Nyssa Sylvatica) Contains Datable Fire Scars That Complement an Existing Fire History

fire

Brief Report Dwarf Blackgum (Nyssa sylvatica) Contains Datable Fire Scars that Complement an Existing Fire History

Thomas Saladyga Department of Social Sciences, Concord University, Athens, WV 24712, USA; [email protected]; Tel.: +1-610-413-0715


Received: 17 November 2019; Accepted: 6 December 2019; Published: 9 December 2019


Abstract: Blackgum (Nyssa sylvatica) is a “consummate subordinate” hardwood tree species consigned to the mid-canopy of many eastern North American forests. Despite its wide distribution and ecological amplitude, blackgum is an underutilized tree species in fire history reconstructions within its range. In this study, I analyzed cross-section samples collected from 19 fire-scarred blackgum trees at a dry, nutrient-poor ridgetop study area in northeastern Pennsylvania. All but two of these samples were successfully crossdated, each containing between one and six fire scars. Fires recorded by blackgum occurred frequently, with site-level mean fire intervals between approximately three and five years. There was an increase in blackgum growth within two years following fire events, but this increase was not statistically significant and it was dependent on local fire regime characteristics. In addition, the blackgum fire-scar data increased the temporal and spatial resolution of an existing local fire history. These results provide evidence for the potential use of blackgum in fire history reconstructions, but applications may be limited by tree age, complacent growth that prevents crossdating, and the degree of rot resistance after scarring.

Keywords: blackgum; Nyssa sylvatica; fire scars; dendrochronology; fire history; fire sensitivity

1. Introduction Blackgum (Nyssa sylvatica Marsh.), known alternatively as black tupelo or sour gum, is a North American hardwood tree species with a geographic range extending from Maine to east Texas and from southern Ontario to central Florida [1,2]. Abrams [3] has referred to blackgum as a “consummate subordinate,” given its wide geographic range and the fact that it rarely dominates the overstory. It grows on xeric, upland sites [4] as well as hydric sites, including swamps and floodplains along the Atlantic and Gulf Coasts [5,6]. Blackgum is shade-tolerant and can persist in the understory for decades, while it can also colonize old fields and disturbed sites [7]. Mature individuals with thick bark display high levels of fire resistance and, when top-killed by fire, blackgum is a prolific sprouter [8]. In addition to its extensive range and ecological amplitude, blackgum is one of the longest-lived hardwood species in eastern North America, capable of reaching ages >600 years [9]. Yet, despite these characteristics that make it one of the most ubiquitous tree species in eastern North America (only rivaled by red maple (Acer rubrum L.)), blackgum has not been effectively utilized in any published fire history study within its range. Fire scars embedded in the annual growth rings of trees are commonly used to reconstruct and infer historical fire regime characteristics, including the frequency, spatial extent, severity, and season of fire occurrence [10]. These scars can develop when a portion of cambium is damaged by the heat of a fire and subsequent growth envelopes the wound (Figure1). Fire scars are assigned to a calendar year when samples are accurately crossdated against a local master growth chronology [11]. In most cases, long-lived tree species that exhibit fire adaptations, such as thick bark and rot-resistance after scarring [12] are targeted for sampling. This means that, even in the species-rich deciduous forests of

Fire 2019, 2, 61; doi:10.3390/fire2040061 www.mdpi.com/journal/fire Fire 2019, 2, x FOR PEER REVIEW 2 of 9

45 set of tree species, including pine (Pinus) species such as Table Mountain pine (P. pungens Lamb.), 46 pitch pine (P. rigida Mill.), red pine (P. resinosa Aiton), shortleaf pine (P. echinata Mill.), and longleaf 47 pine (P. palustris Mill.) as well as a few oak (Quercus) species, including white oak (Q. alba L.), post 48 Fireoak2019 (Q., 2stellata, 61 Wangenh.), black oak (Q. veluntina Lam.), northern red oak (Q. rubra L.), and chestnut2 of 9 49 oak (Q. montana Willd.) [10,13,14]. In a rare instance of sampling hardwood species other than oak in 50 a fire history study, Silver and others [15] dated fire-scarred sourwood (Oxydendrum arboreum (L.) 51 easternDC.) trees, North but America, were unable published to crossdate fire history blackgum reconstructions samples are due typically to complacent based on growth a limited (i.e., sub-set low 52 ofinterannual tree species, ring including-width variability) pine (Pinus and) species short such chronologi as Tablees. Mountain Here, the pine authors (P. pungens concludedLamb.), that pitch the 53 pineinterpretation (P. rigida Mill.),of blackgum red pine annual (P. resinosa rings mayAiton), be particularly shortleaf pine challenging (P. echinata and,Mill.), therefore, and longleaf its potential pine 54 (useP. palustris in fire historyMill.) studies as well limited. as a few oak (Quercus) species, including white oak (Q. alba L.), post oak 55 (Q. stellataThis briefWangenh.), report addresses black oak four (Q. veluntinaquestionsLam.), regarding northern the use red of oak blackgum (Q. rubra inL.), fire and history chestnut studies: oak 56 ((1)Q. montanaCan samplesWilld.) collected [10,13,14 from]. In firea rare-scarred instance trees of sampling at a dry, hardwood nutrient-poor species ridgetop other study than oak area in in a 57 firenortheastern history study, Pennsylvania Silver and be others crossdated? [15] dated (2) Is fire-scarred blackgum sourwooda recorder (ofOxydendrum frequent, low arboreum-intensity(L.) fires? DC.) 58 trees,(3) If so, but how were does unable fire to impact crossdate the annual blackgum growth samples of blackgum? due to complacent (4) Do these growth blackgum (i.e., low fire interannual-scar data 59 ring-widthenhance the variability) interpretation and of short an existing chronologies. local fire Here, history? the authors The answers concluded to these that thequestions interpretation will fill ofa 60 blackgumgap in the annualfire history rings literature may be particularly and help inform challenging future and,fire history therefore, reconstruction its potentialsuse in eastern in fire history North 61 studiesAmerica limited. that incorporate tree species other than pine or oak.

