna wildfires.
Dryad Digital Repository, https://doi.org/10.5061/dryad.rr4xg xd72
Flores, B. M., Fagoaga, R., Nelson, B. W., & Holmgren, M. (2016).
Repeated fires trap Amazonian blackwater floodplains in an open
vegetation state. Journal of Applied Ecology, 53(5), 1597–1603.
https ://doi.or g/10.1111/1365 -266 4.1 2687
Flores, B. M., Piedade, M. T. F., & Nelson , B. W. (2014). Fire disturbance
in Amazonian blackwater floodplain forests. Plant Ecology & Diversit y,
7(1–2), 319–327. ht tps://doi .or g/10 .1080/1755 0 874.2012.716 086
Flores, B. M., Staal, A., Jakovac, C. C., Hirota, M., Holmgren, M., & Oliveira,
R. S. (2020). Soil erosion as a resilience drain in disturbed tropical
forest s. Plant and Soil, 450(1) , 11–25. https ://doi.or g/10.10 07/s1110
4-019-04097 -8
  
|
 11
Journal of Applied Ecology
FLORES E t aL.
Fusco, E. J., Finn, J. T., Balch, J. K ., Nagy, R. C., & Bradley, B. A. (2019).
Invasive grasses increase fire occurrence and frequency across
US ecoregions. Proceedings of the National Academy of Sciences of
the United States of America, 116(47), 23594–23599. https://doi.
org /10.1073/p nas.19082 53116
Hoffmann, W. A., & Haridasan, M. (2008). The invasive grass, Melinis
minutiflora, inhibits tree regeneration in a Neotropical savanna. Austral
Ecology, 33(1), 29–36. ht tps://doi .org/10.1111/j.14 42-9993. 2007.
01 787. x
Hoffmann, W. A., Jaconis , S. Y., Mckinley, K. L., Geiger, E. L.,
Gotsch, S . G ., & Franco, A . C . (2012). Fuels or microclimate?
Understanding the drivers of fire feedback s at savanna–forest
boundaries. Austral Ecolog y, 37(6), 634–64 3. https://doi.org/
10.1111/ j.14 42-9 993 .2011.02324.x
Hoffmann, W. A., Lucatelli, V. M. P. C ., Silva, F. J., Azeuedo, I. N. C., Marinho,
M. D. S., Albuquerque, A. M. S., Lopes, A. D. O., & Moreira, S. P. (2004).
Impact of the invasive alien grass Melinis minutiflora at the savan-
na-forest ecotone in the Brazilian Cerrado. Diversity and Distributions,
10(2), 99–103. https://doi.org/10.1111/j.1366-9516.2004.00 063.x
Jolly, W. M., Cochrane, M. A., Freeborn, P. H ., Holden, Z. A., Brown,
T. J., Williamson, G. J., & Bowman, D. M. (2015). Climate-induced
variations in global wildfire danger from 1979 to 2013. Nature
Communications, 6(1), 7537. ht tps://doi.org/10.1038/ncomm s8537
Kellman, M., & Meave, J. (1997). Fire in the tropical gallery for-
ests of Belize. Journal of Biogeography, 24 (1), 23–34. https://doi.
org /10.1111/j .136 5-269 9.1997.tb 000 47.x
Lawes, M. J., Midgley, J. J., & Clarke, P. J. (2013). Costs and benefits
of relative bark thickness in relation to fire damage: A savanna/
forest contrast. Journal of Ecology, 101(2), 517–524. https://doi.
org /10.1111/1365-2745 .12035
Levis, C., Flores, B. M., Mazzochini, G. G., Manhães, A. P., Campos-Silva,
J. V., de Amorim, P. B., Peroni, N., Hirota, M., & Clement , C. R. (2020).
Help restore Brazil's governance of globally important ecosystem
services. Nature Ecology & Evolution, 4(2), 172–173. https://doi.
org /10.103 8/s4155 9-019-1093-x
Loram-Lourenço, L., Farnese, F. D. S., Sousa, L. F. D., Alves, R. D. F. B.,
Andrade, M. C. P. D., Almeida, S. E. D. S., Moura, L. M. D. F., Costa, A.
C., Silva, F. G., Galmés, J., Cochard, H., Franco, A. C., & Menezes-Silva,
P. E. (2020). A structure shaped by fire, but also water: Ecological
consequences of the variability in bark proper ties across 31 species
from the Brazilian Cerr ado. Frontiers in Plant Science, 10(1) , 1718.
https://doi.org/10.3389/fpls.2019.01718
Mega, E. R. (2020). ‘Apocaly ptic’ fires are r avaging the world's largest
tropical wetland. Nature, 586, 20–21. https://doi.org/10.1038/d4158
6-020-02716 -4
Mistr y, J., Berardi, A ., Andrade, V., Krahô, T., Krahô, P., & Leonardos, O.
(2005). Indigenous fire management in the cerrado of Brazil: The
case of the Krahô of Tocantíns. Human Ecology, 33(3), 365–386.
htt ps://doi.org/10.10 07/s1074 5-0 05- 4143-8
Montoya, E., Rull, V., Stansell, N. D., Abbot t, M. B., Nogué, S., Bird, B.
W., & Díaz, W. A. (2011). Forest–savanna–morichal dynamic s in re-
lation to fire and human occupation in the southern Gran Sabana
(SE Venezuela) during the last millennia. Quaternary Research, 76 (3),
335–344.
