United States 

Department 

of Agriculture 

Forest Service 

Pacific Southwest 

Research Station 

Mechanical and Chemical Release 

Applied to a 16-Yea11-01d Pine 

Plantation 

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

Research Note 

PSW-RN-42S 

April 2000 

Gary O. Fiddler, Philip M. McDonald, 

and Sylvia R. Mori 

Plantation establishment in California is often a difficult task. Earlier studies reported 

that almost all new plantations in the state will be invaded by vegetation in the form 

of hardwoods, woody shrubs, grasses, and forbs. 1 The competition between this 

vegetation and the planted conifers is almost always detrimental to the growth and 

survival of the conifers.2,3 To further complicate matters, this invasion of weedy 

species usually occurs early in the life of the plantation, at which time the planted 

conifers are establishing growth patterns that will be followed at least tUltil crown 

closure. Growth patterns of conifers in plantations tUlder competition are less than 

can be expected from conifers growing in released plantations. Once lost, this growth 

is never recovered.3 In order for the conifers to develop at or near the potential of the 

site, they must be released from competing vegetation early in the life of the 

plantation, probably the first or second year after planting.4

,5,6 

Despite the need for release, untreated conifer plantations 10 years or older 

are common in the western U.S., especially on Federal lands. Ponderosa pine 

(Pinus ponderosa Dougl. ex Laws. var. ponderosa) and Jeffrey pine (Pinus jeffreyi 

Grev. & Balf.) have demonstrated their ability to survive despite extreme 

competition, but this competition results in decreased growth of the planted 

conifers. The fact that pine seedlings are taller than the surrounding vegetation 

does not guarantee that they will grow at the potential of the site. This height 

does not mean rapid or even moderate growth. Will these older plantations 

respond to a release treatment, and if so, what treatment will be best? 

Controlling vegetation of the size and level of development fOtUld in older 

plantations is difficult to accomplish by using commonly applied methods. 

Because of large shrubs and the difficulty of disposing of the cut material, limited 

crew access makes manual methods prohibitively expensive when used with 

older vegetation. The cut material generated with the manual methods must be 

disposed of to avoid creating unacceptable residual slash levels that contribute to 

the fire hazard in the treated areas. Grazing by cattle or sheep is, at best, 

marginally effective.7 Controlling tall, well-developed shrubs is often ineffective, 

even when using herbicides alone. 

To accomplish release in older plantations having large, tall shrubs, Federal 

land managers often choose mechanical means as the most appropriate release 

method. This method involves the use of a mechanical cutter, similar to a lawn 

mower, which cuts the competing vegetation close to the grotUld and leaves the 

chopped stems and foliage on site. However, does this operation reduce the 

competing vegetation long enough to increase the growth of the conifer saplings? 

Results from an earlier study indicated that it does not, but that sprouts grew 

rapidly from the treated vegetation.

s 

This paper discusses the effectiveness of mechanical cutting as a release 

method in an older pine plantation; the effectiveness of applying an herbicide to 

Fiddler, Gary 0.; 

McDonald, Philip M .; 

Mori, Sylvia R. 2000. 

Mechanical and chemical 

release treatments applied 

to a 16-year-old pine 

plantation. Res. Note 

PSW-RN-425.Albany,CA: 

Pacific Southwest Research 

Station, Forest Service, 

U .S. Department of 

Agriculture; 11 p. 

To increase the growth of 

planted conifer saplings, 

the competing vegetation 

in a 16-year-old pine 

plantation on the Plumas 

National Forest in 

northern California was 

mechanically treated with 

the Trac-mac mechanical 

cutter. The largesizeof this 

vegetation (chinkapin, 

greenleaf manzanita, 

whitethorn, huckleberry 

oak) eliminated other 

release methods as feasible 

alternatives. Additional 

treatments were a 

chemical treatment, in 

which 2,4-0 was applied 

to a portion of the study 

site that had been treated 

with the Trac-mac 2 years 

previously, and untreated 

control. Eleven growing 

seasons after treatment, 

mechanical release alone 

did not significantly 

increase diameter, height, 

or crown cover of the pines 

compared to the control. 

