Treatment Duration and Time since

Disturbance Affect Vegetation

Development in a Young California

Red Fir Plantation

Philip M. McDonald Gary O. Fiddler

United States

Department

of Agriculture

Forest Service

Pacific Southwest

Research Station

Research Paper

PSW-RP-233

http://www.psw.fs.fed.us/
Abstract

McDonald, Philip M.; Fiddler, Gary O. 1997. Treatment duration and time since

disturbance affect vegetation development in a young California red fir

plantation. Res. Paper PSW-RP-233. Albany, CA: Pacific Southwest Research Station,

Forest Service, U.S. Department of Agriculture; 14 p.

The density and development of greenleaf manzanita, snowbrush, goldenbush

(rabbitbrush), and graminoids were evaluated in a young California red fir plantation in

northern California from 1986 through 1995. Manual grubbing and herbicides created

treatment regimes that lasted for 3 to 6 years and vegetation recovery times of 4 to 10

years. The duration and timing of the grubbing and spraying operations constituted the

treatments. Species response was mixed: greenleaf manzanita had higher average values

of density, foliar cover, and height when time since disturbance was longest, snowbrush

density was lowest but cover and height were highest, and values for goldenbush and

graminoids in general showed no trend. In the control at the end of the study, graminoids

numbered 82,350 per acre, greenleaf manzanita 10,850, goldenbush 10,800, and

snowbrush 1,850 plants per acre. Foliar cover of manzanita at 7,300 ft2 per acre was more

than that of all other naturally established species combined. Survival of red fir over all

treatments after one growing season was 98 percent and after 10 seasons was 89 percent.

Average height of red fir seedlings ranged from 3.2 feet with intensive release to 1.7 feet

with no release. No release allowed greenleaf manzanita plants to be slightly taller than

red fir seedlings and to place the seedlings in danger of being overtopped.

Retrieval Terms: competing vegetation, northern California, plant succession, red fir

seedlings, timing of release

The Authors

Philip M. McDonald is a research forester assigned to the Station’s Western Forest

Management Research Unit, 2400 Washington Ave., Redding, CA 96001. Gary O. Fiddler

is a silviculturist assigned to the Ecosystem Conservation Staff, Pacific Southwest Region,

USDA Forest Service, San Francisco, and stationed at Redding, Calif.

Publisher:

Albany, California

Mailing address:

PO Box 245, Berkeley CA

94701-0245

510 559-6300

http://www.psw.fs.fed.us

June 1997

Pacific Southwest Research Station

Forest Service

US Department of Agriculture
Treatment Duration and Time since

Disturbance Affect Vegetation

Development in a Young California

Red Fir Plantation

Philip M. McDonald Gary O. Fiddler

Contents:

In Brief . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

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

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

Location and Site Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Study and Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Plant Diversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Greenleaf Manzanita . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Snowbrush . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Goldenbush . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Graminoids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

California Red Fir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Discussion and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Pacific Southwest

Research Station

USDA Forest Service

Research Paper

PSW-RP-233

 June 1997
ii USDA Forest Service Res. Paper PSW-RP-233. 1997.

In Brief

McDonald, Philip M.; Fiddler, Gary O. 1997. Treatment duration and time since

disturbance affect vegetation development in a young California red fir

plantation. Res. Paper PSW-RP-233. Albany, CA: Pacific Southwest Research

Station, Forest Service, U.S. Department of Agriculture; 14 p.

Retrieval Terms: competing vegetation, northern California, plant development,

red fir seedlings, timing of release

This paper presents the density and development of several shrub and

herbaceous species that invaded a young conifer plantation in interior northern

California on a medium site at mid-elevation (5,600 feet). It also quantifies the

survival and growth of planted California red fir seedlings relative to these

invading species. A major influence on all the vegetation was the environment of

the site, which was characterized by short, hot, dry summers and long, cold,

snowy winters.

This study differs somewhat from most studies that evaluate alternatives for

controlling competing vegetation in young conifer plantations. In this study, we

wished to document the recovery of the vegetation after a series of manipulations

that were applied at different times and continued for various durations. We

hypothesized that the amount of vegetation and when it was present, relative to

site preparation and release, would affect the various species in the community

and in turn affect the conifer seedlings. Thus, the manual grubbing and herbicide

that we applied served only to accomplish the treatments. The different timings

and durations were the treatments.

The treatments were:

Treat first 6 years (1986-1991), develop naturally last 4 years,

designated as T-first-6;

Treat first 3 years (1986-1988), develop naturally last 7 years, designated

as T-first-3;

Delay 3 years, treat next 3 years (1989-1991), develop naturally last 4

years, designated as T-second-3;

Control, not treated after site preparation, develop naturally entire 10

years of the study (1986-1995), designated as Control.

Research results and operational implications for forest land managers

follow.

The plant community at the end of the study numbered 17 species plus an

alien (yellow star thistle), which may or may not become established. Relative to

the literature, this is a low number of species for red fir plantations in northern

and central California.

Although the number of species was low, the number of plants that returned 4

to 10 years after grubbing and spraying was large. More than 100,000 plants per

acre, 77 to 89 percent of which were grasses and sedges (graminoids), were present

in each treatment at the end of the study.

Although the number of plants per acre at the end of the study was large, the

amount of horizontal development as manifest in foliar cover was small—

amounting to 13 to 33 percent among treatments.

The various shrub and herbaceous species indicated different density and

developmental trends relative to treatment. For greenleaf manzanita at the end

of the study, the two treatments with the longest recovery times resulted in the

highest number of plants per acre; for snowbrush, the fewest; and for goldenbush

and graminoids, a mixture. A longer recovery time also resulted in higher foliar
USDA Forest Service Res. Paper PSW-RP-233. 1997. iii

cover for manzanita, snowbrush, and goldenbush, and taller plants of manzanita

and snowbrush. Greenleaf manzanita excelled in the control, but the graminoids

faltered, probably because of too much competition.