Natta , A. K., Sinsin, B., & van der Maesen, L. J. G. (2002). Riparian for-
ests, a unique but endangered ecosystem in Benin. Botanische
Jahrbücher, 124 (1), 55–69. https://doi.org/10.1127/0 006 -8152/2002/
0124- 0 055
Nogueira, D. S., Marimon, B. S., Marimon-Junior, B. H., Oliveir a, E. A .,
Morandi, P., Reis, S. M., Elias, F., Neves, E. C., Feldpausch, T. R., Lloyd,
J., & Phillips, O. L. (2019). Impac ts of fire on forest biomass dynam-
ics at the southern amazon edge. Environmental Conservation, 46(4),
285–292. https://doi.org/10.1017/S0376 89291 9000110
Oliveira, P. S., & Marquis, R. J. (20 02). The cerrados of Brazil: Ecology an d
natural history of a neotropical savanna. Columbia University Press.
Parolin, P., De Simone, O., Haase, K., Waldhoff, D., Rottenberger, S.,
Kuhn, U., Kesselmeier, J., Kleiss, B., Schmidt, W., Piedade, M. T. F.,
& Junk, W. J. (2004). Central Amazonian floodplain forests: Tree ad-
aptations in a pulsing system. The Botanical Review, 70(3), 357–380.
Pellegrini, A. F. A., Andereg g, W. R. L., Paine, C. E. T., Hoffmann, W.
A., Kartzinel, T., Rabin, S. S., Sheil, D., Franco, A. C., & Pacala, S. W.
(2017). Convergence of bark investment according to fire and climate
structures ecosystem vulnerability to future change. Ecology Letters,
20(3), 307–316. https://doi.org/10.1111/ele.12725
Pettit , N. E., & Naiman , R . J. (2007). Fire in the riparian zone:
Characteristics and ecological consequences. Ecosystems, 10(5),
673–687. https://doi.org /10.10 07/s1002 1-007-9048-5
Pivello, V. R., V ieira, M . V., Grombone-Guar atini, M. T., & Matos, D. M.
S. (2018). Thinking about super-dominant populations of native spe-
cies–examples from Brazil. Perspectives in Ecology and Conservation,
16(2), 74–82. ht tps://doi.org/10.1016/j.pecon.2018.04.001
R Core Team. (2019). R: A language and environment for statis tical comput-
ing. R Foundation for Statistical Computing. Retrieved from https://
www.R-proje ct.org/
Redford, K. H., & da Fonseca, G. A . (1986). The role of gallery forests
in th zoogeography of the cerrado's non-volant mammalian fauna.
Biotropica, 18(2), 126–135. https://doi.org/10.2307/2388755
Resende, A . F., Nelson, B. W., Flores, B. M., & de Almeida, D. R. (2014).
Fire damage in seasonally flooded and upland forests of the Central
Amazon. Biotropica, 46(6), 64 3–6 46. htt ps://doi. org/10 .1111/
btp.1 2153
Ribeiro, J. F., & Walter, B. M. T. (2008). As principais fitofisionomias do
bioma Cer rado. Cerrado: Ecologia E Flora, 1(1), 151–212.
Rull, V., & Montoya, E. (2014). Mauritia flexuosa palm swamp commu-
nities: Natural or human-made? A palynological study of the Gran
Sabana region (northern South America) within a neotropical context.
Quaternary Science Reviews, 99(1), 17–33 . ht tp s://doi .org/10.1016/j.
quasc irev.2014.06.007
Rull, V., Montoya, E ., Nogue, S., Vegas-Vilarrubia, T., & Safont, E . (2013).
Ecological palaeoecology in the neotropical Gran Sabana region: Long-
term rec or ds of ve ge tatio n dy namic s as a basis for ecol og ic al hyp ot h-
esis testing. Perspectives in Plant Ecolog y, Evolution and Systematics,
15(6), 338–359. https://doi.org/10.1016/j.ppees.2013.07.004
Scheffer, M., Carpenter, S., Foley, J. A., Folke, C., & Walker, B. (20 01).
Catastrophic shifts in ecos ystems. Nature, 413 (6856), 591–596.
Schmidt, I. B., Moura, L. C., Ferreira, M. C ., Eloy, L ., Sampaio, A . B., Dias,
P. A., & Berlinck, C. N. (2018). Fire management in the Brazilian sa-
vanna: First steps and the way forward. Journal of Applied Ecology,
55(5) , 20 94–210 1. h tt ps ://doi.or g/10.1111/1365-266 4.13118
Stark, N. M ., & Jordan, C . F. (1978). Nutrient retention by the root mat
of an Amazonian rain forest. Ecology, 59(3), 434–437. https://doi.
org /10. 23 07/1936571
Strassburg, B. B. N., Brooks, T., Feltran-Barbieri, R., Iribarrem, A.,
Crouzeilles, R., Loyola, R., Latawiec , A. E., Oliveira Filho, F. J. B.,
Scaramuzza, C. A. D. M., Scarano, F. R., Soares-Filho, B., & Balmford,
A. (2017). Moment of truth for the Cerrado hotspot. Nature Ec ology &
Evolution, 1(4), 1–3. https://doi.org/10.1038/s4155 9-017-0099
Van Nes, E. H., Staal, A., Hantson, S ., Holmgren, M., Pueyo, S., Bernardi,
R. E., Flores, B. M., Xu, C., & Scheffer, M. (2018). Fire forbids fif-
ty-fifty forest. PLoS ONE, 13(1), e0191027. htt ps://doi.org /10.1371/
journ al.pone.0191027
Veldman, J. W., Buisson, E., Durigan, G ., Fernandes, G. W., Le Str adic, S.,
Mahy, G., Negreiros, D., Overbeck, G. E., Veldman, R. G., Zaloumis,
N. P., Putz, F. E., & Bond, W. J. (2015). Toward an old-grow th concept
for grasslands, savannas, and woodlands. Frontiers in Ecology and the
Environment, 13(3), 154–162. https://doi.org/10.1890/140270
Veldman, J. W., & Putz, F. E. (2011). Grass-dominated vegetation, not
species-diverse natural savanna, replaces degraded tropic al forests
on t he southern edge of the Amazon Basin. Biological Conservation,
144(5), 1419–1429. https://doi.org/10.1016/j.biocon.2011.01.011
12 
|
  
Journal of Applied Ecology
FLORES E t aL.