62 Figure 1. (a) Blackgum (SPMT19) with basal scar outlined; (b) full cross-section sample (SPMT19); 63 Figure 1. (a) Blackgum (SPMT19) with basal scar outlined; (b) full cross-section sample (SPMT19); (c) (c) close-up of SPMT19 with fire-scar years noted; (d) annual ring-width measurements for SPMT19 64 close-up of SPMT19 with fire-scar years noted; (d) annual ring-width measurements for SPMT19 with with fire-scar years indicated by open circles. 65 fire-scar years indicated by open circles. This brief report addresses four questions regarding the use of blackgum in fire history studies: 66 (1)2. Materials Can samples and Methods collected from fire-scarred trees at a dry, nutrient-poor ridgetop study area in 67 northeasternFieldwork Pennsylvania was conducted be crossdated? in May 2015 (2) on Is Spring blackgum Mountain a recorder in Schuylkill of frequent, County, low-intensity Pennsylvania fires? 68 (3)(40°53′N, If so, how 76°02′W). does fire The impact study thearea annual is a “ridgetop growth of acidic blackgum? barrens (4) comple Do thesex” (or blackgum “ridgetop fire-scar dwarf datatree 69 enhanceforest”) with the interpretation stunted trees of shaped an existing by high local winds fire history? and adapted The answers to frequent to these fire questions growing will on well fill a- 70 gapdrained, in the nutrient fire history poor literature soils of and the helpBuchanan, inform Dakalb, future fire and history Hazleton reconstructions-Clymer series in eastern [16]. Two North oil 71 Americapipeline thatrights incorporate-of-way (i.e., tree potential species otherfire breaks) than pine that or pre oak.-date 1950 [17] divide the study area into 72 three sites, which were previously identified as Spring Mountain East (SME), Spring Mountain 2. Materials and Methods Fieldwork was conducted in May 2015 on Spring Mountain in Schuylkill County, Pennsylvania (40◦530 N, 76◦020 W). The study area is a “ridgetop acidic barrens complex” (or “ridgetop dwarf tree Fire 2019, 2, 61 3 of 9 forest”) with stunted trees shaped by high winds and adapted to frequent fire growing on well-drained, nutrient poor soils of the Buchanan, Dakalb, and Hazleton-Clymer series [16]. Two oil pipeline rights-of-way (i.e., potential fire breaks) that pre-date 1950 [17] divide the study area into three sites, which were previously identified as Spring Mountain East (SME), Spring Mountain Central (SMC), and Spring Mountain West (SMW) [18]—there is no record of prescribed fire being used for management purposes on this privately owned land. Blackgum samples were cut with a chainsaw at 0.25–0.5 m above ground level from 19 individuals exhibiting fire-scar evidence, including a basal scar or “cat face” (Figure1) and the presence of charred bark. Diameter at breast height (dbh) of these trees ranged from 14 cm to 30 cm, with an average of 20.1 cm. The full or partial cross-sections were collected while canvasing the approximately 180 ha study area for fire-scarred pitch pine and sassafras (Sassafras albidum (Nutt.) Nees), both of which were analyzed and described in previous publications [18,19]. Blackgum samples were stored in the Environmental Geography Lab at Concord University and not processed until the fall of 2019. At this time, all samples were surfaced first with an electric planar and then with an orbital sander using progressively finer sandpaper up to 1500 grit. This process revealed at least one and, in most cases, multiple fire scars in the blackgum samples (Figure1). All samples were skeleton plotted and visually crossdated against a local pitch pine chronology and only further analyzed if there was a match between multiple uniquely narrow “pointer” (or “marker”) years (e.g., 1964/65/66, 1988, 1999) [20]. A high-resolution (4800 dpi) image of each sample was then captured with a flatbed scanner (EPSON 1200XL). Annual rings were measured to the nearest 0.01 mm using the image analysis software CooRecorder 8.1 [21]. These measurements were taken along only one radii (i.e., series) due to the small size of most samples and in an effort to avoid the most distorted growth rings. Ring widths were statistically crossdated using the program CDendro 8.1 [21] and quality checked using the program COFECHA [22]. Correlations between each individual series and the master growth chronology are presented as well as two common chronology statistics, series intercorrelation and average mean sensitivity (i.e., interannual ring-width variability) [11]. A raw ring-width chronology was generated for the study area as a whole and for SME and SMC—only one blackgum sample collected at SMW was crossdated. Fire scars identified in each blackgum sample were assigned to a calendar year and, if possible, the season of occurrence based on the relative position to annual growth rings. Fire scars occurring between annual rings (i.e., dormant season) were assigned to the year of callus response [19]. Mean fire interval (MFI), or average number years between fire events, is presented for comparison to other regional fire histories. I used Superposed Epoch Analysis (SEA) in the Fire History Analysis and Exploration System (FHAES) [23] to assess blackgum growth relative to site-specific fire years and non-fire years since 1970, when sample size was consistently greater than five trees at SME and SMC. I tested for significant departures in actual growth (i.e., site raw ring-width chronologies) from simulated growth within an 11-year window lagged five years before, during, and after fire years and non-fire years. In this analysis, 1000 randomly selected sets of 11-year intervals were used to estimate 95% confidence intervals for the growth departures. Site-specific fire years were identified when a minimum of two trees and at least 10% of the recorder (or live) trees of any species (blackgum, pitch pine, or sassafras) were scarred. I included fire years recorded by any of the three species in this analysis for two reasons: (1) The number of site-specific fire years recorded solely by blackgum were limited to seven years at SME and four years at SMC. (2) I hypothesized that blackgum growth would be impacted by a local fire event regardless of which species recorded it. Lastly, I compiled a multi-species fire history for the three Spring Mountain sites using the aforementioned fire-scar filter to identify fire years. I present the number of fire scars and percentage of recorder trees scarred for each year, site, and species. In addition, the locations of trees recording fires during the 1950s (when wildfires were most frequent and extensive in the last 120 years [18,19]) and subsequent decades were mapped to assess change in the fire regime on Spring Mountain. Fire 2019, 2, 61 4 of 9

