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

july 1997

Pacific Southwest Research Station

Forest Service

us Department of Agriculture

Abstract

McDonald, Philip M.; Fiddler, Gary O. 1997. Vegetation trends in a young ponderosa pine

plantation treated bymanual release and mulching. Res. PaperPSW-RP-234. Albany,

CA: Pacific Southwest Research Station, Forest Service, U.s. Department of

Agriculture; 15 p.

On an above-average site in northern California, a complex plant community was

treated by manual release in 2- and 5-foot radii, one and three times. Mulching with a small

(3-footsquare) paper/ asphalt mulch and a control were additional treatments. Results for

a 10-year period are presented for shrubs, a subshrub (whipplea), ferns, forbs, and grasses.

No single category of competing vegetation dominated during the study, and competition

to planted ponderosa pines was from all vegetation combined. In spite of large amounts

of competing vegetation, the pines dominated in all trials, especially if the treated area was

large and the treatment was often. Ponderosa pine seedlings in plots grubbed to as-foot

radius three times had statistically larger diameters and heights than counterparts in

almost all other treatments. The cost of applying this treatment was $402 per acre, the

highest of all treatments, but reasonable compared to similar application in other plant

communities. Much information on density, foliar cover, and height of each category of

vegetation is presented, which in turn portrays changes ina developing plant community

in a young ponderosa pine plantation.

Retrieval Terms: cost, manual release, mulches, northern California, plant community

dynamics, pine seedlings

The Authors

Philip M. McDonald and Gary O. Fiddler are research forester and supervisory

forester, respectively, assigned to the Station's Silviculture Laboratory (2400 Washington

Ave., Redding, CA 96001).

14

tradeoffs. Some managers might opt for the most intensive treatment with 10-

year-old ponderosa pine trees that averaged 14.3 feet tall and were more than 4.6

inches in diameter 12 inches above mean groundline, and believe the cost was

worth it. Other managers might opt for a less intensive treatment like grubbing a

5-foot radius only once and accepting slightly less growth at a lower cost.

A few managers might even opt to allow the plant community that was

present after logging to develop naturally. They would not plant conifer seedlings

or release those that they did plant. This do-nothing strategy has serious

drawbacks. That not one new ponderosa pine seedling was found in the entire

study area for 10 years indicates that no seed source was present or the level of

competition was such that seedlings could not become established. And because

ponderosa pine was a component of the original forest, its absence denotes an

altered ecosystem lacking a key arborescent species. Furthermore, only four

conifer seedlings of Douglas-fir and sugar pine were found, which suggests that

almost no conifers would have stocked the land. Without planting, the

community would have consisted of scattered hardwoods and a dense mass of

shrubS, ferns, forbs, and grasses. It would have been in an even more altered

condition for many years.

Manual release on different treated areas and for two treatment intensities

created several vegetative assemblages, each with different amounts of the

principal species, but with generally similar developmental potentials.

Regardless of treatment, the future plant community will likely consist of

ponderosa pines with a few scattered hardwoods, shrubs, ferns, forbs, and

grasses in the understory. It is the growth rate of the pines in the most intensive

treatments where differences will occur. Here, the pines are growing faster than

planned, which means that the ecosystem manager can achieve the desired forest

condition sooner, and that could mean enhanced habitat for animals, a higher

degree of pleasing scenery in the roadside zone, and other enhancements. Faster

growing trees close crowns sooner, shade out lower branches faster, and create a

gap in the fuel ladder between the living crown and the ground-thus lessening

the propensity for crown fires. And because these fast-growing trees will need to

be thinned sooner than expected, a supply of raw material will come from these

stands, and that raw material will be available sooner to local wood-product

industries in rural America.

References

Crouch, G.L. 1986. Pocket gopher damage to conifers in western forests: a historical and current

perspective on the problem and its control. In: Salmond, T.P., ed. Proceedings of the twelfth

vertebrate pest conference; 1986 March 4 M 6; San Diego, CA. Davis, CA: Univ. California; 196-198.

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

and Row; 300 p.

Dunning, Duncan; Reineke, LH. 1933. Preliminary yield tables for second~growth stands in the

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

Agriculture; 24 p.

Ferguson, Dennis E.; Boyd, Raymond J. 1988. Bracken fern inhibition of conifer regeneration in

Northern Idaho. Res. Paper INT-388. Ogden, UT: Intermountain Research Station, Forest Service,

U.S. Department of Agriculture; 11 p.

