United States

Department of

Agriculture

Forest Service

Southern 

Research Station

General Technical 

Report SRS-129

Disturbance from Southern Pine 

Beetle, Suppression, and Wildfire 

Affects Vegetation Composition in 

Central Louisiana: A Case Study

T.W. Coleman, Alton Martin, Jr., J.R. Meeker, 

S.R. Clarke, and L.K. Rieske
August 2010 

Southern Research Station 

200 W.T. Weaver Blvd. 

Asheville, NC 28804

The Authors: 

T.W. Coleman, Entomologist, U.S. Department of Agriculture Forest 

Service, Forest Health Protection, San Bernardino, CA 92373; Alton 

Martin, Jr., Botanist (retired), U.S. Department of Agriculture 

Forest Service, Ecology and Management of Even-aged Southern 

Pine Forests, Pineville, LA 71360; J.R. Meeker, Entomologist, U.S. 

Department of Agriculture Forest Service, Forest Health Protection, 

Pineville, LA 71360; S.R. Clarke, Entomologist, U.S. Department 

of Agriculture Forest Service, Forest Health Protection, Lufkin, 

TX 75902-0310; L.K. Rieske, Forest Entomologist, University of 

Kentucky, Lexington, KY 40536-0001.

Cover photos: Kisatchie Hills Wilderness Area imaged 2 years postdisturbance (1989) on the top, and same perspective 16 years postdisturbance (2003), below. Courtesy of Alton Martin Jr. (top) and Eric 

Vallery (bottom).
Disturbance from Southern 

Pine Beetle, Suppression, and 

Wildfire Affects Vegetation 

Composition in Central 

Louisiana: A Case Study

T.W. Coleman, Alton Martin, Jr., J.R. Meeker, 

S.R. Clarke, and L.K. Rieske

Abstract

We assessed plant composition and forest succession following tree 

mortality from infestation of southern pine beetle (Dendroctonus frontalis), 

associated suppression, and wildfire in two forest types, pine (Pinus spp.) 

with mixed hardwood and longleaf pine (P. palustris). In this case study, 

vegetation was assessed in 2003 using methodology and experimental 

framework established 16 years earlier. We examined changes in vegetation 

composition from the 1980s to 2003 in each forest stand type and used the 

Forest Vegetation Simulator to predict forest succession.

In the pine-hardwood stand, total plant and woody plant abundance and 

richness increased over the study while total plant evenness decreased. The 

Forest Vegetation Simulator predicts the pine-mixed hardwood will shift to 

loblolly pine-hardwood after 50 years. In the longleaf pine stand, total plant 

abundance and richness increased. The interacting disturbances enhanced 

forb, shrub, and tree abundance. Forb and shrub species richness also 

increased. Modeling predicts the longleaf pine stand will shift to loblolly 

pine (P. taeda) following the disturbance events. Although stand predictions 

are different for each initial forest type, predicted pine and hardwood basal 

area represent high susceptibility to future SPB outbreaks. 

The interaction of these three disturbance events (beetle infestation, 

associated suppression, and wildfire) appears to maintain pine composition, 

but also the potential for additional SPB-caused mortality, though thinning 

may reduce the susceptibility of these stands to bark beetle disturbance. The 

unique opportunity to assess interacting disturbances and natural succession 

was the motivation for our study, but our inferences are limited due to 

constraints of the experimental design.

Keywords: Cut-and-leave suppression, Forest Vegetation Simulator, 

loblolly pine, southern pine beetle, wildfire.

Introduction 

Forest disturbances, such as insect outbreaks or fire, 

alter species composition and potentially influence forest 

succession (Sousa 1984). Bark beetles are a major threat 

to forests worldwide, and in recent years an estimated 

50 species of exotic bark beetles have established in the 

continental United States and Canada (Haack 2001). 

Native bark beetles pose serious threats to forests and can 

exacerbate additional disturbance events (Covington and 

Moore 1994). Southern pine beetle (Dendroctonus frontalis)

(SPB) is an indigenous insect that has likely played a key 

role in shaping and maintaining pine forests of the Southern 

United States, and presents significant management 

challenges (SFIWC 2004). 

SPB aggressively attacks healthy or stressed trees by 

attacking en masse and overwhelming host defenses. Tree 

mortality is required for successful beetle reproduction 

(Payne 1980). Loblolly pine (Pinus taeda) and shortleaf pine 

(P. echinata) are among the most commercially important 

timber species in the southern region (Barker and Langdon 

1990), and are favored hosts (Payne 1980). Pine stands that 

are dense and those under increased abiotic stresses are most 

susceptible to losses by SPB infestation (Belanger 1980). 

During beetle population outbreaks, extensive overstory 

mortality of pines can occur. 

Pine mortality can be reduced by suppression of SPB 

through cutting infested and susceptible pines nearby. A 

common suppression approach is cut-and-leave, which calls 

for felling all infested pines, plus a buffer strip of uninfested 

pines (≥ 10 cm in diameter), and leaving the felled pines 

in place at the front of the expanding infestation (Billings 

1980). In effect, the cut-and-leave approach creates a buffer 

strip that disperses concentrated beetle populations and 

limits centralized attacks on susceptible pines.

Following SPB overstory mortality and cut-and-leave 

suppression, excessive coarse woody debris accumulates 

on the forest floor, a condition that leads to increased 

fuel loads and potentially devastating fire activity (Pyne 

and others 1996). In the Southeastern United States, 

wildfire is a common disturbance that can eliminate latesuccessional plant species and shift stand composition to 

more early-successional species (Oliver and Larson 1990). 

Fire disturbance disrupts the forest floor, creates favorable 

seedbed conditions (Shelton and Cain 2000), promotes 

growth and survival of shade-intolerant species such as 

loblolly and shortleaf pine, and influences plant diversity 

(Allen and Wyleto 1983). 

SPB activity increases the incidence of wildfire. In 

combination, the two disturbance agents (SPB and wildfire) 

are postulated to have influenced the composition and 

structure of historic southern pine forests (Schowalter and 

others 1981). The revegetation of SPB-killed stands, and 

the influence of SPB mortality and/or control on subsequent 

forest composition and structure, has received little attention 

(see Balch 1928, Clarke and others 2000, Harrington and 

others 2000). 