The growth strategy of California red fir was to grow tall with a thin stem and

crown, and then to begin to channel resources to diameter growth. At the end of

the study, average height of red fir ranged from 3.2 feet in the T-first-6 treatment to

1.7 feet in the Control. This was a statistically significant difference. Mean diameter

of red fir did not differ statistically among treatments during the study.

The T-first-3 and T-second-3 treatments were designed specifically to test the

significance of immediate versus delayed release of California red fir. However,

significance was not determined, probably because 10 years is not enough time

for growth relationships to develop. This is important. Studies that aim to

determine red fir seedling diameter and height relationships relative to different

timings and durations of treatment need to be longer than 10 years. Ten years

may be adequate for ponderosa pine and Douglas-fir, but not enough for

California red fir.

The forest land manager now has some idea of the species that could develop

in a young red fir plantation and their density, development, and competitive

potential relative to various timings and durations of manipulation. Survival

and growth of planted California red fir seedlings also are indicated, as are

beginning trends in statistical differentiation among treatments. Ecologically,

the data presented in this study can contribute toward modelling early succession

in this plant community.
USDA Forest Service Res. Paper PSW-RP-233. 1997.

1

Introduction Competition from woody shrubs, forbs, and grasses in new plantations often

is rapid and formidable. On the basis of information from 32 logged areas in

northern and central California, Gordon and Bowen (1978) found that time since

disturbance (site preparation) influenced the composition and development of

the plant community. On the three cutting areas that had only one complete

growing season, an average of 50 percent of the sample locations suitable for

plants were already occupied. All other areas with longer histories (up to 12

years after disturbance) had 69 percent or more of the suitable locations occupied.

Because early growth of red fir seedlings typically is slow and that of shrubs is

often rapid, red fir seedlings often become suppressed. When this happens, the

seedlings do not die, but become overtopped. They then slowly grow through

the shrubs—a process that can take 30-50 years. “Neither this delay nor the

frequently haphazard stocking are acceptable” (Laacke and Fiske 1983).

Plainly, competition must be controlled, and one method for doing so is

release. But knowledge on when to release young California red fir (Abies

magnifica A. Murr.) plantations to achieve dependable seedling survival and

growth is lacking. Furthermore, the timing of release could be dependent on the

species and number of plants that are present in young red fir plantations, how

fast they develop, and their effect on red fir seedling survival and growth.

Timing of release is manifest in several comparisons such as immediate

versus delayed release or releasing for one time span versus another. At some

point, delayed release might be no more effective than never releasing, or

releasing each year for several years might be no more effective than releasing

for 1 or 2 years depending on when the release took place.

Shrinking budgets and a lack of resources have often caused release activities in

young conifer plantations to be postponed until the third growing season. At such

times the cry often is heard: “Where did all that grass and all those shrubs come

from?” and “What will they do to the growth of my conifer seedlings?” Research in

northern and central California on ponderosa pine (Pinus ponderosa Dougl. ex Laws.

var. ponderosa) and Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) has shown that

release from competing vegetation the first year is critical, and that release during

the first 3 years is worthwhile (Fiddler and McDonald 1987, McDonald and Fiddler

1989). However, release after 4 years generally is not cost-effective. The competing

vegetation, which has become large and well established, is not only expensive to

control, but it also has limited site resources to the conifer seedlings and slowed

growth—a process from which it will take time for them to recover. Is release during

the first 3 years also important for California red fir?

To increase knowledge on the ecology of several widespread plant species and on

a plant community that is commonplace in California and Oregon, information was

collected on the growth dynamics and competitive relationships of vegetation

reoccupying a bulldozed brush field in northern California. Planted California red fir

seedlings were part of the plant community. As part of a National Forest Service

Administrative Study on Alternative Release Methods (Fiddler and McDonald 1984),

data were gathered from 1986 to 1995 on vegetation developing after site preparation

in a control and on vegetation manipulated deliberately by grubbing and applying a

herbicide to create different time spans. The time spans, or more specifically “vegetation

recovery times after disturbance by site preparation and release,” are the treatments.

This paper reports the results of these treatments in terms of the recovery

of the plant community 4, 7, and 10 years after manipulation. It also quantifies

the survival and growth of California red fir seedlings after immediate and

delayed release.
2 USDA Forest Service Res. Paper PSW-RP-233. 1997.

Methods

Location and Site Characteristics

The study area, located on land owned by Sierra Pacific Industries in the southern

Cascade mountains, is about 25 airline miles northeast of McCloud, California.

Vegetation in the area has been placed in the montane and subalpine region of

the Sierra Nevada and Cascade Ranges by Rundel and others (1977) and in the

white fir forest vegetation type (Gordon 1980). Before the study began, the area

was a brush field, and probably had been for at least 50 years. It had not always

been a brush field, however, as an occasional blackened stump and log in the

study area indicated that it had once supported trees. The forest stand then

probably was much like that in the nearby forest today. Here, California white fir (Abies concolor var. lowiana [Gord.] Lemm.) is the dominant species with California

red fir second. Sierra lodgepole pine (Pinus contorta var. murrayana [Grev. &

Balf.] Engelm.) and incense-cedar (Libocedrus decurrens Torr.) are occasional

species along with willow (Salix spp.).