Wantzen, K. M., Siqueira, A., Cunha, C. N. D., & Pereira de Sá, M. D. F. (2006).
Stream-valley systems of the Brazilian Cerrado: Impact assessment
and conservation scheme. Aquatic Conservation: Marine and Freshwater
Ecosys tems, 16 (7), 713–732. https://doi.org/10.1002/aqc .807
Wickham, H. (2016). ggplot2: Elegant graphics for data analysis. Springer-
Verlag. Retrieved from https://ggplo t2.tidyv erse.org/. ISBN
978-3-319-24277-4.
Zenni, R. D., Sampaio, A. B., Lima, Y. P., Pessoa-Filho, M., Lins, T. C.,
Pivello, V. R., & Daehler, C. (2019). Invasive Melinis minutiflora out-
performs native species, but the magnitude of the effect is contex t-
dependent. Biological Invasions, 21(2), 657–667. https://doi.org/10.1007/
s1053 0-018-1854-5
SUPPORTING INFORMATION
Additional supporting information may be found online in the
Supporting Information section.
How to cite this article: Flores BM, de Sá Dechoum M,
Schmidt IB, et al. Tropical riparian forests in danger from
large savanna wildfires. J Appl Ecol. 2020;00:1–12. ht t p s ://
doi .org /10.1111/1365-26 64.13794
... While most plant species of the open vegetation communities of the Pantanal are fire tolerant, some that are associated with watercourses are sensitive to high-intensity and frequent wildfires (Pivello et al., 2021;Pott, 1994, 2004;Pott et al., 2011). For instance, riparian and gallery forests are both vulnerable to wildfires in tropical savannas systems (Flores et al., 2020;Pivello et al., 2021). In gallery forests, the canopy is connected between the two sides of the river, while in riparian forests the canopies do not join. ...
... Prescribed burning should be conducted during the wet season, early during the short dry periods, or immediately after the rainy season, when the vegetation is still green and moist and the rains can control the fire . Prescribed burning, particularly when informed by traditional knowledge, acts as micro-disturbance (Mistry et al., 2005;Flores et al., 2020). These smaller fires help to restore landscape heterogeneity and can effectively reduce fuel load by decreasing flammability and consequently, reduce the spread of wildfires (Mistry et al., 2005;Garcia et al., 2021;Santos et al., 2021;de Andrade et al., 2021). ...
... Fire impacts are harder on fire-sensitive species, such as Alchornea castaneifolia, Bactris glaucescens, and Genipa americana (Pott and Pott, 1994;Pott and Pott, 2004;, impacting monodominant stands that are also affected by floods (Manrique-Pineda et al., 2021). Fire also damages the canopy of moist forests, such as gallery and riparian forests (Flores et al., 2020). Recurrent and intensive fires reduce the populations of key species, such as G. americana (Pott and Pott, 2004), which is an important food resource for animals, a species of socio-cultural importance for Indigenous people (Libonati et al., 2020) and a potential raw material for a new kind of sustainable plastic (Santos et al., 2017). ...
Article
In 2020, fires in the Pantanal, the world's largest continuous tropical wetland, made global news. The flames destroyed almost one-third of the biome. Furthermore, 43% of the affected area was burnt for the first time in 20 or even more years. As the combination of extreme drought and anthropogenic actions that caused these extreme wildfires is still prevalent, scientifically informed actions are necessary to prevent catastrophic fires in the future. Fire prevention, as well as restoration need to be spatially prioritised, as it is unfeasible to plan actions for the whole extent (150,355 km2) of the Brazilian Pantanal. In this study, we identified areas of high fire risk based on meteorological fire risk tendency for 1980–2020, fire intensity, last year with fire, the recurrence of fires for 2003–2020, and remaining areas of natural forest vegetation around watercourses. These native remnants include unburnt areas that can serve as refuges for fire-sensitive species and are important for fire prevention. We identified 246 km2 with high fire risk, i.e., high probability of megafires, with vegetation types that support fire-sensitive plant species. We found that while 179 km2 had high or medium natural regeneration potential, 66 km2 had low potential and needed active restoration. Over 3120 km2 have been severely degraded by recent fires. About 93% of these areas have high or medium potential for natural regeneration, where the suggested actions are passive restoration and Integrated Fire Management. We estimated the cost of post-fire restoration for areas with high and medium potential for natural regeneration to be around 123 million USD. In areas with low regeneration potential (219 km2), we suggest active restoration. The cost to restore these areas using transplanted seedlings or enrichment planting is estimated between 28 and 151 million USD.
... Under wildfiredriven increased water temperature and debris flows, post-wildfire mortality was higher, and recovery was found to be lower for invasive fish species than for some native fish species in western North America (Sestrich et al., 2011). However, some problematic invasive species have been found both to impact riverine ecosystem structure negatively and to have high resilience to wildfire, thus further increasing ecosystem vulnerability in degraded ecosystems subject to high-severity fires (Aguiar et al., 2021;Flores et al., 2021;Nagler et al., 2005;Whitney et al., 2015). For example, invasive fish species displayed smaller population declines than native species, and only invasive tadpoles or crayfish were present after consecutive wildfires in Gila River, New Mexico (Whitney et al., 2015). ...
... Preliminary observations from the SFMR case study (Box 2) align with previous literature in that, in wildfire-prone landscapes, the interactions of more natural wildfire and flooding regimes are important for increasing the resilience and resistance of ecosystems to disturbances so that net gains in biodiversity can be achieved (Bixby et al., 2015;Nagler et al., 2005;Robinne et al., 2021). This is particularly relevant given that even broadly unaltered flood and wildfire regimes are often in a state of flux owing to climatic changes (Bisson et al., 2003;Flores et al., 2021). ...