Disturbance from Southern Pine Beetle, 

Suppression, and Wildfire Affects Vegetation 

Composition in Central Louisiana: A Case Study

T.W. Coleman, Alton Martin, Jr., J.R. Meeker, S.R. Clarke, and L.K. Rieske
2

Recent introductions of numerous exotic bark beetle species 

and a long history of widespread mortality from bark beetles 

in the United States (Furniss and Carolin 1977, Price and 

others 1992) have led us to question how bark beetle caused 

mortality, associated suppression, and natural disturbance 

regimes influence forest communities. Our objective was 

to assess how disturbances associated with bark beetle 

impact long-term vegetation succession in the forests of 

Southeastern United States. More specifically, we set out 

to assess the vegetation composition, measure forest stand 

structure, and predict forest stand succession in Kisatchie 

Hills Wilderness following SPB-caused overstory mortality, 

associated cut-and-leave suppression, and wildfire in a pine 

(Pinus spp.) with mixed hardwood stand and in a longleaf 

pine (P. palustris) stand.

We hypothesized that forest canopies dominated by pine 

and mixed hardwood will have limited regeneration of pine 

and other early-successional species because of remnant 

hardwoods restricting gap size. We predicted earlysuccessional communities would be more prominent in 

plots dominated by pine because of continuous overstory 

mortality and reduced competition in the overstory and 

understory. Plots in pine-dominated canopies were expected 

to maintain pine composition, in contrast to plots with a 

mixed forest type which we expected to shift to hardwoods.

Methods

Site Description

In 1984-85, > 1700 ha of pine forests on the Western 

Gulf Coastal Plain in the Kisatchie Hills Wilderness 

(Natchitoches Parish, LA) suffered extensive overstory 

mortality due to SPB (fig. 1). The 3250 ha Kisatchie 

Hills Wilderness (Kisatchie National Forest, central LA) 

is characterized by gently sloping terrain with forest 

canopies dominated by loblolly pine, longleaf pine, mixed 

pine-hardwood, and upland hardwood. Climatologically, 

it is characterized by mean annual maximum temperature 

of 24.7 °C with a minimum mean temperature of 12.6 °C, 

and annual precipitation of 140 cm (National Weather 

Service 2001).

In Kisatchie Hills, SPB infestations initially covered ~147 

ha before suppression tactics were implemented. To suppress 

the rapidly expanding infestations, 70 cut-and-leave 

suppression events occurred during the 2-year period and 

encompassed the majority of the 1700 ha beetle disturbance 

(Nettleton and others 1988). In 1987, a high-intensity 

wildfire covering 3,000 ha caused overstory mortality and 

engulfed most of the beetle disturbed area within Kisatchie 

Hills, including the longleaf pine stand (Clarke 1995) (fig. 

1). The wildfire began in previously disturbed SPB stands 

and expanded into undisturbed forest (489 ha), and was 

eventually contained by hiking trails and the wilderness 

boundary. A second low-intensity wildfire occurred in March 

2000, covering 633 ha, including the pine-mixed hardwood 

stand. Because these wildfires occurred within wilderness 

boundaries, limited information on fire characteristics is 

available; fire intensity and speed of spread are unknown. As 

a result, fire intensity classifications are not direct measures 

and represent general groupings that were defined by pine 

fuel load, time of year, and occurrence of fire following pine 

mortality. In fall 1985, a study was established to assess 

plant succession following the bark beetle outbreak and 

associated suppression (fig. 2) (Pearson and Martin 1991); 

this study was subsequently disturbed by a low-intensity 

wildfire in 2000. Plots established in 1985 were located in 

a pine-mixed hardwood stand with SPB-caused overstory 

mortality and cut-and-leave suppression, and were part 

of the 2000 wildfire. Overstory trees in the pine-mixed 

hardwood stand were 50 years old at the time of the SPB 

outbreak and suppression events and classified as yellow 

pine (loblolly, shortleaf, and longleaf pines) and mixed 

hardwood canopies. 

Figure 1—Kisatchie Hills Wilderness Area (Kisatchie National Forest, 

LA), showing the longleaf pine stand () and pine-mixed hardwood 

stand (•) each with southern pine beetle-caused mortality (SPB), 

associated suppression, and wildfire. Vertical lines represent the 

extent of the 1984-85 SPB suppression, whereas horizontal lines 

depict the 1987 and 2000 wildfires. 

2000 wildfire

1987 wildfire

pine-mixed hardwood

SPB and suppression

longleaf pine
3

Figure 2—Forest stand composition following SPB-caused mortality and associated suppression in pine forests in Kisatchie Hills Wilderness 

Area imaged (A) 2 years post-disturbance (1989) (photo by Alton Martin Jr.), and (B) from the same perspective 16 years post-disturbance (2003) 

(photo by Eric Vallery). Note vegetation succession and the prevalence of hardwoods.

(A)

(B)
4

A second study was established after the 1987 wildfire 

disturbance to the beetle-impacted areas, and examined 

interactions between SPB and fire in shaping forest 

succession (fig. 3) (Pearson and Martin 1991). The second 

study area, established in 1987, was dominated by longleaf 

pine and consisted of SPB-caused overstory mortality, cutand-leave suppression, and the 1989 wildfire (figs. 1, 2, and 

3). Canopy trees in the longleaf pine stand were 60 years old 

(USDA Forest Service 1985). No other major disturbances 

have occurred in these stands following the SPB outbreak 

and wildfires. In both 1985 and 1987, three plots were 

assigned in each disturbed stand, with each plot consisting 

of three parallel 30.5 m transects, separated by > 7.6 m. 

Each set of three parallel transects were considered a plot 

and were grouped as an experimental unit within each stand. 

Plots were separated by > 15.2 m within the stand, and were 

at least 50 m from the stand edge. Plots established in the 

mid-1980s span an area within each stand ≤ 1 ha. In each 

forest type, replicates were established within an individual 

stand boundary. 

The dissimilar forest types, variable fire intensities, and 

different time of fire occurrence did not allow us to compare 

the two forest stands established from the initial study. The 

initial project design further complicated statistical analyses 

by violating the assumption of independence and by lacking 

replication (Hulbert 1984). In spite of the limitations to the 

initial study, the ability to assess the same plots using the 

same methodologies 16 and 14 years later creates a unique 

opportunity to monitor vegetation succession. As a result, we 

focused on the change in forest composition and structure 

(figs. 2 and 3) following each disturbance regime for the two 

different stand classifications.