The mature brush field consisted of 4- to 5-foot tall plants of snowbrush (Ceanothus

velutinus Dougl. ex Hook.), bitter cherry (Prunus emarginata [Hook.] Walp.), and

greenleaf manzanita (Arctostaphylos patula Greene). Goldenbush (Ericameria bloomeri

[A. Gray] J.F. Macbr.) [= Haplopappus bloomeri A. Gray] (Hickman 1993) was scattered

throughout, and most abundant in small openings among these species.

Site quality of the study area is medium-poor with height of dominant

California white firs averaging about 60 feet in 50 years (Biging and Wensel

1984). The soil, which is closely related to the Avis series, is an ashy-skeletal,

frigid Dystric Xerorthent. It was formed from volcanic ash, usually deposited

over and in fractured lava flow rock. It has a stony sandy loam texture and is

about 5 feet deep. Stones, gravel, and sand are abundant throughout. The

elevation is about 5,600 feet, the slope is 1 percent, and the aspect is east. The area

is remarkably uniform with respect to slope, aspect, and soil. Precipitation

averages about 55 inches per year, with about 80 percent falling as snow.

Temperatures range from 20° F to 80° F with the average annual temperature

being 43° F. The growing season is about 100 days.

A portion of the brush field was pushed into windrows with a bulldozer in

spring 1985 and burned in the fall. Very little soil was displaced, and the

windrows could scarcely be seen a few years later.

Container-grown California red fir seedlings were raised in the Ben Lomand

Nursery and out planted as plugs in spring 1986. Spacing was 8 by 8 feet. Survival

of seedlings in all study plots at the end of the first growing season was 98 percent.

The plant community when the study began consisted almost entirely of

plants that had originated from dormant seeds in the soil and from windblown

seeds. Virtually no competition from sprouting root burls was present. In

addition to the planted red fir seedlings, the early plant community consisted

of the same species of shrubs noted earlier, plus a few grasses and forbs.

Several animals were present in the study area and had the potential to

influence the plant community. Deer (Hemionus spp.) were prevalent in the

study area. Ground squirrels (spermophilus spp.) also were numerous, and

rabbits (Lepus spp.) were occasionally seen. Fortunately, no pocket gophers

(Thomomys spp.) were present.

Study and Design

The experimental design was completely randomized with one-way treatment

structure. Four treatments, including the control, were each replicated four

times. A replicate (plot) consisted of about 0.1 acre on which were at least 40

California red fir seedlings surrounded by one to two rows of buffer (seedlings

receiving similar treatment). The study began in 1986 and ended in 1995.

Treatments and treatment dates were:
USDA Forest Service Res. Paper PSW-RP-233. 1997. 3

Treatments

Treat first 6 years (1986-1991), develop naturally last 4 years,

designated as T-first-6;

Treat first 3 years (1986-1988), develop naturally last 7 years,

designated as T-first-3;

Delay 3 years, treat next 3 years (1989-1991), develop naturally last 4

years, designated as T-second-3;

Control, not treated after site preparation, develop naturally entire 10

years of the study (1986-1995), designated as Control.

Plots in the T-first-6 treatment were treated by applying an herbicide to the entire

plot plus the buffer. Plots in the T-first-3 and T-second-3 treatments were grubbed

to a 5-foot radius. Vegetation was grubbed below the root crown with hand tools.

The herbicide (Roundup)1 (2 and 5 percent solutions) was applied directly with a

backpack apparatus according to recommendations on the label. Lingering effects

of the herbicide, if any, have not been documented. Spraying took place between

7 a.m. and 9 a.m. PST on clear days with little or no wind. A guide was used to

ensure uniform coverage of the herbicide and to avoid overlapping and skipped

areas. Crowns of entire plants were sprayed until wet. Plastic bags were used to

cover red fir seedlings.

Grubbing and spraying were performed during the summer at a time when

growth of the red fir seedlings had ceased, but that of the shrubs was continuing.

Sampling

Of the 40 California red fir seedlings in each plot, 25 that appeared to have good

potential of becoming harvestable trees were selected and tagged. Chlorotic and

misshapen seedlings that would be removed in the first precommercial thinning

were excluded. Stem diameter (measured at 12 inches above mean groundline)

and height were measured on each. The seedlings were periodically checked for

injury from chemicals, animals, and insects.

Sampling intensity for evaluating other vegetation was five randomly

selected subplots in each plot. Subplots were centered around red fir seedlings

and encompassed 1 milacre (0.001 acre). The most abundant species were

evaluated for density, foliar cover (the sum of shadows that would be cast by

leaves and stems of individual species expressed as a percentage of the land

surface [Daubenmire 1968]), and average dominant height (average of the three

tallest stems measured from mean ground line to bud). More specifically, number

of plants in each subplot were counted, foliar cover was visually estimated, and

height was measured with a graduated pole.

To test for treatment effects and significant differences among treatments,

one-way analysis of variance of treatment means (fixed effect model, Steel and

Torrie 1980) and Tukey tests were applied (SAS Institute Inc. 1988). Statistical

significance in all tests was at α = 0.05. Data were gathered from permanent plots

measured each year, and where analyses of means from repeated measurements

are concerned, the data are not truly independent. The α levels or type I errors

given for various tests apply to each measurement period and year separately.

To quantify plant diversity, all species were noted on study plots when the

study began and when it ended.

Results

Plant Diversity

Most early seral vegetation in young plantations in California and Oregon

consists of a mixture of shrubs, forbs, and grasses, often from seed and from

sprouts. Rarely is this vegetation dominated by a single class of plants (McDonald

and Radosevich 1992) and rarely is it just from seed. Thus it is of interest to

1This paper neither recommends

the pesticide uses reported nor

implies that the pesticides have

been registered by the appropriate governmental agencies.
4 USDA Forest Service Res. Paper PSW-RP-233. 1997.

ecologists to have knowledge of a plant community dominated by woody and

herbaceous species—all from seed—but from two regeneration strategies (Grime

1979). These were regeneration from windblown seeds and from a persistent

seed bank (dormant seeds in soil).

