United States

Department

of Agriculture

Forest Service

Rocky Mountain

Research Station

Research Paper

RMRS-RP-24

May 2000

Environmental

Characteristics of the

Grand Fir Mosaic and

Adjacent Habitat Types

Dennis E. Ferguson

John C. Byrne
Abstract

Ferguson, Dennis E.; Byrne, John C. 2000. Environmental characteristics of the Grand

Fir Mosaic and adjacent habitat types. Research Paper RMRS-RP-24. Ft. Collins,

CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research

Station. 20 p.

Grand Fir Mosaic habitats differ from adjacent forest habitats in their slow rate of

secondary succession to woody vegetation. Remote monitoring stations were used

to sample the environment at a Grand Fir Mosaic site and three adjacent habitat types.

The Grand Fir Mosaic site has shorter growing seasons, cooler temperatures, and

more soil moisture than the other sites. Soil pH at the Grand Fir Mosaic site cycled from

5.5 to 6.5 in winter months to 4.0 to 5.0 in summer months. These unique site and

environmental characteristics are shown to cause highly acidic soils with high

aluminum availability below pH 5.0.

Keywords: habitat types, forest succession, aluminum toxicity, allophanic soils, nonallophanic soils, soil pH, andisols, climate, weather data, environmental

monitoring

Acknowledgments __________________________

We thank Dale O. (Duke) Coffen for his hard work installing the remote

monitoring stations and for collecting as much data as possible. We also thank

technical reviewers of an earlier draft of this paper: Paul A. McDaniel, Deborah

S. Page-Dumroese, and David C. Powell.

The Authors ________________________________

Dennis E. Ferguson is a research silviculturist with the Rocky Mountain

Research Station in Moscow, Idaho.

John C. Byrne is a forester with the Rocky Mountain Research Station in

Moscow, Idaho.

The use of trade or firm names in this publication is for reader information and does not

imply endorsement by the U.S. Department of Agriculture or any product or service
Contents

Page

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Research Paper number.

Fort Collins Service Center

Telephone (970) 498-1392

FAX (970) 498-1396

E-mail rschneider@fs.fed.us

Web site http://www.fs.fed.us/rm

Mailing Address Publications Distribution

Rocky Mountain Research Station

240 West Prospect Road

Fort Collins, CO 80526

Introduction .............................................................................................. 1

Methods ................................................................................................... 2

Study Sites............................................................................................ 2

Remote Monitoring Stations ................................................................. 3

Analysis .................................................................................................... 4

Results ..................................................................................................... 5

Wind Speed and Direction .................................................................... 5

Rainfall .................................................................................................. 6

Solar Radiation ..................................................................................... 6

Relative Humidity .................................................................................. 7

Air Temperature at 4.5 Feet ................................................................ 10

Soil Surface Temperature ................................................................... 12

Soil Temperature at 1 and 8 Inches.................................................... 12

Soil Water Potential at 1 and 8 Inches ................................................ 15

Soil pH ................................................................................................ 15

Discussion .............................................................................................. 17

References ............................................................................................. 19

USDA Forest Service Res. Pap. RMRS-RP-24. 2000 1

Environmental Characteristics of

the Grand Fir Mosaic and Adjacent

Habitat Types

Dennis E. Ferguson

John C. Byrne

Introduction ____________________

Grand Fir Mosaic habitats are found in upland

forests that form drainages of the Clearwater River

in northern Idaho and in the Blue Mountains of

northeastern Oregon. The Grand Fir Mosaic (GFM)

is named for the dominant conifer, grand fir (Abies

grandis (Dougl. ex D. Don) Lindl.), and the variety of

sizes and shapes of natural openings in the forest

canopy (Ferguson and Johnson 1996). Dominant species in natural openings are Sitka alder (Alnus sinuata

(Regel) Rydb.), bracken fern (Pteridium aquilinum

(L.) Kuhn), and fool’s huckleberry (Menziesia

ferruginea Smith).

The Grand Fir Mosaic is about 500,000 acres, occurring at elevations between 4,200 feet and 6,000 feet,

with most occurrences between 4,500 and 5,500 feet.

GFM forests can occupy all aspects and topographic

positions within this elevation zone. The predominant habitat type is Abies grandis/Asarum caudatum

(grand fir/wild ginger) in northern Idaho (as defined by

Cooper and others 1991) and Abies grandis/Clintonia

uniflora (grand fir/queencup beadlily) in northeastern

Oregon (as defined by Johnson and Clausnitzer 1992).

Other habitat types in the GFM are Abies grandis/

Senecio triangularis (grand fir/arrowleaf groundsel),

Thuja plicata/Asarum caudatum (western redcedar/

wild ginger), Tsuga mertensiana/Streptopus amplexifolius (mountain hemlock/twisted stalk), and Abies

lasiocarpa/Streptopus amplexifolius (subalpine fir/

twisted stalk) (Ferguson and Johnson 1996).

The species composition of conifers in the GFM

differs from non-Mosaic habitats (Ferguson and

Johnson 1996). Grand fir is found most often, followed by Engelmann spruce (Picea engelmannii Parry

ex Engelm.), subalpine fir (Abies lasiocarpa (Hook.)

Nutt.), and Douglas-fir (Pseudotsuga menziesii var.

glauca (Beissn.) Franco). Western white pine (Pinus

monticola Dougl. ex D. Don) and western larch (Larix

occidentalis Nutt.) are found infrequently in northern Idaho, although western larch is common in

northeastern Oregon. Elevations in the GFM are

generally too high for ponderosa pine (Pinus ponderosa Dougl. ex Laws. var. ponderosa). Western

redcedar (Thuja plicata Donn. ex D. Don) and mountain hemlock (Tsuga heterophylla (Raf.) Sarg.) are

only found in certain parts of the GFM in Idaho. Of

special note is lodgepole pine (Pinus contorta Dougl.

ex Loud.), which is found in higher and lower elevation forests adjacent to the GFM, but rarely in the

GFM.

Investigations on this ecosystem were begun because of the slow rate of secondary succession to woody

vegetation (conifers and shrubs) following disturbance,

such as timber harvest. Initially, land managers

were concerned about the lack of conifer regeneration,

but over time, it became apparent that ecological

processes in the GFM were unlike those of other

habitats in the northern Rocky Mountains. More information was needed to properly manage GFM sites.

In the Grand Fir Mosaic, northern pocket gophers

(Thomomys talpoides), bracken fern, and western coneflower (Rudbeckia occidentalis Nutt.) rapidly invade

cutover forests. Several factors could account for the

lack of succession to woody species. Competition for

space, light, water, and nutrients is one of the first

considerations, but more factors appeared to be involved. While competition could account for the lack of

some shrubs and conifers, adjacent ecosystems at

higher and lower elevations have a plentiful supply of

shrubs and conifers. It seems unlikely that competition is the only factor.