Article
Full-text available
Background: Historically, wildfire regimes produced important landscape-scale disturbances in many regions globally. The “pyrodiversity begets biodiversity” hypothesis suggests that wildfires that generate temporally and spatially heterogeneous mosaics of wildfire severity and post-burn recovery enhance biodiversity at landscape scales. However, river management has often led to channel incision that disconnects rivers from their floodplains, desiccating floodplain habitats and depleting groundwater. In conjunction with predicted increases in frequency, intensity, and extent of wildfires under climate change, this increases the likelihood of deep, uniform burns that reduce biodiversity. Predicted synergy of river restoration and biodiversity increase: Recent focus on flood-plain re-wetting and restoration of successional floodplain habitat mosaics, developed for river management and flood prevention, could reduce wildfire intensity in restored floodplains and make the burns less uniform, increasing climate-change resilience; an important synergy. According to theory, this would also enhance biodiversity. However, this possibility is yet to be tested empirically. We suggest potential research avenues. Illustration and future directions: We illustrate the interaction between wildfire and river restoration using a restoration project in Oregon, USA. A project to reconnect the South Fork McKenzie River and its floodplain suffered a major burn (“Holiday Farm” wild-fire, 2020), offering a rare opportunity to study the interaction between this type of river restoration and wildfire; specifically, the predicted increases in pyrodiversity and biodiversity. Given the importance of river and wetland ecosystems for biodiversity globally, a research priority should be to increase our understanding of potential mechanisms for a “triple win” of flood reduction, wildfire alleviation, and biodiversity promotion.
... Furthermore, when uncontrolled, fire in these ecosystems causes chemical and water stress in the soil, which drastically alters the amount of biomass, making these ecosystems more susceptible to megafires, which-when recurrent-convert forests into more open vegetation ecosystems (Dezzeo and Chacón, 2005). With this, we can affirm that the practice of protection maintains these firesensitive ecosystems, also known as "Fire refugia" (Meddens et al., 2018), and consequently conserves important ecological functions for the entire biome, because these sites help maintain trophic chains, act as a refuge for fauna, and function as a seed bank to repopulate burned areas (Meddens et al., 2018;Flores et al., 2021). Complementary to protection, prevention is done in savanna and grassland ecosystems. ...
... Drastic changes in the planet's climate are a real problem to be mitigated (IPCC, 2021) and several studies have shown that high temperatures, extreme droughts and accumulation of combustible material are the main causes of the megafires that have been occurring more frequently in tropical savannas and that prescribed burning may be a feasible solution for this problem (Eloy et al., 2018a;Fidelis et al., 2018;Mistry et al., 2018;Schmidt et al., 2018;Moura et al., 2019;Schmidt and Eloy, 2020;Pivello et al., 2021;Roberts et al., 2021). Flores et al. (2021) stated that integrated management plans require strategies that consider forests as a vulnerable element of the system. The practices proposed by scientists are part of the strategies carried out by small-scale societies throughout the history of occupation of the South American savannas, but our results show that prevention and ecosystem protection do not maintain ecosystems on their own (Figure 4). ...
Article
Full-text available
The tropical South American savannas have been occupied and manipulated by humans since the late Pleistocene. Ecologists consider that soils, hydrology, and seasonal precipitation influence the structure and composition of plants and the fire-proneness of savannas. However, the human influence on these dynamics remains uncertain. This is because little is known about human activities and what influence they have on the diversity of ecosystems. Considering this, our study sought to synthesize the management practices used by small-scale societies of the South American savannas, compile the species that are the focus of direct management, and demonstrate the role of this management in maintaining the diverse ecosystems that make up the savannas. We also set out to test the hypotheses that forms of management differ depending on the ecosystem and cultural matrices. To do so, we conducted a systematic review, in which we collected 51 articles with information about the management carried out by small-scale societies. From this, we categorized 10 management practices directed to ecosystems: protection of the ecosystem, enrichment of species, topographic changes, increased soil fertility, cleaning, prevention of fire, resource promotion, driving of game, swidden-fallow, and maintenance of ecosystem structure. We identified 19 native plant species whose populations are managed in-situ . These management practices have proven capable of keeping savanna and grassland ecosystems open and increasing the occurrence of forest ecosystems in the mosaic, as well as favoring plants of human interest in general. We note that there is a relationship between management practices with ecosystems and cultures, which suggests that both factors influence the management of landscapes. We conclude that management practices of small-scale societies are responsible for domesticating South American tropical savannas and that these savannas are composed of a mosaic of culturally constructed niches. The small-scale societies that inhabit these environments have important traditional ecological knowledge and strategies that enable the use, conservation, and restoration of savannas, extremely threatened by agribusiness today. Systematic Review Registration : [website], identifier [registration number].
... Essas alterações no padrão chuvoso associados a condições mais atmosféricas de secura oferecem condições favoráveis para o aumento de FC naturais no Brasil, assim como também facilita a propagação de incêndios por indução humana (Vasconcelos et al., 2015;Pereira & Silva, 2016). Destaca-se o aumento significativo no número de FC no Mato Grosso do Sul, situado no Bioma Pantanal, com valores entre 10-25 mil FC, motivado pelo longo período de estiagem resultante da escassez de chuvas conforme constatado por Marengo et al. (2021), que resultou em grandes incêndios no período (Flores et al., 2021). Os incêndios florestais pan-tropicais aumentarão a vulnerabilidade das florestas a medida que estas forem danificadas e menos resistentes ao fogo cobrirem a paisagem e ocorrerem episodicamente mais severos durante os eventos de El Niño (Cochrane, 2003). ...