With minor exceptions, the plant species in the study area were found in all

treatments. The plant community on all plots near the beginning of the study

consisted of planted California red fir, 5 species of shrubs, 3 forbs, and 1

graminoid. By the end of the study, vegetation in the study plots included a few

natural seedlings of 2 conifer species (not red fir), 5 shrubs, 6 forbs, and 4

graminoids for a total of 17 species. Two species of shrubs: bush chinquapin (Chrysolepis sempervirens [Kellogg] Hjelmq.) and bitter cherry, noted initially,

could not be found at the end of the study. Bush chinquapin is not common in the

area, but bitter cherry, which initially was present in all treatments, was. Its

density in terms of seedlings per acre by year averaged over all treatments was:

1986 1987 1988 1989 1990 1991 1995

487 325 175 38 12 0 0

Most bitter cherry seedlings originated in 1986 and 1987. One new seedling was

found in 1989. Seedlings were heavily browsed in 1987 and 1988, but browsing

alone was not responsible for the complete demise of the species in the plantation.

Competition-induced drought is more probable. One forb, known locally as

woolly nama (Nama spp.), was present on two subplots in one treatment from

1988 through 1991, but disappeared thereafter. Ominously, 23 plants averaging

2.5 feet tall of the alien yellow star thistle (Centaurea solstitialis L.) were sampled

on one subplot near the access road in 1995. Given the harsh winters, this species

may have difficulty becoming established in the plantation.

Greenleaf Manzanita

Greenleaf manzanita, an evergreen, fast-growing shrub, was the most abundant

species in the control in 1986 (3,400 plants per acre) and remained abundant

throughout the study. In 1987 and 1988, we noted that “many greenleaf manzanita

seedlings are becoming established in the study area, especially on the recently

treated plots.” Manzanita also was noted as being browsed in 1988, 1989, and 1990.

Average density of greenleaf manzanita in the control was highest in 1989 at

11,250 plants per acre and declined to 10,850 plants per acre in 1995 (table 1).

Foliar cover and height increased throughout the study period and reached 7,300

ft

2

 per acre and 1.8 feet tall in 1995. At the end of the study, manzanita cover was

greater than for all other species combined. During the 10-year study (1986-

1995), the average number of manzanita plants in the control increased 219

percent, cover increased by 7300 percent and height by 1700 percent.

Among treatments, manzanita density in 1995 portrays the recovery

capability of the species at various times after grubbing and spraying. When the

time since last disturbance was 4 years, as in the T-first-6 and T-second-3

treatments, density ranged from 3,950 to 5,450 plants per acre (table 2). When

disturbance ended 7 years earlier as in the T-first-3 treatment, manzanita plants

numbered more than 9,000 plants per acre. And when it ended 10 years earlier, as

in the control, more than 10,800 plants per acre were present. Average foliar

cover and height followed a similar trend. More than 5 times more foliar cover

was present in plots grubbed and sprayed 7 years earlier than in those where

disturbance had ended 4 years earlier; 67 to 100 percent more for the longer time

span for manzanita height. Foliar cover and height of manzanita were

significantly greater in the control than in any other treatment.

Snowbrush

Snowbrush, which is commonplace in California and Oregon, also is evergreen

and considered to grow even faster than greenleaf manzanita. However, this
USDA Forest Service Res. Paper PSW-RP-233. 1997. 5

Table 1—Density, cover, and height, with standard errors (SE), of greenleaf manzanita, snowbrush, goldenbush, and graminoids

in the control, northern California, 1986-1995

Year Density SE Cover SE Height SE

------ plants/acre ----- ------- ft2/acre ----- ------------ ft ----------

Greenleaf manzanita 1986 3,400 1,476 0 0 0.1 0.0

1989 11,250 4,181 900 265 0.5 0.1

1991 10,300 3,047 2,400 622 0.8 0.1

1995 10,850 3,953 7,300 998 1.8 0.1

Difference

 (pct increase) +219 + huge +1700

Snowbrush 1986 750 206 50 50 0.1 0.1

1989 4,050 618 500 100 0.4 0.1

1991 3,600 716 1,050 189 0.7 0.1

1995 1,850 359 1,800 408 1.5 0.1

Difference

 (pct increase) +147 +3500 +1400

Goldenbush 1986 600 600 50 50 0.6 0.1

1989 11,700 11,368 800 735 0.4 0.2

1991 9,650 8,212 1,700 1,567 0.6 0.2

1995 10,800 5,605 2,150 1,636 0.8 0.2

Difference

 (pct increase) +1700 +4200 +33

Graminoids 1986 600 346 100 58 0.5 0.3

1989 48,100 15,148 2,550 741 1.6 0.2

1991 48,400 12,326 2,600 1,149 1.3 0.2

1995 82,350 17,249 2,850 888 1.5 0.2

Difference

 (pct increase) + huge +2750 +200

Table 2—Density, cover, and height of greenleaf manzanita, snowbrush, goldenbush, and graminoids after