3. Results and Discussion

3.1. Blackgum Growth and Fire-Scar Data A total of 17 samples (89%) collected from fire-scarred blackgum trees were crossdated and analyzed (SME = 8, SMC = 8, SMW = 1) (Table1). The blackgum growth chronology developed from these fire-scarred trees spans 96 years (1919–2014), but only one sample pre-dates 1954. Fire(s) burning across the entire study area in 1954 likely caused high rates of above-ground mortality and abundant resprouting of blackgum [19]. Correlations between each individual blackgum series and the blackgum master growth chronology ranged from 0.18 to 0.64 (interseries correlation = 0.42). Although 0.18 is a relatively low correlation, confidence in the dating of this sample (SPMT59) was confirmed first by crossdating against the local pitch pine chronology and then by comparing annual growth to corresponding pointer years in the blackgum master growth chronology (see Figure A1). Average mean sensitivity for all dated series was 0.25, indicating a year-to-year tree growth variability sufficient for crossdating [11]. This differs from the complacent growth described by Silver and others [15], although the authors did not report a mean sensitivity value. Ring width was 1.84 mm per year on average (SME = 1.97mm; SMC = 1.68 mm), which is more than two times the radial growth rate of blackgum in Virginia [24] and more than three times the rate observed at an old-growth site in Pennsylvania [25]. In these cases, blackgum was growing in the understory for upwards of 170 years before being released into the overstory. The rapid growth rate observed in the Spring Mountain samples is possibly due to the comparatively young age of the trees, but is more likely the result of frequent fire disturbance and maintenance of an open canopy, particularly since the 1970s (Figure2). Conclusions drawn from these comparisons are limited, however, since only fire-scarred samples were included in this analysis.

Table 1. Blackgum annual growth data and fire-scar years.

Sample Inner-Ring Outer-Ring Ring Width Correlation with Master Site Fire Year(s) 2 ID Year Year (mm) 1 Chronology (r) SPMT14 SMC 1955 2014 2.08 1.10 0.45 2004, 2005 ± SPMT16 SMC 1919 2013 1.10 0.55 0.32 1986 ± 1977, 1978, 1993, SPMT19 SMC 1954 2014 1.90 0.98 0.52 ± 1999, 2006 SPMT20 SMC 1957 2013 1.56 0.86 0.51 1992, 1997 ± SPMT21 SMC 1954 2013 1.46 0.79 0.40 1985, 1992, 2007 ± 1983, 1985, 1992, SPMT22 SMC 1971 2014 2.32 1.26 0.57 ± 1998, 1999, 2000 SPMT24 SMC 1955 2014 1.17 0.50 0.36 2003 ± SPMT27 SMC 1956 2014 1.84 0.72 0.55 1993 ± SPMT45 SMW 1958 2014 2.10 0.84 0.64 1986 ± SPMT57 SME 1964 2014 2.05 0.67 0.54 1990, 2003 ± SPMT58 SME 1970 1997 3.19 1.11 0.38 1986, 1993, 1995 ± 1999, 2004, 2007, SPMT59 SME 1962 2012 1.67 1.44 0.18 ± 2009, 2012 1993, 1999, 2005, SPMT60 SME 1972 2014 2.96 1.36 0.27 ± 2009 SPMT61 SME 1969 2013 1.54 0.77 0.24 1998, 2002, 2008 ± SPMT62 SME 1954 2014 1.53 0.69 0.47 1993, 2000 ± SPMT63 SME 1955 2014 1.31 0.72 0.43 2006, 2008 ± 1979, 1997, 2004, SPMT64 SME 1961 2014 1.53 0.58 0.25 ± 2005, 2006 Notes: 1 Mean 1 standard deviation. 2 All fire scars were located between annual growth rings and were assigned to the year of callus± tissue response (i.e., spring fires). Bold inner-ring year indicates pith.