This research is one of several studies on the GFM to

determine probable causes for the slow rate of secondary succession to woody vegetation. Other studies have

dealt with soil genesis (Johnson-Maynard 1995;

Johnson-Maynard and others 1997, 1998; Sommer

1991), pocket gophers (Ferguson 1999), ecology

(Ferguson and Johnson 1996), and allelopathy (Ferguson

1991; Ferguson and Boyd 1988).

The objective of this study was to compare environmental conditions in the GFM with adjacent

non-Mosaic habitats to see if unique environmental

characteristics of the GFM could account for the slow

rate of secondary succession to woody species. We

discuss results of monitoring the above- and belowground environment in the GFM and three adjacent

habitat types.
2 USDA Forest Service Res. Pap. RMRS-RP-24. 2000

Methods _______________________

Study Sites

Four study sites were chosen on the Nez Perce

National Forest in Idaho to represent four different

environments in and near the GFM. The study sites

are located in the vicinity of Lookout Butte (fig. 1).

Study sites were selected to be as physically similar as

Figure 1—Location of remote monitoring stations near Lookout Butte on the

Nez Perce National Forest. The shaded area is the Grand Fir Mosaic Ecosystem.

1 = THPL Station; Thuja plicata/Asarum caudatum habitat type, not in the

Mosaic. 2 = ABGR Station; Abies grandis/Asarum caudatum habitat type, not

in the Mosaic. 3 = Mosaic Station: Abies grandis/Asarum caudatum habitat

type, in the Mosaic. 4 = ABLA Station; Abies lasiocarpa/Xerophyllum tenax

habitat type at Lookout Butte above the elevation range of the Mosaic.

possible. All sites were located in clearcuts with southto-southwest aspects, upper slope topographic position, and 10 to 20 percent slopes. The habitat types

represented are Abies grandis/Asarum caudatum (two

sites), Thuja plicata/Asarum caudatum, and Abies

lasiocarpa/Xerophyllum tenax. Following is a description for each site. Abbreviations for non-Mosaic study

sites are named for the climax conifer; for example, the

THPL site is named for THuja PLicata.

1 4

3

2
USDA Forest Service Res. Pap. RMRS-RP-24. 2000 3

1. THPL site. This is the lowest elevation of the

four sites, representing the Thuja plicata/Asarum

caudatum habitat type at an elevation of 4,720 feet;

T31N, R6E, S10; latitude 46° 2' 43.1079"N; longitude

115° 41' 43.7869"W. The clearcut has good representation of woody species such as snowberry (Symphoricarpos albus (L.) Blake), thimbleberry (Rubus

parviflorus Nutt.), pachistima (Pachistima myrsinites

(Pursh) Raf.), rose (Rosa spp.), huckleberry (Vaccinium

globulare Rydb.), and serviceberry (Amelanchier

alnifolia Nutt.). Regeneration of the following species

is present at this site: planted ponderosa pine and

Douglas-fir, and natural grand fir, western redcedar,

and Pacific yew (Taxus brevifolia Nutt.). Bracken fern,

western coneflower, and pocket gophers are infrequent.

2. ABGR site. This site is an Abies grandis/Asarum

caudatum habitat type but is not in the Grand Fir

Mosaic. Elevation is 4,850 feet; T30N, R6E, S3; latitude 45° 57' 44.5276"N; longitude 115° 41' 38.7602"W.

The area was chosen for monitoring because it occurs

at a lower elevation than the GFM but is the same

habitat type as commonly found in the Mosaic. There

are more shrubs (both number of species and percent

coverage) than the Mosaic site described below.

Woody vegetation includes snowberry, shinyleaf

ceanothus (Ceanothus velutinus Dougl. ex Hook.),

pachistima, elderberry (Sambucus racemosa L.), twinflower (Linnaea borealis L.), huckleberry, fool’s huckleberry, thimbleberry, and serviceberry. Conifer regeneration in the clearcut includes natural grand fir

and planted Douglas-fir, ponderosa pine, and Engelmann spruce. Also, beargrass (Xerophyllum tenax

(Pursh) Nutt.) is common in the clearcut. This site also

has little coverage by bracken fern and western coneflower, and there is some pocket gopher activity.

3. Mosaic site. This site represents an Abies

grandis/Asarum caudatum habitat type in the GFM.

Elevation is 5,700 feet; T31N, R6E, S23; latitude 46° 0'

25.7599"N; longitude 115° 40' 48.0855"W. Woody vegetation in the clearcut includes elderberry, thimbleberry, snowberry, and mountain ash (Sorbus scopulina

Greene), but only in minor amounts. There are patches

of fool’s huckleberry and Sitka alder in the clearcut

that were present before the stand was harvested.

Western coneflower and bracken fern are abundant.

The Mosaic site has been planted several times.

Only scattered Engelmann spruce have survived to

provide stocking along with some natural Engelmann

spruce regeneration. Pocket gopher activity is very

high, which probably resulted in the plantation failures. This site was used by Ferguson (1999) to study

the effects of pocket gophers and successional plant

communities on survival and growth of conifers.

4. ABLA site. This site is southwest of the lookout

tower at Lookout Butte and is at the highest elevation

of the four stations (5,840 feet); T31N, R6E, S12;

latitude 46° 2' 41.1209"N; longitude 115° 39' 40.8869"W.

The top of Lookout Butte exceeds the higher elevation limits of the surrounding Grand Fir Mosaic. The

habitat type is Abies lasiocarpa/Xerophyllum tenax.

There are no lodgepole pine, Douglas-fir, or western

larch in the vicinity. This site is warmer than a typical

Abies lasiocarpa/Xerophyllum tenax habitat type as

described by Cooper and others (1991). Indicators of

this warmer environment include lack of grouse

whortleberry (Vaccinium scoparium Leiberg), and the

occasional occurrence of wild ginger (Asarum caudatum

Lindl.) and evergreen synthyris (Synthyris platycarpa

Gail and Pennell). Shrubs found in the vicinity are

huckleberry, spiraea (Spiraea betulifolia (Doublas.)

Hitchc.), snowberry, elderberry, Rocky Mountain

maple (Acer glabrum Torr.), thimbleberry, currant

(Ribes spp.), bittercherry (Prunus emarginata (Dougl.)

Walpers), and ninebark (Physocarpus malvaceus

(Greene) Kuntze). The clearcut has abundant

beargrass. Ponderosa pine was planted in the clearcut, but it grows slowly at this elevation and stems

are deformed by snow. Bracken fern, western coneflower, and pocket gophers are infrequent.