In contrast, the Trac-mac 

plus herbicide (chemical) 

treatment statistically 

increased conifer crown 

cover compared to the 

other two treatments. Pine 

diameter and height were 

also larger in the chemical 

treatment than in the other 

two treatments, but not 

(continued on page 2) 
.) 

the mechanically cut shrubs 2 years after cutting; the cost and production of all 

treatments; and the pine growth response in diameter, height, and crown cover 

to the treatments and an untreated control, as well as responses of the treated and 

untreated shrub community. 

Methods 

The study site, known as Third Water, is located on the Quincy Ranger District of 

the Plumas National Forest in northeastern California. The site is about 90 air 

miles southeast of Redding, California. The study i.s part of a national 

administrative study on vegetation management in young conifer plantations 

started in 1980 in northern California.9 Before timber harvest, the study site 

supported a forest of ponderosa pine, California white fir (Abies concolor var. 

lowiana [Gord.] Lemm.), incense cedar (Libocedrus decurrens Torr.), and sugar pine 

(Pinus lambertiana Dougl.). The understory consisted of small amounts of 

greenleaf manzanita (Arctostaphylos patula Greene), mountain whitethorn 

(Ceanothus cordulatus Kell.), and Sierra chinkapin (Castanopsis sempervirens [Kell.] 

Dudl.). A few scattered Prunus species and small numbers of grasses and forbs 

were also present. 

The site was harvested in 1964 or early 1965. Site preparation was done in 

July 1965; a crawler tractor was used to crush the shrubs in preparation for 

burning. The tractor, with the blade about 1 foot above the ground, made two 

passes in opposite directions, which resulted in a fuel arrangement less than 2 

feet high. Large snags and large downed woody debris were removed before 

burning. The site was broadcast burned in fall 1965 and spring 1966. Ponderosa 

pine and Jeffrey pine seedlings from a local seed source were raised at the USDA 

Forest Service nursery at Placerville, California, and hand planted as 1-year-old, 

bare-root stock in spring 1966. About 300 trees per acre were planted. Survival at 

the time the study began, September 1982, was between 140 and 240 planted trees 

per acre. 

In fall 1982, 17 years after site preparation, the area supported, in addition to 

the planted conifers, a dense cover of greenleaf manzanita, mountain whitethorn, 

Sierra chinkapin, and huckleberry oak (Quercus vaccinifolia Kellogg) as sprouts 

from plants in the previous stand and new seedlings. Height of these shrubs 

ranged from 2 to 4 feet. The most common shrubs were greenleaf manzanita and 

whitethorn, which totalled about 35,000 plants per acre. Grass, mostly from the 

genera Bromus and Stipa, was present in small numbers on the site. 

Elevation of the study site is 5,500 feet with slopes of 5 to 15 percent and 

aspects of northwest and south. The climate is characterized by warm, dry 

summers and cold, moist winters. Mean annual precipitation is about 70 inches 

with 50 to 60 percent falling as snow. The mean January temperature is 38°F, 

mean July temperature is 65°F, and the mean annual temperature is 52°F. The 

frost-free season is from early May until mid-October. 

The soil is of the Gibsonville family, which is found on ridge tops and side 

slopes. It is moderately deep, well drained, and formed from weathered volcanic 

material. The soil is sandy loam and may be gravely or cobbly. 

On the basis of the height-age relationship of dominant mixed conifer trees, 

site quality of the study area before harvesting was 65 feet in 50 years.10 Slope and 

site quality are very uniform throughout the study area. 

Evidence of deer (Hemionus spp.) was common throughout the study area. 

Small rodents and birds were seen. Pocket gophers (Thomomys spp.) were noticed 

in the area. 

The study, which began in fall 1981, includes data recorded through 10 

growing seasons. The experimental design was a complete randomized block 

with one three-level treatment. Differences among treatments were detected by 

analysis of variance of treatment meansll and Tukey tests.12 Statistical significance 

in all tests was at a. = 0.05. Because information is gathered from permanent plots 

USDA Forest Service Research Note. PSW-RN-042S. 2000. 

(continued from page 1) 

significantly. Mean crown 

cover was 120 percent 

greater in the saplings in 

the chemical treatment 

than for pines in the 

control, height was 35 

percen t grea ter, and 

diameter was 50 percent 

greater. Relative costs were 

$218 per acre for the 

mechanical treatment and 

$267 per acre for the Tracmac plus herbicide 

(chemical). The most costeffective treatment was 

Trac-mac plus herbicide. 