... Esse padrão crescente no número de FC é resultante das ações antrópicas como o desmatamento para o extensivo uso e ocupação do solo para agricultura(Assis et al., 2021). O desmatamento é uma prática comum no processo de transformação de florestas em terras para atividades agropecuárias(Dias et al., 2016;Oliveira-Júnior et al., 2021), sendo verificado em diversas regiões na AS(Fonseca et al., 2017;Diniz et al., 2019;Flores et al., 2021). Este processo de conversão ocorre de duas formas: (i) os agricultores desmatam a floresta, cultivam a terra, deixando-a se restaurar ao estado natural de floresta; e (ii) realizado com a intenção de se estabelecer permanentemente atividades agropecuárias(Assis et al., 2021;.Além dos fatores antrópicos, a atuação do ENOS também condiciona a ocorrência de FC ao longo do Brasil (Santos et al., 2014). ...
Article
Full-text available
The emergence of forest fires may be of anthropic or natural origin, both of which cause significant socioeconomic and environmental damage, and in the good part of these occurrences are resulting from Fire Foci (FF) occurrence. In recent years, Brazil has suffered from a significant increase in FF, resulting in large fires. In this way, the objective of the present study was to diagnose the spatiotemporal FF behavior in Brazil between 1999 à 2020, based on the BDQueimadas data of the CPTEC/INPE. The handling and processing of the data used the R version 3.4-1 environment software. After the data storage, it calculated the total, annual, and monthly records. And the composition of the most significant years, in this case, the years 2015, 2017, 2019, and 2020. The results pointed out that the most significant total and average annual accumulations ranged between 10-50 thousand FF and 0.5-1.5 thousand FF, respectively, concentrated in the central-northern region of Brazil, mainly in Maranhão, Pará, and the Tocantins. This pattern of high FC records is related to deforestation and agricultural expansion in these regions. On a monthly scale, the most significant occurrences of FF occur between August and November, with 0.2-0.45 thousand FF, due to starvation. In recent years, the El Niño-Southern Oscillation influenced the annual FF performance through the persistence of long stretches of styling, which resulted in a shortage of rainfall and large fires verified in 2020 in the Pantanal biome.
... Saritha et al. (2019) observed a loss of more than 50% of riparian forest, which is associated with braid bars in the Chalakudy river of Western Ghats due to the 2018 flood in Kerala. Flores et al. (2021) indicated the effect of large savanna wildfires on tropical riparian forests. They observed a drop in canopy cover from 90 to 20% after the wildfire in 2017. ...
Article
Ecosystems across the globe, be it terrestrial, marine or transitional in nature are under pressure due to multiple drivers of changes including anthropogenic. Restoring the vitality of degraded systems is crucial for fulfilling the UN-Sustainable Development Goals in a timely manner. It is also essential for attaining the targets of the ambitious UN-Decade on Ecosystem Restoration (UN-DER). Riparian ecosystems are one among systems undergoing drastic changes due to anthropogenic pressures. They are a heterogeneous and biodiversity rich system due to its transitional zone occurrence between terrestrial and aquatic realms, including riverbanks, floodplains and wetlands, and provide ecosystem services on both local as well as global levels. Here we review the prospects of restoring riparian ecosystems in the context of the UNDER. Even though the momentum for restoring riparian habitats began in the 1970s, our study reveals that intensive restoration programmes across the world are sparse and more efforts are needed to restore degraded riparian systems for regaining ecosystem health and complexity. Furthermore, an in-depth analysis of various strategies deployed for restoring riparian ecosystems around the world reveals that a participatory approach and site-specific strategies are needed for better output. Also, active along with passive restoration is required for better recovery. We suggest a three-stage strategy-preassessment, restoration activities and post monitoring and maintenance. It includes the involvement of stakeholders across all stages, which also supports their livelihoods. The restoration of riparian ecosystems supports the targets of UNDER while providing both global as well as local ecosystem services.
... High FRP values towards the end of the dry season are consistent with a significant increase in fuel curing, leading to higher fire intensity, extent and severity in open savannas (Rissi et al., 2017;Rodrigues et al., 2021;Dos Santos et al., 2021). These late dry season wildfires commonly affect fire-sensitive vegetation, such as riparian forests, with high severity and negative impacts (Flores et al., 2020). However, the relationship between fire size and FRP in savannas and grasslands is complex, depending on the spatial fuel continuity, fuel load, fire season and moisture content (Laurent et al., 2019). ...
Article
The Brazilian savanna (Cerrado) is considered the most floristically diverse savanna in the world, home to more than seven thousand species. The region is a mosaic of savannas, grasslands and forests whose unique biophysical and landscape attributes are on the basis of a recent ecoregional map, paving the way to improved region-based strategies for land management actions. However, as a fire-prone ecosystem, Cerrado owes much of its distribution and ecological properties to the fire regime and contributes to an important parcel of South America burned area. Accordingly, any attempt to use ecoregion geography as a guide for management strategies should take fire into account, as an essential variable. The main aim of this study is to complement the ecoregional map of the Cerrado with information related to the fire component. Using remotely sensed information, we identify patterns and trends of fire frequency, intensity, seasonality, extent and scar size, and combine this information for each ecoregion, relying on a simple classification that summarizes the main fire characteristics over the last two decades. Results show a marked north-south fire activity gradient, with increased contributions from MATOPIBA, the latest agricultural frontier. Five ecoregions alone account for two thirds of yearly burned area. More intense fires are found in the Arc of Deforestation and eastern ecoregions, while ecoregions in MATOPIBA display decreasing fire intensity. An innovative analysis of fire scars stratified by size class shows that infrequent large fires are responsible for the majority of burned area. These large fires display positive trends over many ecoregions, whereas smaller fires, albeit more frequent, have been decreasing in number. The final fire classification scheme shows well defined spatially-aggregated groups, where trends are found to be the key factor to evaluate fire within their regional contexts. Results presented here provide new insights to improve fire management strategies under a changing climate.