Remote Monitoring Stations

Electronic monitoring of the four sites was done with

OmnidataTM remote monitoring stations installed in

June 1988 and removed in June 1996. Replication was

not possible because of limited funding. Sensors attached to computer hardware were programmed to

record data at specified time intervals. Data were

stored on site, then periodically removed and transported to the office where the data were transferred

to computers.

Time was synchronized among the stations so that

information from sensors was collected and recorded

at the same time. Stations were installed in the same

manner with sensors at the same height and position.

For example, the solar radiation sensor was 6 feet

above the base of the weather station in a level position

on a platform that extended from the south side of the

station, rain gauges were all located on the west side

of the station, and so on.

Placement of soil sensors used techniques to minimize soil disturbance. Soil water potential and temperature sensors at 1 inch and 8 inches were placed in the

same soil pit. The pH sensor was buried in a separate

location because it was removed during the dry part of

the summer. For the water potential and temperature

sensors, a small pit was dug about 9 inches deep. Loose

soil was cleaned from the uphill vertical face of the

pit. Horizontal holes for the sensors were dug at 1 and

8 inches from the soil surface, then sensors were

placed in these holes. Wires leading from the sensors

to the computer hardware were positioned to run
4 USDA Forest Service Res. Pap. RMRS-RP-24. 2000

downhill from the sensor for 6 to 12 inches. This

prevented water from running down the wires to

sensors. The soil was then replaced.

Manufactured soil temperature sensors are covered

with a black waterproof covering. Those sensors used

to record soil surface temperature were painted white

to lessen the effect of solar radiation heating the

sensor. A white neoprene paint was used because of its

flexibility and adhesion properties.

Table 1 shows the type of sensors along with

specifics on data collection. Sensors were scanned

every 15 minutes and reports were written to the

data storage pack either at 2-hour or 6-hour intervals. Two-hour reports were used for variables that

changed most rapidly and 6-hour reports were used

for variables that changed slowly. Averages of the

15-minute scans were recorded for most sensors.

The maximum and minimum soil surface temperatures found during the scans for 2-hour periods were

also recorded. This makes it possible to determine

the maximum and minimum daily surface temperature. Wind direction was read instantaneously at

the end of each 2-hour period. Precipitation was

recorded as the cumulative total during the 2-hour

period, as recorded by a tipping-bucket rain gauge.

The pH sensors are model 613 pH transducers

manufactured by IC ControlsTM in Ontario, Canada.

They operate well in moist environments and compensate for temperature changes, but they were removed when soils dried to about –10.0 bars. Each pH

sensor was calibrated between pH 3.0 and pH 7.0

with known buffers before field use, whenever they

were removed from the field during dry soil periods, or

annually in the field.

Table 1—Information collected at four remote monitoring stations on the Nez Perce National Forest.

Each sensor was scanned at 15-minute intervals.

Unit of Report Report

Sensor Position measurement Interval modea

Wind speed 9 feet mph 2 hours Ave.

Wind direction 9 feet azimuth 2 hours Inst.

Precipitation 3 feet inches 2 hoursb Cum.

Solar radiation 6 feet Langleys 2 hours Ave.

Relative humidity 4.5 feet percent 2 hours Ave.

Air temperature 4.5 feet °F 2 hours Ave.

Soil temperature surface °F 2 hours Ave., min., max.

Soil temperature 1 inch °F 2 hours Ave.

Soil temperature 8 inches °F 6 hours Ave.

Soil water potential 1 inch bars 6 hours Ave.

Soil water potential 8 inches bars 6 hours Ave.

Soil pH 1 inch pH 6 hours Ave.

a

Ave. = average. Cum. = cumulative. Inst. = instantaneous (one reading).

b

Report interval was 6 hours prior to June 1991.

Analysis _______________________

The remote monitoring stations generally provided

reliable, accurate data, but data were often missing or

not usable for a variety of reasons. Animals often

chewed on wires, broke wires, or dug up sensors.

Snowloads bent sensors out of proper position. Sometimes the electronic components of sensors quit working. Data on precipitation are not accurate during the

winter months when snow buries the rain gauge. Even

if the rain gauge is not buried by snow, the snow that

does accumulate can blow away before it melts. Sometimes the air temperature and relative humidity sensors at 4.5 feet were also buried by snow. Occasionally,

the soil froze at 1 inch during the winter, which gave

a false reading for soil water potential. Another interesting source of bad data occurred when the wind

direction sensor was frozen in place by a buildup of ice.

Because these sites are remote and not accessible

during the winter months, there can be long periods of

missing and bad data. Sensors that break go undetected until the next visit, then it may take several days

to complete repairs. Data were carefully screened to

eliminate bad data before analyses. Once the data

were screened, we considered appropriate ways to

deal with missing data. Other researchers have calculated values for missing data by using available data

from other sites (Finklin 1983a, b). We chose not to

calculate missing values because too many sites were

missing the same data for some time periods, and we

wanted to compare actual data rather than mask

differences by mixing actual and predicted values. We

also decided to analyze only data collected during

the growing season because all sites are covered with
USDA Forest Service Res. Pap. RMRS-RP-24. 2000 5

snow during the winter. Learning how to best maintain the weather stations to assure accurate measurements took 1 to 2 years; 1988 and 1989 often had large

data gaps as methods were established and appropriate

sensors selected.

Data used for analyses are as follows:

1. Data recorded from April 1 through October 31 of

each year.

2. Years of monitoring from 1990 through 1996.

3. There must be at least 3⁄4 of the reports per day

in order to calculate daily averages (nine of the 12

2-hour reports or three of the four 6-hour reports).

4. There must be at least 20 days with valid data in

order to calculate an average for a month.

5. There must be at least 4 of the 7 years of monthly

data that is common to all four stations in order to

calculate monthly averages. However, this means

that different monthly averages can have different

years used in the computations.

Standard statistical analyses for comparing data

between sites were not possible because there was

no replication of experimental units. Since the GFM

site was the focus of research, we summarized the

data in different ways for comparing the other sites to

the Mosaic site. We carried out two major types of

summarization to compare sites. First, for those

months with sufficient data (based on the criteria

previously described), we calculated summary statistics for each sensor by site including mean, standard

deviation, minimum, and maximum. Second, differences between non-Mosaic sites and the Mosaic site

were calculated at the 2-hour or 6-hour time frame and

then summarized to obtain mean monthly differences

along with standard deviations. To visually detect

differences between the Mosaic and other sites, bar

charts showing mean monthly differences ±2 standard deviations were graphed for each month against

a zero difference line. Lack of overlap of these bar

graphs with the zero difference line suggests where

true differences between a site and the Mosaic site

exist. Summary statistics were only calculated where

sufficient data existed for all four sites, whereas the

comparison graphs use means and standard deviations where sufficient data existed between just the

individual site of interest and the Mosaic site. Additional data summaries were also done for some sensors

and are discussed where appropriate in the results

section.