Retrieval Terms: competing 

vegetation, cost, growth, 

mechanical release, 

mechanical and chemical 

release, Jeffrey pine, 

ponderosa pine, shrub 

sprouts 

2 
measured each year, the data are not truly independent from year to year. The ex 

levels or type I errors apply to each measurement and year separately. The 

overall error rate could increase by as much as the given amount for each 

measured variable each year. S-Plus 200013 by Mathsoft, Inc. was used for graphic 

displays and exploratory analysis. 

Treatments, each replicated three times (three blocks), included mechanical, 

chemical (mechanical plus an herbicide), and a control. A replicate consisted of 

about one-seventh of an acre with 30 to 40 ponderosa or Jeffrey pine saplings 

surrounded by two or three rows of buffer (saplings receiving the same treatment). 

Twenty of these pines per replication were chosen for measurement of height, stem 

diameter at 4.5 feet above mean ground line, and crown cover. Those chosen were 

thrifty saplings that had good potential of becoming harvestable trees; small, 

misshapen, and discolored saplings were not part of the study. 

Sampling intensity for evaluating competing vegetation consisted of nine 

randomly selected plots in each replication. Plots were centered around conifers 

and were 1 milacre (0.001) in size. Vegetation was evaluated for density, foliar 

cover (the sum of shadows that would be cast by leaves and stems of individual 

species expressed as percentage of the land surface),14 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 was counted, foliar 

cover was visually estimated, and height was measured with a graduated pole. 

Cover values of less than 0.5 square foot per species in each plot were not 

recorded. The most common species-chinkapin, greenleaf manzanita, 

whitethorn, and huckleberry oak-were analyzed separately. In addition, after 

combining these four species with the other shrubs in the study, a separate 

analysis was made using this grouping. 

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

study began and when it ended. 

Mechanical treatment consisted of cutting the woody shrubs with a Tracmacl5-a machine with a large rotary cutting head that has three free-swinging 

blades. The cutting head is mounted on an all-terrain, tracked vehicle similar in 

size to a medium-sized log skidder. The Trac-mac resembles a common rotary 

lawnmower, but cuts a 4-foot swath. With experienced operators, as in this 

study, the Trac-mac works efficiently on slopes up to about 40 percent. 

Production rates of 3 to 4 acres per day are common. Current (1998) bids for this 

type of equipment on Forest Service contracts are about $200 per acre. Severed 

material remains in place. Cutting was done in summer 1981. 

Chemical treatment consisted of applying 3 pounds acid equivalent of 2,4-D16 

in 10 gallons of solution per acre to the foliage of sprouting shrubs the second 

year after cutting. The herbicide was applied in August 1983 by using a carbon 

dioxide pressurized boom. Nozzles on the boom were the same type as those 

used in helicopter application; hence, rate of application and droplet size were 

similar to those used in aerial application of herbicides. The boom, which covered 

a 9-foot swath, was held about 12 inches above the shrubs, and the spray was 

directed downward. The system was calibrated by using trial runs with water to 

determine the proper walking speed to apply the correct amount of herbicide to 

each replication. The entire seventh-acre replicate, plus half of the buffer width, 

was sprayed. The area treated around each pine had at least a 5-foot radius. 

Workers guided the applicator at each side of the swath to ensure even coverage 

and no overlap. 

A control served to show the response of naturally developing vegetation 

and its effects on the planted conifers. 

Production data were gathered for each treatment. The basis for production 

was hourly records; the basis for costs was $87.20 per hour (the 1998 rate for 

equipment of the type used in the study) and $11.39 per hour (the rate for a 

Laborer-1, u.S. Department of Labor, as of June 1997). 

USDA Forest Service Research Note. PSW-RN-'42S. 2000. 3 
Results 

Data on survival, stem diameter, height, and crown cover are presented for the 

planted ponderosa and Jeffrey pine saplings, and information on density, foliar 

cover, and height for chinkapin, greenleaf manzanita, whitethorn, and 

huckleberry oak is reported. Because competition to the pine saplings results 

from the interaction of the different species found in the plant community, not 

from individual members of it, information is also presented for a grouping of 

shrubs called "combined shrubs." 

Ponderosa and Jeffrey Pine 

No planted pine saplings died during the study (1982-1993), and no damage to 

the planted conifers from the Trac-mac itself or from flying debris generated by 

the machine during the release operation was noted. 

