DOI: 10.5061/dryad.vq83bk3s5
title: Data from: Size, species, and fire behavior predict tree and liana mortality from experimental burns in the Brazilian Amazon

description: Anthropogenic understory fires have affected large areas of tropical
 forest in recent decades, particularly during severe droughts. Yet, the
 mechanisms that control fire-induced mortality of tropical trees and
 lianas remain ambiguous due to the challenges associated with documenting
 mortality given variation in fire behavior and forest heterogeneity. In a
 seasonally dry Amazon forest, we conducted a burn experiment to quantify
 how increasing understory fires alter patterns of stem mortality. From
 2004 to 2007, tree and liana mortality was measured in adjacent 50-ha
 plots that were intact (B0 – control), burned once (B1), and burned
 annually for 3 years (B3). After 3 years, cumulative tree and liana
 mortality (≥1 cm dbh) in the B1 (5.8% yr−1) and B3 (7.0% yr−1)
 plots significantly exceeded mortality in the control (3.2% yr−1).
 However, these fire-induced mortality rates are substantially lower than
 those reported from more humid Amazonian forests. Small stems were highly
 vulnerable to fire-induced death, contrasting with drought-induced
 mortality (measured in other studies) that increases with tree size. For
 example, one low-intensity burn killed &gt;50% of stems
 &lt;10 cm within a year. Independent of stem size,
 species-specific mortality rates varied substantially from 0% to 17%
 yr−1 in the control, 0% to 26% yr−1 in B1, and 1% to 23%
 yr−1 in B3, with several species displaying high variation in
 their vulnerability to fire-induced mortality. Protium
 guianense (Burseraceae) exhibited the highest fire-induced
 mortality rates in B1 and B3, which were 10- and 9-fold greater than the
 baseline rate. In contrast, Aspidosperma
 excelsum (Apocynaceae), appeared relatively unaffected by fire
 (0.3% to 1.0% mortality yr−1 across plots), which may be
 explained by fenestration that protects the inner concave trunk portions
 from fire. For stems ≥10 cm, both char height (approximating fire
 intensity) and number of successive burns were significant predictors of
 fire-induced mortality, whereas only the number of consecutive annual
 burns was a strong predictor for stems &lt;10 cm. Three years
 after the initial burn,
 62 ± 26 Mg ha−1 (s.e.) of
 live biomass, predominantly stems &lt;30 cm, was transferred
 to the dead biomass pool, compared with
 8 ± 3 Mg ha−1 in the control.
 This biomass loss from fire represents ∼30% of this forest's
 aboveground live biomass (192 (±3) Mg ha−1;
 &gt;1 cm DBH). Although forest transition to savanna has been
 predicted based on future climate scenarios, our results indicate that
 wildfires from agricultural expansion pose a more immediate threat to the
 current carbon stocks in Amazonian forests.
description: These files contain the abundance data of trees in two fire
 experiments. Both experiments are located in a transitional forest in Mato
 Grosso, Brazil, in the southern part of the Amazon Basin
 (13o04’S,52o23’W). In the first experiment, three 50 ha (50 x 1000 m)
 plots bordering a crop field were established in 2004 (“Big-plot”
 experiment from hereafter). In each plot, transects of 500 m in length and
 20 m in width were created at 10, 30, 100, 250, 500, and 750 m from the
 forest edge and all trees with diameter at breast height (i.e., 1.3 m from
 the ground; dbh) greater than 20 cm were measured within these transects.
 One of these plots was left unburned (i.e., Control), one plot was burned
 thrice (2004, 2007, and 2010; hereafter “B3yr” treatment) and the
 remaining plot was burned yearly from 2004 to 2010, except in 2008
 (hereafter “B1yr” treatment). Trees were measured in 2004, 2008, 2010,
 2012 and 2016, always prior to the experimental fires. Additional details
 regarding this experiment are available in Balch et al. (2011). 
 The second experiment evaluated the effect of fuel addition and
 fire frequency on fire intensity and tree mortality. This experiment
 followed a randomized block design, with a total of 6 blocks and 4 plots
 of 40 m x 40 m within each block (“Block” experiment from hereafter). All
 trees with dbh greater than 5 cm were measured within these plots.
 Treatments consisted of unburned plots (control area), plots burned once
 in 2016 under natural conditions (i.e., no fuel addition), plots burned
 twice (2013 and 2016) under natural conditions, and plots burned twice
 (2013 and 2016) with fuel addition (50% increase in fine fuel loads) only
 before the 2013 fire. In this experiment, trees were measured yearly from
 2011 to 2018, except for 2017, always prior to the experimental fires.
 Additional details regarding this experiment are available in Brando et
 al. (2016). 
description: For the "Big-plot" data, the column "treat"
 corresponds to the fire treatments: "C"= control plot
 (unburned), "B3yr"=plot burned thrice, and "B1yr"=plot
 burned yearly. The columns "d.edge" and "year"
 correspond to distance to edge of the forest and calendar year,
 respectively. Forest inventory were always conducted prior to the
 experimental fires. All the remaining columns have the acronyms of the
 corresponding species. The full name associated with the acronyms for each
 species is given in the file "Species Tanguro" in the
 spreadsheet "Bigplot". Numbers in each cell are the number of
 trees for a particular species, in a particular transect and year. Only
 trees greater than 20 cm in diameter at breast height were
 included. For the "Block" data, the column
 "treat" corresponds to the fire treatments:
 "fire2016"= plot burned once in 2016,
 "control"=control plot (unburned), "fire2013.2016"=
 plot burned twice (once in 2013 and once in 2016), and
 "fire2013.2016.fuel.addition"= plot burned twice (once in 2013
 and once in 2016) with fuel addition in 2013. The columns "plot"
 and "year" correspond to the plot identified and calendar year,
 respectively. Forest inventory were always conducted prior to the
 experimental fires. All the remaining columns have the acronyms of the
 corresponding species. The full name associated with the acronyms for each
 species is given in the file "Species Tanguro" in the
 spreadsheet "Block". Numbers in each cell are the number of
 trees for a particular species, in a particular plot and year. Only trees
 greater than 5 cm in diameter at breast height were included.