Results ________________________

Wind Speed and Direction

Winter conditions (heavy snows and freezing/

refreezing) caused problems with the wind speed

sensors and it was often not until the summer months

that sensors could be put back into working condition.

Therefore, summary statistics were only calculated

for the months of July, August, and September, which

had 4 of 6 years of data available for every site.

Average wind speeds increased with increasing elevation, and standard deviations roughly followed the

same pattern (table 2). The THPL site had the lowest

average wind speed (1.7 mph) followed by the ABGR

site (2.7 mph), the Mosaic site (3.1 mph), and the

ABLA site (3.7 mph).

The comparison graphs in figure 2 generally follow

the trend shown in table 2. For all months from June

to October, except July, wind speed was less at the

THPL site than at the Mosaic site. Wind speed at the

ABGR site was less than the Mosaic site in the spring

months (April to June) and also in October. The wind

speed was greater at the ABLA site than the Mosaic

site only in the month of October.

The wind direction sensor at the ABGR site rarely

functioned properly, so we based our assessment of

wind direction only on the other three sites where

data were fairly reliable (only May had insufficient

data; the other months mostly had 5 of 6 years

available). Figure 3 shows star charts for these sites.

The star charts show the percent of observations of

wind direction that occur in each of eight 45-degree

segments. The three sites are similar in that the

predominant wind direction is from the west, with

the next prevalent winds from the east. Winds at the

Table 2—Summary statistics for wind speed (miles per hour).

Number of Standard

Site observations Mean deviation Minimum Maximum

THPL 4394 1.7 1.5 0.0 15.0

ABGR 4284 2.7 2.3 0.0 13.0

Mosaic 4290 3.1 2.2 0.0 15.0

ABLA 4399 3.7 2.9 0.0 23.0

Note: Data for July, August, and September only.
6 USDA Forest Service Res. Pap. RMRS-RP-24. 2000

ABLA site more often come from the northwest than

the west.

Rainfall

Rainfall sensors were quite reliable. Data were

available to calculate monthly averages using 4 years

of data for May, 5 years of data for April and October,

and 6 years of data for the remaining months of the

growing season.

Average daily rainfall did not follow an elevational

pattern. Rainfall was highest at the Mosaic (0.12

inches) and THPL (0.11 inches) sites, and lowest at

the ABGR (0.09 inches) and ABLA (0.08 inches) sites

(table 3). Standard deviations for rainfall were ranked

similar to the averages. Maximum rainfall per day

varied between 2.32 inches at the ABGR site to 2.48

inches at the THPL site. Maximums are ranked similar to the averages.

Figure 2—Average wind speed (mph) at the Mosaic site, and differences in average wind speed from

the Mosaic site for the THPL, ABGR, and ABLA sites.

Patterns of rainfall over the growing season were

not different between the THPL and Mosaic sites

except in April when the THPL site had more rain

(fig. 4). The higher rainfall at the THPL site may be

due to warmer spring temperatures. Rainfall at the

ABGR and ABLA sites was consistently less than

the Mosaic site, but all averages were within two

standard deviations of the mean.

Solar Radiation

Solar radiation was measured in Langleys per minute (1 Langley/minute = 1 calorie per square meter per

minute). Pyranometers are reliable sensors that record

solar radiation in the wavelength range of 400 to 1100

nanometers. Summer and fall months had very complete data (July through September had 6 of 6 years

of data, October had 5 of 6 years). However, spring

months were less dependable because of damage to
USDA Forest Service Res. Pap. RMRS-RP-24. 2000 7

Figure 3—Star charts of wind direction at the THPL (top),

Mosaic (middle), and ABLA (bottom) sites. Each chart shows

the percent of observations by 45-degree segments.

Table 3—Summary statistics for average daily rainfall (inches).

Number of Standard

Site observations Mean deviation Minimum Maximum

THPL 823 0.11 0.27 0.00 2.48

ABGR 818 0.09 0.22 0.00 2.32

Mosaic 825 0.12 0.26 0.00 2.42

ABLA 838 0.08 0.20 0.00 2.33

NW

25

N

13 NE

7

E

10

SE

11

S

7

SW

7

W

20

ABLA

NW

15

N

5 NE

5

E

19

SE

11

S

1

SW

6

W

38

MOSAIC

NW

12

N

4 NE

7

E

26

SE

7

S

4

SW

11

W

29

THPL sensors during the winter, with May having insufficient data for summarization, while April had 4 of

7 years of data and June had 5 of 7 years of data. Solar

radiation data from the ABLA site were not used

because the sensor gave readings about 20 percent

low, which was not detected until the data were

analyzed.

An index of solar radiation was developed in order

to compare the three sites (THPL, ABGR, and Mosaic). Each of the 2-hour averages was expanded to

the 2-hour period, then summed for the day. This

calculated the total number of Langleys/day at each

site. The average number of Langleys/day was essentially the same for the THPL (204,000) and ABGR

(206,000) sites (table 4). There was an increase at the

Mosaic site to 215,000 Langleys/day. This increased

solar radiation at the Mosaic site is likely related to

the elevational difference between the Mosaic site

and the ABGR and THPL sites (850 feet higher than

ABGR and 980 feet higher than THPL).

Comparison graphs in figure 5 show that the THPL

site has lower solar radiation averaging about 12,000

Langleys/day from April through July (excluding May).

The ABGR is lower by about 10,000 Langleys/day in

July and August. These reductions are similar to those

seen in the overall averages in table 4.

Relative Humidity

Adequate data for relative humidity are available

for the months of July, August, and September. Those

three months had 4 years of data. Data for April, May,

and June were lacking because relative humidity

sensors had to be replaced each spring and access to

sites was not possible until after snowmelt.

Average relative humidity was calculated for July,

August, and September to see if humidity differences

could cause differences in evapotranspiration rates.

The ABGR site averaged the highest humidity at 58.8

percent and the highest standard deviation (table 5).

Next highest in humidity was the Mosaic site, averaging 54.1 percent. The THPL and ABLA sites had

similar humidities at 52.8 percent for the THPL

site and 52.5 percent for the ABLA site. Only the

ABGR site showed any difference from the Mosaic
8 USDA Forest Service Res. Pap. RMRS-RP-24. 2000

Figure 4—Average rainfall (inches) at the Mosaic site, and differences in average rainfall from the Mosaic site for the THPL, ABGR,

and ABLA sites.

Table 4—Summary statistics for average daily solar radiation (Langleys per day to

the nearest thousand).