Forty-eight dormant season fire scars were identified and dated in the blackgum samples (Table1; Figure2). The earliest fire scar was recorded in 1977 and the most recent in 2012, with the majority (79%) occurring between 1990 and 2009. In samples with pith (n = 10), the first fire scar was recorded within the first 31 years of growth on average. At the site level, 26 fire scars were dated in SME samples (3.2 scars/sample), 21 fire scars were dated in SMC samples (2.6 scars/sample), and one fire scar was Fire 2019, 2, 61 5 of 9

Fire 2019, 2, x FOR PEER REVIEW 5 of 9 datedFire in 2019 a single, 2, x FOR SMW PEERsample REVIEW (Table1). Mean fire interval (MFI) was 2.7 years at SME (n = 6 intervals)5 of 9 150 6 intervals) and 4.7 years at SMC (n = 3 intervals) when a minimum of two trees and at least 10% of and 4.7 years at SMC (n = 3 intervals) when a minimum of two trees and at least 10% of the recorder 151150 the6 intervals) recorder and trees 4.7 were years scarred. at SMC These (n = 3MFIs intervals) are only when slightly a minimum shorter of than two those trees observedand at least in central10% of trees were scarred. These MFIs are only slightly shorter than those observed in central Pennsylvania 152151 Pennsylvaniathe recorder trees where were remnant scarred. pitch These pine MFIs was areused only to reconstruct slightly shorter the pre than-suppression those observed era fire in historycentral where remnant pitch pine was used to reconstruct the pre-suppression era fire history at two ridgetop 153152 atPennsylvania two ridgetop where sites remnant[26] and pitchare at pine the waslower used range to reconstructof MFIs observed the pre at-suppression nearby sites era in fire Schuylkill history 154153sites County [at26 two] and ridgetop [18]. are at thesites lower [26] and range are ofat the MFIs lower observed range of at MFIs nearby observed sites in at Schuylkill nearby sites County in Schuylkill [18]. 154 County [18].

155

156155 FigureFigure 2. (a 2.) Blackgum (a) Blackgum raw raw ring-width ring-width chronology chronology (thick (thick black black line)line) withwith ring ring-width-width meas measurementsurements for 157 individualfor individual trees (gray trees lines) (gray and lines) sample and sample size over size time over (dashed time (dashed line); line); (b) number (b) number of fire of scars fire scars recorded 156 Figure 2. (a) Blackgum raw ring-width chronology (thick black line) with ring-width measurements 158 recorded by blackgum trees per year. 157 by blackgumfor individual trees trees peryear. (gray lines) and sample size over time (dashed line); (b) number of fire scars 158 recorded by blackgum trees per year. 159 AnalysisAnalysis of blackgum of blackgum growth growth relative relative to to firefire and and non non-fire-fire years years indicates indicates a marked, a marked, but not but not 160159statistically statisticallyAnalysis significant, sign ofificant, blackgum increase increase growth in in growth growth relative within within to fire two andtwo years non years-fire following following years indicates a fire, a fire, particularly a particularly marked, at but SMC not at SMC 161160(Figure (Figurestatistically3). Blackgum 3). Blackgum significant, growth growth increase was was comparatively in comparatively growth within unchanged unchanged two years at at bothfollowing both sites sites in ain thefire, the fivefive particularly yearsyears precedingpreceding at SMC and 162161following and(Figure following non-fire 3). Blackgum non years.-fire growth Dinh years. and was Dinh otherscomparatively and [others27] found [27] unchanged found that increased that at both increased sites growth in gro the afterwth five after a years fire a eventprecedingfire event occurred 163 162during occurredand the following immature during non the phase-fire immature years. of 60% Dinh phase of fire-scarredand of others 60% of [27] fireblack found-scarred oak that( Q. black increased velutina oak (Q.Lam.) gro velutinawth samples after Lam.) a fire collected samples event in a 164 collected in a remnant oak savanna. The authors attributed this finding to a greater sensitivity of 163remnant occurred oak savanna. during the The immature authors phase attributed of 60% this of fire finding-scarred to black a greater oak ( sensitivityQ. velutina Lam.) of immature samples trees 165 immature trees to light availability associated with fire disturbance. The blackgum samples analyzed 164to lightcollected availability in a remnant associated oak savanna. with fire The disturbance. authors attributed The blackgum this finding samples to a greater analyzed sensitivity in this of study 166165 in this study were all relatively young and site-specific differences in growth response to fire are wereimmature all relatively trees young to light and availability site-specific associated differences with fire in disturbance. growth response The blackgum to fire are samples likely analyzed related to the 167166 likelyin this related study towere the alllocal relatively fire regime young (i.e., and fire sitefrequency-specific and differences intensity) in and growth resulting response forest tostructure. fire are local fire regime (i.e., fire frequency and intensity) and resulting forest structure. In 2015, I observed 168167 Inlikely 2015, related I observed to the local predominately fire regime scrub(i.e., fire (or frequency bear) oak and (Q. intensity) ilicifolia Wangenh.)and resulting interspersed forest structure. with 169168predominately isolatedIn 2015, blackgum I observed scrub (orand predominately bear) pitch oakpine ( Q.at scrubSME, ilicifolia while (or Wangenh.) bear) SMC oak was (Q. interspersedcharacterized ilicifolia Wangenh.) by with a mosaic isolated interspersed of closed blackgum withand and 170169pitch openisolated pine pine at blackgum SME,-hardwood while and forest SMCpitch [19]. pine was Consistent at characterized SME, while light availabilitySMC by awas mosaic characterized at SME of would closed by make anda mosaic opentree growthof pine-hardwood closed at andthis 171170forest siteopen [19 less]. pine Consistentsensitive-hardwood to fire light forest disturbance availability [19]. Consistent compared at SME ligh tot wouldavailabilitySMC, where make at less SME tree frequent would growth firemake at occasionally thistree growth site less opened at sensitivethis 172171to firethesite disturbance canopyless sensitive and comparedtemporarily to fire disturbance toincreased SMC, compared where resources less to available SMC, frequent where for fire tree less occasionally growth. frequent fire openedoccasionally the canopyopened and 172temporarily the canopy increased and temporarily resources increased available resources for tree available growth. for tree growth.