In 1988, the mature stands adjacent to the study site were attacked by the 

Douglas-fir tussock moth (Orgyia pseudotsugata). Many of the trees, especially the 

California white fir, in these stands were killed by the infestation. Numerous 

cocoons were attached to the branches of the trees. Little if any damage was 

noted to the saplings in the study area. This infestation had collapsed by the time 

of the next measurement period in 1992. 

Differences among treatments in ponderosa pine crown cover and height 

were evident in 1984, the first growing season after initial treatment (jig. 1). A 

Tukey test showed that by the end of 1988, cover of the pines was significantly 

larger in the chemical treatment than in the control (table 1). By the end of the 

study in 1992, pine cover in the chemical treatment was significantly larger than 

pine cover in the other two treatments. Pine diameter and height never differed 

significantly among treatments during the life of the study. 

Chinkapin 

The evergreen shrub chinkapin was the third most abundant vegetation in the 

study, outnumbered by greenleaf manzanita and whitethorn (table 2). In 1982, 

density averaged 4,733 plants per acre in the control. Density peaked in 1984 at 

5,267 plants per acre. By the end of the study in 1992, density was reduced to 

3,600 plants per acre, a decrease of 24 percent. Cover in the control started at 933 

ft2/acre in 1982, increased to 1,067 ft2/acre in 1984, and declined to 200 ft2/acre 

by the end of the study. This was a 79 percent decline. Height in the control 

increased from more than 2 feet in 1982 to almost 3 feet by 1992, which is an 

increase of 36 percent. 

By the end of the 1992 growing season, the height of chinkapin in the 

chemical treatment was significantly shorter-1.75 feet-than the height of the 

chinkapin in the control-2.77 feet (table 3). There were never any significant 

differences among treatments in density or foliar cover during the study. 

Greenleaf Manzanita 

The fast-growing evergreen shrub greenleaf manzanita was the most abundant 

woody species at the start of the study and remained in this dominant position 

throughout the life of the study. In 1982, density averaged 23,333 plants per acre 

in the control (table 2). Density peaked at 23,467 plants per acre in 1984 and 

declined to 15,000 plants per acre by the end of the study in 1992. This represented 

a decline of 36 percent. Foliar cover started at 24,333 ft2/acre, increased to 32,133 

ft2/acre in 1986, and then declined in 1992 to almost the same amount as at the 

start of the study. Foliar cover showed only a slight decline (1 percent) during the 

study period. Height started at 3.71 feet and increased steadily throughout the 

study, reaching 5.34 feet by the end of 1992. This was an increase of 31 percent. 

Greenleaf manzanita was by far the tallest woody shrub in the control. 

By the end of the study in 1992, foliar cover in the chemical treatment 

amounted to 67 ft2/ acre, which was significantly smaller than the 24,067 ftl / acre 

USDA Forest Service Research Note. PSW·RN·425. 2000. 4 
in the control (table 3). Height in both the chemical treatment and the mechanical 

treatments-2.04 and 3.31 feet, respectively-was significantly shorter than the 

average height in the control-5.34 feet. Density never differed significantly 

among treatments during the study. 

Whitethorn 

In fall 1982, density of whitethorn plants in the control was 11,600 plants per acre 

with 7,667 ff/acre of foliar cover and 2.09 feet of height (table 2). By the end of the 

study in the fall of 1992, density had decreased by 57 percent to 4,933 plants per 

acre, foliar cover had decreased by 76 percent to 1,867 ft2/ acre, but height had 

increased by 11 percent to 2.31 feet. Although the whitethorn was the second 

most abundant shrub on the plots at the beginning of the study, this species was 

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USDA Forest Service Research Note. PSW·RN·425. 2000. 

1986 19BB 1990 1882 1994 

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Figure 1 

Average diameter, crown 

cover, and height of 

ponderosa and Jeffrey pine 

in treated (mechanical and 

chemical) and control 

plots, Third Water 

plantation, Plumas 

National Forest, California, 

1982-1992. 

5 
Table I-Average diameter, crown cover, and height of 

ponderosa and Jeffrey pine in treated and control plots, Third 

Water plantation, Plumas National Forest, California, 1982-

1992. 