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

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

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

Fiske, John N. 1986. Growth standards for average potential crop trees. N1,emo on file at Pacific

Southwest Research Station, Redding, Calif. 4 p.

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

of California Press; 1400 p.

McDonald, Philip M.; Fiddler, Gary O. 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,

USDA Forest Service Res, Paper PSW-RP~234. 1997.
iv

1993, height in both of these treatments differed significantly from pines in all

other treatments (2-foot radius one and three times, 3-foot square mulches,

control), which did not differ significantly from each other. Plainly, too small a

treatment area remains too small no matter how many times it is treated.

Similarly, a larger area is effective if treated only once-but this once must be

immediately after planting. Another caveat is that the treated area must equal or

exceed the minimum effective area that we defined in earlier studies. That

minimum is a 5-foot radius.

A fundamental adage in vegetation management is that a conifer seedling

grows best when it becomes established before the competitors, is separated

from the competitors in the sense of having space above- and belowground in

which to expand, and the competitors are at least temporarily weak. Another

adage is that plant species in addition to conifer seedlings are desirable in many

ways (Walstad and Kuch 1987). The multi-grubbed 5-foot-radius treatment in

this study fulfilled these conditions. At the study'S end, the 33 naturally

established species in it, plus planted ponderosa pine, amounted to 182,345

plants per acre, and covered 71 percent of the ground to the point that they cast a

solid shadow. Of this 71 percent cover, 91 percent was by ponderosa pines that

averaged 14.3 feet in height and 4.7 inches in diameter-values that exceeded

average Forest Service growth rates in California. Equally important was that

these rapidly growing pines have high potential to become a forest, which

probably was the prelogging condition.

USDA Forest Service Res.Paper P5W·RP-234. 1997.
Production and Cost

Not surprisingly, grubbing a 5-foot radius one and three times were the most

expensive treatments. Grubbing a 2-foot radius was relatively inexpensive,

regardless of number of times performed:

Discussion and Conclusions

After site preparation, the study area consisted of mostly bare ground, planted

ponderosa pines, a few hardwood sprouts, and bracken ferns. These species,

plus many more with plants from buried seeds and seeds that blew in on the

wind, quickly invaded the plantation. By the end of the first growing season,

several categories of vegetation, including shrubs, forbs, ferns, and grasses, were

well represented. Together, they supported a total foliar cover of 37,600 ft' per

acre or 86 percent of the ground surface. A species of vetch virtually exploded

throughout the plantation and was a major contributor to this total. Cheatgrass

and whipplea were just becoming established, especially in the control.

After 5 years, the makeup of the plant community was changing-probably

influenced most by the burgeoning ponderosa pines that were rapidly expanding

in height and width. Some species were declining, others were increasing. A

Grasses

Like the forbs, certain species increased and declined within the 10-year study

period. Diary records indicate that cheatgrass became present very early in the

study, peaked in density and cover in 1989, and declined to a few short, scattered

plants by 1993. Other grasses, particularly three species of fescue (Festuea spp.), a

species of needlegrass (Achnatherum spp.), blue wildrye (Elymus glaucus Buckley),

and a tall brome (Bromus spp.), found the environment of the treated plots to be

favorable. These species are all perennials and mostly taller than cheatgrass.

They comprised the bulk of the grass data in 1993. As a whole, grasses more than

doubled in density in the control from 1989 to 1993, but decreased dramatically

in cover, while inCreasing only slightly in height (table 2). In 1993 grasses in the

control had a lower density than in any other treatment (table 3), although not

statistically so. In general, the grasses were more dense in those treatments that

were grubbed only in 1984 and allowed to recover over time. Here, mean density

values ranged from more than 113,000 to more than 118,000 plants per acre. The

treatment with the highest density was mulching and supported almost 138,000

plants per acre by the end of the study (table 3). We noticed that the grasses were

quite dense along the edge of the mulch and leaned over it. Apparently when the

mulches decayed, the grass seeds effectively colonized the area. In all treatments,

foliar cover was low or zero, as in mulched plots and those grubbed to a 2-foot

radius three times. Like mean density, mean height did not differ significantly

among the treatments during the study.