Vegetation and Stand Structure

Annual vegetation assessments began in 1985 in the pinemixed hardwood stand and in 1987 in the longleaf pine 

stand. The assessments continued through 1989. Plant 

composition and stand structure from pre-disturbed or 

undisturbed pine stands (controls) were not assessed. In 

2003, 18 years following the initial census, plots were recensused using original methodology (Parker and Harris 

1959). Each permanently located transect in each stand 

had 100 points designated for vegetation assessment at 0.3 

m intervals. There were 300 points within each plot for 

vegetation assessment, for a total of 900 points per stand 

treatment. At each point the percent of bare soil, rock, 

leaf litter, coarse woody debris (> 6 cm diameter), and 

vegetative cover were assessed by viewing through a 0.02 

m diameter circular loop positioned 0.3 m above the ground 

(Parker and Harris 1959). Plants with foliage within the 

sample loop were identified by species and used to compute 

plant composition. Plant cover was recorded if vegetation 

fell within the loop, regardless of aboveground height, using 

the following classification scheme: grasses (Families: 

Poaceae and Cyperaceae), forbs (non-grass herbaceous 

species), shrubs (woody species < 10 m and woody vines), 

and trees (woody species > 10 m). Woody plant cover was 

included if it was ≤ 0.3 m in height. To record woody plants 

> 0.3 m, a line-intercept method was used at the same 0.3 

m intervals along the same transects (Canfield 1941). Using 

this approach, an imaginary line was extended vertically. 

All species intercepting this line were used to calculate 

plant composition using absolute frequency. At 7.6, 15.2, 

and 22.9 m divisions along each transect, canopy cover 

was recorded in each cardinal direction using a spherical 

densiometer (Lemmon 1956). In the censuses of the 1980s, 

basal area (m2

/ ha) of pines and hardwood species were 

calculated using a 5.7 m2/ ha basal area factor (10-factor 

prism) at the midpoint of each transect. Only trees > 12.7 

cm d.b.h. were used to assess pine and hardwood species 

basal area.

In the 2003 census only, three 0.04 ha fixed-size plots were 

established in the middle of one randomly chosen transect 

at each plot to further describe stand characteristics and 

the canopy composition (USDA Forest Service 2003) in 

each disturbance regime. All woody species (≥ 12.7 cm 

d.b.h.) were measured for diameter (d.b.h.), height (m), and 

frequency in the 0.04 ha plot following protocols of the 

Common Stand Exam (USDA Forest Service 2003). Canopy 

species composition and basal area (m2

/ha) were then 

assessed in each 0.04 ha plot. In addition, within each 0.04 

ha plot, five 0.0004 ha subplots were positioned centrally, 

and in the four corners of the whole plot to survey the 

understory woody species (< 12.7 cm d.b.h.), where height, 

diameter (d.b.h., if applicable), and count were assessed for 

each species (USDA Forest Service 2003). Data from the 

0.04 and 0.0004 ha plots were used only to calculate forest 

stand structure.

Forest Modeling

Whole and subplot vegetation measurements from the 

2003 assessments were modeled 50 years into the future 

using the southern variant of the Forest Vegetation 

Simulator (FVS) and assuming no further disturbance 

(USDA Forest Service 2001). We modeled the forest 

type, basal area for hardwoods, and the pine component 

for each forest stand. Assessed tree data and landscape 

variables, including species, d.b.h., height, height to 

crown, radial growth, and ecological region, were 

incorporated into FVS to calibrate and model forest 
5

Figure 3—Forest stand composition following SPB-caused mortality, associated suppression, and wildfire in pine forests in Kisatchie Hills 

Wilderness Area imaged (A) 2 years post-disturbance (1991) (photo by Alton Martin Jr.), and (B) from the same perspective 14 years postdisturbance (2003) (photo by Eric Vallery). Note vegetation succession and the prevalence and patchiness of pines in the 2003 photo.

(A)

(B)
Table 1—Vegetation composition following southern pine beetle-caused overstory mortality, cut-and-leave suppression, and wildfire 

in a pine-mixed hardwood stand and a longleaf pine stand 

Pine-mixed hardwood Longleaf pine

Parameter Effect 1987 2003 Effect 1989 2003

A. Plant community

Abundance 30.91, 2/ *** 31 (6.23) 184 (12.6) 1231, 2/ *** 123 (11.9) 227 (8.5)

Richness 17.61, 2/ ** 9 (1.07) 20 (1.4) 79.91, 2/ *** 16 (0.93) 28 (1.36)

Diversity 6.541, 2/ n.s. 1.79 (0.14) 2.24 (0.11) 2.461, 2/ n.s. 2.11 (0.14) 2.46 (0.1)

Evenness 17.91, 2/ ** 0.87 (0.02) 0.75 (0.03) 0.21, 2/ n.s. 0.76 (0.04) 0.73 (0.02)

B. Grasses

Abundance 0.231, 2/ n.s. 5 (2.1) 5 (1.05) 0.051, 2/ n.s. 43 (7.2) 39 (8.66)

Richness 3.181, 2/ n.s. 1 (0.35) 3 (0.62) 2.381, 2/ n.s. 5 (0.73) 7 (0.96)

C. Forbs

Abundance 2.681, 2/ n.s. 2 (1.43) 6 (3.45) 6.391, 2/ n.s. 30 (4.71) 37 (5.14)

Richness 2.291, 2/ n.s. 0 (0.24) 1 (0.29) 36.91, 2/ ** 4 (0.36) 10 (0.74)

D. Shrubs

Abundance 70.91, 2/ *** 13 (3.39) 61 (7.31) 1281, 2/ *** 32 (6.38) 80 (10.9)

Richness 23.91, 2/ ** 4 (0.74) 9 (0.65) 60.81, 2/ ** 5 (0.29) 8 (0.50)

E. Trees

Abundance 1291, 2/ *** 8 (1.24) 118 (6.94) 42.11, 2/ ** 17 (3.99) 72 (9.62)

Richness 1231, 2/ *** 3 (0.39) 7 (0.75) 5.261, 2/ n.s. 2 (0.32) 4 (0.77)