... An additional threat is forest expansion over savannas, which reduces savanna biodiversity. The resultant lower herbaceous fuel also feeds back to the system, by reducing fire in the wet season and potentially increase the risk of catastrophic fires in the dry season, as the forest vegetation is more sensitive (Durigan and Ratter, 2016;Flores et al., 2021;Hoffmann et al., 2012a). ...
Article
Humans have changed vegetation dynamics in Neotropical savannas by suppressing fires, allowing trees and shrubs to expand into ancient savanna landscapes in a process known as woody encroachment. This woody encroachment drives the loss of biodiversity and modifies the functioning of savanna ecosystems. Here we combine satellite data analysis with an experimental approach to test the hypothesis that long-term management by clear-cutting helps restore the diversity and functional composition of open savannas. First, we used Landsat time series of the Normalized Difference Water Index, to assess changes in vegetation structure, comparing experimental areas with open savannas in the same region. We then obtained field experimental evidence comparing areas managed during 30 years versus unmanaged areas, including data on vegetation structure and composition. Our results from satellite image analyses indicate that, before the first clear-cutting, vegetation structure was similar in managed and unmanaged sites, and both differed from open savanna. When clear-cutting manipulation started, NDWI of managed areas became persistently lower than that of unmanaged control areas. In the field, we found that in managed areas, species diversity and richness of typical savanna species had increased, and that species composition had changed to become more similar to open savannas. We also observed the recovery of savanna functional composition, suggesting that ecosystem processes were restored by clear-cutting management. Our findings reveal that the repeated removal of dominant woody species by clear-cutting has contributed to maintain the diversity and functioning of savannas degraded by forest encroachment.
... Dry and wet grasslands and savannas cover most of the landscape and occur in between streams. Dry deciduous forests are found at the northwest edge of the park, whereas riparian evergreen forests are most common at the southwest edge of the park (Flores et al., 2020). In total, the CVNPK comprises 77% of savanna formation, and about 10% corresponds to the forest fragments (Porto et al., 2011). ...
Article
Tropical savanna ecosystems play a major role in the seasonality of the global carbon cycle. However, their ability to store and sequester carbon is uncertain due to combined and intermingling effects of anthropogenic activities and climate change, which impact wildfire regimes and vegetation dynamics. Accurate measurements of tropical savanna vegetation aboveground biomass (AGB) over broad spatial scales are crucial to achieve effective carbon emission mitigation strategies. UAV-lidar is a new remote sensing technology that can enable rapid 3-D mapping of structure and related AGB in tropical savanna ecosystems. This study aimed to assess the capability of high-density UAV-lidar to estimate and map total (tree, shrubs, and surface layers) aboveground biomass density (AGBt) in the Brazilian Savanna (Cerrado). Five ordinary least square regression models estimating AGBt were adjusted using 50 field sample plots (30 m × 30 m). The best model was selected under Akaike Information Criterion, adjusted coefficient of determination (adj.R2), absolute and relative root mean square error (RMSE), and used to map AGBt from UAV-lidar data collected over 1,854 ha spanning the three major vegetation formations (forest, savanna, and grassland) in Cerrado. The model using vegetation height and cover was the most effective, with an overall model adj-R2 of 0.79 and a leave-one-out cross-validated RMSE of 19.11 Mg/ha (33.40%). The uncertainty and errors of our estimations were assessed for each vegetation formation separately, resulting in RMSEs of 27.08 Mg/ha (25.99%) for forests, 17.76 Mg/ha (43.96%) for savannas, and 7.72 Mg/ha (44.92%) for grasslands. These results prove the feasibility and potential of the UAV-lidar technology in Cerrado but also emphasize the need for further developing the estimation of biomass in grasslands, of high importance in the characterization of the global carbon balance and for supporting integrated fire management activities in tropical savanna ecosystems. Our results serve as a benchmark for future studies aiming to generate accurate biomass maps and provide baseline data for efficient management of fire and predicted climate change impacts on tropical savanna ecosystems.
Article
Full-text available
Tropical forests are complex systems containing myriad interactions and feedbacks with their biotic and abiotic environments, but as the world changes fast, the future of these ecosystems becomes increasingly uncertain. In particular, global stressors may unbalance the feedbacks that stabilize tropical forests, allowing other feedbacks to propel undesired changes in the whole ecosystem. Here, we review the scientific literature across various fields, compiling known interactions of tropical forests with their environment, including the global climate, rainfall, aerosols, fire, soils, fauna, and human activities. We identify 170 individual interactions among 32 elements that we present as a global tropical forest network, including countless feedback loops that may emerge from different combinations of interactions. We illustrate our findings with three cases involving urgent sustainability issues: (1) wildfires in wetlands of South America; (2) forest encroachment in African savanna landscapes; and (3) synergistic threats to the peatland forests of Borneo. Our findings reveal an unexplored world of feedbacks that shape the dynamics of tropical forests. The interactions and feedbacks identified here can guide future qualitative and quantitative research on the complexities of tropical forests, allowing societies to manage the nonlinear responses of these ecosystems in the Anthropocene. Tropical forests are complex systems containing myriad interactions and feedbacks with their biotic and abiotic environments, but as the world changes fast, the future of these ecosystems becomes increasingly uncertain. Our findings reveal an unexplored world of feedbacks that shape the dynamics of tropical forests. The interactions and feedbacks identified can guide future qualitative and quantitative research on the complexities of tropical forests, allowing societies to manage the nonlinear responses of these ecosystems in the Anthropocene.
