New Fertilizer Promising For Southern 
Pines
Foresters have traditionally been
reluctant to use fertilizers, because of
economic factors, despite a consistent
response to nitrogen by pines. How-
ever, in the past 20 years, more fertil-
izer has been used, generally urea,
because of its high nitrogen content.
Recent AAES research, however, in-
dicates a new fertilizer being devel-
oped by the Tennessee Valley Au-
thority (TVA) may be more appli-
cable than urea for pines.
Urea nitric phosphate (UNP) is a
relatively new fertilizer developed
by the TVA. Research indicates UNP
has the potential to reduce ammonia
loss by as much as 50% over urea.
Ammonia retention is critical to pre-
vent urea toxicity to seed and seed-
lings.
In tests on a 14-year-old pine stand
near Auburn, researchers compared
growth of trees treated with UNP,
urea plus triple superphosphate (TSP),
and no treatment. The UNP-treated
trees one year after treatment aver-
aged 43.5 feet tall, compared to 42.8
for the urea plus TSP-treated trees,
and 42.5 for untreated trees. Bole dry
weight of the UNP-treated trees aver-
aged 107.3 poundsper tree, compared
to 105.3 for the urea plus TSP-treated
trees, and 103.5 for the untreated trees.
D. Crawford and B. G. Lockaby
Acid Rain and Ozone Effects on Loblolly
Pine Growth
Data from remeasurements of
Forest Inventory and Assessment
plots in the South indicate the possi-
bility of a recent, unexplained decline
in the growth rate of pines in some
portions of this region. These obser-
vations, along with reports of forest
damage and growth decline in high
elevation forests of the Eastern U.S.
and southern California, have led to
an increase in public concern.
Drought, disease, hardwood com-
petition, changes in stand age and
previous use (old fields), and air pol-
lution (primarily acid rain and ozone)
have been implicated as possible
causal or contributing factors to these
declines.
Auburn researchers used a modi-
fied open-top chamber, or "outdoor
greenhouse," to study the effect of
continued on page 2
RESEARCH UPDATE
.-1991
FORESTRY
Regenerating
Bottomland Hardwood
Forests
Hardwood forests in Alabama are
becoming increasingly valuable for
use in wood products and as habitat
and food suppliers for wildlife.
Managing these forests is generally
more complex than managing pine
stands, primarily because a wider
diversity of species (with varied
ecological characteristics and val-
ues) is involved.
Auburn researchers found that in
two different stands, where clear-cut-
ting was applied 7 years earlier, along
with treatment of undesirable trees,
good establishment of commercial
species has occurred. Commercially
valuable hardwoods taller than one-
foot totaled 1,691 and 1,792 per acre
in the two stands within seven
growing seasons after clearcutting.
When compared to the preharvest
stands, water and willow oaks, green
ash, and sweetgum increased or re-
mained stable in numbers and pro-
portions in the regenerated stand.
However, both cherrybark and
swamp chestnut oaks (two of the
most highly valued species) de-
clined in numbers and proportions.
continued on page 2
?AAAM-RIUTUAEXEIMN STAIi' I. U
LOWELL ~ ~ ~ ~ ~ ~ ~ 1:' T.FomDRCO uUR NVRIY LBM
Acid Rain and Ozone, continued
acid rain and ozone on pine seedlings.
This chamber allows researchers to
apply different treatments of acid
rain and ozone to trees while they
are growing in the ground.
After 2 years, results indicate that
acid rain is not having a deleterious
effect on above-ground growth or
productivity, but soil chemistry
near the roots (rhizosphere) may be
altered slightly. Ozone at high con-
centrations causes a significant reduc-
tion in foliar biomass, chlorophyll
content, photosynthesis, and alters
nitrogen status; slight reduction in
height and diameter growth; and an
increase in visible injury.
A. H. Chappelka
Regenerating Hardwoods, continued
The decline of these species probably
can be attributed largely to a lack of
advance regeneration present when
the stands were cut. Thedevelopment
of reliable techniques to increase ad-
vance regeneration will be neces-
sary in order to consistently regen-
erate these species successfully.
M. S. Golden
Tree Harvests and Environmental Quality in Forested Wetlands
Forested wetlands are among the
most productive ecosystems in the
world. They harbor high diversity of
plants and animals, and they protect
water quality by attenuating floods,
filtering out sediments and nutrients,
and shading streams. Because the use
of forested wetlands for recreation
and wood production has increased
dramatically in recent years, there
are concerns that water quality may
become degraded.