F. Ground cover (percent)

Bare soil 1.001, 2/ n.s. 0 (0) 0.3 (0.11) 01, 2/ n.s. 4.7 (0.6) 4.9 (0.62)

Rock 1.001, 2/ n.s. 0.5 (0.23) 0.9 (0.3) — 0 (0) 0 (0)

Leaf-litter 4.651, 2/ n.s. 82.8 (1.07) 80.6 (1.01) 31.81, 2/ ** 46.1 (1.18) 68.8 (0.97)

Coarse woody debris 7.621, 2/ n.s. 7.6 (0.88) 1.4 (0.39) 7.301, 2/ n.s. 11.8 (1.07) 0.4 (0.22)

Vegetation 6.321, 2/ n.s. 8.7 (0.69) 16.7 (0.91) 4.011, 2/ n.s. 37.3 (1.14) 25.7 (0.89)

Means (s.e.) from analysis: Fdf / P-value. 

n.s.= P > 0.1.

*** = P < 0.01.

** = P < 0.05.

— = not available for statistical analysis.

6

stand succession on a 5-year cycle (Donnelly and others 

2001). Predicted forest type and stand characteristics were 

obtained from the FVS by using the main output and the 

stand and stocking simulators.

The FVS is an individual-tree nonspatial forest growth 

model built from the core model Prognosis (Stage 1973), 

and adapted from previous models developed for forests of 

the Western United States. Although the southern variant 

of the FVS is a relatively new extension, FVS was found 

to be most adaptable to key features identified among 

several other individual-tree growth models (Robinson and 

Monserud 2003). FVS incorporates site-specific variables 

for calibration. Furthermore, FVS is adequate for simulating 

long-term processes where growth is the main component 

(Teck and others 1996). 

Analyses

We compared vegetation from 2 years post-disturbance, 

1987 for the pine-mixed hardwood stand and 1989 for 

the longleaf pine stand, to assessments from 2003. Plant 

species abundance was assessed, and richness, diversity, 

and evenness calculated for all transects for each year under 

analysis. Individual abundance (total number of tallies) 

and richness for grasses, forbs, shrubs, and trees were 

calculated, along with total plant abundance and richness. 

Diversity and evenness were calculated for total plant 

communities. Diversity was calculated using the Shannon 

index (H’ = -∑ pi lnpi) where pi is the relative abundance 

of the ith species per transect (Magurran 1988). Evenness 

was calculated as J’ (J’ = H’/lnS) where S, richness, is the 

number of species sampled along a transect (Magurran 

1988). The calculated parameters are a measure of relative 

ground cover at the 0.3 m increments along the transects, 
7

and may not be exact counts of species density (Pearson and 

Martin 1991). In our case, species abundance is actually the 

frequency of tallies along a transect. Only data collected 

from transects were utilized to calculate plant indices.

A mixed model analysis of variance (PROC MIXED, SAS 

1997) was used to describe differences in plant abundance, 

diversity, richness, evenness, canopy cover, and ground 

cover within each disturbance regime over the 16-year (pinemixed hardwood) and 14-year (longleaf pine) durations of 

the study. The change in time was used as the fixed effect, 

with transects designated as random effects. Three transects 

were treated as a plot and grouped as an experimental 

unit for each disturbance regime (N=3). Data was log 

transformed if underlying assumptions were not met for 

the analyses of variance. Treatment effects were considered 

statistically significant if P ≤ 0.05. Forest characteristics 

(pine basal area, hardwood basal area, and canopy cover) 

were also analyzed using a mixed model analysis of 

variance (PROC MIXED, SAS 1997). The 1980s data was 

compared to 2003, and the 2003 data to predicted 2053 FVS 

data. Pine and hardwood basal area were calculated only 

from the 0.04 ha plots for the 2003 analyses. Whole plots, 

rather than transects, were used as random effects. 

Results

A total of 5,047 plants representing 117 species were tallied 

from the transects over the 16-year study, including 29 

grasses, 33 forbs, 30 shrubs, and 25 tree species (app. 1). 

Grasses comprised 16 percent of the total plants surveyed 

(820 tallies; app. 1A). Forbs comprised 13 percent of the 

total plants surveyed, with 666 tallies (app. 1B). Shrubs 

comprised 33 percent of the total plants, with 1,681 tallies 

counted (app. 1C). Trees were the most abundant vegetative 

class surveyed, comprising 39 percent of individuals (1,946 

tallies; app. 1D). 

Pine-Mixed Hardwood

Plant abundance and richness significantly increased by 

494 percent and 92 percent in the pine-mixed hardwood, 

respectively, from 1987 to 2003 (table 1A). Mortality to the 

pine overstory and wildfire also decreased plant evenness 14 

percent, whereas plant diversity did not differ (table 1A).

Forty-nine individual grasses representing four grass species 

were observed in 1987 and 42 grasses from 12 species 

in 2003 (app. 1A). The two most abundant grass species 

in the pine-mixed hardwood stand in 1987 were little 

bluestem (Schizachyrium scoparium) and longleaf woodoats 

(Chasmanthium sessiliflorum), whereas no grass species 

dominated in 2003. 

Twenty-one forbs representing two species were observed 

in 1989 and 59 forbs representing eight species in 2003 

(app. 1B). Western bracken fern (Pteridium aquilinum) 

was overwhelmingly the most abundant forb species and 

increased in occurrence from 1987 to 2003. Grass and forb 

species abundance and richness did not significantly vary 

over the duration of the study (tables 1B and 1C).

In pine-mixed hardwood plots, 125 shrubs comprising 10 

species were surveyed in 1987 and 543 shrubs from 23 

species in 2003 (app. 1C). The two most abundant shrub 

species in 1987 were Elliott’s blueberry (Vaccinium elliottii) 

and muscadine (Vitis rotundifolia). In 2003, yaupon (Ilex 

vomitoria) and farkleberry (Vaccinium arboretum) were 

the most abundant shrub species. Over the 16-year period, 

shrub abundance and richness increased by 79 percent and 

56 percent in the pine-mixed hardwood stand, respectively 

(table 1D).