Year Treabnent Diameter Cover Height 

inches ft'/tree ft 

1982 Mechanical 9.32a1 6.67 a 

Chemical 9.75 a 6.88 a 

Control 7.70 a 6.40 a 

Standard error 0.88 0.27 

1984 Mechanical 2.36 a 18.67 a 8.50 a 

Chemical 2.75 a 22.00 a 9.07 a 

Control 2.21 a 14.35 a 8.13 a 

Standard error 0.21 2.35 0.47 

1986 Mechanical 2.87 a 24.44 a 9.87 a 

Chemical 3.54 a 30.68 a 11.45 a 

Control 2.56 a 19.68 a 9.44 a 

Standard error 0.27 3.43 1.06 

1988 Mechanical 3.51 a 32.67 ab 11.49 a 

Chemical 4.68 a 49.03 b 14.24 a 

Control 3.22 a 25.43 a 11.16 a 

Standard error 0.36 4.42 0.86 

1992 Mechanical 4.76 a 51.83 a 15.08 a 

Chemical 6.61 a 87.48 b 20.20 a 

Control 4.40 a 39.81 a 14.95 a 

Standard error 0.45 6.51 1.21 

1 For each year, treatment means in each column followed by the same 

letter do not differ significantly according to a Tukey test (ex = 0.05). 

being crowded out and overtopped by the more aggressive greenleaf manzanita 

and chinkapin. 

In the fall of 1992, height of whitethorn in the chemical treatment was 

significantly shorter than that in the control (table 3). Density and foliar cover did 

not differ significantly at the close of the study. 

Huckleberry Oak 

Huckleberry oak, the low and expansive evergreen shrub, was the least abundant 

woody species at the start of the study and remained in that position throughout 

the study. In 1982, average density was 3,933 plants per acre in the control (table 2). 

Density reached a maximum at 4,600 plants per acre in 1984 and then declined 

steadily to 3,000 plants per acre by the end of the study in fall 1992. This was a 24 

percent decline during the study. Foliar cover was at 400 ft2/acre at the start of 

the study, increased to 800 ft2/ acre in 1984, and then steadily declined to 133 ft2/ 

acre in the fall of 1992. This represented a decline of 67 percent during the study. 

Height started at 1.33 feet in 1982 and steadily increased through the 1988 

growing season, reaching a height of 1.85 feet. By the end of the study in 1992, 

height had declined from the 1988 high to 1.44 feet. Height increased by 8 percent 

during the study. 

After 10 growing seasons, density, foliar cover, or height of huckleberry oak 

did not differ significantly among treatments (table 3). 

Combined Shrubs 

Competition to the conifer saplings results from the interaction of the different 

species found in the plant community, not from individual members of it. Data 

USDA Forest Service Research Note. PSW·RN·425. 2000. 6 
Table 2-Density, cover, and height, with standard errors (SE), of chinkapin, 

greenleaf manzanita, whitethorn, huckleberry oak, and conbined shrubs in the 

control, 1982-1992. 

Species Density SE Cover SE Height SE 

plants/acre ff/acre ft 

Chinkapin 

1982 4,733 1,444 933 467 2.04 0.67 

1984 5,267 1,881 1,067 677 1.83 0.32 

1986 5,000 1,922 933 742 2.41 0.33 

1988 4,067 1,671 733 437 2.83 0.39 

1992 3,600 1,311 200 115 2.77 0.31 

Change (pct)] -24 -79 +36 

Greenleaf manzanita 

1982 23,333 7,565 24,333 6,533 3.71 0.16 

1984 23,467 7,142 28,533 6,567 4.54 0.12 

1986 23,067 6,982 32,133 7,880 4.89 0.10 

1988 20,600 7,159 30,200 9,928 5.31 0.10 

1992 15,000 6,401 24,067 9,145 5.34 0.38 

Change (pct) -36 -1 +31 

Whitethorn 

1982 11,600 4,588 7,667 3,830 2.09 0.22 

1984 10,933 3,886 7,467 3,868 2.45 0.16 

1986 10,333 3,349 7,467 4,001 2.73 0.16 

1988 9,133 2,839 4,133 2,219 2.76 0.22 

1992 4,933 1,940 1,867 961 2.31 0.13 

Change (pet) -57 -76 +11 

Huckleberry oak 

1982 3,933 3,078 400 200 1.33 0.13 

1984 4,600 3,219 800 416 1.40 0.25 

1986 4,333 2,963 400 231 1.76 0.11 

1988 4,200 2,996 200 115 1.85 0.15 

1992 3,000 2,610 133 133 1.44 0.24 

Change (pct) -24 -67 +8 

Combined shrubs 

1982 45,000 10,938 35,933 7,378 2.61 0.08 

1984 46,800 11,343 41,467 9,405 2.87 0.07 

1986 45,133 10,811 44,467 10,104 3.26 0.08 

1988 40,000 9,880 37,933 11,338 3.66 0.11 

1992 28,400 9,488 27,467 9,551 3.31 0.16 

Change (pct) -37 -24 +27 

] Difference between 1982 and 1992 values expressed as a percent increase or decrease. 