To determine impacts of tree har-
vests on wetland ecosystem func-
tions, a joint project among AAES,
Scott Paper Company, the Tennessee
Valley Authority, the National
Council of the Paper Industry for
Air and Stream Improvement, and
N.C. State University was recently
initiated. With a focus on small
stream drainages in the Alabama
Coastal Plain, the 3-year study will
determine the impact of helicopter
logging and conventional tree skid-
ding on nitrogen cycling, tree regen-
eration, plant productivity, and soil
physical properties.
In wetlands, the removal of trees
by conventional rubber-tired skid-
ders can cause deep soil ruts and soil
compaction. This in turn can enhance
soil erosion, alter the species of tree
regenerated, and decrease stand pro-
ductivity. Helicopter logging can
minimize these impacts. Quantifying
environmental consequences of the
two harvesting methods is a critical
part of the study. The use of helicop-
ters will provide a unique opportu-
nity to determine independent ef-
fects of tree removal and soil distur-
bance on wetland system functions.
Additional components of the
study will evaluate rates of sedi-
mentation in wetland forests caused
by harvesting in adjacent upland for-
ests, and potentially beneficial effects
of forest buffer strips on groundwa-
ter nitrate concentrations and surface
erosion. The study will be capped by
a technology transfer program to in-
form foresters, loggers, and landown-
ers about environmental conse-
quences of tree harvests in wetlands.
R. H. Jones
Weed Control Improves Tree Survival and Growth
The Auburn University Silvicul-
tural Herbicide Cooperative is a
southeastern regional research coop-
erative among the School of Forestry,
Alabama Agricultural Experiment
Station, State of Alabama, 17 forest
industries, and the USDA Forest Ser-
vice. Collectively, this group owns
or controls over 30 million acres of
commercial forest land in the South.
The objectives of the Cooperative
include: developing competition
control techniques to increase tree
survival and growth and an under-
standing of relationships among
site characteristics, competing veg-
etation, and tree growth.
Projections indicate the South must
dramatically increase timber pro-
duction over the next 40 years in
order to counter the reduction in old-
growth forests in the Pacific North-
west. A major obstacle to forest pro-
ductivity in the South is competition
from herbaceous and woody weeds.
Cooperative studies demonstrate
exceptional initial tree growth re-
sponse and improved survival
under drought conditions following
herbaceous weed control treatments.
Indications are that all sites in the
South will respond to competition
control. On most sites, herbaceous
species are most important in re-
stricting pine growth and develop-
ment in plantations up to 
4 years old,
with hardwood and shrub competi-
tion being most important after age
5. Research has shown that in-
creases in diameter, height, basal
area, and volume production of
loblolly pines on stands with herba-
ceous weed control can be main-
tained for at least 12 years under
continued on page 3
Weed Control, continued
diverse site conditions.
Research also has shown that
pines released from hardwood com-
petition at age 3 or 4 have produced
up to 80% more volume 8 years after
treatment. These short-term results
indicate that when weed control is
applied early in the life of a forest,
rotation length will likelybereduced
by 2-3 years.
The dramatic growth responses
shown in various studies suggest
that most forest lands have a weed
problem and that appropriate weed
control technology must be devel-
oped and implemented if future de-
mand for forest products is to be met.
D. H. Gjerstad
Mortality in CRP Plantings
The Conservation Reserve Pro-
gram resulted in more than 2,000,000
acres of erodible farm land converted
from conventional row crop agricul-
ture to timber production. 
However,
on a reasonably large percentage of
the acreage planted (10-15%) com-
plete to nearly complete tree mortal-
ity was observed, despite no apparent
cause. Replanting these sites often
resulted in repeated pine failure.
AAES researchers found that root
feeding insects, primarily white
fringe beetle larvae, in association
with nematode - fungal pathogen in-
teractions, were largely responsible
for the excessive mortality. These
agents were exacerbated by the pres-
ence of a well developed plow-pan,
particularly in years of drought. In
addition, it was conclusively shown
that herbicide residues from past
crop production and herbicides used
in pine culture to control weeds were
not directly involved in the mortal-
ity problems.
This research solved a regenera-
tion problem and it is a prime ex-
ample that large regeneration 
efforts,
such as the CRP, can uncover signifi-
cant unforseen problems that can be
solved through research. This is
particularly important in light of the
massive tree planting programs that
are proposed to combat predicted
global warming and increasing COC
levels in the atmosphere.