173 173 174 Figure 3. Normalized growth departures in fire-scarred blackgum five years before, during, and after 175 “fire years” and “non-fire years” at (a) Spring Mountain East (SME) and (b) Spring Mountain Central 174 FigureFigure 3. Normalized 3. Normalized growth growth departures departures in in fire-scarredfire-scarred blackgum blackgum five five years years before, before, during, during, and after and after 175 “fire years”“fire years” and and “non-fire “non-fire years” years” at at (a ()a Spring) Spring Mountain Mountain East East (SME) (SME) and and (b) ( bSpring) Spring Mountain Mountain Central Central (SMC). See Table2 for site-specific fire years (n = 9). Site-specific non-fire years include all other years since 1970 (n = 31). No statistically significant (p < 0.05) departures in tree growth were detected. Fire 2019, 2, 61 6 of 9

3.2. Multi-Species Fire History (1954–2014) Samples collected from fire-scarred blackgum were combined in a multi-species fire history with previously analyzed pitch pine and sassafras samples [18,19] (Table2). This fire history begins in 1954 because only one blackgum and one sassafras sample pre-date this year, when more than 20% of pitch pine recorded fire at each of the three sites on Spring Mountain. Between 1954 and 2014, there were a total of 18 unique fire years occurring every 3.5 years on average, but with a ~20-year “fire free” period between 1956 and 1976 (Table2). The persistence of young blackgum and sassafras trees provides evidence for a near complete absence of fire during this time period since these individuals would have been highly vulnerable to top-kill by fire [7]. After 1992, pitch pine recorded fire in only one year (2005), while the two hardwood species recorded 11 fire years combined (Table2). The 1993 fire recorded by blackgum (SME/SMC) and sassafras (SMC/SMW) is important because it highlights a relatively large fire event that did not scar any pitch pine. The post-1992 fire years, therefore, suggest a shift to low-intensity fires that scarred 40 to 60-year old blackgum and sassafras, but were not hot enough to injure more fire resistant pitch pine. This differential scarring potential is the primary benefit of a multi-species fire history, in which the three species described here are situated along a continuum of fire resistance, with mature pitch pine being the most fire resistant, followed by blackgum and then sassafras [7,28]. In other words, a fire history inferred from only pitch pine would suggest that fire was infrequent and of minor importance on Spring Mountain after 1992.

Table 2. Spring Mountain fire years (1954–2014) with site- and species-specific fire-scar data. Pitch pine and sassafras samples were analyzed and described in previous publications [18,19].

Fire year 1 Site Species Fire Scars Trees Scarred (%) 1954 SME Pitch pine 5 62.5 SMC Pitch pine 3 21.4 SMW Pitch pine 6 46.2 1956 SME Pitch pine 2 25.0 1976 SMC Pitch pine 2 11.8 1982 SMC Pitch pine 2 11.8 1985 SMC Blackgum 2 25.0 1991 SME Pitch pine 3 21.4 1992 SME Pitch pine 3 21.4 SMC Blackgum 3 37.5 1993 SME Blackgum 3 37.5 SMC Blackgum 2 25.0 SMC Sassafras 5 71.4 SMW Sassafras 2 100.0 1996 SMC Sassafras 2 28.6 1999 SME Blackgum 2 28.6 SMC Blackgum 2 25.0 2000 SMC Sassafras 2 28.6 2004 SME Blackgum 2 28.6 2005 SME Blackgum 2 28.6 SME Pitch pine 2 14.3 SMC Sassafras 2 28.6 2006 SME Blackgum 2 28.6 2008 SME Blackgum 2 28.6 2009 SME Blackgum 2 28.6 2012 SMC Sassafras 3 42.9 2014 SMC Sassafras 5 71.4 Notes: 1 Minimum 2 trees and 10% scarred.