ten growing seasons by treatment, northern California

 Treatment Density Cover Height

plants/acre ft2/acre ft

Greenleaf manzanita Treated first 6 years 3,950.a1 300 a 0.6 a

Treated first 3 years 9,100 a 1,550 a 1.0 b

Treated second 3 years 5,450 a 300 a 0.5 ac

Control 10,850 a 7,300 b 1.8 d

Standard error 3,632 632 0.1

Snowbrush Treated first 6 years 4,400 a 100 a 0.4 a

Treated first 3 years 3,550 a 800 ab 0.9 b

Treated second 3 years 4,500 a 200 a 0.5 ab

Control 1,850 a 1,800 b 1.5 b

Standard error 1,224 307 0.2

Goldenbush Treated first 6 years 10,500 a 1,100 a 0.9 a

Treated first 3 years 14,550 a 1,800 a 1.0 a

Treated second 3 years 15,350 a 1,600 a 0.9 a

Control 10,800 a 2,150 a 0.8 a

Standard error 4,268 893 0.1

Graminoids Treated first 6 years 93,550 a 4,050 a 1.9 a

Treated first 3 years 116,250 a 5,450 a 1.8 a

Treated second 3 years 85,100 a 4,650 a 2.3 a

Control 82,350 a 2,850 a 1.5 a

Standard error 18,193 923 0.2

_______________________________________________________________________________ 1

For each species, treatment means in each column followed by the same letter do not differ statistically

at the 0.05 level.
6 USDA Forest Service Res. Paper PSW-RP-233. 1997.

rating probably is based on sprout growth. In 1985, Conard and others noted that

little was known about seedling development (as opposed to sprout development)

in various environments. Published data on snowbrush seedling growth in

plantations were scarce in 1996 as well. In our study, visual records indicated

that many new snowbrush seedlings were becoming established in recently

disturbed plots in 1987 and 1988. Snowbrush was lightly browsed in 1988 and

1990 and heavily browsed in 1989.

Average density of snowbrush in the control was 750 plants per acre in

1986, peaked at more than 4,000 plants per acre in 1989, and declined steadily

to 1,850 plants per acre in 1995 (table 1). Snowbrush foliar cover and height

increased steadily and reached 1,800 ft

2

 per acre and 1.5 feet tall, respectively,

at the end of the study. For the 10 years of the study, the average number of

snowbrush plants in the control increased 147 percent, foliar cover increased

3500 percent, and height 1400 percent.

Among treatments, plots that had been disturbed last had the most plants,

indicating recruitment of new seedlings after 6 years. In 1995, for example, the

most snowbrush seedlings were in T-first-6 and T-second-3 plots (table 2). Here

the seedlings, although numerous, had the least cover (100-200 ft

2

 per acre) and

were shortest (0.4 to 0.5 feet tall). Plants in T-first-3 plots had at least 4 times

more cover (800 ft

2

 per acre) and roughly twice as much height (0.9 feet) as

counterparts in plots that had been disturbed last. No disturbance after site

preparation as in the control resulted in fewer plants but at least twice as much

foliar cover (1,800 ft

2

 per acre) and almost twice as much height (1.5 feet) as in

any other treatment.

Goldenbush

Once called “rabbitbrush” and now Bloomer goldenbush or rabbitbrush

goldenweed, goldenbush, like other species in the genera Chrysothamnus,

Haplopappus, and Ericameria, is noted for its abundance and ability to grow well

on poor sites (Sampson and Jespersen 1963). It is rated as a severe competitor to

conifer seedlings in young plantations (Click and others 1989). Deep roots and

heavy litterfall make it useful for erosion control (Deitschman and others 1974).

It also has value as food for deer in late fall and early winter, but rates only fairpoor in palatability (Sampson and Jespersen 1963).

Seed production of goldenbush is reported to begin at age 2 with dispersal

by wind as soon as seeds mature (Deitschman and others 1974). Good seed crops

are produced almost every year; dispersion is wide; and once established, growth

is rapid. Mozingo (1987) noted that rabbitbrush (goldenbush) is one of the first

shrubs to invade a disturbed area. In our study, goldenbush seedlings were

noted as being the first to reinvade the newly grubbed plots in the T-second-3

treatment. No browsing was noticed during the study.

In the control, average goldenbush density was relatively low in 1986 (600

plants per acre), peaked in 1989 (11,700 plants per acre), and then decreased

slightly by 1995 (10,800 plants per acre) (table 1). Average foliar cover increased

steadily from 50 to 2,150 ft

2

 per acre and height erratically from 0.6 to 0.8 feet

during the study.

Among treatments in 1995, time since disturbance did not appear to be a factor

affecting density, foliar cover, or height. Density ranged from 10,500 to 15,350 plants

per acre, foliar cover from 1,100 to 2,150 ft

2

 per acre, and height from 0.8 to 1.0 feet

(table 2). No differences among treatment means were statistically significant.

Graminoids

Almost all plants in this category were from the genera Sitanion, Achnatherum

(formerly Stipa; Hickman 1993), and Carex. As early as fall 1986, a few grass

plants were noted as invading recently sprayed plots. New grass seedlings also

were mentioned as being present on most plots in 1988 and “flooding” into them
USDA Forest Service Res. Paper PSW-RP-233. 1997. 7

in 1989. Some browsing was noted on grass in fall 1990.

Graminoids in the control numbered 600 per acre in 1986 with only minor

amounts of foliar cover and height (table 1). However, by 1989, density had

increased to more than 48,000 plants per acre with more than 2,500 ft2

 of foliar

cover per acre and an average height of 1.6 feet. These values remained relatively

similar through 1995 with the exception of graminoid density, which increased

greatly to more than 82,000 plants per acre.

Among treatments in fall 1995, average density ranged from 82,350 to 116,250

plants per acre, foliar cover from 2,850 to 5,450 ft2 per acre, and height from 1.5 to

2.3 feet (table 2). No statistical differences were found among treatments for

density, foliar cover, or height.

California Red Fir

Damage to these conifer seedlings was surprisingly light. In spite of many

sightings of deer in the study area, light browsing damage was noted only in

1987 and 1989. Visual records also indicated some terminal buds killed by late

spring frost in 1991 and some needles burned by dry summer winds that fall.