R. J. Mitchell
Genetic Influences on the Nutrient Efficiency of Loblolly Pine
During the past 30 years, signifi-
cant strides have been made in the
genetic improvement of loblolly
pine. The vast majority of seedlings
now planted in the region are "ge-
netically improved," meaning they
are fast growing and disease resis-
tant. Auburn researchers are trying
to maximize the productivity of ge-
netic improvement by studying the
interaction between genotype (family
origin) and nutrient efficiency. It is
possible that specific genotypes or
families could be matched to site
characteristics to maximize growth
or that certain genotypes may re-
spond to fertilizer application more
effectively than others.
Studies done by the AAES com-
pared four families of loblolly pine
for differences in productivity and
nutrient use under fertilized versus
nonfertilized conditions in the field.
Family differences were found in
biomass production, component
biomass allocation, and nutrient use.
One family was shown to be most
productive and most nutrient effi-
cient under both fertilized and
unfertilized treatments. 
In general,
nutrient use was found to closely mir-
ror biomass production, suggesting
that the traditional approach to nu-
trient use was confounded with
growth.
To find an approach to nutrient
efficiency that is not confounded by
biomass, another study was initi-
ated. Variables, such as nutrient and
biomass accumulation, element ra-
tios, nutrient uptake efficiency, and
internal translocation 
efficiency,
were examined. Results indicated
distinct family differences between
uptake patterns and internal cycling
of certain elements. Family varia-
tion in element ratios, and internal
translocation efficiency generally did
not mirror family productivity dif-
ferences. Hopefully, these ap-
proaches will provide additional in-
formation on specific mechanisms
through which various genotypes
use nutrients most effectively, un-
der different site conditions.
D. Crawford and B. G. Lockaby
Nitrate Movement in Forest Tree Nursery Soils
Tree nurseries are essential to
modem forest management because
they produce the seedlings that are
used to regenerate harvested forests.
Nurseries are highly specialized
operations that use significant
amounts of fertilizers and pesticides
to maximize the production of seed-
lings that have suitable quality to
survive and grow after lifting, stor-
age, transportation, and field plant-
continued on page 4
I
Seed Efficiency: A
Goal of the Nursery
Cooperative
Forest industries invest millions
of dollars each year to improve the
genetic potential of loblolly pine
seed, some of which is in turn lost
due to poor management practices in
the nursery. For example, in some
areas in Canada, the seed efficiency
for pines grown in operational con-
tainer nurseries is usually less that
50 percent.
A major goal of the Auburn Uni-
versity Southern Forest Nursery
Management Cooperative is to im-
prove management practices that
will increase seed efficiency in bare-
root nurseries. In 1975, seed efficiency
for many bare-root nurseries in the
South was about 66 percent. How-
ever, Cooperative research involv-
ing herbicides and fungicides has
helped to increase the number of
seedlings surviving till lifting.
Research with lowering seedbed
densities, seed stratification, and pre-
cision sowing has helped to reduce the
percentage of culls. As a direct result,
many bare-root nurseries in the South
now obtain seed efficiencies above 80
percent. Research aimed at obtaining
high seed efficiencies in bare-root
nu rseri es should help keep the cost of
pine seedling production to near the
lowest among the developed nations.
D. B. South
ED)ITOR'S NOTE
Mention of company or trade names does not
indicate endorsement Of one brand over another
by the Alabama Agricultural Experiment Sta-
t ion or Auburn University. Any mention of non-
label uses or applications in excess of labeled rates
of pesticides or other chemicals does not constitute
a recommendation. Such use in research is simply
part of the scientific investigation necessary to
fully evaluate materials and treatments.
Information contained herein is available to all
persons without regard to race, color, sex, or
national origin.
March 1991 7.5M
Nitrate Movement, continued
ing, despite adverse weather condi-
tions.
Pine nurseries are generally lo-
cated on light (sandy) soils. Soil type,
along with normally high levels of
fertilizer application and a shallow
non-fibrous root system on most tree
species, may create conditions of ex-
cess nitrate nitrogen which has the
potential to leach downward and
into underground water. Nitrates
are of particular concern because
the EPA has established maximum
acceptable levels of nitrate concen-
trations in drinking water at 10 ppm.
Research to study the movement
of nitrate nitrogen in forest tree
nurseries has been initiated by the
AAES. Water samples are being col-
lected throughout the nursery sea-
son from wells. By analyzing these
well samples for nitrate concentra-
tions and then using computer mod-
els which calculate the movement
of soil water through the profile
based on weather records and soil
type, an estimation can be made as
to the quantity, if any, of nitrate
movement into underground water
sources.
K. L McNabb
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