on a combination of shrub species best shows this relationship. The density, 

foliar cover, and height of chinkapin, greenleaf manzanita, whitethorn, and 

huckleberry oak were combined with data from bitter cherry (Prunus emarginata 

[Dougl.] Walp.), cof£eeberry (Rhamnus purshiana DC), snowberry (Symphoricarpos 

spp.), silktassel (Garrya fermontii Torr.), and service-berry (Amelanchier utahensis 

Koehne) and presented as "combined shrubs." 

In fall 1982, combined shrubs in the control numbered 45,000 plants per acre, 

had 35,933 square feet of foliar cover, and were 2.61 feet tall (table 2). Density 

increased to 46,800 plants by the end of the 1984 growing season. It declined to 

28,400 plants per acre by the end of the study in fall 1992, which is a decrease of 

37 percent. Foliar cover continued to increase until the end of the 1986 growing 

season when it reached a value of 44,467 ft2/ acre. After 1986, foliar cover declined 

until the end of the study, with 27,467 fe/acre. This represented a decline of 24 

percent during the study. Height started at 2.61 feet in 1982 and increased 

through the 1988 growing season when it reached 3.66 feet. By the end of the 

study, height had-declined from its 1988 value to 3.31 feet. Throughout the study, 

height of combined shrubs had a 27 percent gain. 

USDA Forest Service Research Note. PSW-RN-42S. 2000. 7 
Table 3-Density, cover, and height of chinkapin, greenleaf manzanita, 

whitethorn, huckleberry oak, and combined shrubs in treated and control 

plots, Plumas National Forest, 1992. 

Species and Treabnent Density Cover Height 

plants/acre ff/acre ft 

Chinkapin 

Mechanical 3,200 a1 600 a 2.41 ab 

Chemical 7,533 a 133 a 1.75b 

Control 3,600 a 200 a 2.77 a 

Standard error 1,758 168 0.18 

Greenleaf manzanita 

Mechanical 21,733 a 7,933 ab 3.31 b 

Chemical 5,000 a 67b 2.04 b 

Control 15,000 a 24,067 a 5.34 a 

Standard error 4,431 4,634 0.35 

Whitethorn 

Mechanical 7,200 a 1,533 a 1.79 ab 

Chemical 5,933 a 267 a 1.56b 

Control 4,933 a 1,867 a 2.31 a 

Standard error 1,791 609 0.11 

Huckleberry oak 

Mechanical 2,133 a 733 a 1.56 a 

Chemical 1,400 a 200 a 1.60 a 

Control 3,000 a 133 a 1.44 a 

Standard error 1,440 438 0.12 

Combined shrubs 

Mechanical 36,267 a 12,067 ab 2.31 b 

Chemical 21,000 a 800b 1.75b 

Control 28,400 a 27,467 a 3.31 a 

Standard error 6,248 4,859 0.14 

lFor each species and combination, treabnent means in each column followed by the 

same letter do not differ statistically at the 0.05 level. 

At the end of the study, foliar cover differed significantly between treatments 

(table 3). With a value of 800 ft2/ acre combined shrubs in the chemical treatment 

were significantly smaller than those in the control (27,467 ff/acre). Also, shrub 

height showed a noticeable difference. Heights in the chemical treatment and the 

mechanical treatment (1.75 and 2.31 feet, respectively) were significantly shorter 

than the shrub heights in the control (3.31 feet). Density did not differ among 

treatments at the end of the study. 

Cost and Production 

Cost data for the mechanical treatment came from daily inspection records that 

were kept by Quincy Ranger District personnel who inspected the service contract 

for the work. Production rates for the equipment used to apply the treatments to 

the competing vegetation came from District records. Cost and production data 

for herbicide application in the chemical treatment came from project records. 