Number of Standard

Site observations Mean deviation Minimum Maximum

THPL 932 204 95 4 359

ABGR 936 206 89 8 358

Mosaic 945 215 99 10 376

ABLA 0

Note: Pyranometer measures solar radiation in the wavelength range of 400-1100

nanometers. Not enough data were obtained for May, so it was not used in calculations.
USDA Forest Service Res. Pap. RMRS-RP-24. 2000 9

Figure 5—Solar radiation (Langleys/day) at the Mosaic site, and differences in solar radiation from the Mosaic site for the THPL,

and ABGR sites.

Table 5—Summary statistics for relative humidity (percent) at 4.5 feet above

ground.

Number of Standard

Site observations Mean deviation Minimum Maximum

THPL 4158 52.8 19.8 13.1 93.8

ABGR 4071 58.8 20.6 9.8 100.0

Mosaic 4077 54.1 17.3 16.2 93.7

ABLA 4379 52.5 16.4 14.3 87.4

Note: Data for July, August, and September only.
10 USDA Forest Service Res. Pap. RMRS-RP-24. 2000

site (fig. 6) and then only in September, where it

showed about a 6 percent increase over the Mosaic

site. The bar graphs of the other sites all crossed the

zero difference line.

Air Temperature at 4.5 Feet

Air temperature sensors had 4 years of data for

April, May, and October. For the remaining months of

the growing season, there were 5 years of data available for analysis.

The Mosaic site was the coolest of the four sites,

averaging 49.6 °F at 4.5 feet above the ground for

April through October (table 6). However, the average

temperature at the Mosaic site was only slightly

cooler than the ABGR (50.3 °F ) and ABLA (50.4 °F ) sites.

The ABGR site was warmer than the Mosaic site in

April, May, and June, but the sites were not different in

July through October (fig. 7). The ABLA site was

slightly warmer than the Mosaic site, but none of the

months are different from the Mosaic site. Air temperature at the THPL site was the highest of the four

Figure 6—Average relative humidity (percent) at the Mosaic site, and differences in average relative humidity from the Mosaic

site for the THPL, ABGR, and ABLA sites.
USDA Forest Service Res. Pap. RMRS-RP-24. 2000 11

Table 6—Summary statistics for average air temperature (°F) at 4.5 feet above

ground.

Number of Standard

Site observations Mean deviation Minimum Maximum

THPL 11522 53.8 13.2 19.6 93.7

ABGR 11449 50.3 13.5 17.4 92.3

Mosaic 11578 49.6 12.8 16.0 86.0

ABLA 11686 50.4 12.7 17.4 87.4

Figure 7—Average air temperature at 4.5 feet (°F) at the Mosaic site, and differences in average air temperature from the Mosaic

site for the THPL, ABGR, and ABLA sites.
12 USDA Forest Service Res. Pap. RMRS-RP-24. 2000

sites, averaging 4.2 °F higher than at the Mosaic site.

This higher temperature was consistent for all months

during the growing season (fig. 7).

Soil Surface Temperature

Soil surface temperature sensors were very reliable.

The surface sensors among the sites had 4 years of

data for May and June, 5 years of data for April and

October, and 6 years of data for the remaining months.

The surface temperature sensors were installed to

sample conditions that would be experienced by germinating seeds. The sensors were also used to determine the day snowpack melted in the spring. Presence

of a snowpack was obvious because a temperature

sensor covered by snow has a constant temperature

slightly above freezing. Once the snowpack melts,

surface temperatures begin to fluctuate.

The average date that the snowpack melted varied

by site. Average snowmelt date for the THPL site was

March 18, with a range from February 21 to April 11,

which averages 52 days earlier than the Mosaic site.

Average snowmelt date at the ABGR site was April 6,

24 days before the Mosaic site, with a range from

March 8 to April 24. The ABLA site was April 30, 9

days earlier than the Mosaic site, with a range from

March 31 to May 16. The latest date of snowpack melt

was the Mosaic site, averaging May 9, with a range

from April 14 to May 27.

Surface temperatures were lowest at the Mosaic site

where they averaged 52.0 °F (table 7). The THPL site

was warmest at 57.7 °F, and this warmer temperature

was consistent during the growing season (fig. 8). The

warmer average April temperature is due to earlier

snowmelt at the THPL site. The warmer May temperature at the THPL site also reflects earlier snowmelt, but

the higher standard deviation reflects the yearly variability of snowmelt at the Mosaic site in May.

The ABLA site had nearly the same average surface

temperature (52.1 °F) as the Mosaic site, and there

were no differences by months during the growing

season (fig. 8). Average surface temperature at the

ABGR site was 54.5 °F, an increase of 2.5 °F over the

Mosaic site. Most of this difference can be attributed to

the months of April and May (fig. 8) where there was

earlier snowmelt at the ABGR site.

Table 7—Summary statistics for average soil surface temperature (°F).

Number of Standard

Site observations Mean deviation Minimum Maximum

THPL 13290 57.7 23.2 19.8 144.0

ABGR 13217 54.5 21.0 14.9 129.2

Mosaic 13183 52.0 22.0 17.2 137.3

ABLA 13493 52.1 24.1 17.8 143.8

Since high surface temperatures can kill newly

germinated seedlings and thus affect secondary succession, the data were analyzed for maximum daily

temperatures. We chose 120 °F as a threshold temperature to compare sites since this is the approximate

temperature that results in heat girdling of conifer

seedlings (Haig and others 1941).

During the growing season, the THPL site averaged

21.2 days when surface temperature was ≥120 °F, an

increase of 13.6 days over the Mosaic site. The ABGR

site averaged 5.2 days ≥120 °F, 2.3 days less than the

Mosaic site. Surprisingly, the ABLA site averaged

30.3 days ≥120 °F, an increase of 22.8 days over the

Mosaic site. The warmer maximum temperatures are

also evident in figure 9. The THPL site is warmer in

April, June, and July, while the ABGR site is warmer

only in April because of earlier snowmelt.

Minimum surface temperatures are similar at the

Mosaic, ABGR, and ABLA sites (fig. 10). Only the

minimum temperatures at the THPL site were warmer

than the Mosaic site, from May through September.

The diurnal fluctuations for temperature sensors

were greatest at the soil surface, so surface temperatures were analyzed to see which sites might be

experiencing the greatest changes. The difference

between the maximum and minimum daily surface

temperatures was lowest at the Mosaic site, averaging 36.4 °F. At the ABGR site, diurnal fluctuations

averaged 40.6 °F. The ABLA and THPL sites had the

highest diurnal fluctuations, averaging 42.8 °F

(ABLA) and 43.2 °F (THPL).