Eighty-four trees representing nine species were tallied in 

1987 and 1,058 trees from 18 species in 2003 (app. 1D). The 

two most abundant tree species in 1987 were loblolly pine, 

followed by southern red oak (Quercus falcata). In 2003, post 

oak (Q. stellata) and mockernut hickory (Carya tomentosa)

were the most abundant tree species. Bitternut hickory 

(C. cordiformis) and sweetgum (Liquidambar styraciflua) 

were also abundant species (> 50 frequency) in 2003. Tree 

abundance increased by 1375 percent from 1987 to 2003 

(table 1E). Tree species richness significantly increased by 

120 percent over the same time period (table 1E). 

Ground cover did not differ over the study period in the 

pine-mixed hardwood stand. However, coarse woody debris 

decreased by 57 percent and vegetation cover increased by 

92 percent from 1987 to 2003, but the changes were not 

significant. Pine regeneration was evident by 2003 where 

hardwood basal area declined, but neither was statistically 

significant. Canopy cover significantly increased by 146 

percent from the initial assessments to 2003 (table 2A).

The FVS designated the pine-mixed hardwood stand as a 

loblolly pine-hardwood forest type in the 2003 stand census, 

and the forest type did not change throughout the modeling 

projection. Dominant species were predicted to be southern 

red oak, loblolly pine, and mockernut hickory, in that order. 

Basal area increased by 247 percent for pine and 65 percent 

for hardwoods during the model projection, but the increases 

were not significant. 
 

Table 2—Stand characteristics (A) and predicted stand characteristics (B) following southern pine beetle-caused mortality, cut-andleave suppression, and wildfire in a pine-mixed hardwood stand and in a longleaf pine stand 

Pine-mixed hardwood Longleaf pine

A. Stand characteristics Year effect 1987 2003 Year effect 1989 2003

Pine basal area (m2/ha) 2.411, 16/ n.s. 0.0(0) 6.3(4.07) 5.371, 16/ n.s. 0.0 (0) 0.9 (0.39)

Hardwood basal area (m2/ha) 1.271, 16/ n.s. 11.7(3.39) 8.4(4.05) 3.471, 16/ n.s. 0.51 (0.51) 0.2 (0.10)

Canopy cover (percent) 12.71, 16/ * 36.7(5.72) 90.3(2.11) 14.91, 16/ * 3.6(1.46) 65 (6.5)

Loblolly-hardwood Post-blackjack oak Loblolly pine

B. Predicted stand characteristics Year effect 2003 2053 Year effect 2003 2053

Pine basal area (m2/ha) 8.461, 16/ n.s. 6.3 (4.07) 21.9 (7.89) 1.871, 16/ n.s. 0.9 (0.39) 24.3 (13.4)

Hardwood basal area (m2/ha) 4.691, 16/ n.s. 8.4 (4.05) 13.9 (5.83) 0.061, 16/ n.s. 0.2 (0.10) 15.5 (9.82)

Means (s.e.) from analysis: Fdf / P-value. 

n.s.= P>0.1. 

* = P<0.1. 

8

Longleaf Pine

Plant abundance significantly increased by 84 percent over 

the 16-year duration (table 1A). Similar increases were 

observed for plant richness over the same time period 

(92 percent) (table 1A). The interaction of overstory pine 

mortality and fire did not impact plant diversity or plant 

evenness from 1989 to 2003. In the longleaf pine stand, 384 

grasses from 14 species were tallied in 1989 and 345 grasses 

from 20 species in 2003 (app. 1A). Panicgrass (Panicum

spp.) and little bluestem were the most abundant grasses in 

1989, but little bluestem was the most abundant in 2003. 

Grass abundance and richness did not vary from 1989 to 

2003 (table 1B). 

In longleaf pine plots, 263 forbs comprising 12 species were 

assessed in 1989 and 323 forbs from 28 species in 2003 

(app. 1B). Bracken fern was the most abundant forb, but 

slightly decreased in abundance from 1989 to 2003. Wildfire 

and canopy loss increased forb species richness (150 

percent) from 1989 to 2003 (table 1C).

Two hundred ninety-four shrubs representing 13 species 

were surveyed in 1989 and 719 shrubs from 17 species in 

2003 (app. 1C). In 1989, yaupon and winged sumac (Rhus 

copallinum L. var. latifolia) were the two most abundant 

species. Yaupon was again the most abundant species 

in 2003 with farkleberry second in abundance. Shrub 

abundance significantly increased by 150 percent from 1989 

to 2003, and shrub species richness increased by 89 percent 

(table 1D).

In longleaf pine plots, 164 trees comprising six tree species 

were observed in 1989, and 640 trees comprising 17 species 

in 2003 (app. 1D). Bluejack oak (Q. incana) and post oak 

were the two most abundant species in 1989 and 2003. In 

2003, loblolly pine and longleaf pine were also prevalent. 

The interacting disturbances significantly increased tree 

abundance by 935 percent from 1989 to 2003 (table 1E). 

The accumulation of leaf-litter in the longleaf pine stand was 

significant (49 percent) (table 1F). Woody debris decreased 

by 97 percent from 1989 to 2003, but the decline was not 

significant. Pine and hardwood basal area increased from 

1989 to 2003, but neither were significant. Canopy cover 

significantly increased by 1,700 percent from the initial 

assessments to 2003 (table 2A).

In the longleaf pine stand, FVS designated the forest type as 

post oak-bluejack oak in 2003. The post oak-bluejack oak 

forest type shifted to a loblolly-hardwood forest type before 

transitioning to and maintaining a loblolly pine canopy in 

the 2053 projection. The predicted canopy is dominated by 

loblolly pine and bluejack oak; longleaf pine is also evident 

in the canopy while post oak is evident in the midstory.

Discussion

This was an opportunistic study whereby we utilized 

the framework from a preexisting study established 

in the mid-1980s to assess the successional trajectory 

following mortality caused by SPB suppression measures 

and wildfire. In spite of limitations associated with the 

original experimental design, we were able to use the exact 

methodologies at the exact locations to assess vegetation 

succession. Although the constraints imposed by the original 

study limit the inferences we are able to make (Hulbert 
9

1984), the opportunity to study forest succession using 

the original protocols under these interacting disturbance 

regimes was a strong impetus. Forest disturbance from 

SPB, suppression, and subsequent wildfire altered plant 

composition and stand characteristics after 14 years.