Treatment

Manual release

2-£00t radius, one time

2-foot radius, three times

5-foot radius, one time

5-foot radius, three times

Mulching

3-foot square

Control

Laborer hours/acre

11

21

24

46

15

o

Dollars/acre

96

184

210

402

131

o

12 USDA Forest Service Res. Paper PSW·RP·234. 1997. 
2

seedlings one, two, and three times at 2- to 3-year intervals. We also grubbed

entire plots two times. After 10 years, only pines in the entire grubbed plot

differed significantly in mean diameter and height from counterparts in the

control (McDonald and Fiddler 1996). In a fourth study we grubbed a 2- and 4-

foot radius around ponderosa pine seedlings and also expanded a 2-foot radius

to 4 feet and a 4-foot radius to 6 feet after 2 years. Only pines in the expanded 4-

foot radius were significantly larger in diameter and height relative to the control

after 5 years (McDonald and Fiddler 1990).

For all these studies, treatment costs ranged from $90 to $1696 per acre

depending on the kind and amount of vegetation, amount of area treated, and

number of times the treatment was applied. These studies also support the

earlier finding (Fiddler and McDonald 1984) that manual release must be done

soon after planting and consist of a treated area with at least a 5-foot radius.

This paper portrays changes in the density and development of planted

ponderosa pines, shrubs, forbs, ferns, and grasses that were present in six trials

that involved various treated areas and number of times treated. It also quantifies

the diameter, height, and needle length of ponderosa pine seedlings in these

treatments and shows differences among them. Treatment costs and biological

responses then are combined to show cost effectiveness-a measure that provides

managers with options suited to their particular goals, constraints, and budgets.

Methods

Location and Site Characteristics

The study area is located on the Yolla Bolla Ranger District of the Shasta-Trinity

National Forests about 45 airline miles southwest of Redding, California. The

area was logged in the early 1970's, and the remaining stand consisted of a

scattered overstory of large Douglas-fir, sugar pine (Pinus lambertiana Doug!.),

and ponderosa pine trees that had high potential to produce seed. A more

extensive lower stratum was composed of mostly shade-tolerant Douglas-fir,

California white fir (Abies concolor var. lowiana [Gord.] Lemm.), and hardwoods

that occurred in small groves and as single trees. The hardwoods were Pacific

madrone (Arbutus menziesii Pursh) and giant chinkapin (Castanopsis chrysophylla

[Doug!.] A. DC), with canyon live oak (Quercus chrysolepis Liebm.) a distant

third. Shrubs of the genera Arctostaphylos, Rubus, Ribes, and Symphoricarpos were

scattered between trees and in small openings.

Because of the potential for heavy competition to planted conifer seedlings

from hardwoods and shrubs, site preparation and plantation release were judged

as necessary. After harvest in 1983 the hardwoods and logging slash were pushed

into piles with a brushrake-equipped bulldozer and burned in the fal!. Very little

soil was windrowed, and after 3 years the windrows were barely visible.

The plant community when the study began consisted mostly of plants that

originated from dormant seeds in the soil and from windblown seeds. A few

hardwood root masses escaped site preparation, and clumps of rapidly growing

sprouts from them contributed to the plant community. In addition to the

planted ponderosa pine seedlings, bracken fern (Pteridium aquilinum (L.) Kuhn

var. pubescens L. Underw.) was the most abundant species in the study area.

The early community was characterized by many species and large numbers of

plants in several categories such as shrubs, ferns, forbs, and grasses. Grass

genera were Bromus, Festuca, Elymus, and Stipa (now classified as Achnatherum

by Hickman [1993]).

Ponderosa pine seedlings from a local seed source were raised in a private

nursery at Aberdeen, Washington and outplanted in augured holes in spring

USDA Forest Service Res. Paper PSW-RP-234. 1997.
10

mulched plots (table 3). The only statistical difference noted for density was

between the high values in mulched plots and lower values in plots of all other

treatments. In general, foliar cover was low in all treatments and did not differ

statistically among them. Average height ranged from 0.6 to 1.7 feet and also did

not differ among treatments.

USDA Forest Service Res. Paper PSW-RP-234. 1997.
4

Study and the current wage-$8.74 per hour-the rate for a WG-l laborer, U.S.

Department of Labor, as of June 1993. No allowance for travel, equipment, or

overhead was included.

Sampling

In each plot, 30 healthy ponderosa pine seedlings, identified as potential crop

trees, were randomly chosen and permanently tagged. As their name implies,

these were well-developed seedlings that had good potential of becoming

harvestable trees. Small, misshapen, and chlorotic seedlings were not included

because their chance of being alive and present at the time of first thinning was

smalL On each of the sample seedlings, stern diameter and height were measured.