Mortality also was low. After one growing season 8 seedlings had died in the

control, but none in the other treatments. Thus first-year survival for the entire

study was 98 percent. Mortality, attributed to drought, was scattered among the

treatments over time and no single event was noted. At the end of the study,

percent survival by treatment was:

T-first-6 99

T-first-3 89

T-second-3 93

Control 76

Only one seedling died in the T-first-6 treatment during the 10-year study.

Analysis of transformed survival values (arcsin) indicated that survival

differed significantly between seedlings in the T-first-6 and control

treatments. Overall, 10-year survival of red fir seedlings on all study plots in

all treatments was 89 percent.

Average height of California red fir seedlings increased steadily in all

treatments and by the end of the study in 1995 ranged from 3.2 feet in the T-firstTable 3—Stem diameter and height of California red fir seedlings, by treatment,

northern California, 1986-1995

_______________________________________________________________________________

Treatment 1986 1989 1991 1995

_______________________________________________________________________________

--------------------- Diameter (inches) ------------------

Treated first 6 years - a.

1 0.23 a 0.48 a 0.95 a

Treated first 3 years - a. 0.24 a 0.46 a 0.82 a

Treated second 3 years 0.10 a. 0.23 a 0.40 a 0.70 a

Control 0.10 a. 0.21 a 0.29 a 0.58 a

Standard error 0.03. 0.02 0.05 0.09

------------------------ Height (feet) ----------------------

Treated first 6 years 0.53 a 1.30 ab 2.13 b 3.16 b

Treated first 3 years 0.56 a 1.46 b 2.12 b 2.77 ab

Treated second 3 years 0.52 a 1.15 ab 1.81 ab 2.48 ab

Control 0.56 a 1.04 a 1.29 a 1.71 a

Standard error 0.02 0.09 0.20 0.31

_____________________________________________________________________________ 1

For each year, treatment means followed by the same letter do not differ

significantly at the 0.05 level.
8 USDA Forest Service Res. Paper PSW-RP-233. 1997.

6 treatment to 1.7 feet in the control (fig. 1). Statistical differences among

treatments for red fir height first became evident in fall 1989 with seedlings in the

T-first-3 plots being significantly taller than those in the control (table 3). By 1991,

seedlings in both the T-first-3 and T-first-6 plots were significantly taller than

those in the control. By 1995, only seedlings in the T-first-6 plots differed

significantly from those in the control.

Figure 1—Relative development of

California red fir seedlings and

surrounding plant community, by

treatment, fall 1995 (A) T-first-6, (B)

T-first-3, (C) T-second-3, and (D)

Control.

C

A
USDA Forest Service Res. Paper PSW-RP-233. 1997. 9

B

D
10 USDA Forest Service Res. Paper PSW-RP-233. 1997.

Stem diameter, measured at 12 inches above mean groundline, increased

slowly and by the end of the study ranged from 1.0 inch in T-first-6 plots to 0.6

inch in the control (table 3). Like stem height, diameter values for the T-first-3 and

T-second-3 plots were intermediate in response. Mean diameter never differed

significantly among treatments at the 5 percent level. However, differences were

achieved in 1995 at the 8 percent level.

The ratio of height to diameter helps explain the effect of treatment. In all

treatments from 1989 through 1995 the height-diameter ratio decreased,

suggesting that stem diameter was expanding faster than stem height. In 1995,

with the exception of the control, the lowest ratios were for the T-first-6 and Tfirst-3 treatments, with the highest ratio being in the T-second-3 treatment. Thus,

stem diameter was expanding slower, relative to height in the T-second-3

treatment, than in the other treatments. Surprisingly, the treatment with the

lowest ratio was the control. Unlike the overall strategy of California red fir

seedlings, which is to grow tall and thin, that of stressed red fir seedlings seems

to be to thicken stem diameter in place of height development (fig. 2).

Discussion and Conclusions

A major need in forestry today is to develop knowledge on plant species and

communities that develop after site preparation and after additional disturbance

such as that incurred in release. Another need is to develop treatments and

treatment schedules that provide consistent and reliable conifer seedling survival

and growth rates.

As noted by Gordon and Bowen (1978), time since disturbance is an

Figure 2—Besieged by competing vegetation, this 10-year-old California red fir seedling has a relatively thick, short stem,

and is in danger of being overtopped.
USDA Forest Service Res. Paper PSW-RP-233. 1997. 11

important factor affecting the amount of natural vegetation that develops in a

given area. In this study, the grubbing and herbicide-application schedules

resulted in plant community recovery times of 4 years in the T-first-6 and Tsecond-3 treatments, 7 years in the T-first-3 treatment, and 10 years in the

control. Some general relationships, most of which were not statistically

significant, indicate a young, dynamic plant community with species that have

different density and developmental trajectories. For greenleaf manzanita in

1995, the two treatments with the longest recovery times resulted in the highest

number of plants per acre; for snowbrush, the fewest; and for goldenbush and

graminoids, a mixture. A longer recovery time also meant more foliar cover for

all three shrub species, and taller plants for greenleaf manzanita and snowbrush.

In the treatment with the longest recovery time (the control), greenleaf manzanita

developed best in terms of density, foliar cover, and height. Foliar cover of

snowbrush and goldenbush also excelled in the control. Graminoids, however,

had lower density and development values in the control than in any other

treatment, probably because of competition from the shrubs. McDonald and

Abbott (1997) noted a similar relationship of grass to shrubs on a site of similar

quality at a lower elevation near Mt. Shasta.