Pine-Mixed Hardwood

In the pine-mixed hardwood stand, loss of the codominant 

pine component increased the growing space and 

altered conditions on the forest floor. However, remnant 

hardwoods restricted gap size and limited growth of early 

successsion, shade-intolerant species, like grasses and 

forbs. Increases in total plant abundance and richness 

resulted from increases in the woody plant community, 

including yaupon, farkleberry, post oak, hickories, and 

sweetgum. The plant community became less evenly 

distributed, probably due to the dominance of the woody 

community. Elliott and others (1997) report a similar 

increase in plant richness but no change in plant diversity 

following a clearcut in southern Appalachia.

The early season (March) fire, coupled with the diminished 

fuel load from canopy mortality 14 years earlier, most 

likely impacted primarily understory vegetation, with only 

a limited influence on canopy vegetation. This allowed 

persistence of undisturbed hardwoods that decrease light 

exposure and air currents and prevent loss of soil moisture, 

promoting shade-tolerant and mesic-favoring woody plants, 

including Elliott’s blueberry and muscadine, which were 

abundant in the pine-mixed hardwood plots (Gleason and 

Cronquist 1991, USDA NRCS 2005).

Post oak, two species of hickories, and sweetgum were 

prominent in the pine-mixed hardwood stand in 2003, but 

pine basal area was comparable to hardwood basal area. 

Modeling predicts the pine basal area to double, thus 

maintaining the pine-mixed hardwood stand, but with 

loblolly pine dominating instead of several pine species. 

Ten years after small-scale canopy disturbances caused 

by SPB, Balch (1928) reported pine dominated canopies 

were transitioning to similar pine-oak canopies in North 

Carolina. The pine-mixed hardwood stand in 2003 had a 

two-story structure with hardwoods in dominant positions 

in the canopy and pine and hardwood regeneration in the 

midstory. Similarly, mortality of small patches of pine 

caused by SPB also increased structural complexity in latesuccessional pine-hardwood stands (Harrington and others 

2000). The interacting disturbances altered the initial evenaged stand, and reduced the susceptibility to stand replacing 

disturbances from future SPB outbreaks, thereby potentially 

enhancing forest health.

Longleaf Pine

Two years following widespread pine mortality, subsequent 

wildfire eliminated the pine and hardwood component, 

creating extensive gaps that favored pioneer and earlysuccessional species in the longleaf pine stand. Significant 

increases in canopy cover from 1989 to 2003, and minimal 

hardwood basal area in 1989 (table 2A), accurately depict 

these widespread losses. Disturbances reduced competition 

and increased sunlight penetration which increased total 

plant abundance and richness, forb richness, and tree 

abundance. Similar increases in plant richness were 

documented following fire in a second growth pineland in 

northern Florida (Mehlman 1992). Wildfire can eliminate 

competition, create greater sun exposure, increase bare 

soil, and reduce soil moisture (Walker 1962). As we 

expected, fire promoted plant species that can colonize 

quickly and withstand dry conditions created by minimal 

canopy cover, as well as species otherwise associated 

with disturbed habitats (Gleason and Cronquist 1991, 

USDA NRCS 2005). The three dominant grasses in the 

longleaf pine stand, similar to old fields or dry areas, 

were panicgrass, little bluestem, and tapered rosette 

grass (Dichanthelium acuminatum). The overwhelming 

abundance of bluestem, in particular Andropogon spp. and 

Schizachyrium spp., found in our longleaf pine plots are 

common to the fire-driven longleaf pine ecosystems of the 

Southeastern United States. These grass genera facilitate 

ignition and spread of fire during the growing season, 

sustaining longleaf pine composition (Landers 1991).

Bluejack and post oaks were the most abundant trees in 

2003, with loblolly and longleaf pines in lower densities. 

Modeling predicts that the less abundant loblolly pine will 

eventually attain dominance, shifting the longleaf pine 

stand to loblolly pine. Loss of longleaf pine represents a 

loss of a highly desirable forest type, and also represents 

a shift from a less susceptible to a highly susceptible host 

of SPB.

The FVS predicts pine either as a dominant or codominant 

component in each forest type. Modeling predicts that the 

future forest (2053) having pine basal area of 21.9 m2

/ha 

in the loblolly pine-hardwood stand and 24.3 m2/ha in the 

loblolly pine. Although model predictions forecast a forest 

moderately susceptible to SPB (Mason and others 1985), 

these dense pockets (of basal area) represent high hazards 

for SPB-caused mortality. The presence of scattered 

hardwoods may inhibit local spread of SPB within a stand 

(Hedden and Billings 1979), but hardwoods ultimately 

increase stress to pines by enhancing competition for 

resources, thereby escalating susceptibility to SPB. 
10

Interacting disturbances from SPB, associated suppression, 

and wildfire sustained the pine component. But without 

additional management, stands are predicted to become 

increasingly susceptible to SPB-caused mortality. Modeling 

predicts loblolly pine to dominate in the initially disturbed 

longleaf pine stand, enhancing susceptibility to SPB, 

and understory grasses increase fuel loads, enhancing 

susceptibility to wildfire. SPB and wildfire have historically 

played critical roles in influencing the successional 

trajectories of southern forests, and our modeling suggests 

that these disturbances are likely to continue shaping 

southern forest composition and succession.

Acknowledgments

We thank Kisatchie Ranger District (Natchitoches, LA), 

U.S. Department of Agriculture Forest Service, Southern 

Research Station, Pineville, LA and James H. Scarborough 

for use of facilities during this project and Jason Pieratt 

(University of Kentucky) for consultation about statistical 

analysis. We thank Brian Strom and additional anonymous 

reviewers for reviewing an earlier draft of this manuscript. 

This research was supported by funds from the Forest 

Service Forest Health Protection and their Pest Trend Impact 

Plot System program, the Southern Research Station Forest 

Insect Research Work Unit, and McIntire Stennis funds from 

the Kentucky Agricultural Experiment Station. Research 

support was provided through PTIPS, Region 8 (2004-2006) 

and is published as Experiment Station Project 06-08-011.