The cost and production data generated by this study, although based on 

rates for smaller areas, compared favorably with rates from contracts awarded 

on several National Forests in northern California for similar work. This similarity 

was not unexpected since both the contract work and this study shared 

comparable terrain, competing plant species, types of treatments, and worker 

motivation. 

USDA Forest Service Research Note. PSW-RN-42S. 2000. 8 
Cost and labor to apply the chemical made this treatment more expensive 

than the mechanical treatment: 

Treatment 

Mechanical 

Chemical 

Production rate 

Hours/acre 

2.5 

5.5 

Cost 

Dollars/acre 

218 

267 

Dollars per acre are for labor, equipment time, and chemical; they do not 

include overhead costs. All costs are updated to the most current rates available 

for labor and equipment of the type used on the study. 

Plant Diversity 

At the beginning of the study in 1982, the plant community consisted of 10 

shrubs, 8 forbs, planted ponderosa and Jeffrey pine, and 2 graminoids. After 11 

years, the community consisted of the same species with the addition of one fern 

and another species of forb. Many of the forbs, grasses, and shrubs were few in 

number and finding them was difficult because of their small size. The planted 

conifers, greenleaf manzanita, whitethorn, and chinkapin dominated the 

plantation, to the detriment of other species. 

Discussion and Conclusions 

In order to survive and remain thrifty, most conifer plantations in northern 

California must be released at least once in their lifetime. Considering both 

economics of the operation and effectiveness of the treatment, early release, 

usually within the first couple of years after outplanting, is the best time for this 

treatment. Despite the best efforts of land managers, many plantations do not 

receive this release treatment in a timely manner and often are not released until 

they are 10 to 12 years old. The size and amount of woody shrubs and other 

competing vegetation in these older plantations greatly complicate the choice of 

a release method. Many of the more commonly used methods are not effective 

when applied under the conditions found in these older plantations. Manual 

methods are prohibitively expensive when trying to control competing 

vegetation of this size and are seldom effective in accomplishing the release 

objective. Grazing by cattle or sheep is usually not an option because most of the 

vegetation is not palatable, and the vegetation that is desirable to the grazing 

animals is so tall that it is out of reach. Herbicides alone are ineffective when 

trying to control older, well-developed competing vegetation. Some kind of 

mechanical treatment is usually chosen to accomplish the release in older 

plantations. 

Eleven growing seasons after treatment, mechanical release applied to a 16-

year-old pine plantation did not significantly increase diameter, height, or crown 

cover of the saplings compared to the control. The mechanical release treatment 

costs $218 per acre. In a variation to the mechanical treatment, herbicide was 

applied to the treated vegetation 2 years after the initial cutting operation. The 

application of the herbicide, including the chemical and the labor to apply it, cost 

$49.42 per acre. The cost of the chemical treatment was the cost of mechanically 

cutting the competing vegetation ($218/acre) plus the cost of applying the 

herbicide ($49) for a total of $267 per acre. The added cost of the chemical 

application resulted in an increase in conifer diameter, height, and crown cover 

in the chemical treatment, when compared to the mechanical treatment and 

control. By 1992, conifer crown cover was significantly larger in the chemical 

treatment than in the other treatments, increasing by 69 percent compared to the 

mechanical treatment and 120 percent compared to the control. Conifer diameter 

and height were , also larger in the chemical treatment than in the other two 

treatments, but not significantly. This difference in conifer height and diameter 

USDA Forest Service Research Note. PSW-RN-'I2S. 2000. 9 
values between the chemical treatment and the other two treatments expanded at 

an increasing rate (jig. 1). If this rate continues, statistically significant differences 

should occur in the near future in conifer height and diameter, as is already 

evident in cover. Diameter in the chemical treatment was 39 percent larger than in 

the mechanical treatment and 50 percent larger than in the control. Pine height 

was 34 percent greater in the chemical treatment than in the mechanical treatment 

and 35 percent greater than in the control. 

At the Third Water plantation, mechanical release alone was not an effective 

nor a cost-efficient release method. This finding was probably a result of the fact 

that the mechanical treatment left the root systems of the treated plants intact, 

allowing for rapid sprouting and continued occupation of the site by the 

nonconifer species. The planted conifers survived in all three treatments for at 

least 11 years after treatment application, but those in the control were growing as 

well as those in the mechanical treatment. Therefore, the mechanical treatment 

did little for the benefit of the conifers. For this reason, land managers will need to 

decide if even the most successful treatment (the addition of herbicide to a 

mechanical release treatment) is worth the cost and effort, since only conifer 

crown cover was increased significantly. Whether this increased crown growth 

will result in adequate conifer growth depends on future needs of the products 

from this plantation. Early release in the first few years of the life of the plantation 

would have minimized this dilemma. 

