Item I.D.
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acorn
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Comparison of Acorn
Production and Damage on Sites with
Abundant and with Sparse Oak
Regenderation
CURRENT REPORT 36
JUNE 1962
West Virginia
University Agriculture Experiment
Station |
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inside front
cover |
THE AUTHORS
E. H. Tryon is Professor of Silviculture
and Silviculturist. K. L. Carvell is
Associate Professor of Silviculture and
Associate Silviculturist.
The Cover
Seed traps are used to help determine
the number of acorns produced and the
damage from various causes.
Acknowledgment
Photographs showing acorn damage are
courtesy of C. K. Dorsey, Professor of
Entomology and Entomologist.
west virginia university agricultural
experiment station
college of agriculture, forestry, and
home economics A. H. vanlandingham,
director
MORGANTOWN
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Comparison of Acorn Production and
Damage on Sites with Abundant and with
Sparse Oak Regeneration
E. H. TRYON and K. L. CARVELL
A study of site factors which affect
the amount of oak regeneration under
mature oak stands is in progress, and is
being conducted by foresters and
entomologists of the West Virginia
Agricultural Experiment Station. Site
factors being studied are those within
the four main groups—topographic,
biotic, edaphic, and climatic—which are
considered or found to have an important
direct effect on the acorn, its
germination, and establishment and
juvenile growth of the oak seedling.
Valuable information is being gained by
this study concerning the conditions
needed for the natural regeneration of
oak stands. With the accumulation and
application of such information, better
silvicultural practices will be used in
the management of oak forests.
The main purpose of this report is to
present the results of a study of agents
affecting acorns collected from oak
stands under which abundant reproduction
occurs, and from oak stands beneath
which sparse reproduction occurs. An
earlier publication1 indicated that
little difference in acorn production
occurred between the two conditions.
However, the more intensive study
reported here is based on a longer
period of time, and it treats the
importance of the individual agents
affecting acorns on each of the two
conditions where abundant and where
sparse oak regeneration occur.
Plot Establishment
Seven paired areas supporting mature
oak stands were selected for the study.
The two portions of each paired area
were as similar as could be found from
the standpoint of elevation, topography,
and stand composition and age. However,
one portion of each pair had abundant
oak reproduction, whereas on the other,
reproduction was sparse. Two large oaks,
one northern red (Quercus rubra
L.) and one white (Quercus alba
L.), were selected as plot trees on each
portion of the paired area. Thus, four
plot trees were on each of the seven
paired areas, making a total of 28
plots.
'Tryon, B. H. and K. L. Carvell.
1958. Regeneration Under Oak Stands.
West Virginia University Agricultural
Experiment Station Bulletin 424T. 22 pp.
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Two quarter-milacre
seed traps and two quarter-milacre
ground quadrats were established on the
ground within the horizontal projection
of the crown of each of the 28 oaks from
which acorns were collected. Collections
were made in the fall and spring during
a five-year period, from 1954 to 1958
inclusive. By examination of the acorns,
the total number of acorns and the
amount of damage to and loss of acorns
by destructive agents were computed.2
To test differences statistically, the
count data were transformed by Vx+1, and
the percentage data by the arcsin
transformation for more efficient
testing. Results
The amount of oak reproduction, stems
less than 0.5 inches d.b.h., differed
greatly between the two portions of the
paired areas. The sites with abundant
oak reproduction had approximately five
times as much as the sites with sparse
oak reproduction, the former averaging
13,490 oak seedlings per acre as
compared with only 2,615 oak seedlings
per acre on the latter sites. This
difference in amount of regeneration
between the two situations is
significant at the 1 per cent level.
A comparison of total acorn
production and types of damage for areas
with abundant and with sparse oak
reproduction is presented in Table 1.
For the conditions listed, none of the
differences between numbers of acorns on
the areas with abundant and with sparse
oak reproduction is statistically
significant. Although a somewhat larger
number of acorns was produced on the
sites with sparse oak reproduction, more
sound acorns were produced when the
reproduction was abundant. The
differences however, were not large and,
as indicated above, not significant.
