Evaluating the Extent and Nature of Pine Health Issues in the Southeastern U.S.
Kamal J.K. Gandhi1 , David R. Coyle1, Kier D. Klepzig2, Frank H. Koch2, Lawrence A. Morris1, John T. Nowak2,
2
2
William J. Otrosina , and William D. Smith
1University
of Georgia, Warnell School of Forestry; 2USDA Forest Service, Southern Research Station & Forest Health Protection
Introduction
Research Objectives
Preliminary Results & Conclusions
During the last several decades, dieback and mortality
of loblolly pine (Pinus taeda) has been reported
throughout the southeastern U.S. (Fig. 1) (1).
1. Assess the relative contributions of a) predisposing (e.g., forest
composition and structure, land-use history, and soil type); b) inciting
(e.g., forest management activities such as prescribed fire, short-term
subcortical insect and root fungal pathogen activity and weather
conditions); and c) contributing (e.g., subcortical insect and root fungal
pathogen activity) factors to pine health.
A total of 29 stands have been sampled in Alabama and
Georgia. A similar incidence of Leptographium spp. and
Heterobasidion spp. was found in symptomatic and
asymptomatic stands (Fig. 4).
Little work has been conducted on the relative
contributions of abiotic and biotic factors that may be
interacting with pine trees under varying conditions.
Our preliminary work indicated that ~3% of total FIA
plots showed negative net pine growth (Fig. 2). The
average nearest neighbor distance analyses produced
similar index values for the negative net growth plots
and all plots. This indicates that both sets of plots
exhibit a clustered spatial pattern, which is expected for
most tree species whose regional distributions are
shaped by physiographic and climatic constraints.
Similar index values suggest that there is no distinct
regional pattern of abnormally high pine mortality, and
that tree mortality is at local scale (Fig. 2).
2. Build decision models based on site and weather conditions,
management history, and presence of subcortical insects and root
fungal species. These models will assist with effectively managing pine
health issues for sustainable forests in the southeastern U.S.
Methods
Soil Sampling: Soils are sampled in 0-15 and 16-30 cm depth
increments. Each sample consists of a composite of 5 individual 2-cm
diam. samples from within the plot. Soils are being analyzed for
physical (texture) and chemical (pH, N, P, K, and micronutrients)
characteristics.
Root Sampling: In each plot, roots are sampled from up to three
mature pine trees. Sections from a small (~1 cm diam.), medium (2-5
cm) and large (>7 cm) root are removed. Roots are surface sterilized
and subsections of each root are plated on selected agar media to
culture Heterobasidion and Leptographium spp. that will be identified to
species-level using morphological and molecular techniques.
Study Sites: We selected stands that are (symptomatic)
or are not (healthy) showing decline symptoms in
Alabama and Georgia. In each stand, one transect with
four FIA-style 10 m radius plots is established every
250 m along a line in similar soil series.
GA Symptomatic
GA Symptomatic
GA Healthy
AL Symptomatic
AL Healthy
500
GA Healthy
AL Symptomatic
400
AL Healthy
300
ppm
Methods
200
100
0
SAND
16
Leptographium spp.
14
CLAY
SILT
Ca
8
6
4
2
0
1
2
3
4
5
8
9
10
11
32
Site
Fig. 4. Incidence of Heterobasidion and Leptographium spp. in Alabama.
Our preliminary results
suggest that there are no
clear patterns of pine
dieback in the Southeast,
dieback is variable and at
local scale, and that
multi-level abiotic and
biotic factors may be
affecting pine health in
this region (Fig. 5).
Fig. 5. Multiple factors affecting pine health in
FIA plots.
Acknowledgements
Field sampling indicated that soils were sandy-clayey and generally
nutrient deficient across all sites (Fig. 3). Soils from symptomatic sites
in Alabama were especially low in P and Zn. pH was nearly equal
among states and site types, ranging from 4.7 to 5.1.
90
80
70
60
50
40
30
20
10
0
Heterobasidion irregulare
10
Stand and Tree Sampling: Stand level data collection includes stand
age and area, silvicultural and disturbance history, and local weather
conditions during the last 10 years. Within each plot, we are collecting
the following data on each tree (>2.5 cm DBH): 1) species; 2) DBH; 3)
tree dead or alive. We are also collecting crown condition on a 0-4
rating, crown symptoms and any evidence of symptoms, damage and
type of damage (abiotic or biotic).
%
As a multi-disciplinary and multi-agency team, we are
conducting a regional-level study to better understand
pine health issues in Alabama and Georgia.
18
12
Preliminary Results & Conclusions
Fig. 2. Analysis of Forest Inventory and Analysis plots in the Southeast (results shown for AL, GA
and part of SC) where (A) indicates pine growth, and (B) indicates pine mortality in the region.
Similarly, both the root fungal species were found in 0, 250,
and 500 m plots with no clear patterns related to site
conditions.
Number of infected trees
Fig. 1. Typical dieback and mortality in
a southern pine stand.
Dieback symptoms include
loss of crown, reduction in
annual growth, presence of
root pathogens such as
Phytophthora cinnamomi,
Heterobasidion irregulare, and
Leptographium spp. (2). In
addition, root-attacking
weevils, Hylastes, Hylobius,
and Pachylobius spp., have
been reported (2,3).
K
Mg
Mn
Fig. 3. Texture and chemical characteristics in symptomatic and healthy soils in Alabama and Georgia.
We are grateful to Dale Starkey (USDA Forest Service),
Chip Bates and Scott Cameron (Georgia Forestry
Commission), and Brittany Barnes, Steven Hughes,
Kristopher Smoot, and Courtney Brissey (University of
Georgia) for assistance on the project. Funding was
provided by the USDA Forest Service Evaluation Monitoring
Program, USDA Forest Service Southern Research Station,
and the University of Georgia.
Literature Cited
(1) Eckhardt, L.G. et al. 2007. For. Sci. 35: 84-92.
(2) Eckhardt, L.G. and Menard, R.D. 2009. AL Treasured Forest
Magazine Volume XXV111: 10-12.
(3) Eckhardt, L.G. et al. 2010. South. J. Appl. For. 34: 138-141.