DOI: 10.5061/dryad.vm692vr
title: Data from: Longleaf pine proximity effects on air temperatures and hardwood top-kill from prescribed fire

description: Background Regulation of the dominance of sprouting understory hardwoods
 is a common objective for prescribed fire in open-canopy longleaf pine
 woodland of the southeastern USA. Nevertheless, little is known about the
 influence of individual pines on fire and hardwood mortality. We studied
 growing-season fires in stem-mapped stands in southwest Georgia USA which
 displayed large variation in structure due to cutting treatments applied 7
 yr earlier. We measured air temperature and heating duration, and measured
 post-fire sprouting behavior of four guilds of understory hardwoods: mesic
 oaks, upland oaks, xeric oaks, and fleshy-fruited hardwoods. Mean air
 temperature (i.e., of flames, buoyant plume and smoldering combustion) and
 heating duration (time over 60°C) were analyzed with respect to fuel-bed
 conditions and neighboring tree density. Hardwood top-kill was analyzed
 with respect to neighboring tree density and hardwood height. Results Size
 of and distance to longleaf pines strongly affected time over 60°C, which
 increased linearly from a mean of 87 s to a mean of 234 s across a
 gradient of pine basal area from 0 to 30 m2 ha-1. Mean air temperature
 during prescribed fire was unaffected by pine density but increased
 linearly from a mean of 114°C to a mean of 148°C across a gradient of
 wiregrass cover from 0 to 100%. Neighborhood models showed that time over
 60°C during the burns was longest at the base of pines and decreased by
 two-thirds at 3.3 m distance. Pines affected hardwood top-kill probability
 at a similar scale, the effect at 4.4 m decreasing by two-thirds compared
 to at the base of the pine. The four hardwood guilds were readily
 top-killed when ≤ 1 m tall, but at 2 m height upland and xeric oaks had
 become more resistant to top-kill than mesic oaks or fleshy fruited
 broadleaved trees. Conclusions The influence of individual pine trees on
 heating duration and top-kill power of prescribed fire drops by ⅔ of
 maximum within 3 to 4 m of a tree, compared to a maximum at the base of
 the tree. Neighborhood models provide a method to estimate tree effects on
 prescribed fire heating duration and top-kill probability, and thus a way
 of predicting stand structures that provide ecological benefits of
 openings while remaining below thresholds that trigger vigorous hardwood
 response.
description: MinimalCensusData4TCThese are diameter at breast height (cm) for trees, mostly longleaf pines, measured in 2014 in plots that compose an experiment in ecological forestry. Only trees in the neighborhood of thermocouples are included. X & y coordinates (local coordinate system) are included, along with Plot IDs.Fire_intensity_2016Contains summary of thermocouple data from 2016 burns: Plotid (1-18), X & Y UTM coordinates, BA is basal area estimated with a 10-factor (ft2/ac) prism, height of herbaceous fuel layer (Herb Ht), height of shrub layer (Shrb Ht), Wiregrass cover (%) is Arst, number of trees &lt; 10 cm dbh, number of trees with 0 &lt; dbh &lt; 10 cm (Tree Ct), time when temperature reached 60 Celsius (First Temp Spike), duration of temperatures &gt;= 60 degrees Celsius (Seconds Over), and maximum temperature (K Type Max).2016_burn_data$Fuel.moistureContains live fuel moisture data collected during fires. Includes Date, Time of collecion, and gravimetric fuel moisture expressed on dry fuel weigh basis (g/g)TCnonSpatial.RPerforms the multiple linear regression and relative importance analysisTCspatial.RPerforms maximum likelihood, neighborhood analysis on flame temperaturesCrownsprout.RPerforms maximum likelihood, neighborhood analysis on understory hardwood top-killHardwoodLocation.csvContains a numeric location identifier (Point), and X and Y location coordinates in Zone 16 UTM (coords.x1 coords.x2) for locations where hardwoods were sampled.HardwoodCensushas one record (line) for each genetic individual (rootstock) encountered. Contains a identifier (1-18) that identifies experimental stand (Plot); identifier for location where hardwood were sampled ("Point", 1-945, which matches with "Point" in HardwoodLocation.csv); A 4 letter identifier for the understory hardwood species; number of ramets &gt;=1 m in height from the rootstock (Count); stem height estimated to nearest 0.33 m (Stem.H.); scorch height, estimated to nearest 0.33 m (Scorch H), and location of post-fire sprouting, if any (B=base, C=Crown); and explanatory notes (Notes).