Soil Temperature at 1 and 8 Inches

Soil temperature was monitored at 1-inch and 8-inch

depths. The 1-inch depth was chosen as an indicator

of the rooting environment for newly germinated

seeds. The 8-inch depth was chosen as an indicator of

the environment for larger plants. Soil temperature

sensors were among the most reliable sensors used at

the monitoring stations. For most of the growing

season months, data were available for at least 5 of

the 7 possible years, with the exception of May where

we have data for 4 of the 7 years.

Average soil temperatures at both depths (tables

8 and 9) had an inverse relationship with elevation
USDA Forest Service Res. Pap. RMRS-RP-24. 2000 13

Figure 8—Average soil surface temperature (°F) at the Mosaic site, and

differences in surface temperature from the Mosaic site for the THPL, ABGR,

and ABLA sites.

Figure 9—Average daily maximum soil surface temperature (°F) at the

Mosaic site, and differences in maximum surface temperature from the

Mosaic site for the THPL, ABGR, and ABLA sites.
14 USDA Forest Service Res. Pap. RMRS-RP-24. 2000

Figure 10—Average daily minimum soil surface temperatures (°F) at the Mosaic site, and differences in

minimum surface temperature from the Mosaic site for the THPL, ABGR, and ABLA sites.

Table 8—Summary statistics for average soil temperature (°F) at 1 inch.

Number of Standard

Site observations Mean deviation Minimum Maximum

THPL 14033 56.7 12.0 32.9 98.1

ABGR 13960 56.0 15.1 32.2 113.9

Mosaic 13924 51.7 13.5 32.0 107.6

ABLA 14223 50.9 12.1 31.4 86.9

Table 9—Summary statistics for average soil temperature (°F) at 8 inches.

Number of Standard

Site observations Mean deviation Minimum Maximum

THPL 4670 54.9 8.2 33.8 72.5

ABGR 4643 53.4 7.9 33.3 68.4

Mosaic 4631 50.0 9.9 32.4 69.8

ABLA 4740 48.9 8.3 32.1 65.8
USDA Forest Service Res. Pap. RMRS-RP-24. 2000 15

130

100

70

40

0 12 24 36 48 60 72

1"

8"

Surface

Time

Temperature

Figure 11—Soil temperatures (°F) over a 72-hour period

(July 29-31, 1994) at the Mosaic site, showing differences

among the surface, 1-inch, and 8-inch temperatures. The

amount of heat transferred from the soil surface to lower

depths diminished with distance from the surface, and there

is a definite time lag. This figure is for a dry soil; moist soils

had a similar pattern.

of the sites, with the lowest elevation site (THPL)

having the highest temperatures, progressing to the

highest elevation site (ABLA) having the lowest

temperatures. Average temperatures were always

cooler at the 8-inch depth, compared to the 1-inch

depth, by about 2 °F for all sites. Standard deviations were always higher at the 1-inch depth than

the 8-inch depth, reflecting the greater insulating

effect of the soil at a greater depth. Warm surface

temperatures take a longer time to change soil

temperature at 8 inches than at 1 inch (fig. 11).

The minimum temperatures indicate that soil rarely

freezes at the 1-inch depth (only the ABLA site dropped

below freezing) and never freezes at the 8-inch depth

during the growing season. Soil freezing at the ABLA

site occurred after the insulating snow cover had left

in the early spring but before the chance of belowfreezing temperatures passed. Soils at all four sites

rarely froze during the winter months because of the

insulating effect of deep snowpack.

Comparing the graphs of differences between the

three non-Mosaic sites and the Mosaic site (fig. 12 and

13), the THPL site is consistently warmer for all

months than the Mosaic site by about 4 to 5 °F at both

the 1-inch and 8-inch depths. The THPL site is about

8 to 9 °F warmer in April and May, reflecting earlier

snowmelt on the THPL site. Also, the variability of

differences in soil temperatures in May is greater

than the other months for all sites due to the timing of

snowmelt, as discussed previously for surface temperature. Soil temperatures at the ABGR site are

higher than the Mosaic site in spring (April through

June) and fall (September and October) at both depths.

Warmer spring temperatures are consistent with

the air and surface temperature trends on the ABGR

site but warmer fall temperatures are not consistent

with the air and surface temperatures. The ABLA

site is 2 to 3 °F cooler than the Mosaic site from June

to August at the 1-inch depth and from June to

September at the 8-inch depth.

Soil Water Potential at 1 and 8 Inches

Soil water potential sensors were very reliable, with

6 years of data for the 1-inch depth from June to

September and 5 years of data for April and October.

The 8-inch depth had 1 less year of data for all months

than the 1-inch depth. Insufficient data were available

for the 8-inch depth in May, so no May statistics are

reported for either the 8-inch or 1-inch depths.

Tables 10 and 11 show average soil water potential

at 1 and 8 inches in bars. The ABLA site has the lowest

average soil water potential at –4.2 bars at 1 inch and

–5.0 bars at 8 inches. The THPL site is the second

lowest at –4.1 bars at 1 inch and –3.9 bars at 8 inches.

Third lowest is the ABGR site at –4.0 and –3.4 bars.

The Mosaic site is the least dry during the growing

season. Average soil water potential is –3.3 bars at 1 inch

and –3.0 bars at 8 inches.

Another way to consider differences in soil water

potential is to look at the number of years soil water

potential equals or is less than –15.0 bars (permanent

wilting point for plants). Soils at the ABLA site dried

to –15.0 bars in 6 of 6 years at 1 inch from 1990 to 1995,

averaging 30.5 days per growing season ≤–15.0 bars.

Soils at the ABGR site also dried to –15.0 bars in 6 of

6 years, also averaging 30.5 days ≤–15.0 bars. The

THPL site dried 4 of 5 years at 1 inch, averaging 35.0

days. The Mosaic site dried to –15.0 bars in only 3 of 6

years at 1 inch, averaging 26.0 days.

Soils were moister at 8 inches, compared to 1 inch,

but the patterns among the stations were similar.

The ABLA site dried to ≤–15.0 at 8 inches in 5 of 5

years, averaging 37.8 days per growing season. The

ABGR site dried in to ≤–15.0 bars in 4 of 6 years,

averaging 20.5 days. The THPL site dried to ≤–15.0 in

4 of 5 years, averaging 32.2 days. The Mosaic site was

the least dry, drying to ≤–15.0 in only 2 of 6 years at

8 inches, averaging 18.5 days per growing season.

Soil pH

Soil pH sensors performed well in the field, but

there are many periods of missing data. Sensors

were removed when the soil began to dry in the

summer (< about –10.0 bars), as recommended by the

manufacturer. Animals disturbed some pH sensors by

pulling on the wires, which broke the direct contact

between the sensor and the soil. Sensors sometimes
16 USDA Forest Service Res. Pap. RMRS-RP-24. 2000

Figure 12—Average soil temperature (°F) at 1 inch at the Mosaic site, and

differences in average soil temperature for the THPL, ABGR, and ABLA sites.