Also, a tendency existed for both insect
and animal damage to acorns to be
slightly higher on the areas where the
sparse reproduction occurred.
In order to compare the condition of
the acorns, especially damage on the two
sites on the basis of equal acorn
numbers, the sound and damaged acorns
also are presented as a percentage of
the total number produced on each site
(Table 1). Again, none of the
differences in percentage of acorns
between the two sites for any condition
is statistically significant. However,
the trend for a higher proportion of
sound acorns on the sites with abundant
oak reproduction may again be observed,
as well as the tendency for greater
animal and insect damage on the sites
with sparse oak regeneration.
Thus, neither the amount of animal
nor insect damage to acorns differ
appreciably between the sites with
abundant oak regeneration and those with
sparse oak regeneration.
2A more detailed account of the
method is presented in West Virginia
University Agricultural Experiment
Station Bulletin 466T by E. H. Tryon and
K. L. Carvell entitled Acorn
Production and Damage. 18 pp. 1962.
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A—A healthy acorn. The solid, fleshy
portion filling the shell Is made up of
the cotyledons. B—This acorn has been
completely destroyed by the acorn weevil
larvae.
C—This acorn has been destroyed by
the acorn caterpillar.
Heavy damage to the acorn crops by
insects and animals is indicated. On
each of the two sites, over 80 per cent
of the acorns were damaged by these
agents.
table 1. condition of acorns by
numbers per mii.acre and percentage on
sites with abundant and with sparse oak
reproduction
(5-YEAR basis)
acokn
condition |
NUMBKR |
pkrckntac.k |
abundant oak
reproduction |
spars k oak
rkproduction |
abundant oak
kkproiiuction |
sparse oak
rkphoduction |
|
108 190 312
159 40 113 5 |
71 246 SM
241 32 123 3 |
Per Cinl
17.6 30.9 50.8 25.9 fi.6
18.3 0.5 |
Per Cent
10.0 34.2 55.4 33.7 4.5 17.2
0.4 |
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Cut, on
ground ...... |
Missing from
ground ........ Missing from
tree ............ Other |
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615 |
710 |
100.0 |
100.0 |
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Conclusions
Relatively small differences were found
between sites with abundant oak
reproduction and sites with sparse oak
reproduction in: (1) total acorn
production, (2) number of sound acorns
produced, (3) damage to acorns by
insects, and (4) damage to and loss of
acorns by animals. The sites with
abundant oak reproduction had nearly
five times as many oak seedlings as
those with sparse oak reproduction
(13,490 oak seedlings per acre to
2,615). Therefore, acorn production and
damage to the acorns by all or any
single damaging agent were not primarily
responsible for differences in amount of
oak reproduction between the two
situations studied.
Site factors affecting seedlings
establishment, from the time of acorn
germination through the juvenile growth
period, are considered to be more
important in determining the amount of
oak reproduction than those factors
directly affecting the acorn. Jn
general, it is believed that the ability
of oak regeneration to persist on a
specific site is more closely related to
environmental conditions than is its
ability to become established.3 The
environmental factors favoring oak
regeneration beneath mature oak stands
include increased sunlight resulting
from past light logging operations, and
reduced competition on the forest floor
resulting from past fires and gra/ing,
and also dry sites where stands tend to
be open.
Although regular and abundant acorn
crops are usually necessary to establish
large numbers of oak seedlings, only
through favorable environmental
conditions can each wave of seedlings
persist on the site to build up the
advanced reproduction which will assure
satisfactory species composition in the
next rotation. On certain sites these
conditions may exist without the aid of
silvicultural treatment; however, on
other areas an adjustment of conditions
on the forest floor will be necessary
during the decade prior to the
regeneration period.
3Carvell, K. L. and E. H. Tryon.
1961. The Effect of Environmental
Factors on the Abundance of Oak
Regeneration Beneath Mature Oak Stands.
Forest Science 7 :98-105.
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Animals cause heavy damage and loss of
acorns. Damaged acorns often give clues
as to the animal causing the damage. The
acorns in (A) were damaged by gray
squirrels, and those in (B) were damaged
by the white footed mouse. |
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