Article
As a result of anthropogenic pressure, three drives are expected to affect Brazilian savannas: an increase in the dry season, more frequent fire events, and defaunation. These drivers are a trigger for biodiversity loss and undermine the ecosystems services like carbon storage. Here our goal was to analyze how these drivers can affect the structure and dynamics of the savanna's tree species and how they impact the savanna's total estimating aboveground biomass (AGB). We analysed eight sites that comprise a physiognomic gradient from open savanna to savanna woodland. The species were classified by three traits: phenological strategies (deciduous or evergreen), fire resistance (resprouting or non-resprouting), and dispersal syndrome (animal or non-animal). Then, we modelled AGB loss in a dry season in the austral winter, a 2 • C increase in daily temperature, five fire events by decadal-series, and a defaunation scenario. Although climate change, change in fire frequency, and defau-nation effects impact AGB separately, they also have a synergistic effect. This effect was observed in functional strategies and also in the total AGB of the community. In some cases, the total AGB loss exceeded 70%. The negative effects on performance were highest in species which were decidual, non-resprouting, and which employed animal dispersal for their seed. If different types of disturbances are not controlled in the near future, savanna communities will be dominated by evergreen, resprouters, and non-animal dispersed species, representing a steeply decline in the diversity of species and ecosystem functions.
Article
Full-text available
Bark is a structure involved in multiple physiological functions, but which has been traditionally associated with protection against fire. Thus, little is known about how the morpho-anatomical variations of this structure are related to different ecological pressures, especially in tropical savanna species, which are commonly subjected to frequent fire and drought events. Here we evaluated how the structural and functional variations of bark are related to the processes of resilience and resistance to fire, as well as transport and storage of water in 31 native species from the Brazilian Cerrado. Because of their thick bark, none of the trees analyzed were top-killed after a severe fire event. The structural and functional variations of the bark were also associated with water storage and transport, functions related to properties of the inner bark. In fact, species with a thicker and less dense inner bark were the ones that had the highest water contents in the wood, bark, and leaves. Lower bark density was also related to higher stem hydraulic conductivity, carbon assimilation, and growth. Overall, we provide strong evidence that in addition to protection from fire, the relative investment in bark also reflects different strategies of water use and conservation among many Cerrado tree species.
Article
Full-text available
Over recent decades, biomass gains in remaining old-growth Amazonia forests have declined due to environmental change. Amazonia’s huge size and complexity makes understanding these changes, drivers, and consequences very challenging. Here, using a network of permanent monitoring plots at the Amazon–Cerrado transition, we quantify recent biomass carbon changes and explore their environmental drivers. Our study area covers 30 plots of upland and riparian forests sampled at least twice between 1996 and 2016 and subject to various levels of fire and drought. Using these plots, we aimed to: (1) estimate the long-term biomass change rate; (2) determine the extent to which forest changes are influenced by forest type; and (3) assess the threat to forests from ongoing environmental change. Overall, there was no net change in biomass, but there was clear variation among different forest types. Burning occurred at least once in 8 of the 12 riparian forests, while only 1 of the 18 upland forests burned, resulting in losses of carbon in burned riparian forests. Net biomass gains prevailed among other riparian and upland forests throughout Amazonia. Our results reveal an unanticipated vulnerability of riparian forests to fire, likely aggravated by drought, and threatening ecosystem conservation at the Amazon southern margins.
Article
Full-text available
Background Tropical forests are threatened by intensifying natural and anthropogenic disturbance regimes. Disturbances reduce tree cover and leave the organic topsoil vulnerable to erosion processes, but when resources are still abundant forests usually recover. Scope Across the tropics, variation in rainfall erosivity – a measure of potential soil exposure to water erosion – indicates that soils in the wetter regions would experience high erosion rates if they were not protected by tree cover. However, twenty-first-century global land cover data reveal that in wet South America tropical tree cover is decreasing and bare soil area is increasing. Here we address the role of soil erosion in a positive feedback mechanism that may persistently alter the functioning of disturbed tropical forests. Conclusions Based on an extensive literature review, we propose a conceptual model in which soil erosion reinforces disturbance effects on tropical forests, reducing their resilience with time and increasing their likelihood of being trapped in an alternative vegetation state that is persistently vulnerable to erosion. We present supporting field evidence from two distinct forests in central Amazonia that have been repeatedly disturbed. Overall, the strength of the erosion feedback depends on disturbance types and regimes, as well as on local environmental conditions, such as topography, flooding, and soil fertility. As disturbances intensify in tropical landscapes, we argue that the erosion feedback may help to explain why certain forests persist in a degraded state and often undergo critical functional shifts.
Article
Full-text available
Extensively managed grasslands are recognized globally for their high biodiversity and their social and cultural values. However, their capacity to deliver multiple ecosystem services (ES) as parts of agricultural systems is surprisingly understudied compared to other production systems. We undertook a comprehensive overview of ES provided by natural and semi‐natural grasslands, using southern Africa (SA) and northwest Europe as case studies, respectively. We show that these grasslands can supply additional non‐agricultural services, such as water supply and flow regulation, carbon storage, erosion control, climate mitigation, pollination, and cultural ES. While demand for ecosystems services seems to balance supply in natural grasslands of SA, the smaller areas of semi‐natural grasslands in Europe appear to not meet the demand for many services. We identified three bundles of related ES from grasslands: water ES including fodder production, cultural ES connected to livestock production, and population‐based regulating services (e.g., pollination and biological control), which also linked to biodiversity. Greenhouse gas emission mitigation seemed unrelated to the three bundles. The similarities among the bundles in SA and northwestern Europe suggest that there are generalities in ES relations among natural and semi‐natural grassland areas. We assessed trade‐offs and synergies among services in relation to management practices and found that although some trade‐offs are inevitable, appropriate management may create synergies and avoid trade‐offs among many services. We argue that ecosystem service and food security research and policy should give higher priority to how grasslands can be managed for fodder and meat production alongside other ES. By integrating grasslands into agricultural production systems and land‐use decisions locally and regionally, their potential to contribute to functional landscapes and to food security and sustainable livelihoods can be greatly enhanced.