Diameters were recorded at 12 inches above mean groundline, and needle length

was measured to the nearest 0.1 inch. Seedlings were checked periodically for

injury from both biotic and abiotic agents.

Sampling intensity for evaluating vegetation other than ponderosa pine

seedlings was five randomly selected subplots in each plot. Subplots were

centered around pine seedlings in all treatments. To measure competing

vegetation in the control and mulched plots, a square milacre (0.001 acre) and a

square 3-foot metal frame, respectively, were used. For radius plots, sampling

took place only in the treated area.

All vegetation other than ponderosa pine was sampled for density in

terms of number of plants per milacre plot and expanded to a per-acre basis.

Because new entities of whipplea and bracken fern arise from belowground

structures, defining a "plant" was necessary. Excavation and pulling on

sterns showed rhizome length to vary widely in depth and length of

internodes. Consequently, single sterns and small clumps of sterns were

counted as one plant. Determining the density of the shorter grasses also was

difficult. In places, the plants were so numerous and so close together that it

was almost impossible to determine individual plants. Foliar cover (the sum

of shadows that would be cast by leaves and sterns of individual species

expressed as a percentage of the land surface [Daubenmire 1968]) and average

dominant height (average of the three tallest sterns measured from mean

groundline to bud) also were measured.

Unfortunately, limitations in budget and staffing affected early sampling,

and only partial data sets were obtained for ponderosa pine and other vegetation.

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 ex~ 0.05. Data were gathered from

permanent plots measured periodically, and where analyses of means from

repeated measurements are concerned, the data are not truly independent.

The ex levels or type I errors given for various tests apply to each measurement

and year separately.

To quantify plant diversity on study plots, species were noted whenever

the plantation was visited. All species were recorded at the beginning and

end of the study.

Results

Plant Diversity

Early in the study, the plant community consisted of 1 species of conifer from

seed, 3 hardwoods, 8 shrubs, 12 forbs, 4 grasses, and bracken fern.

USDA Forest Service Res. Paper PSW-RP-234. 1997.
Mean stem diameter, measured at 12 inches above mean groundline, was the

first variable to show statistical significance. In 1988, mean stem diameter of

pines grubbed to a 5-foot radius three times (jig. 2) was significantly larger

than that of counterparts in the mulched treatment (table 1). In fall 1993 or at the

end of the 10th growing season, pine seedlings in plots grubbed to a 5-foot

radius both one and three times had significantly larger stem diameters than

pines in the mulched treatment. This also proved true for average pine height

in 1993, the first time that statistical significance for this variable was found.

Significant differences in needle length showed a similar trend. Mean needle

length of pines in plots released to a 5-foot radius three times was longer than

that of pines in all other treatments in both 1989 and 1993 (table 1).

Shrubs

The most abundant shrub species in the study area were from the genera Rosa,

Rubus, and Symphoricarpos, which were evenly distributed in all treatments.

After one growing season, mean foliar cover of all shrubs in the control was 3,740

ft' per acre (table 2). After five growing seasons, cover decreased to 2,000 ft' per

acre, but then increased to 3,333 ft' per acre after 10 seasons (table 2). This

increase in cover was accompanied by an increase in density from 800 plants per

acre in 1989 to more than 5,000 plants per acre in 1993. Average height of shrubs

in the control decreased from 2.5 to 1.5 feet during the 1989-1993 period.

Average shrub density in 1993 ranged from 3,586 plants per acre in plots

grubbed to a 5-foot radius three times to more than 13,200 plants per acre in

Figure 2-This S·year~old ponde~

rosa pine, released by grubbing a S~

foot radius around it three times, is

growing well in diameter and height.

8 USDA Forest Service Res. Paper PSW~RP~234. 1997. 
Figure I-Ponderosa pine seedlings

in the various treatments in April

1986: (A) 2-foot radius grubbed two

of the scheduled three times, (B) 5-

foot radius grubbed two of the

scheduled three times, (C) 3-foot

square mulch with only the fiberglass

strands showing, and (D) control.

Note the dense herbaceous

vegetation where not grubbed, and

particularly the many half-developed

vetch plants in the control.

A

B

6 USDA Forest Service Res. Paper PSW·RP-234. 1997. 
Figure I-Ponderosa pine seedlings

in the various treatments in April

1986: (A) 2-foot radius grubbed two

of the scheduled three times, (B) 5-

foot radius grubbed two of the

scheduled three times, (C) 3-foot

square mulch with only the fiberglass

strands showing, and (D) control.