Time since disturbance has not caused a major change in the plant

community during the first 10 years. Although trends seem to be developing,

plant diversity, density, and development do not differ markedly among

treatments. The same species, including forbs, are present. Although too few and

poorly distributed to be statistically analyzed, the forbs do not seem to be losing

ground to the shrubs and grasses. The species that were present initially are

present at the end of the study, and their overall density and development are

similar. One forb (Monardella spp.) actually increased in density, albeit erratically,

to 1,200 seedlings per acre over all treatments during the study. Relative to other

young plantations in our National Administrative Study, the 18 species recorded

in this study (17 species plus 1 alien) caused it to rank next to last in plant

diversity (range of 17-41 species) (McDonald and Fiddler 1993).

Time since disturbance also has not greatly affected plant density. Both on an

individual species and a total vegetation basis, no marked differences were

found. At the end of the study, more than 100,000 plants per acre were present in

all treatments, with 77 to 89 percent being graminoids. Plant development,

especially foliar cover and height of greenleaf manzanita and snowbrush, was

where statistically significant differences among treatments were developing.

Foliar cover and height were higher for treatments with longer recovery times (7

and 10 years) than for treatments with a shorter recovery time (4 years). But even

then, total cover of all vegetation ranged from only 13 to 33 percent, indicating

that much area, at least above ground, was unoccupied. Was similar area below

ground unoccupied? Perhaps not, given the natural tendency of plants in harsh

environments to occupy more space below ground than above.

At the elevation of the study, the soil becomes very dry, the winters are

severe, and the growing season is short. Annual precipitation during the study

was about normal for this location. During the study, precipitation in 1986, 1993,

and 1995 was generally above normal; in 1987, 1988, and 1994 below normal; and

in 1989 through 1992 about average.

The natural form and growth pattern of California red fir seedlings is to

grow tall with a thin stem and crown (fig. 3). Height growth rates of 0.3 foot and

diameter increments of 0.1 inch per year are common. Thus this conifer is best

described as having slow seedling growth rates. Growth of California red fir, at

least for the first 10 years, differs from that of ponderosa pine in amount and

allocation. Height and diameter growth of ponderosa pine seedlings on a site of

similar quality would be at least double these amounts. Ponderosa pine seedlings

also tend to allocate a significant amount of resources to diameter growth at an

early age. On a slightly better site in the southern Cascades of California,
12 USDA Forest Service Res. Paper PSW-RP-233. 1997.

McDonald and Fiddler (1990) found that stem diameter of ponderosa pine

seedlings at 12 inches above mean groundline differed significantly between

most and least effective release treatments before differences in stem height

occurred, and that this difference became statistically evident at the 5 percent

level after only two growing seasons. In contrast, mean diameter of red fir in this

study did not differ significantly among treatments after 10 years.

The density and developmental trends in the control suggest the future

composition of a plant community that received only a minimum amount of

manipulation. As in most other studies (see McDonald and Fiddler 1995 for

example), shrub density at age 10 is flat or declining as weaker plants die and

surviving plants become wider and taller. Certainly greenleaf manzanita with its

relatively high density, foliar cover, and height values will be the dominant

shrub in the control. Snowbrush, while not as numerous, has a tendency to grow

tall and wide and will also be part of the future shrub community. Goldenbush,

although numerous, is made up of mostly shorter plants, with many existing

beneath taller plants. Its role in the future community will probably be that of

occupying small openings among other species. The graminoids probably are

scheduled for an eventual decline of major proportion. They apparently do not

grow well with shrubs. Thus in the community of the future, they also will exist

on the fringes of shrubs and in small openings.

The future species composition of plants in the treatments that received

some form of release probably will be similar to that in the control. It is likely that

the main effect of the manual grubbing and herbicide application was to postpone

the development of the various components of the early successional plant

community for 4 to 10 years. It will be interesting to see if the plant community in

grubbed and sprayed plots a decade from now will be similar to that of the

control in 1995.

Figure 3—Typical form of California red fir seedlings. Note the thin stem, narrow crown, and short internodes.
USDA Forest Service Res. Paper PSW-RP-233. 1997. 13

Early removal of competing vegetation by site preparation and release denies

undesirable plants the chance to utilize the high levels of site resources typically

present after disturbance. Timing of release is critical. Early release allows the

conifer seedlings to capture adequate site resources, become established, and

grow well. They then should be able to stress the competing plants—not be

stressed by them.

In this study, the T-first-3 and T-second-3 treatments were designed

specifically to test early versus delayed release for California red fir.

Unfortunately, the test was inconclusive, probably because more time is needed

for diameter and height to develop and relationships to be clarified.

Nevertheless, results from this study indicated that California red fir

seedlings in the T-first-6 and T-first-3 treatments were significantly taller than

counterparts in the control in 1991. This, plus the significant difference in survival

and height between the T-first-6 and control treatments in 1995, suggest that

early removal of competing vegetation enhances the establishment and growth

of California red fir seedlings.

However, early control of competing vegetation is not the only reason for the

high red fir seedling survival values found in this study (98 percent after year 1;

89 percent after year 10). As noted earlier, survival was high in the other

treatments and even in the control—much higher than that reported in the

literature. For example, Click and others (1989) reported that average third-year

survival (1982 through 1988) of planted red fir bare-root stock in the California

region of the USDA Forest Service ranged from 5 to 54 percent, with that in the

last 3 years averaging 35 percent. Drought, competing vegetation, and pocket

gophers are major barriers to successful seedling establishment (Laacke and

Fiske 1983). The most likely reason for the high survival values of California red

fir seedlings in this study was excellence in every step in the nursery-plantingsite preparation process, including high quality planting stock and storage

procedures, and a good job of outplanting and site preparation.

An important factor when evaluating the timing of release is cost. Delaying

release usually means larger plants and often large, deep roots. And if the plants

become well established, then an additional round of treatments may be needed.