End Notes and References 

IFiddler, Gary 0.; McDonald, Philip M. 1990. Manual release contracting: production rates, costs, 

and future. Western Journal of Applied Forestry 5(3):83-85. 

2Gjertadn, Dean H., ed. 1993. Proceedings of the international conference on forest vegetation 

management; 1992 April 27-May 1; Auburn, AL: Auburn School of Forestry; 310 p. 

"Stewart, Ronald E.; Gross, Larry 1.; Honkala, Barbara H. 1984. Effectiveness of competing vegetation 

on forest trees: bibliography with abstracts. Gen. Tech. Rep. WO-43. Washington, DC: Forest 

Service, U.S. Department of Agriculture; loose-leaf. 

4McDonald, Philip M. 1982. Adaptations of woody shrubs. In: Hobbs, S.D.; Helgerson, O.T., eds. 

Proceedings of a workshop on reforestation of skeletal soils; 1981 November 17-19; Medford, OR. 

Corvallis, OR: Forest Research Laboratory, Oregon State University; 21-29. 

sMcDonald, Philip M.; Fiddler, Gary 0.1986. Release of Douglas-fir seedlings: growth and treatment 

costs. Res. Paper PSW-182. Berkeley, CA: Pacific Southwest Forest and Range Experiment Station, 

Forest Service, U.S. Department of Agriculture; 9 p. 

6Newton, Michael; Preest, David S. 1988. Growth and water relations of Douglas-fir seedlings under 

different weed control regimes. Weed Science 36: 653-662. 

7McDonald, Philip M.; Fiddler, Gary O. 1993. Vegetative trends in a young conifer plantation after 10 

years of grazing by sheep. Res. Paper PSW~RP-215. Albany, CA: Pacific Southwest Research 

Station, Forest Service, U.S. Department of Agriculture; 9 p. 

8Fiddler, Gary 0 .; McDonald, Philip M. 1997. Mechanical and chemical release in a 12-year-old 

ponderosa pine plantation. Res. Paper PSW-RP-232. Albany, CA: Pacific Southwest Research 

Station, Forest Service, U.S. Department of Agriculture; 12 p. 

9Fiddler, Gary 0 .; McDonald, Philip M. 1984. Alternatives to herbicides in vegetation management: a 

study. In: Proceedings of the 5th annual forest vegetation management conference; 1983 November 

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

lODunning, D.; Reineke, 1.H. 1933. Preliminary yield tables for second-growth stands in the 

California pine region. Tech. Bulletin FS-354. Washington, DC: Forest Service, U.S. Department of 

Agriculture; 23 p. 

llSteel, Robert C.D.; Torrie, James H. 1980. Principles and procedures of statistics. 2nd ed. New York: 

McGraw-Hill Book company; 218-220. 

12SAS Institute, Inc. 1988. SAS procedures guide, release 6.03 edition. Cary, NC: SAS Institute, Inc. 

13Mathsoft, Inc. 1993. S-Plus 2000, guide to statistics. Seattle, WA: Data Analysis Product Division, 

Mathsoft, Inc. 

USDA Forest Service Research Note. PSW-RN-42S. 2000. 10 
14Daubenmire, R.F. 1968. Plant communities: a textbook on plant synecology. New York: Harper 

and Row; 300 p. 

IsTrade names and commercial products are mentioned solely for information. No endorsement by 

the U.S. Department of Agriculture is implied. 

16This note neither recommends the herbicide uses reported nor implies that the herbicides have 

been registered by the appropriate agencies. 

USDA Forest Service Research Note. PSW-RN-42S. 2000. II 
The Authors 

Gary o. Fiddler and Philip M. McDonald are Silviculturist and Research 

Forester, respectively, with the Pacific Southwest Research Station's Western 

Forests Ecology and Silviculture Program, Silviculture Laboratory, 2400 

Washington Avenue, Redding, CA 96001. Sylvia R. Mori is Mathematical 

Statistician with the Pacific Southwest Research Station, 800 Buchanan Street, 

Albany, CA 94710. 

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