Note the dense herbaceous

vegetation where not grubbed, and

particularly the many half-developed

vetch plants in the control.

A

B

6 USDA Forest Service Res. Paper PSW·RP-234. 1997. 
Mean stem diameter, measured at 12 inches above mean groundline, was the

first variable to show statistical significance. In 1988, mean stem diameter of

pines grubbed to a 5-foot radius three times (jig. 2) was significantly larger

than that of counterparts in the mulched treatment (table 1). In fall 1993 or at the

end of the 10th growing season, pine seedlings in plots grubbed to a 5-foot

radius both one and three times had significantly larger stem diameters than

pines in the mulched treatment. This also proved true for average pine height

in 1993, the first time that statistical significance for this variable was found.

Significant differences in needle length showed a similar trend. Mean needle

length of pines in plots released to a 5-foot radius three times was longer than

that of pines in all other treatments in both 1989 and 1993 (table 1).

Shrubs

The most abundant shrub species in the study area were from the genera Rosa,

Rubus, and Symphoricarpos, which were evenly distributed in all treatments.

After one growing season, mean foliar cover of all shrubs in the control was 3,740

ft' per acre (table 2). After five growing seasons, cover decreased to 2,000 ft' per

acre, but then increased to 3,333 ft' per acre after 10 seasons (table 2). This

increase in cover was accompanied by an increase in density from 800 plants per

acre in 1989 to more than 5,000 plants per acre in 1993. Average height of shrubs

in the control decreased from 2.5 to 1.5 feet during the 1989-1993 period.

Average shrub density in 1993 ranged from 3,586 plants per acre in plots

grubbed to a 5-foot radius three times to more than 13,200 plants per acre in

Figure 2-This S·year~old ponde~

rosa pine, released by grubbing a S~

foot radius around it three times, is

growing well in diameter and height.

8 USDA Forest Service Res. Paper PSW~RP~234. 1997. 
4

Study and the current wage-$8.74 per hour-the rate for a WG-l laborer, U.S.

Department of Labor, as of June 1993. No allowance for travel, equipment, or

overhead was included.

Sampling

In each plot, 30 healthy ponderosa pine seedlings, identified as potential crop

trees, were randomly chosen and permanently tagged. As their name implies,

these were well-developed seedlings that had good potential of becoming

harvestable trees. Small, misshapen, and chlorotic seedlings were not included

because their chance of being alive and present at the time of first thinning was

smalL On each of the sample seedlings, stern diameter and height were measured.

Diameters were recorded at 12 inches above mean groundline, and needle length

was measured to the nearest 0.1 inch. Seedlings were checked periodically for

injury from both biotic and abiotic agents.

Sampling intensity for evaluating vegetation other than ponderosa pine

seedlings was five randomly selected subplots in each plot. Subplots were

centered around pine seedlings in all treatments. To measure competing

vegetation in the control and mulched plots, a square milacre (0.001 acre) and a

square 3-foot metal frame, respectively, were used. For radius plots, sampling

took place only in the treated area.

All vegetation other than ponderosa pine was sampled for density in

terms of number of plants per milacre plot and expanded to a per-acre basis.

Because new entities of whipplea and bracken fern arise from belowground

structures, defining a "plant" was necessary. Excavation and pulling on

sterns showed rhizome length to vary widely in depth and length of

internodes. Consequently, single sterns and small clumps of sterns were

counted as one plant. Determining the density of the shorter grasses also was

difficult. In places, the plants were so numerous and so close together that it

was almost impossible to determine individual plants. Foliar cover (the sum

of shadows that would be cast by leaves and sterns of individual species

expressed as a percentage of the land surface [Daubenmire 1968]) and average

dominant height (average of the three tallest sterns measured from mean

groundline to bud) also were measured.

Unfortunately, limitations in budget and staffing affected early sampling,

and only partial data sets were obtained for ponderosa pine and other vegetation.

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 ex~ 0.05. Data were gathered from

permanent plots measured periodically, and where analyses of means from

repeated measurements are concerned, the data are not truly independent.

The ex levels or type I errors given for various tests apply to each measurement

and year separately.

To quantify plant diversity on study plots, species were noted whenever

the plantation was visited. All species were recorded at the beginning and

end of the study.

