DOI: 10.5061/dryad.56hb7gf
title: Data from: Rare frost events reinforce tropical savanna-forest boundaries

description: 1) The ability of vegetation to ameliorate or exacerbate environmental
 extremes can generate feedbacks that mediate the distribution of biomes.
 It has been suggested that feedbacks between vegetation and frost damage
 may be important for maintaining savanna, particularly at the edge of the
 tropics. 2) We quantified frost damage and air temperature across a
 network of 30 permanent plots distributed across tropical savanna-forest
 boundaries in Brazil during an uncommonly hard frost. 3) Tree cover
 strongly buffered temperatures during frost events, such that forest sites
 were up to 5°C warmer than nearby sites occupied by open shrub savanna.
 Consequently, in forest, woody plants were not damaged, but in savanna
 there was extensive dieback of trees and shrubs. Within savanna, frost had
 disproportionately large effects on small individuals, likely due to
 colder temperatures near the ground and the lower thermal mass of thin
 stems. Across species, frost tolerance was strongly correlated with
 latitudinal range limit, revealing the importance of minimum temperature
 as a species filter at the regional scale. Counterintuitively, savanna
 species, which are adapted to open habitats where frost is more likely,
 were more vulnerable to cold than were forest species and experienced more
 than twice the amount of leaf damage as co-occurring forest species. 4)
 Synthesis: Frost reinforces the effects of fire on vegetation structure by
 preferentially damaging trees in open environments and generating high
 loads of dead, flammable fuels. However, frost does not currently occur
 with sufficient frequency in the region to maintain open savanna by
 itself. Nevertheless, it occurs with sufficient frequency and severity
 that it likely acts as a partial environmental filter and evolutionary
 pressure for some of the most frost-sensitive species.
description: r code for
 analysesFrostAnalyses.rPhylogenic tree of principal species.This is the phylogenetic tree used for performing phylogenetically corrected tests.FrostPhylogeny.txtSpecies data for phylogenetic analysesA) species: binary latin name. B) T50: The estimated temperature at which 50% of individuals were damaged (C). C) Type: s = savanna specialist, f = forest specialist or generalist. D) Lat: Latitude of southern range limit (degrees) E) Bio6: The climatological mean temperature of the coldest month from the WorldClim 2.0 database (http://www.worldclim.org/) at the cold limit of the species range.FrostTraits.csvData file with individual-level frost damage data.This file contains the following fields:A) P: Plot identifier number. B) PlotBasalArea: Tree basal area of the plot (m^2/ha). C) MinTemp: Predicted minimum air temperature on the coldest night at height of 1 m (C). D) Phys: Physiognomy of the plot 0 = shrub savanna, 1 = tree savanna, 2 = forest. E) TagNumber: Identifier number for trees that were permanently tagged. F) Species: Binomial latin name. G) Species.Code: Four-letter abbreviation of species. H) Type: S = savanna specialist, F = forest specialist or generalist. I) InitialHeight: Height prior to frost (cm) J) FinalHeight: Height one year after frost (cm) K) LeafDamage: Fraction of leaf area damaged, as visually estimated several days after the coldest frost event (cm). L) DiebackHeight: The height from which the stem resprouted, as determined one year after the severe frost (cm). M) Dieback.length: The loss amount of stem height lost due to dieback (cm). N) CrownExposure: A unitless index of canopy exposure: 1 = receiving no direct light; 2 = receiving some direct lateral light; 3 = receiving some direct overhead light, but with &lt;90% of the crown exposed to overhead light; 4 = receiving direct overhead light on &gt;90% of the vertical projection of the crown; 5 = receiving direct light on all sides (an emergent tree or open-grown savanna tree). O) dieback.binary: A binary indicator of damage. 0 = no damage; 1 = damaged. A plant was considered damaged if it exhibited at least 50% leaf damage. For individuals without leaf damage data, an individual was considered damaged if it exhibited any amount of stem dieback. P) RegrowthLength: The recovery of height, from the point of dieback, for plants experiencing any amount of stem dieback (cm) Q) NetChange: The net increase or decrease in height as determined one year after the severe frost (cm). This net change is equal to InitialHeight-FinalHeight and is also equal to RegrowthLength-Dieback.length.FrostDamage.csv