After the 1950s, not only were blackgum and sassafras the primary recorders of fire on Spring Mountain, but its occurrence was concentrated in three locations (Figure4). The decreased spatial extent of fire, with the exception of the 1993 fire(s), is indicative of repeated fire caused by the same Fire 2019, 2, x FOR PEER REVIEW 7 of 9

200 After the 1950s, not only were blackgum and sassafras the primary recorders of fire on Spring 201 FireMountain,2019, 2, 61 but its occurrence was concentrated in three locations (Figure 4). The decreased spatial7 of 9 202 extent of fire, with the exception of the 1993 fire(s), is indicative of repeated fire caused by the same 203 people in the same location [18], a decrease in response times by local fire departments [29], a wetter people in the same location [18], a decrease in response times by local fire departments [29], a wetter 204 climate [19], or a combination of all three factors. These spatial patterns should be interpreted with climate [19], or a combination of all three factors. These spatial patterns should be interpreted with 205 caution, however, since the fire-scar data were filtered and the sampling strategy only included trees caution, however, since the fire-scar data were filtered and the sampling strategy only included trees 206 with visible fire-scar evidence. with visible fire-scar evidence.

207 Figure 4. Spatial distribution of trees recording fire during the (a) 1950s and (b) post-1950s (see Table2 208 Figure 4. Spatial distribution of trees recording fire during the (a) 1950s and (b) post-1950s (see Table for specific fire years). Oil pipeline rights-of-way divide the study area into three sites: Spring Mountain 209 2 for specific fire years). Oil pipeline rights-of-way divide the study area into three sites: Spring East (SME), Spring Mountain Central (SMC), and Spring Mountain West (SMW). 210 Mountain East (SME), Spring Mountain Central (SMC), and Spring Mountain West (SMW). 4. Conclusions 211 4. Conclusions This brief report provides new insights into the use of blackgum in fire history studies. In revisiting 212 my initialThis briefquestions, report I can provides conclude new the insights following: into (1) the Samples use of collectedblackgum from in fire fire-scarred history studies. blackgum In 213 treesrevisiting on Spring my initial Mountain questions, can be I accuratelycan conclude crossdated, the following: with the (1) exception Samples of collected two samples from infire this-scarre study.d 214 (2)blackgum These treestrees areon Spring recorders Mountain of frequent, can be low-intensity accurately crossdated, fires (MFI with< 5 years).the exception (3) Blackgum of two samples growth 215 increasedin this study. within (2) two These years trees following are recorders a fire event, of frequent, but this increase low-intensity is not statistically fires (MFI significant < 5 years). and (3) 216 isBlackgum dependent growth on the increased local fire regime within and two forest years structure. following 4) a Fire-scar fire event, data but derived this from increase blackgum is not 217 samplesstatistically added significant temporal and and is spatialdependent resolution on the tolocal an existingfire regime fire and history forest and structure. documented 4) Fire a- changescar data in 218 thederived fire regimefrom blackgum on Spring samples Mountain. added Application temporal and of thesespatial findings resolution to other to an regionalexisting fire fire history histories and is 219 possible,documented but maya change be limited in the by fire the regime age of on blackgum Spring Mountain. trees (~60 years Application in this study), of these complacent findings to growth other 220 thatregional prevents fire histories crossdating, is possible, and the but degree may of be rot limited resistance by the after age scarring of blackgum in individual trees (~60 trees. years in this 221 study), complacent growth that prevents crossdating, and the degree of rot resistance after scarring 222 Funding:in individualThis researchtrees. received no external funding. Acknowledgments: I am grateful for the efforts of Joseph Saladyga and Joseph Besitka, who coordinated site access 223 andFunding: provided This logisticalresearch supportreceived on no Spring external Mountain. funding. Concord University undergraduate students Chance Raso and Caitlin Testerman assisted with sample collection. Comments from three anonymous reviewers improved the 224 qualityAcknowledgments: of this brief report. I am grateful for the efforts of Joseph Saladyga and Joseph Besitka, who coordinated site 225 access and provided logistical support on Spring Mountain. Concord University undergraduate students Conflicts of Interest: The author declares no conflicts of interest. 226 ChanceFire Raso2019, 2,and x FOR Caitlin PEER REVIEW Testerman assisted with sample collection. Comments from three anonymous8 of 9 227 Appendixreviewers improved A the quality of this brief report. 228 230Conflicts Appendix of Interest: A The author declares no conflicts of interest. 229

231 Figure A1. Comparison between annual ring-width measurements (z-scores) for SPMT59 and the 232 Figure A1. Comparison between annual ring-width measurements (z-scores) for SPMT59 and the 233 blackgumblackgum master master growth growth chronology. chronology. Fire-scar Fire-scar years years areare indicated by by open open circles. circles.

