USDA Forest Service Research Note RMRS-RN-14. 2002 1

Relationship of Seed Microsite to

Germination and Survival of

Lodgepole Pine on High-Elevation

Clearcuts in Northeastern Utah

Deborah S. Page-Dumroese

R. Kasten Dumroese

Connie M. Carpenter

David L. Wenny

United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

Research Note

RMRS-RN-14

September 2002

Abstract—On two high-elevation sites (~3,000 m) in northeastern

Utah, lodgepole pine (Pinus contorta var. latifolia) seeds germinated best (53 percent) on large mineral microsites (5 x 5 m), and

percentage survival of germinating seeds was best on microsites

covered with forest floor material. Seed predation was severe at both

study sites; protecting seeds increased germination three to ten

times. On harvested sites dependent on natural regeneration for

seedling establishment, some predation control may be necessary to

achieve rapid and complete stocking. After harvesting, maintenance of a combination of mineral soil and forest floor is critical for

long-term seedling success.

Introduction ____________________

In the Intermountain West, lodgepole pine (Pinus contorta

var. latifolia) occupies a niche in high-elevation forest

sites. It is well known as a seral species and can regenerate

rapidly if soil and site conditions are favorable. In fact, in

areas where competition is not severe, mineral soil is exposed, serotinous and nonserotinous cones are available,

Deborah S. Page-Dumroese is Project Leader and Research Soil Scientist with the Rocky Mountain Research Station at the Forestry Sciences

Laboratory in Moscow, ID. She completed a B.S. degree in natural resource

management at Grand Valley State University, an M.S. degree in forest soils

at Michigan Technological University, and a Ph.D. degree in forest soils at the

University of Idaho.

R. Kasten Dumroese is Plant Physiologist with the Southern Research

Station stationed at the Forestry Sciences Laboratory in Moscow, ID. He

completed a B.S. degree in forestry at Michigan Technological University, and

M.S. and Ph.D. degrees in forest resources at the University of Idaho.

Connie M. Carpenter is an Environmental Scientist with North State

Resources, Environmental Consultants in Redding, CA. She completed a B.S.

degree in range management and an M.S. degree in forest resources from the

University of Idaho.

David L. Wenny is Professor at the University of Idaho in Moscow. He

completed a B.S. degree and an M.S. degree in forestry from Humboldt

University and a Ph.D. degree in forest resources at the University of Idaho.

He is currently Director of the University of Idaho Forest Research Nursery.

and daytime ambient air temperatures average 24 oC, lodgepole has a regenerative advantage over other conifer species

(Lotan 1975). On some high-elevation sites, however, regeneration may take years to establish.

Often, predation is the primary reason for lodgepole pine

seed mortality or loss from a site because it is an important

source of food for many small mammals (Lotan and Perry

1983). After dispersal from cones, lodgepole pine seeds are

often consumed by mice (Peromyscus spp.), voles (Microtus

spp. and Clethrionomys spp.), or chipmunks (Eutamias spp.)

(Halverson 1986; Lotan and Perry 1983). Seed germination

may be enhanced by the use of rodent exclosures or reforestation cones (the cones modify temperature and moisture

conditions around the seeds). Consequently, our objective

was to determine seed germination and seedling success

after seedbed modification and protection on a variety of

high-elevation forest microsites after harvest and site

preparation.

Methods _______________________

We selected two sites on the Ashley National Forest in the

Uinta Mountain Range of northeastern Utah. Both sites

have similar elevations (~3,000 m), aspect (north), and

habitat type. Soils are loamy-skeletal, mixed, Oxyaquic

Cryoboralf with quartzite parent material (Soil Survey

Staff 1999). Soil coarse-fragment content ranged from 10 to

55 percent with scattered bedrock outcroppings. Mean annual precipitation is 191 cm with snowfall comprising 81

percent of the total (Western Regional Climate Center 2000).

Mean annual air temperature for January is –6 oC and for

July is 21 oC. Both sites were clearcut in 1995; the logging

slash was piled on one-half of the site and burned. Clearcut

size was approximately 2 hectares.

Lodgepole cones from surrounding uncut stands were

collected in July 1999. Seeds were extracted after submerging cones for approximately 50 seconds in a 78 oC water bath
2 USDA Forest Service Research Note RMRS-RN-14. 2002

(Krugman and Jenkinson 1974). Cones were spread on drying racks and placed in a greenhouse for 1 week where

daytime temperatures reached 43 oC. Following drying, cones

were manually shaken and pulled apart to release seed.

Viability of extracted seed was nearly 100 percent under

laboratory conditions (8 hours of light at 30 oC and 16 hours

of dark at 20 oC).