Results

Plant Diversity

Early in the study, the plant community consisted of 1 species of conifer from

seed, 3 hardwoods, 8 shrubs, 12 forbs, 4 grasses, and bracken fern.

USDA Forest Service Res. Paper PSW-RP-234. 1997.
10

mulched plots (table 3). The only statistical difference noted for density was

between the high values in mulched plots and lower values in plots of all other

treatments. In general, foliar cover was low in all treatments and did not differ

statistically among them. Average height ranged from 0.6 to 1.7 feet and also did

not differ among treatments.

USDA Forest Service Res. Paper PSW-RP-234. 1997.
2

seedlings one, two, and three times at 2- to 3-year intervals. We also grubbed

entire plots two times. After 10 years, only pines in the entire grubbed plot

differed significantly in mean diameter and height from counterparts in the

control (McDonald and Fiddler 1996). In a fourth study we grubbed a 2- and 4-

foot radius around ponderosa pine seedlings and also expanded a 2-foot radius

to 4 feet and a 4-foot radius to 6 feet after 2 years. Only pines in the expanded 4-

foot radius were significantly larger in diameter and height relative to the control

after 5 years (McDonald and Fiddler 1990).

For all these studies, treatment costs ranged from $90 to $1696 per acre

depending on the kind and amount of vegetation, amount of area treated, and

number of times the treatment was applied. These studies also support the

earlier finding (Fiddler and McDonald 1984) that manual release must be done

soon after planting and consist of a treated area with at least a 5-foot radius.

This paper portrays changes in the density and development of planted

ponderosa pines, shrubs, forbs, ferns, and grasses that were present in six trials

that involved various treated areas and number of times treated. It also quantifies

the diameter, height, and needle length of ponderosa pine seedlings in these

treatments and shows differences among them. Treatment costs and biological

responses then are combined to show cost effectiveness-a measure that provides

managers with options suited to their particular goals, constraints, and budgets.

Methods

Location and Site Characteristics

The study area is located on the Yolla Bolla Ranger District of the Shasta-Trinity

National Forests about 45 airline miles southwest of Redding, California. The

area was logged in the early 1970's, and the remaining stand consisted of a

scattered overstory of large Douglas-fir, sugar pine (Pinus lambertiana Doug!.),

and ponderosa pine trees that had high potential to produce seed. A more

extensive lower stratum was composed of mostly shade-tolerant Douglas-fir,

California white fir (Abies concolor var. lowiana [Gord.] Lemm.), and hardwoods

that occurred in small groves and as single trees. The hardwoods were Pacific

madrone (Arbutus menziesii Pursh) and giant chinkapin (Castanopsis chrysophylla

[Doug!.] A. DC), with canyon live oak (Quercus chrysolepis Liebm.) a distant

third. Shrubs of the genera Arctostaphylos, Rubus, Ribes, and Symphoricarpos were

scattered between trees and in small openings.

Because of the potential for heavy competition to planted conifer seedlings

from hardwoods and shrubs, site preparation and plantation release were judged

as necessary. After harvest in 1983 the hardwoods and logging slash were pushed

into piles with a brushrake-equipped bulldozer and burned in the fal!. Very little

soil was windrowed, and after 3 years the windrows were barely visible.

The plant community when the study began consisted mostly of plants that

originated from dormant seeds in the soil and from windblown seeds. A few

hardwood root masses escaped site preparation, and clumps of rapidly growing

sprouts from them contributed to the plant community. In addition to the

planted ponderosa pine seedlings, bracken fern (Pteridium aquilinum (L.) Kuhn

var. pubescens L. Underw.) was the most abundant species in the study area.

The early community was characterized by many species and large numbers of

plants in several categories such as shrubs, ferns, forbs, and grasses. Grass

genera were Bromus, Festuca, Elymus, and Stipa (now classified as Achnatherum

by Hickman [1993]).

Ponderosa pine seedlings from a local seed source were raised in a private

nursery at Aberdeen, Washington and outplanted in augured holes in spring

USDA Forest Service Res. Paper PSW-RP-234. 1997.
Production and Cost

Not surprisingly, grubbing a 5-foot radius one and three times were the most

expensive treatments. Grubbing a 2-foot radius was relatively inexpensive,

regardless of number of times performed:

Discussion and Conclusions

After site preparation, the study area consisted of mostly bare ground, planted

ponderosa pines, a few hardwood sprouts, and bracken ferns. These species,

plus many more with plants from buried seeds and seeds that blew in on the

wind, quickly invaded the plantation. By the end of the first growing season,

several categories of vegetation, including shrubs, forbs, ferns, and grasses, were

well represented. Together, they supported a total foliar cover of 37,600 ft' per

acre or 86 percent of the ground surface. A species of vetch virtually exploded

throughout the plantation and was a major contributor to this total. Cheatgrass

and whipplea were just becoming established, especially in the control.