234 References

235 1. Little, E.L. Atlas of United States Trees, Volume 1. Conifers and Important Hardwoods; Miscellaneous Publication 236 1146; United State Department of Agriculture, Forest Service: Washington, DC, USA, 1971. 237 2. United States Department of Agriculture, Natural Resources Conservation Service (NRCS). PLANTS 238 Database. Available online: https://plants.usda.gov/ (accessed on 2 November 2019). 239 3. Abrams, M.D. Tales from the blackgum, a consummate subordinate tree. BioScience 2007, 57, 347–359, 240 doi:10.1641/B570409. 241 4. Harrod, J.C.; White, R.D. Age structure and radial growth in xeric pine-oak forests in western Great Smoky 242 Mountains National Park. J. Torrey Bot. Soc. 1999, 126, 139–146, doi:10.2307/2997290. 243 5. Gemborys, S.R.; Hodgkins, E.J. Forests of small stream bottoms in the coastal plain of southwestern 244 Alabama. Ecology 1971, 52, 70–78, doi:10.2307/1934738. 245 6. Doumlele, D.G.; Fowler, B.K.; Silberhorn, G.M. Vegetative community structure of a tidal freshwater 246 swamp in Virginia. Wetlands 1984, 4, 129–145, doi:10.1007/BF03160492. 247 7. Burns, R.M.; Honkala, B.H. Silvics of North America, Volume 2: Hardwoods; Agricultural Handbook 654; 248 United States Department of Agriculture: Washington, DC, USA, 1990. 249 8. Harmon, M.E. Survival of trees after low-intensity surface fires in Great Smoky Mountains National Park. 250 Ecology 1984, 65, 796–802, doi:10.2307/1938052. 251 9. Sperduto, D.D.; Nichols, W.F.; Crowley, K.F.; Bechtel, D.A. Black Gum (Nyssa sylvatica Marsh.) in New 252 Hampshire; New Hampshire Natural Heritage Inventory, Department of Resources & Economic 253 Development, Concord, NH., 2000. 254 10. Lafon, C.W.; Naito, A.T.; Grissino-Mayer, H.D.; Horn, S.P.; Waldrop, T.A. Fire History of the Appalachian 255 Region: A Review and Synthesis; Gen. Tech. Rep. SRS-219; Southern Research Station USDA Forest Service: 256 Asheville, NC, USA, 2017; pp. 1–97. 257 11. Speer, J.H. Fundamentals of Tree-Ring Research; University of Arizona Press: Tucson, AZ, USA, 2010; ISBN 258 0816526850. 259 12. Smith, K.T.; Sutherland, E.K. Terminology and biology of fire scars in selected central hardwoods. Tree Ring 260 Res. 2001, 57, 141–147. 261 13. Guyette, R.P.; Dey, D.C.; Stambaugh, M.C.; Muzika, R.M. Fire Scars Reveal Variability and Dynamics of 262 Eastern Fire Regimes. In Proceedings of the Fire in Eastern Oak Forests Conference, Columbus, OH, USA, 263 15–17 November 2005; Dickinson, M.B., Ed.; USDA Forest Service, Northern Research Station: Newtown 264 Square, PA, USA, 2006; Gen. Tech. Rep. NRS-P-1, pp. 20-39. 265 14. Hart, J.L.; Buchanan, M.L. History of Fire in Eastern Oak Forests and Implications for Restoration. In 266 Proceedings of the 4th Fire in Eastern Oak Forests Conference, Springfield, MO, USA, 17–19 May 2011; 267 USDA Forest Service, Northern Research Station: Newtown Square, PA, USA.; Gen. Tech. Rep. NRS-P-102, 268 pp. 34–51.