At each site, three microsite types were delineated: (1) large

area (5 x 5 m) with mineral soil exposed microsite, (2) small

area (1 m2

) with mineral soil exposed, and (3) no mineral soil

exposed area (3 x 3 m) covered with forest floor material. The

small-mineral and forest-floor-only microsites were a mosaic within the treatment area. In September 1999, five

replications of each microsite were located at each site, and

20 seeds each were placed either (1) on the soil surface with

no predation protection (fig. 1), (2) on the soil surface with a

predation cage surrounding the seed (fig. 2), or (3) on the soil

surface with a reforestation cone for climate modification

and a predation cage. Reforestation cones were made of

durable plastic and measured 7.5 cm on the bottom, 1.8 cm

on the top, and were 8 cm tall (fig. 3). Seeds were placed into

a 7-cm metal ring to aid in relocation. Predation cages were

constructed of 6-mm mesh wire folded to form a square,

open-bottomed box (12 x 10 cm). Metal rings, reforestation

cones, and predation cages were all secured to the ground

with a 15-cm-long landscape staple. Onset Stowaway temperature loggers (Onset Corp, Pocasset, MA) were secured to

the soil surface both inside and outside of the reforestation

cones to monitor soil surface temperature from September

1999 through September 2000.

Germinants were counted July 2000, and first growing

season survival was tallied in September 2000. Germinants

were considered successful when the primary root had

penetrated the soil surface and cotyledons were present.

Results and Discussion __________

Lodgepole pine is prolific in its regeneration success,

particularly after disturbance. However, where lodgepole

pine is a climax species, regeneration can be limited by

temperature extremes or lack of moisture, or seed may be a

preferred food source for birds and rodents (Lotan and Perry

1983).

Often, soil surface temperature determines the success of

germination (Lotan and others 1985). Seed for this study

was placed on site in the fall of 1999, and this likely subjected

the seeds to damage by frost, as minimum surface temperatures reached –10 oC prior to snowfall (data not shown).

During the growing season of 2000, soil surface mean high

temperatures for reforestation cones versus no cone were

within 0.2 oC (fig. 4). Yearly average, minimum, and maximum temperatures were not significantly affected by surface soil condition. Temperatures recorded during the field

season of 2000 did not reach the threshold level of 15 oC

known to suppress lodgepole pine seed germination (Lotan

and Perry 1983).

 Seed germination rate and number of surviving seedlings

were lowest on the forest floor microsites. However, overall

seedling survival rate and number of seeds versus surviving

seedlings was greatest on microsites with surface organic

matter (table 1). This may be due to the slightly warmer

Figure 3—Putting a reforestation cone over the seeds.

Predation cages were placed over the reforestation

cone on this typical forest floor microsite.

Figure 1—Seeds without predation protection on a mineral

soil microsite.

Figure 2—Seeds and predation control cage on a mineral

soil microsite.
USDA Forest Service Research Note RMRS-RN-14. 2002 3

Figure 4—Soil temperature as affected by soil

microsite and presence of reforestation cone.

seedling survival of the seeds that germinated was 35

percent greater than the large mineral soil microsite.

Seed protection from predation is a key factor for seeds to

reach seedling stage on these sites (table 2). All microsites

showed substantial increases in germination and seedling

survival with a predation cage over the seeds. Improving the

seed germination environment with a reforestation cone

also produced an environment more conducive to seed germination and growth than seed exposed on the soil surface.

Management Implications ________

On these high-elevation sites, seed viability does not seem

to be the limiting factor in regeneration success. Predation

appears to be the largest single factor in determining the

success of seed germination on any given soil surface

microsite. Large areas of exposed mineral soil provided the

best opportunity for germination; however, the largest number of seedlings produced from germinated seed was on the

forest floor microsites. A balance between mineral soil for

germination and forest floor material for temperature moderation and moisture retention, along with some form of

predation control, can provide the optimum conditions for

natural regeneration of lodgepole pine. Although reforestation cones increased seed germination success along with

predation cages, cone usage may be limited to sensitive or

Table 1—Comparison of lodgepole pine seed germination, survival, and seed versus germinant and seedling ratios

among microsites in high-elevation clearcuts in northeastern Utah.

Seeds Germination Seeds: Surviving Survival Seeds: surviving

Microsite germinateda rate germinants seedlings rate seedling

percent percent

Forest floor 486 9 11 432 89 12

Small mineral 2,052 38 3 1,026 50 5

Large mineral 2,862 53 2 1,674 58 3

a5,400 total seeds were put on each soil microsite type.

temperatures recorded during the growing season (fig. 4). In

contrast, Schmidt and Lotan (1980) determined that mineral soil seedbeds were more conducive to warm temperatures and, therefore, greater germination. The forest floor

material may have acted to modify temperature extremes,

evaporation rates, or frost heaving in the spring (Cochran

1973). All these factors could have improved germinant

success on forest floor material. In addition, sites with forest

floor intact or accessible to seedling roots after germination

may have better growth and health because organic matter

can provide a source of moisture and nutrients (PageDumroese and others 1990). Organic materials may also act

to physically protect seed from soil erosion by slowing down

the rate of water movement on the soil surface (Elliot and

others 1999).