After 5 years, the makeup of the plant community was changing-probably

influenced most by the burgeoning ponderosa pines that were rapidly expanding

in height and width. Some species were declining, others were increasing. A

Grasses

Like the forbs, certain species increased and declined within the 10-year study

period. Diary records indicate that cheatgrass became present very early in the

study, peaked in density and cover in 1989, and declined to a few short, scattered

plants by 1993. Other grasses, particularly three species of fescue (Festuea spp.), a

species of needlegrass (Achnatherum spp.), blue wildrye (Elymus glaucus Buckley),

and a tall brome (Bromus spp.), found the environment of the treated plots to be

favorable. These species are all perennials and mostly taller than cheatgrass.

They comprised the bulk of the grass data in 1993. As a whole, grasses more than

doubled in density in the control from 1989 to 1993, but decreased dramatically

in cover, while inCreasing only slightly in height (table 2). In 1993 grasses in the

control had a lower density than in any other treatment (table 3), although not

statistically so. In general, the grasses were more dense in those treatments that

were grubbed only in 1984 and allowed to recover over time. Here, mean density

values ranged from more than 113,000 to more than 118,000 plants per acre. The

treatment with the highest density was mulching and supported almost 138,000

plants per acre by the end of the study (table 3). We noticed that the grasses were

quite dense along the edge of the mulch and leaned over it. Apparently when the

mulches decayed, the grass seeds effectively colonized the area. In all treatments,

foliar cover was low or zero, as in mulched plots and those grubbed to a 2-foot

radius three times. Like mean density, mean height did not differ significantly

among the treatments during the study.

Treatment

Manual release

2-£00t radius, one time

2-foot radius, three times

5-foot radius, one time

5-foot radius, three times

Mulching

3-foot square

Control

Laborer hours/acre

11

21

24

46

15

o

Dollars/acre

96

184

210

402

131

o

12 USDA Forest Service Res. Paper PSW·RP·234. 1997. 
iv

1993, height in both of these treatments differed significantly from pines in all

other treatments (2-foot radius one and three times, 3-foot square mulches,

control), which did not differ significantly from each other. Plainly, too small a

treatment area remains too small no matter how many times it is treated.

Similarly, a larger area is effective if treated only once-but this once must be

immediately after planting. Another caveat is that the treated area must equal or

exceed the minimum effective area that we defined in earlier studies. That

minimum is a 5-foot radius.

A fundamental adage in vegetation management is that a conifer seedling

grows best when it becomes established before the competitors, is separated

from the competitors in the sense of having space above- and belowground in

which to expand, and the competitors are at least temporarily weak. Another

adage is that plant species in addition to conifer seedlings are desirable in many

ways (Walstad and Kuch 1987). The multi-grubbed 5-foot-radius treatment in

this study fulfilled these conditions. At the study'S end, the 33 naturally

established species in it, plus planted ponderosa pine, amounted to 182,345

plants per acre, and covered 71 percent of the ground to the point that they cast a

solid shadow. Of this 71 percent cover, 91 percent was by ponderosa pines that

averaged 14.3 feet in height and 4.7 inches in diameter-values that exceeded

average Forest Service growth rates in California. Equally important was that

these rapidly growing pines have high potential to become a forest, which

probably was the prelogging condition.

USDA Forest Service Res.Paper P5W·RP-234. 1997.
14

tradeoffs. Some managers might opt for the most intensive treatment with 10-

year-old ponderosa pine trees that averaged 14.3 feet tall and were more than 4.6

inches in diameter 12 inches above mean groundline, and believe the cost was

worth it. Other managers might opt for a less intensive treatment like grubbing a

5-foot radius only once and accepting slightly less growth at a lower cost.