Fire 2019, 2, 61 8 of 9

References

1. Little, E.L. Atlas of United States Trees, Volume 1. Conifers and Important Hardwoods; Miscellaneous Publication 1146; United State Department of Agriculture, Forest Service: Washington, DC, USA, 1971. 2. United States Department of Agriculture, Natural Resources Conservation Service (NRCS). PLANTS Database. Available online: https://plants.usda.gov/ (accessed on 2 November 2019). 3. Abrams, M.D. Tales from the blackgum, a consummate subordinate tree. BioScience 2007, 57, 347–359. [CrossRef] 4. Harrod, J.C.; White, R.D. Age structure and radial growth in xeric pine-oak forests in western Great Smoky Mountains National Park. J. Torrey Bot. Soc. 1999, 126, 139–146. [CrossRef] 5. Gemborys, S.R.; Hodgkins, E.J. Forests of small stream bottoms in the coastal plain of southwestern Alabama. Ecology 1971, 52, 70–78. [CrossRef] 6. Doumlele, D.G.; Fowler, B.K.; Silberhorn, G.M. Vegetative community structure of a tidal freshwater swamp in Virginia. Wetlands 1984, 4, 129–145. [CrossRef] 7. Burns, R.M.; Honkala, B.H. Silvics of North America, Volume 2: Hardwoods; Agricultural Handbook 654; United States Department of Agriculture: Washington, DC, USA, 1990. 8. Harmon, M.E. Survival of trees after low-intensity surface fires in Great Smoky Mountains National Park. Ecology 1984, 65, 796–802. [CrossRef] 9. Sperduto, D.D.; Nichols, W.F.; Crowley, K.F.; Bechtel, D.A. Black Gum (Nyssa sylvatica Marsh.) in New Hampshire; New Hampshire Natural Heritage Inventory, Department of Resources & Economic Development: Concord, NH, USA, 2000. 10. Lafon, C.W.; Naito, A.T.; Grissino-Mayer, H.D.; Horn, S.P.; Waldrop, T.A. Fire History of the Appalachian Region: A Review and Synthesis; Gen. Tech. Rep. SRS-219; Southern Research Station USDA Forest Service: Asheville, NC, USA, 2017; pp. 1–97. 11. Speer, J.H. Fundamentals of Tree-Ring Research; University of Arizona Press: Tucson, AZ, USA, 2010; ISBN 0816526850. 12. Smith, K.T.; Sutherland, E.K. Terminology and biology of fire scars in selected central hardwoods. Tree Ring Res. 2001, 57, 141–147. 13. Guyette, R.P.; Dey, D.C.; Stambaugh, M.C.; Muzika, R.M. Fire Scars Reveal Variability and Dynamics of Eastern Fire Regimes. In Proceedings of the Fire in Eastern Oak Forests Conference, Columbus, OH, USA, 15–17 November 2005; Gen. Tech. Rep. NRS-P-1. Dickinson, M.B., Ed.; USDA Forest Service, Northern Research Station: Newtown Square, PA, USA, 2006; pp. 20–39. 14. Hart, J.L.; Buchanan, M.L. History of Fire in Eastern Oak Forests and Implications for Restoration. In Proceedings of the 4th Fire in Eastern Oak Forests Conference, Springfield, MO, USA, 17–19 May 2011; Gen. Tech. Rep. NRS-P-102. USDA Forest Service, Northern Research Station: Newtown Square, PA, USA; pp. 34–51. 15. Silver, E.J.; Speer, J.H.; Kaye, M.; Reo, N.J.; Howard, L.F.; Anning, A.K.; Wood, S.W.; Wilbur, H.M. Fire history and age structure of an oakpine forest on Price Mountain, Virginia, USA. Nat. Areas J. 2013, 33, 440–446. [CrossRef] 16. Fike, J. Terrestrial Palustrine Plant Communities of Pennsylvania; Pennsylvania Bureau of Forestry, Department of Conservation and Natural Resources: Harrisburg, PA, USA, 1999. 17. United States Geological Survey. Conyngham Quadrangle, Pennsylvania. 7.5 Minute Series (Topographic Map); United States Geological Survey: Reston, VA, USA, 1949. 18. Saladyga, T.; Standlee, A. Historical drivers and contemporary perceptions of wildfire in a post-industrial rural landscape. Fire 2018, 1, 33. [CrossRef] 19. Saladyga, T. Reconstructing a cultural fire regime in the Pennsylvania Anthracite Region. Phys. Geogr. 2017, 38, 404–422. [CrossRef] 20. Schweingruber, F.H.; Eckstein, D.; Serre-Bachet, F.; Bräker, O.U. Identification, presentation and interpretation of event years and pointer years in dendrochronology. Dendrochronologia 1990, 8, 9–38. 21. Larsson, L.Å.C. CooRecorder/CDendro Package, version 8.1; Computer Software; Saltsjöbaden, Sweden. 2016. 22. Holmes, R.L. Computer assisted quality control in tree-ring dating and measurement. Tree Ring Bull. 1983, 43, 69–78. Fire 2019, 2, 61 9 of 9

23. Brewer, P.W.; Velásquez, M.E.; Sutherland, E.K.; Falk, D.A. Fire History Analysis and Exploration System. (FHAES), version 2.0.2; Computer Software; 2016. Available online: http://www.fhaes.org (accessed on 7 October 2019). 24. Orwig, D.A.; Abrams, M.D. Contrasting radial growth and canopy recruitment patterns in Liriodendron tulipifera and Nyssa sylvatica: Gap-obligate versus gap-facultative tree species. Can. J. For. Res. 1994, 24, 2141–2149. [CrossRef] 25. Abrams, M.D.; Copenheaver, C.A.; Black, B.A.; Gevel, S.V.D. Dendroecology and climatic impacts for a relict, old-growth, bog forest in the Ridge and Valley Province of central Pennsylvania, USA. Can. J. Bot. 2001, 79, 58–69. [CrossRef] 26. Marschall, J.; Stambaugh, M.; Jones, B.; Guyette, R.; Brose, P.; Dey, D. Fire regimes of remnant pitch pine communities in the Ridge and Valley region of central Pennsylvania, USA. Forests 2016, 7, 224. [CrossRef] 27. Dinh, T.; Hewitt, N.; Drezner, T.D. Fire history reconstruction in the black oak (Quercus velutina) savanna of High Park, Toronto. Nat. Areas J. 2015, 35, 468–475. [CrossRef] 28. Burns, R.M.; Honkala, B.H. Silvics of North America, Volume 1: Conifers; Agricultural Handbook 654; United States Department of Agriculture: Washington, DC, USA, 1990. 29. Kurilla, R.; (Forest District 18, Assistant District Forester, Pennsylvania Bureau of Forestry, Ebensburg, PA, USA). Personal communication, 2016.

© 2019 by the author. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).