Figure 13—Average soil temperature (°F) at 8 inches at the Mosaic site, and

differences in average soil temperature for the THPL, ABGR, and ABLA sites.
USDA Forest Service Res. Pap. RMRS-RP-24. 2000 17

became uncalibrated. Because of the lack of continuous pH data, there were not enough data to calculate

meaningful monthly averages as described in the

analysis section. Instead, we graphed available pH

data as a way to look at variation among the stations

throughout the year.

Soil pH provided interesting insights into unique

processes in the GFM. The Mosaic site had a definite

yearly fluctuation in pH (fig. 14). Soil pH in the spring

was between 5.5 and 6.5, but began dropping in April

through July. In August and September, pH began

rising again. In most years, pH was below 5.0, and

often was below 4.0. A pH of <5.0 is the value where

aluminum saturation becomes high enough to cause

aluminum toxicity in plants (Shoji and others 1993).

Because pH 5.0 is a critical value for aluminum

toxicity, a reference line has been placed on graphs in

figure 14.

Soil pH at the ABLA site is rather erratic and somewhat cyclic (fig. 14). pH drops below 5.0 during the

summer, but seldom goes below 4.5. Soil pH at the

THPL and ABGR sites stays between 5.5 and 7.0, and

does not drop below 5.0.

We considered the possibility that the pH fluctuations at the Mosaic site were due to soils drying in the

spring and then wetting in the fall. Perhaps decreased

moisture would increase the concentration of acids in

the soil. Circumstances in 1993 and 1994 allowed us to

address this question. The summer of 1993 was wet,

and soil water potential at the Mosaic site did not

Table 11—Summary statistics for average soil water potential (bars) at 8 inches.

Number of Standard

Site observations Mean deviation Minimum Maximum

THPL 9142 –3.9 5.6 –15.0 –0.4

ABGR 9107 –3.4 5.4 –15.0 –0.3

Mosaic 9223 –3.0 5.2 –15.0 –0.3

ABLA 8867 –5.0 6.1 –15.0 –0.3

Note: Since only 3 years of data were available for all stations in the month of May, May data

were not included in the statistics.

Table 10—Summary statistics for average soil water potential (bars) at 1 inch.

Number of Standard

Site observations Mean deviation Minimum Maximum

THPL 10713 –4.1 5.7 –15.0 –0.2

ABGR 10676 –4.0 5.7 –15.0 –0.4

Mosaic 10779 –3.3 5.2 –15.0 –0.4

ABLA 10898 –4.2 5.8 –15.0 –0.3

Note: Since only 3 years of data were available for all stations in the month of May for soil

water potential at 8 inches, May data were not included in the statistics so the 1 inch and 8 inch

data could be compared.

exceed –5.0 bars (even the THPL site did not reach

–15.0 bars in 1993). Conversely, 1994 was dry. Soil

water potential at the Mosaic site reached –15.0 bars

by early August and remained there until the middle

of October. Even though the two years had much

different moisture patterns, pHs were very similar

(fig. 15).

Regression analysis was used to predict 1993 and

1994 Mosaic soil pH at 1 inch from Julian date, soil

temperature at 1 inch, and soil water potential at 1 inch.

Soil water potential alone accounted for 3.9 percent of

the variation in 1993 and 4.6 percent of the variation

in 1994. Soil temperature alone accounted for 76.2

percent of the variation in 1993 and 60.0 percent in

1994. The best regression, using all three variables,

accounted for 85.8 percent of the variation in 1993 and

93.7 percent in 1994. The conclusion drawn from this

analysis is that soil water potential is not a good

predictor of soil pH.

Discussion _____________________

In this section we draw conclusions based on the

results of this study, show how these results fit with

other research on the GFM, and link these findings

to research on the genesis and properties of volcanic

ash soils.

The GFM has a shorter growing season than the

other sites, even though it is not at the highest elevation. Compared to the Mosaic site, the ABLA site is
18 USDA Forest Service Res. Pap. RMRS-RP-24. 2000

Figure 15—Average daily soil pH at 1 inch for the Mosaic site

in 1993 (wet year) and 1994 (dry year).

Figure 14—Average daily soil pH at 1 inch for the Mosaic, THPL, ABGR, and ABLA sites.

Available data are shown for 1989 through 1995.

free of snow 9 days earlier, the ABGR site 24 days

earlier, and the THPL site 52 days earlier. The Mosaic

site ranked the coolest for temperatures at 4.5 feet

above the ground and on the soil surface, and ranked

second for soil temperatures at 1 and 8 inches.

Soil water potential was lowest at the Mosaic site

during the growing season. Soil water potential at

8 inches dried to –15.0 bars in only 2 of 6 years for

the Mosaic site, while that threshold was reached

4 of 6 years at the ABGR site, 4 of 5 years at the

THPL site, and 5 of 5 years at the ABLA site. Moist

conditions at the GFM site should favor establishment of conifers and shrubs, especially since this

moisture is accompanied by cooler temperatures.

However, the GFM site has very little woody vegetation. Other environmental characteristics help explain this apparent contradiction.

Soil pH at 1 inch was very strongly acidic at the

GFM site. From May through September, soil acidity

typically dropped below pH 5.0, and often was below
USDA Forest Service Res. Pap. RMRS-RP-24. 2000 19

pH 4.0. Soil acidity during the winter at the Mosaic

was typically between pH 5.5 and 6.5.

Forest soils of northern Idaho and adjacent states

are heavily influenced by volcanic ash (Nimlos and

Zuuring 1982), mostly from the eruption of Mount

Mazama (Crater Lake, Oregon) about 6,850 years ago

(Bacon 1983). Mount Mazama volcanic ash is rich in

silicon and aluminum, with an average composition of

73.0 percent SiO2 and 14.4 percent Al2O3 by weight

(Johnson-Maynard 1995).

Typically, silicon and aluminum contained in volcanic ash weather to form various combinations of allophane and imogolite, which are noncrystalline hydrous aluminosilicates (Shoji and others 1993). Soils

dominated by allophane and imogolite in the clay-size

fraction are referred to as allophanic soils. They are

characterized by moderately-to-slightly acid pH and

low aluminum availability. As a result, aluminum

phytotoxicity is rare in allophanic soils.

Under certain conditions, such as non-forested

openings in the GFM, aluminum-humus complexes

are preferentially formed instead of allophane and

imogolite. This process gives rise to non-allophanic

soils. Non-allophanic ash soils are strongly acidic, and

aluminum toxicity is common to many crops below

about pH 5.0 (Shoji and others 1993). Soils of the GFM

have non-allophanic characteristics reflected in low

seasonal pH, high water availability in most years,

high organic matter inputs from forb communities

dominated by bracken fern and western coneflower

(Johnson-Maynard and others 1997), and a source of

aluminum from the weathered volcanic ash.

