Minnesota Forestry
Research Notes
No. 210
October 15, 1969
OCCURRENCE AND DISTRIBUTION OF PINE REPRODUCTION
IN ITASCA STATE PARK, MINNESOTA
Vilis Kurmis and Henry L. Hansenll
This is the second report dealing with the advance reproduction in Itasca
State Park. The general patterns of advance reproduction in upland forest
communities were discussed in the preceding report (Kurmis and Hansen, 1969).
This report focuses attention on pine reproduction and analyzes the relationships
to motherstands and forest types using the synecological coordinate method
( Ba ku zis, 1959).
Pine reproduction is emphasized because of the management problems related
to securing pine continuity in the park. Red pine (Pinus resinosa Ait.) and
white pine (Pinus strobus L.) stands were an important component of the pre­
settlement forest, and they are of great aesthetic value. However, attrition
in old growth red pine and white pine stands is high. Such stands are predomi­
nantly 140 to 160 and 200 to 250 years old, and jack pine (Pinus banksiana Lamb.)
stands are from 70 to 90 years old. Young pine stands are almost absent.
Distribution Patterns of Mature Pine. Figure 1 compares distribution of the
three native pines by basal area. Reproduction by age groups is also shown in
relationship to mothertrees, local forest types, and moisture-nutrient gradients.
The diagrams in Figure 1 clearly reflect the concentration of jack pine tree s on
dry, nutrient-poor sites and red pine on dry to mesiC, intermediate nutrient
sites. White pine is more evenly distributed over the upland forest complex,
mainly as an admixture species in a variety of forest stands. The basal areas of
pines are shown in relationship to total stand basal area by forest types in
Figure 2-1.
White Pine Reproduction. The distribution pattern of white pine reproduction
shows its superior competitive ability (Figure 1). Young white pine seedlings
are able to withstand competition for some time even in jack pine-red pine­
liverleaf, red pine-sweet cicely, and aspen-birch-oak-arrow wood types with high
shrub densities (Figures 1, 2-2, and 2-3). However, the persistence of white
pine seedlings is limited. Seedlings older than 10 years show a bi-modal distri­
bution being present on dry, nutrient-poor sites, mainly in the jack pine-bearberry
type, and on mesic, nutrient-rich sites in the maple-basswood-leatherwood type
(Figure 1). Reproduction older than two years reaches its peak in the jack pine­
bearberry type with about 1,500 seedlings per acre followed by maple-basswood­
leatherwood type with about 400 seedlings per acre (Figure 2-3).
i1Research
Associate and Professor, respectively, School of Forestry, University of
Minnesota.
Published by the School of forestry. University of Minnesota. St. Paul. Minnesota 5S tOI. cooperating with the Division of forestry Minne·
sola Conservation Department. and forest Industries of Minnesota
BASAL AREA OF MOTHER TREES
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Figure 1. Distribution of basal areas of white pine, red pine, and jack pine and their
reproduction by age groups and local forest types in the moisture-nutrient
coordinates (edaphic field) of upland forests in Itasca State Park, Minnesota.
30
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~ TOTAL BASAL AREA
FOREST TYPES JACK PINE -BEARBERRY
JACK PINE -RED PINE - L\VERLEAF
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Figure 2. (1) Stand basal area, (2) number of shrubs, and number of pine
seedlings, (3) older than two years, and, (4) taller than one foot
in height by local forest types in Itasca State Park, Minnesota.
6
The number of white pine seedlings taller than one foot (Figure 2-4) indicates
a satisfactory height growth only in the jack pine-bearberry type. White pine
seedlings in the maple-basswood-leatherwood type with dense tree cover and strong
competition of hardwood reproduction, although relatively numerous, have not
reached a foot of height even at the age of 15 years. The lack of white pine and
other pine seedlings in height classes over une foot in most of the forest types,
except jack pine-bearberry type, is striking. This indicates that although there
is some initial seedling establishment, further development is a critical problem,
particularly with white pine. Red and jack pine seedlings do not establish even
initially except for a scattered occurrence in the jack pine-bearberry type. In
general, white pine is an invading species becoming initially established over a
wide range of site and stand conditions. However, it does not survive under
strong shrub or tolerant hardwood competition. Total shrub density and the pr­
portion of beaked hazel (Corylus cornuta Marsch.) is shown by forest types in
Figure 2-2.
Red Pine and Jack Pine Reproduction. The distribution pattern of red pine
and jack pine seedlings in the edaphic field differs considerably from that of
white pine seedlings (Figure 1). The distribution range of these seedlings is
narrower than that of mature red pine and jack pine trees. Scattered red pine
and jack pine seedlings in all age groups are largely confined to dry, nutrient­
poor sites, mainly in the jack pine-bearberry type. Even in this type ground
cover species, mainly halfshrubs, grasses, and invading shrubs appear to be
serious competitors of pine seedlings for soil moisture. Furthermore, forest
communities of the jack pine-bearberry type constitute only a small fraction of
the total area of upland forests in the park. Without some disturbance such as
fire even this forest type is unsuitable f or new pine establishment. The complete
lack of one to two-year old red and white pine seedlings on dry, nutrient-poor
sites (Figure 1) is probably a result of an inadequate seed supply and severe
drought in July, 1965 preceding data collection. The total number of red pine
and jack pine seedlings per acre has some significance only in the jack pine­
bearberry type. There are about 300 red pine seedlings per acre in this type
(Figure 2-3). Jack pine seedlings are more abundant than red pine; however, jack
pine seedlings were heavily browsed and their survival questionable.
Red and jack pine seedlings can be found on roadsides, old gravel pits, and
in openings along trails. However, the area occupied is minute compared to the
acreage of mature red pine and jack pine stands.
Perpetuation of Present Pine Stands. It seems clear that without major dis­
turbances or special silvicultural measure the present area of pine dominated
stands will continue to decline. While white pine seedlings establish initially,
they do not survive the competition of dense shrub canopies or tolerant hardwood
trees. By contrast, red and jack pine seedlings do not even establish initially
under present stand and site conditions.
Literature Cited
Bakuzis, E. V. 1959. Synecological coordinates in forest classification and
in reproduction studies. Ph.D. thesis, Univ. Minnesota. 244 pp.
Kurmis, V. and H. L. Hansen. 1969. Reproduction characteristics of upland forest
communities in Itasca State Park, Minnesota. Minn. For. Res. Notes No. 209.
4 pp.
Published as Sci. Jour. Sere Paper No. 7079 of the Univ. of Minn. Agr. Expt. Sta.