Although costs were not recorded in this study, some general observations were

noted: spraying took less time than grubbing, grubbing young small plants as in

the T-first-3 treatment was much easier than initially grubbing the larger 3-yearold plants in the T-second-3 treatment, and additional treatment applications

after the initial work as in the T-first-6 treatment will be much more expensive

than a treatment such as T-first-3 that had fewer visits.

The different treatments, which spanned plant recovery times of 4 to 10

years, created similar plant communities, but with different amounts of the same

species that further differed in terms of development. Although the community

has not changed greatly, one minor component—bitter cherry—is no longer

present, and one major component—conifer seedlings—now is part of the

community. California red fir seedlings in all treatments, with the possible

exception of the control, are plentiful, well established, and have good potential

to outgrow the competing vegetation. Restoring the arboreal component, which

historically has been part of the community, should create a forest stand, and a

more desirable and sustainable vegetative assemblage.

References

Biging, Greg S; Wensel, Lee C. 1984. Site index equations for young-growth mixed conifers of

northern California. Res. Note 8. Berkeley: Department of Forestry and Resource Management,

University of California; 13 p.

Click, Chris, and others 1989. Alternatives to herbicides—update based on the five-year herbicide

use moratorium in the USDA Forest Service Pacific Southwest Region. In: Proceedings, 10th
14 USDA Forest Service Res. Paper PSW-RP-233. 1997.

annual forest vegetation management conference; 1988 November 1-3; Eureka, CA. Redding,

CA: Forest Vegetation Management Conference; 49-90.

Conard, Susan G.; Jaramillo, Annabelle; Cromack, Kermit, Jr.; Rose, Sharon, comps. 1985. The role

of the genus Ceanothus in western forest ecosystems. Gen. Tech. Rep. PNW-182. Portland, OR:

Pacific Northwest Forest and Range Experiment Station, Forest Service, U.S. Department of

Agriculture; 72 p.

Daubenmire, R.F. 1968. Plant communities: a textbook on plant synecology. New York: Harper

and Row; 300 p.

Deitschman, Glenn H.; Jorgensen, Kent R.; Plummer, A. Perry. 1974. Chrysothamnus Nutt.

Rabbitbrush. In: Schopmeyer, C.S., tech. coord. Seeds of woody plants in the United States.

Agric. Handb. 450. Washington, DC: Forest Service, U.S. Department of Agriculture; 326-328.

Fiddler, Gary O.; McDonald, Philip M. 1984. Alternatives to herbicides in vegetation management:

a study. In: Proceedings, 5th annual forest vegetation management conference; 1983 November

2-3; Sacramento, CA. Redding, CA: Forest Vegetation Management Conference; 115-126.

Fiddler, Gary O.; McDonald, Philip M. 1987. Alternative treatments for releasing conifer seedlings:

a study update. In: Proceedings, 8th annual forest vegetation management conference; 1986

November 4-6; Sacramento, CA. Redding, CA: Forest Vegetation Management Conference; 64-69.

Gordon, Donald T. 1980. White fir. In: Eyre, F.H., ed. Forest cover types of the United States and

Canada. Washington, DC: Society of American Foresters; 92-93.

Gordon, Donald T.; Bowen, Eugene E. 1978. Herbs and brush on California red fir regeneration

sites: a species and frequency sampling. Res. Note PSW-329. Berkeley, CA: Pacific Southwest

Forest and Range Experiment Station, Forest Service, U.S. Department of Agriculture; 10 p.

Grime, J.P. 1979. Plant strategies and vegetation processes. New York: John Wiley and Sons; 222 p.

Hickman, James C., ed. 1993. The Jepson manual, higher plants of California. Berkeley: University

of California Press; 1,400 p.

Laacke, Robert J.; Fiske, John N. 1983. Red fir and white fir. In: Burns, Russell M., tech. comp.

Silvicultural systems for the major forest types of the United States. Washington, DC: Forest

Service, U.S. Department of Agriculture; 41-43.

McDonald, Philip M.; Abbott, Celeste S. 1997. Vegetation trends in a 31-year-old ponderosa pine

plantation: effect of different shrub densities. Res. Paper PSW-RP-231. Albany, CA: Pacific

Southwest Research Station, Forest Service, U.S. Department of Agriculture; 30 p.

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ecology and control. Gen. Tech. Rep. PSW-113. Berkeley, CA: Pacific Southwest Forest and

Range Experiment Station, Forest Service, U.S. Department of Agriculture; 26 p.

McDonald, Philip M.; Fiddler, Gary O. 1990. Ponderosa pine seedlings and competing vegetation:

ecology, growth, and cost. Res. Paper PSW-199. Berkeley, CA: Pacific Southwest Research

Station, Forest Service, U.S. Department of Agriculture; 10 p.

McDonald, Philip M.; Fiddler, Gary O. 1993. Feasibility of alternatives to herbicides in young

conifer plantations in California. Canadian Journal of Forest Research 23: 2015-2022.

McDonald, Philip M.; Fiddler, Gary O. 1995. Development of a mixed shrub- ponderosa pine

community in a natural and treated condition. Res. Paper PSW-224. Berkeley, CA: Pacific

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McDonald, Philip M.; Radosevich, Steven R. 1992. Chapter 4. General principles of forest vegetation

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management in Pacific Northwest forests. Gen. Tech. Rep. PNW-GTR-287. Portland, OR: Pacific

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PSW-RP-233

Research PaperResearch StationPacific SouthwestForest Serviceof AgricultureDepartmentUnited States

Red Fir PlantationDevelopment in a Young CaliforniaDisturbance Affect VegetationTreatment Duration and Time since
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