A few managers might even opt to allow the plant community that was

present after logging to develop naturally. They would not plant conifer seedlings

or release those that they did plant. This do-nothing strategy has serious

drawbacks. That not one new ponderosa pine seedling was found in the entire

study area for 10 years indicates that no seed source was present or the level of

competition was such that seedlings could not become established. And because

ponderosa pine was a component of the original forest, its absence denotes an

altered ecosystem lacking a key arborescent species. Furthermore, only four

conifer seedlings of Douglas-fir and sugar pine were found, which suggests that

almost no conifers would have stocked the land. Without planting, the

community would have consisted of scattered hardwoods and a dense mass of

shrubS, ferns, forbs, and grasses. It would have been in an even more altered

condition for many years.

Manual release on different treated areas and for two treatment intensities

created several vegetative assemblages, each with different amounts of the

principal species, but with generally similar developmental potentials.

Regardless of treatment, the future plant community will likely consist of

ponderosa pines with a few scattered hardwoods, shrubs, ferns, forbs, and

grasses in the understory. It is the growth rate of the pines in the most intensive

treatments where differences will occur. Here, the pines are growing faster than

planned, which means that the ecosystem manager can achieve the desired forest

condition sooner, and that could mean enhanced habitat for animals, a higher

degree of pleasing scenery in the roadside zone, and other enhancements. Faster

growing trees close crowns sooner, shade out lower branches faster, and create a

gap in the fuel ladder between the living crown and the ground-thus lessening

the propensity for crown fires. And because these fast-growing trees will need to

be thinned sooner than expected, a supply of raw material will come from these

stands, and that raw material will be available sooner to local wood-product

industries in rural America.

References

Crouch, G.L. 1986. Pocket gopher damage to conifers in western forests: a historical and current

perspective on the problem and its control. In: Salmond, T.P., ed. Proceedings of the twelfth

vertebrate pest conference; 1986 March 4 M 6; San Diego, CA. Davis, CA: Univ. California; 196-198.

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

and Row; 300 p.

Dunning, Duncan; Reineke, LH. 1933. Preliminary yield tables for second~growth stands in the

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

Agriculture; 24 p.

Ferguson, Dennis E.; Boyd, Raymond J. 1988. Bracken fern inhibition of conifer regeneration in

Northern Idaho. Res. Paper INT-388. Ogden, UT: Intermountain Research Station, Forest Service,

U.S. Department of Agriculture; 11 p.

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

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

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

Fiske, John N. 1986. Growth standards for average potential crop trees. N1,emo on file at Pacific

Southwest Research Station, Redding, Calif. 4 p.

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

of California Press; 1400 p.

McDonald, Philip M.; Fiddler, Gary O. 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,

USDA Forest Service Res, Paper PSW-RP~234. 1997.

Publisher:

Albany. California

Mailing address:

PO Box 245, Berkeley CA

94701-0245

510 559-6300

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

july 1997

Pacific Southwest Research Station

Forest Service

us Department of Agriculture

Abstract

McDonald, Philip M.; Fiddler, Gary O. 1997. Vegetation trends in a young ponderosa pine

plantation treated bymanual release and mulching. Res. PaperPSW-RP-234. Albany,

CA: Pacific Southwest Research Station, Forest Service, U.s. Department of

Agriculture; 15 p.

On an above-average site in northern California, a complex plant community was

treated by manual release in 2- and 5-foot radii, one and three times. Mulching with a small

(3-footsquare) paper/ asphalt mulch and a control were additional treatments. Results for

a 10-year period are presented for shrubs, a subshrub (whipplea), ferns, forbs, and grasses.

No single category of competing vegetation dominated during the study, and competition

to planted ponderosa pines was from all vegetation combined. In spite of large amounts

of competing vegetation, the pines dominated in all trials, especially if the treated area was

large and the treatment was often. Ponderosa pine seedlings in plots grubbed to as-foot

radius three times had statistically larger diameters and heights than counterparts in

almost all other treatments. The cost of applying this treatment was $402 per acre, the

highest of all treatments, but reasonable compared to similar application in other plant

communities. Much information on density, foliar cover, and height of each category of

vegetation is presented, which in turn portrays changes ina developing plant community

in a young ponderosa pine plantation.

Retrieval Terms: cost, manual release, mulches, northern California, plant community

dynamics, pine seedlings

The Authors

Philip M. McDonald and Gary O. Fiddler are research forester and supervisory

forester, respectively, assigned to the Station's Silviculture Laboratory (2400 Washington

Ave., Redding, CA 96001).
United States

Department

of Agriculture

Forest Service

Pacific Southwest

Research Station

Research Paper

PSW-RP-234

mV

Vegetation Trends in aYoung Ponderosa r.lline

PlantationTreated by Manual Release and Mulching