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13

Species name Common name Pine-mixed hardwood Longleaf pine

1987 2003 1989 2003

A. Grasses

Family Cyperaceae

 Cyperus retrofractus Rough flatsedge 0 0 8 0

 Eleocharis spp. Spikerush 0 0 2 0

 Rhynchospora glomerata Cluster beaksedge 0 0 1 1

 Scleria ciliata Fringed nutrush 0 5 8 7

 Scleria oligantha Littlehead nutrush 0 0 0 2

Family Poaceace

 Andropogon elliottii Elliott’s bluestem 2 0 3 0

 Andropogon ternarius Splitbeard bluestem 1 0 28 4

 Andropogon virginicus Broomsedge bluestem 0 0 0 13

 Aristida purpurascens Arrowfeather threeawn 0 1 7 12

 Aristida spp. Threeawns 0 0 1 1

 Chasmanthium laxum Slender woodoats 0 1 0 0

 Chasmanthium sessiliflorum Longleaf woodoats 20 9 0 0

 Dichanthelium aciculare Needleleaf rosette grass 0 2 0 7

 Dichanthelium acuminatum Tapered rosette grass 0 1 0 23

 Dichanthelium boscii Bosc’s panicgrass 0 0 0 1

 Dichanthelium scoparium Velvet panicum 0 5 0 2

 Dichanthelium sphaerocarpon Roundseed panicgrass 0 0 0 3

 Dichanthelium spp. Rosette grass 0 1 0 1

 Digitaria ischaemum Smooth crabgrass 0 0 4 0

 Eragrostis spectabilis Purple lovegrass 0 0 0 2

 Gymnopogon ambiguus Bearded skeletongrass 0 1 0 3

 Muhlenbergia expansa Cutover muhly 0 0 6 1

 Panicum spp. Panicgrass 0 0 221 0

 Paspalum floridanum Florida paspalum 0 0 0 1

 Paspalum plicatulum Brownseed paspalum 0 0 1 0

 Polypogon spp. Beard grass 0 6 0 0

 Schizachyrium scoparium Little bluestem 26 7 87 247

 Schizachyrium tenerum Slender little bluestem 0 0 0 12

 Sorghastrum nutans Indiangrass 0 3 7 2

Total grass and graminoid plants 49 42 384 345

B. Forbs 

Family Aristolochiaceae

 Aristolochia serpentaria Virginia snakeroot 0 1 0 4

Family Asteraceae

 Aster dumosus Rice button aster 0 0 0 1

 Erigeron canadensis Canadian horseweed 0 0 11 0

 Helianthus angustifolius Swamp sunflower 0 0 5 3

 Heterotheca graminifolia Narrowleaf silkgrass 1 0 1 20

 Heterotheca pilosa Soft goldenaster 0 0 1 3

 Kuhnia eupatorioides False boneset 0 0 0 1

 Liatris pycnostachya Prairie blazing star 0 0 0 2

 Rudbeckia hirta Blackeyed Susan 0 0 0 1

 Solidago odora Anisescented goldenrod 0 1 17 12

Family Cistaceae

 Lechea minor Thymeleaf pinweed 0 0 1 0

Family Dennstaedtiaceae

 Pteridium aquilinum Western bracken fern 20 46 208 178

Family Euphorbiaceae

 Acalypha gracilens Slender threeseed mercury 0 0 0 1

 Euphorbia corollata Flowering spurge 0 0 0 8

 Tragia smallii Small’s noseburn 0 1 0 31

 Tragia urens Wavyleaf noseburn 0 0 0 5

 Tragia urticifolia Nettleleaf noseburn 0 1 1 9

Family Fabaceae

 Cassia fasciculata Sleepingplant 0 0 14 0

 Clitoria mariana Atlantic pigeon-wings 0 0 0 4

 Desmodium lineatum Sand ticktrefoil 0 0 0 1

 Galactia erecta Erect milkpea 0 0 0 4

continued

Appendix—Temporal changes in vegetation species in a pine (Pinus spp.)-mixed hardwood stand and a longleaf pine (Pinus 

palustris) stand suffering overstory mortality from southern pine beetle (Dendroctonus frontalis)-caused mortality, associated 

suppression, and subsequent wildfire
14

Species name Common name Pine-mixed hardwood Longleaf pine

1987 2003 1989 2003

Family Fabaceae (continued)