In a study conducted by Lotan and Perry (1977), the ratios

of onsite seed to successful seedlings are often extremely

high (625:1 to 2,160:1). On our study sites, this ratio is much

better (3:1 to 12:1), depending on soil microsite conditions,

but is likely due to protection from predation on 66 percent

of the microsites.

Although laboratory germination was nearly 100 percent,

seed germination in the field was much less. Overall, seed

germination was most successful on the large mineral soil

microsites (53 percent); however, total surviving seedlings

in this microsite at the end of the growing season was only

58 percent. In contrast, seedling germination rate in the

microsites with forest floor was extraordinarily low, but

Table 2—Lodgepole pine seed germination and seedling survival

(percent) among soil microsites with predation cages or

reforestation cones.

Predation

Microsite control Germination Survival

............ percent ..........

Forest floor None 3 (0.1)a 4 (0.2)

Predation cage 10 (0.3) 7 (0.5)

Predation cage and 18 (1.9) 14 (1.6)

 reforestation cone

Small mineral None 8 (0.8) 5 (0.2)

Predation cage 22 (1.5) 16 (1.3)

Predation cage and 78 (3.2) 40 (2.4)

 reforestation cone

Large mineral None 18 (1.3) 17 (1.4)

Predation cage 70 (3.3) 30 (1.5)

Predation cage and 60 (3.3) 43 (2.5)

 reforestation cone

aValues in parentheses are standard error of the mean.

6.3

6.4

6.5

6.6

6.7

6.8

6.9

Temperature (°c)

Large mineral Small mineral Forest floor

Without reforestation cone

With reforestation cone
4 USDA Forest Service Research Note RMRS-RN-14. 2002

fragile areas with very little seedling success, as they are

time and labor intensive.

References _____________________

Cochran, P. H. 1973. Natural regeneration of lodgepole pine in

south-central Oregon. Res. Note PNW-RN-204. Portland, OR:

U.S. Department of Agriculture, Forest Service, Pacific Northwest Station. 18 p.

Elliot, W. J.; Page-Dumroese, D. S.; Robichaud, P. 1999. The effects

of forest management on erosion and soil productivity. Chapter

12. Soil quality and soil erosion. New York: Soil Water Conservation Society: 195–209.

Halvorson, C. H. 1986. Influence of vertebrates on conifer seed

production. In: Conifer tree seed in the Inland Mountain West;

1985 August 5–6; Missoula, MT. Gen. Tech. Rep. INT-GTR-203.

Ogden, UT: U.S. Department of Agriculture, Forest Service,

Intermountain Research Station: 201–222.

Krugman, S. L.; Jenkinson, J. L. 1974. Pinus L. Pine. In: Schopmeyer

C. S., tech. coord. Seeds of woody plants in the United States.

Agric. Handb. 450. Washington, DC: U.S. Department of Agriculture, Forest Service: 598–638.

Lotan, J. E. 1975. Regeneration of lodgepole pine forests in the

Northern Rocky Mountains. In: Baumgartner, D. M., ed. Management of lodgepole pine ecosystems symposium proceedings;

1974. Pullman: Washington State University Cooperative Extension Service: 516–535.

Lotan, J. E.; Perry, D. A. 1977. Effects of residue utilization on

regeneration of lodgepole pine clearcuts. In: Terrestrial and

aquatic ecological studies of the Northwest; 1976 March 26–27;

Cheney, WA. Cheney: Washington State College Press: 125–133.

Lotan, J. E.; Perry, D. A. 1983. Ecology and regeneration of lodgepole pine. Agric. Handb. 606. Washington, DC: U.S. Department

of Agriculture, Forest Service. 51 p.

Page-Dumroese, D. S.; Loewenstein, H.; Graham, R. T.; Harvey, A. E.

1990. Soil source, seed source, and organic matter content effects

on Douglas-fir seedling growth. Soil Science Society of America

Journal. 54: 229–233.

Schmidt, W. C.; Lotan, J. E. 1980. Establishment and initial development of lodgepole pine in response to residue management.

Ogden, UT: U.S. Department of Agriculture, Forest Service,

Intermountain Forest and Range Experiment Station. 16 p.

Soil Survey Staff. 1999. Soil taxonomy: a basic system of soil classification for making and interpreting soil surveys. Washington, DC:

U.S. Department of Agriculture, Natural Resource Conservation

Service, U.S. Government Printing Office. 869 p.

Western Regional Climate Center. 2000. Precipitation maps for the

Western United States, 1961–1990. URL: http://wrcc.sage.dri.edu

(accessed April 2000).
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