Research has demonstrated that allophanic and

non-allophanic soils exist side by side in the GFM

(Johnson-Maynard 1995). Although allophanic soil

characteristics develop under forest canopies, canopy

openings can result in the formation of non-allophanic

soils in just a few years. This rapid change in soil properties appears to be tied to the disruption of organic

matter cycling that accompanies the establishment of

successional forb communities (Johnson-Maynard and

others 1997).

The development of non-allophanic soil characteristics in forest openings is only one factor limiting

establishment of woody species in GFM habitats. The

allelopathic potential of bracken fern and western

coneflower has been demonstrated (Stewart 1975;

Gliessman 1976; Ferguson 1991). Allelopathy, which

is an additional factor beyond competition, can prevent germination of seed, delay germination, reduce

growth, or reduce the plant’s ability to survive.

Pocket gophers are also a factor limiting shrubs and

trees. Although woody vegetation is not a preferred

food source, it is eaten at certain times of the year,

especially in winter when preferred food sources are

absent (Teipner and others 1983; Marsh and Steele

1992; Ferguson 1999). Many GFM clearcuts have been

planted several times without success because of seedling mortality or damage caused by pocket gophers.

The recognition that four factors cause the slow rate

of secondary succession to woody vegetation is essential to successful management of GFM sites. First is

competition for space, light, water, and nutrients.

Second is allelopathy caused by species such as bracken

fern and western coneflower. Third is the effect of

pocket gophers. And fourth is non-allophanic soils.

Management of GFM sites that is based on recognition of all factors can be successful, but ignoring any

one of the four factors could lead to regeneration

failures. The order of limiting factors is also important. For example, the most limiting factor for plantation success is pocket gophers. If pocket gophers

are controlled or gopher populations are low, then

increments in survival and growth are possible from

controlling bracken fern and western coneflower. Additional gains could be made by planting species that

are adapted to acidic soils and by controlling other

vegetation. In order to meet management objectives,

planning must be matched to the unique combination

of ecosystem processes in the GFM.

References _____________________

Bacon, C. R. 1983. Eruptive history of Mount Mazama and Crater

Lake caldera, Cascade Range, USA. Journal of Volcanology and

Geothermal Research. 18:57-155.

Cooper, S. V.; Neiman, K. E.; Roberts, D. W. 1991. Forest habitat

types of northern Idaho: a second approximation. Gen. Tech. Rep.

INT-236. Ogden, UT: U.S. Department of Agriculture, Forest

Service, Intermountain Research Station. 143 p.

Ferguson, D. E. 1991. Allelopathic potential of western coneflower (Rudbeckia occidentalis). Canadian Journal of Botany.

69:2806-2808.

Ferguson, D. E. 1999. Effects of pocket gophers, bracken fern, and

western coneflower on planted conifers in northern Idaho—an

update and two more species. New Forests. 18:199-217.

Ferguson, D. E.; Boyd, R. J. 1988. Bracken fern inhibition of conifer

regeneration in northern Idaho. Res. Pap. INT-388. Ogden, UT:

U.S. Department of Agriculture, Forest Service, Intermountain

Research Station. 11 p.

Ferguson, D. E.; Johnson, F. D. 1996. Classification of Grand Fir

Mosaic habitats. Gen. Tech. Rep. INT-337. Ogden, UT: U.S.

Department of Agriculture, Forest Service, Intermountain Research Station. 16 p.

Finklin, A. I. 1983a. Summarizing weather and climatic data—a

guideline for wildland managers. Gen. Tech. Rep. INT-148. Ogden,

UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. 43 p.

Finklin, A. I. 1983b. Climate of Priest River Experimental Forest,

northern Idaho. Gen. Tech. Rep. INT-159. Ogden, UT: U.S.

Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. 53 p.

Gliessman, S. R. 1976. Allelopathy in a broad spectrum of environments as illustrated by bracken. Linnean Society Botanical

Journal. 73:95-104.

Haig, I. T.; Davis, K. P.; Weidman, R. H. 1941. Natural regeneration

in the western white pine type. Tech. Bull. 676. Washington, DC:

U.S. Department of Agriculture, Forest Service. 99 p.

Johnson, C. G., Jr.; Clausnitzer, R. R. 1992. Plant associations of

the Blue and Ochoco Mountains. R6-ERW-TP-036-92. U.S. Department of Agriculture, Forest Service, Wallowa-Whitman

National Forest. 207 p.
20 USDA Forest Service Res. Pap. RMRS-RP-24. 2000

Johnson-Maynard, J. 1995. Alteration of andisols in the Grand

Fir Mosaic Ecosystem following invasion by bracken fern

successional plant communities. University of Idaho. Moscow.

M.S. thesis. 91 p.

Johnson-Maynard, J. L.; McDaniel, P. A.; Ferguson, D. E.; Falen, A. L.

1997. Chemical and mineralogical conversion of andisols following

invasion by bracken fern. Soil Science Society of America Journal.

61:549-555.

Johnson-Maynard, J. L.; McDaniel, P. A.; Ferguson, D. E.; Falen,

A. L. 1998. Changes in soil solution chemistry of andisols following invasion by bracken fern. Soil Science. 163:814-821.

Marsh, R. E.; Steele, R. W. 1992. Chapter 10—Pocket gophers.

In: Black, H. C. (tech. ed.). Silvicultural approaches to animal

damage management in Pacific Northwest forests. Gen. Tech.

Rep. PNW-287. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station:

205-230.

Nimlos, T. J.; Zuuring, H. 1982. The distribution and thickness of

volcanic ash in Montana. Northwest Science. 56:190-198.

Shoji, S.; Nanzyo, M.; Dahlgren, R. A. 1993. Volcanic ash soils:

genesis, properties, and utilization. Elsevier Science Publishers.

Amsterdam, The Netherlands. 288 p.

Sommer, M. R. 1991. Soils of the Grand Fir Mosaic. University of

Idaho. Moscow. M. S. thesis. 97 p.

Stewart, R. E. 1975. Allelopathic potential of western bracken.

Journal of Chemical Ecology. 1:161-169.

Teipner, C. L.; Garton. E. O.; Nelson, L., Jr. 1983. Pocket gophers in

forest ecosystems. Gen. Tech. Rep. INT-154. Ogden, UT: U.S.

Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. 53 p.

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The Rocky Mountain Research Station develops scientific information and technology to improve management, protection, and use of

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Studies accelerate solutions to problems involving ecosystems,

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Research Locations

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Fort Collins, Colorado* Albuquerque, New Mexico

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*Station Headquarters, Natural Resources Research Center,

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