 Galactia volubilis Downy milkpea 0 1 0 4

 Lespedeza virginica Slender lespedeza 0 1 0 1

 Rhynchosia difformis Doubleform snoutbean 0 0 0 2

 Rhynchosia reniformis Dollarleaf 0 0 0 2

 Stylosanthes biflora Sidebeak pencilflower 0 0 0 6

 Tephrosia virginiana Virginia tephorsia 0 0 2 11

Family Lamiaceae

 Pycnanthemum albescens White mountainmint 0 0 1 4

Family Lobeliaceae 

 Lobelia puberula Downy lobelia 0 0 0 1

Family Rubiaceae

 Galium pilosum Hairy bedstraw 0 0 0 1

 Mitchella repens Partridgeberry 0 7 0 0

Family Scophulariaceae

 Agalinis spp. False foxglove 0 0 0 3

Family Selaginellaceae

 Seliginella spp. Spikemoss 0 0 1 0

Total forbs 21 59 263 323

C. Shrubs

Family Agavaceae

 Yucca louisianensis Gulf Coast yucca 0 0 0 3

Family Anacardiaceace

 Rhus aromatica Fragrant sumac 0 3 0 0

 Rhus copallinum var. latifolia Winged sumac 0 3 40 28

 Toxicodendron radicans Eastern poison ivy 0 2 0 0

 Toxicodendron toxicarium Atlantic poison oak 0 0 0 10

Family Aquifoliaceae

 Ilex vomitoria Yaupon 14 144 148 417

Family Bignoniaceae

 Bignonia capreolata Crossvine 1 7 0 0

Family Caprifoliaceae

 Viburnum dentatum Southern arrowwood 0 3 0 0

 Viburnum rufidulum Rusty blackhaw 0 6 0 0

Family Ericaceae

 Rhododendron canescens Sweet mountain azalea 10 17 0 0

 Vaccinium arboreum Farkleberry 5 116 32 89

 Vaccinium elliottii Elliott’s blueberry 46 41 4 49

 Vaccinium stamineum Deerberry 0 15 36 63

 Vaccinium virgatum Small flower blueberry 7 63 0 4

Family Hypericaceae

 Hypericum hypericoides St. Andrews cross 2 0 1 0

Family Smilacaceae

 Smilax bona-nox Saw greenbrier 0 1 0 1

 Smilax glauca Cat greenbrier 2 13 12 13

 Smilax pumila Sarsparilla-vine 10 17 0 0

 Smilax rotundifolia Roundleaf greenbrier 0 4 0 0

Family Loganiaceae

 Gelsemium sempervirens Evening trumpetflower 1 9 9 21

Family Rhamnaceae

 Berchemia scandens Alabama supplejack 1 0 0 0

 Ceanothus americanus New Jersey tea 0 0 1 3

Family Rosaceae

 Crataegus marshallii Parsley hawthorn 0 0 0 1

 Crataegus spathulata Littlehip hawthorn 0 1 0 0

 Rubus spp. Blackberry 0 0 0 1

 Rubus trivialis Southern dewberry 0 0 3 0

Family Styracaceae

 Styrax grandifolius Bigleaf snowbell 8 20 0 0

Family Verbenaceae

 Callicarpa americana American beautyberry 1 16 1 8

continued

Appendix—Temporal changes in vegetation species in a pine (Pinus spp.)-mixed hardwood stand and a longleaf pine (Pinus 

palustris) stand suffering overstory mortality from southern pine beetle (Dendroctonus frontalis)-caused mortality, associated 

suppression, and subsequent wildfire (continued)
15

Species name Common name Pine-mixed hardwood Longleaf pine

1987 2003 1989 2003

Family Vitaceae

 Vitis aestivalis Summer grape 2 8 3 1

 Vitis rotundifolia Muscadine 16 40 4 5

Total shrubs 125 543 294 719

D. Trees 

Family Aceraceae

 Acer rubrum Red maple 0 22 0 1

Family Aquifoliaceae

 Ilex opaca American holly 2 0 0 0

Family Cornaceae

 Cornus florida Flowering dogwood 7 43 0 7

Family Ebenaceae

 Diospyros virginiana Common persimmon 0 0 0 1

Family Fagaceae

 Quercus falcata Southern red oak 9 191 13 51

 Quercus incana Bluejack oak 0 0 94 245

 Quercus marilandica Blackjack oak 0 8 0 0

 Quercus nigra Water oak 0 9 0 0

 Quercus stellata Post oak 4 151 24 88

Family Hamamelidaceae

 Liquidambar styraciflua Sweetgum 1 54 0 1

Family Juglandaceae

 Carya cordiformis Bitternut hickory 0 75 0 0

 Carya tomentosa Mockernut hickory 0 143 0 4

Family Lauraceae

 Persea borbonia Redbay 0 0 0 3

 Sassafras albidum Sassafras 0 0 18 11

Family Myricaceae

 Myrica cerifera Wax myrtle 6 11 7 11

Family Nyssaceae

 Nyssa sylvatica Blackgum 2 6 0 3

Family Oleaceae

 Chionanthus virginicus White fringetree 0 4 0 6

 Fraxinus pennsylvanica Green ash 0 4 0 0

Family Pinaceae

 Pinus echinata Shortleaf pine 0 11 0 11

 Pinus palustris Longleaf pine 0 0 0 26

 Pinus taeda Loblolly pine 46 361 0 56

Family Rosaceae

 Prunus serotina Black cherry 0 4 8 0

 Prunus umbellata Hog plum 0 0 0 1

Family Sapotaceae

 Bumelia lanuginosa Gum bully 5 1 0 0

Family Styracaceae

 Halesia diptera Two-wing silverbell

0 5

0 0

Total trees 84 1,058 164 640

Total individuals 278 1,753 1,105 1,911

Species names follow USDA, NCRS PLANTS database (2005).

Numbers indicate frequency of tallies along transects for A. Grasses (Families Poaceae and Cyperaceae), B. Forbs (non-grass herbaceous 

species), C. Shrubs (woody plants < 10m), and D. Trees (woody plants > 10m). 

Appendix—Temporal changes in vegetation species in a pine (Pinus spp.)-mixed hardwood stand and a longleaf pine (Pinus 

palustris) stand suffering overstory mortality from southern pine beetle (Dendroctonus frontalis)-caused mortality, associated 

suppression, and subsequent wildfire (continued)



Coleman, T.W.; Martin, Alton, Jr.; Meeker, J.R. [and others]. 2010. Disturbance from 

southern pine beetle, suppression, and wildfire affects vegetation composition in central 

Louisiana: a case study. Gen. Tech. Rep. SRS–129. Asheville, NC: U.S. Department of 

Agriculture Forest Service, Southern Research Station. 15 p.

We assessed plant composition and forest succession following tree mortality from infestation 

of southern pine beetle (Dendroctonus frontalis), associated suppression, and wildfire in two 

forest types, pine (Pinus spp.) with mixed hardwood and longleaf pine (P. palustris). In this 

case study, vegetation was assessed in 2003 using methodology and experimental framework 

established 16 years earlier. We examined changes in vegetation composition from the 1980s 

to 2003 in each forest stand type and used the Forest Vegetation Simulator to predict forest 

succession.

In the pine-hardwood stand, total plant and woody plant abundance and richness increased 

over the study while total plant evenness decreased. The Forest Vegetation Simulator predicts 

the pine-mixed hardwood will shift to loblolly pine-hardwood after 50 years. In the longleaf 

pine stand, total plant abundance and richness increased. The interacting disturbances 

enhanced forb, shrub, and tree abundance. Forb and shrub species richness also increased. 

Modeling predicts the longleaf pine stand will shift to loblolly pine (P. taeda) following 

the disturbance events. Although stand predictions are different for each initial forest type, 

predicted pine and hardwood basal area represent high susceptibility to future SPB outbreaks. 

The interaction of these three disturbance events (beetle infestation, associated suppression, 

and wildfire) appears to maintain pine composition, but also the potential for additional SPBcaused mortality, though thinning may reduce the susceptibility of these stands to bark beetle 

disturbance. The unique opportunity to assess interacting disturbances and natural succession 

was the motivation for our study, but our inferences are limited due to constraints of the 

experimental design.

Keywords: Cut-and-leave suppression, Forest Vegetation Simulator, loblolly pine, southern 

pine beetle, wildfire.
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