Article
Full-text available
The year 2017 was a megafire year, when huge areas burned on different continents. In Brazil, a great extension of the Cerrado burned, raising once more the discussion about the "zero-fire" policy. Indeed, most protected areas of the Cerrado adopted a policy of fire exclusion and prevention, leading to periodic megafire events. Last year, 78% of the Chapada dos Veadeiros National Park burned at the end of the dry season, attracting media attention. Furthermore, 85% of the Reserva Natural Serra do Tombador burned as a result of a large accumulation of fuel caused by the zero-fire policy. In 2014, some protected areas started to implement the Integrate Fire Management (IFM) strategy. During 2017, in contrast to other protected areas, the Estação Ecológica Serra Geral do Tocantins experienced no megafire events, suggesting that a few years of IFM implementation led to changes in its fire regime. Therefore, we intended here to compare the total burned area and number of fire scars between the protected areas where IFM was implemented and those where fire exclusion is the adopted policy. The use of fire as a management tool aimed at wildfire prevention and biodiversity preservation should be reconsidered by local managers and environmental authorities for most Cerrado protected areas, especially those where open savanna physiognomies prevail. Changing the paradigm is a hard task, but last year's events showed the zero-fire policy would bring more damage than benefits to Cerrado protected areas.
Article
Full-text available
Impacts of invasive species are context-dependent owing to genetic differences in the invasive species, in the abiotic environment or the recipient biotas. Here, we tested how these factors affected the invasive grass Melinis minutiflora and its impacts on native plants in Hawai’i (USA) and in the Brazilian Cerrado under four environmental conditions. We sampled M. minutiflora and three native species from each studied region and conducted two equivalent greenhouse experiments. In each experiment, we manipulated shade, irrigation, soil nutrients, and interspecific competition. We found that M. minutiflora had low genetic polymorphism, and two distinct genetic clusters exist. Both clusters exist in Hawai’i and Brazil. Melinis minutiflora biomass was three-times greater in Brazil compared to Hawai’i. Both in Brazil and Hawai’i, M. minutiflora was affected by shade, irrigation, and competition. While in Brazil the identity of the competing native species did not matter for M. minutiflora, in Hawai’i the identity of the native species affected M. minutiflora when shade was applied. Brazilian native species were all affected by shading, two of them by competition with M. minutiflora, and one of them by fertilization. Two Hawaiian native plants were affected by shade and competition with M. minutiflora, whereas one native species was not affected by any of the experimental factors. In summary, both biotic and abiotic factors affected native and invasive species. However, in all cases native species were outperformed by the invader.
Article
Infernos in South America’s Pantanal region have burnt twice the area of California’s fires this year. Researchers fear the rare ecosystem will never recover. Researchers fear South America’s Pantanal region will never recover.
Article
Fire-prone invasive grasses create novel ecosystem threats by increasing fine-fuel loads and continuity, which can alter fire regimes. While the existence of an invasive grass-fire cycle is well known, evidence of altered fire regimes is typically based on local-scale studies or expert knowledge. Here, we quantify the effects of 12 nonnative, invasive grasses on fire occurrence, size, and frequency across 29 US ecoregions encompassing more than one third of the conterminous United States. These 12 grass species promote fire locally and have extensive spatial records of abundant infestations. We combined agency and satellite fire data with records of abundant grass invasion to test for differences in fire regimes between invaded and nearby “uninvaded” habitat. Additionally, we assessed whether invasive grass presence is a significant predictor of altered fire by modeling fire occurrence, size, and frequency as a function of grass invasion, in addition to anthropogenic and ecological covariates relevant to fire. Eight species showed significantly higher fire-occurrence rates, which more than tripled for Schismus barbatus and Pennisetum ciliare. Six species demonstrated significantly higher mean fire frequency, which more than doubled for Neyraudia reynaudiana and Pennisetum ciliare . Grass invasion was significant in fire occurrence and frequency models, but not in fire-size models. The significant differences in fire regimes, coupled with the importance of grass invasion in modeling these differences, suggest that invasive grasses alter US fire regimes at regional scales. As concern about US wildfires grows, accounting for fire-promoting invasive grasses will be imperative for effectively managing ecosystems.
Article
Despite growing recognition of the conservation values of grassy biomes, our understanding of how to maintain and restore biodiverse tropical grasslands (including savannas and open‐canopy grassy woodlands) remains limited. To incorporate grasslands into large‐scale restoration efforts, we synthesised existing ecological knowledge of tropical grassland resilience and approaches to plant community restoration. Tropical grassland plant communities are resilient to, and often dependent on, the endogenous disturbances with which they evolved – frequent fires and native megafaunal herbivory. In stark contrast, tropical grasslands are extremely vulnerable to human‐caused exogenous disturbances, particularly those that alter soils and destroy belowground biomass (e.g. tillage agriculture, surface mining); tropical grassland restoration after severe soil disturbances is expensive and rarely achieves management targets. Where grasslands have been degraded by altered disturbance regimes (e.g. fire exclusion), exotic plant invasions, or afforestation, restoration efforts can recreate vegetation structure (i.e. historical tree density and herbaceous ground cover), but species‐diverse plant communities, including endemic species, are slow to recover. Complicating plant‐community restoration efforts, many tropical grassland species, particularly those that invest in underground storage organs, are difficult to propagate and re‐establish. To guide restoration decisions, we draw on the old‐growth grassland concept, the novel ecosystem concept, and theory regarding tree cover along resource gradients in savannas to propose a conceptual framework that classifies tropical grasslands into three broad ecosystem states. These states are: (1) old‐growth grasslands (i.e. ancient, biodiverse grassy ecosystems), where management should focus on the maintenance of disturbance regimes; (2) hybrid grasslands, where restoration should emphasise a return towards the old‐growth state; and (3) novel ecosystems, where the magnitude of environmental change (i.e. a shift to an alternative ecosystem state) or the socioecological context preclude a return to historical conditions.