Introduction

Bearclover (Chamaebatia foliolosa Benth),1,2 Rosaceae, is a perennial evergreen

shrub, endemic to northern and central California, that is prevalent on south- and

west-facing slopes at elevations between 1,000 and 6,000 feet in the Sierra Nevada

of California, and to a lesser extent on lower slopes in the southern Cascade

Range. With the exception of isolated stands near Burney in Shasta County, near

Greenville in Plumas County, and in Kern County in southern California, most

stands of this shrub are located between Yuba and Tulare Counties in the Sierra

Nevada. The stands occupy areas that range from small patches to hundreds of

acres. The species excels in partial shade, particularly in that cast by an overstory

of scattered ponderosa pines (Pinus ponderosa Dougl. ex Laws. var. ponderosa)1,2

and incense-cedars (Libocedrus decurrens Torr.), and it grows well in sunlit

environments. Bearclover persists in shade, but has thinner crowns and taller

stems in this setting. Although less common on north and east exposures,

bearclover is capable of occupying almost all aspects, site qualities, and soil types

within its natural range.3

Bearclover produces heavily scented, glandular, and fern-like foliage on

short flexible stems that arise from below-ground structures. Large numbers of

stems (up to 104 per square foot)4

 and rapid growth (6 to 8 inches the first year)

combine to make bearclover a very competitive species. The root system

contributes even more toward the species’ competitiveness. It consists of an

extensive network of roots and rhizomes 4 to 16 inches below the soil surface and

taproots that often extend to depths of 6 feet or more.5

 Lateral extension of

rhizomes from mature plants in undisturbed areas is reported in general as

slow5,6 and fairly rapid after burning.7 But whether slow or rapid, extension over

time is impressive. One rhizome in a previous study was traced for a distance of

almost 90 feet.4

Together, the above- and below-ground plant parts portray the mechanism of

competition in bearclover.8,9 In the spring, the roots efficiently gather moisture

and the plant uses it to attain a maximum amount of photosynthesis and early

growth. In midsummer, when soil moisture is low, bearclover plants endure high

internal moisture stress, reduced photosynthesis, and low growth rates. But they

survive. The strategy of maximizing early growth, using all available soil

moisture, and then withstanding the environmental stress of summer and fall,

denies soil moisture to competing plants and helps to ensure their absence.

Bearclover’s competitiveness probably is enhanced by additional

mechanisms: fine roots are nodulated and may be active nitrogen fixers, the

species reproduces from seed, and visual evidence of allelopathy has been noted.5

McDonald, Philip M.;

Fiddler, Gary O. 1999.

Recovery of a bearclover

(Chamaebatia foliolosa)

plant community after site

preparation and planting of

ponderosa pine seedlings. Res.

Note PSW-RN-423. Albany,

CA: Pacific Southwest

Research Station, Forest

Service, U.S. Department of

Agriculture; 7 p.

Bearclover inhabits thousands of acres of forest land

in northern and central

California, but little

quantification of its recovery

after timber harvest, site

preparation, and planting is

available. And the species

composition and development of the ensuing plant

community is largely

unknown. Density, foliar

cover, and height of planted

ponderosa pine seedlings,

bearclover, whiteleaf

manzanita, forbs, and

grasses were documented

from 1986 through 1996 in

northern California. After 11

growing seasons, bearclover

and planted ponderosa

pines were dominating,

whiteleaf manzanita was

increasing, grasses were still

numerous, and the forbs had

come and gone. A total of 12

plant species were present at

the beginning and end of the

study, although 20 species

were found during the study

period. Elongation of

bearclover rhizomes took

place for 2 years after site

preparation and then

abruptly ceased.

Retrieval Terms: bearclover,

plant community, ponderosa pine seedlings,

recovery, species development, vegetation

management.

Recovery of a Bearclover (Chamaebatia

foliolosa) Plant Community after Site

Preparation and Planting of Ponderosa

Pine Seedlings

Philip M. McDonald Gary O. Fiddler

United States

Department

of Agriculture

Forest Service

Pacific Southwest

Research Station

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

Research Note

PSW-RN-423

December 1999
USDA Forest Service Research Note. PSW-RN-423. 1999.

2

Heisey and others10 found direct evidence of nitrogen fixation on nodulated

bearclover plants in an area with little organic matter on the soil surface because

of an intense forest fire a decade earlier. No nodulation was found in an

undisturbed area nearby that had a deep organic layer. They noted that

nodulation was uncommon on nonleguminous plants, especially among the

Rosaceae (which includes bearclover). Furthermore, in cross-section, the nodules

were strikingly similar to those of snowbrush (Ceanothus velutinus Hook., family

Rhamnaceae)11 and in a later study12 to deerbrush (Ceanothus integerrimus Hook.

& Arn.)—two common associates of bearclover.

Foresters first began studying bearclover in California in 1911.4 Early studies

detailed the capability of the species to recover rapidly from disturbance and

quantified its ability to restrict the establishment of both natural and planted

conifer seedlings. Indeed, survival of planted conifer seedlings often is less than

20 percent. In addition to erosion control, beneficial attributes of bearclover

include browse for deer,13,14 and use as a medicine by Native-Americans.15

This note reports the diversity, density, and development of bearclover,

planted ponderosa pines, whiteleaf manzanita, forbs, and grasses from the time

of mostly bare ground after site preparation through the next 11 years.

Methods

The study area was located about 16 airline miles north of the small town of

Pioneer in Amador County, California. Elevation is about 4,000 feet, and aspect

is northeast with 20 percent slopes. Annual precipitation is about 40 inches with

60 percent falling as snow. The soil is of the Cohasset Series and is deep, reddish,

and moderately well drained. Surface texture is loam, grading to clay loam

below 20 inches. This environment is considered above average for growing

ponderosa pines. Before timber harvest, the forest consisted of scattered trees

and clumps of trees, which were mostly ponderosa pine and incense-cedar. An

almost continuous cover of mature bearclover that was 15- to 18-inches tall and

of scattered larger whiteleaf manzanita (Arctostaphylos viscida C. Parry) was

present beneath the trees. In fall 1985, after timber harvest, the site was prepared

for planting by piling slash and remaining vegetation with a brushrake-equipped

bulldozer. During the two operations (harvesting and site preparation), the

tractor crushed, scraped, and severed the bearclover at groundline. It sprouted

the following spring.

The three plots in this study were randomly chosen and located throughout a

5-acre relatively homogeneous area. Each encompassed about 0.15 acre and

contained 25 to 30 ponderosa pine seedlings. The pine seedlings, from seed

gathered in the appropriate seed zone, were grown for 1 year in the Placerville

Nursery and out-planted in March 1986 at a 10- by 10-foot spacing. This was the

equivalent of 436 seedlings per acre. For them, density was fixed at their spacing,

and height was averaged over the number of surviving seedlings in the plot. All

vegetation was sampled annually for the first five growing seasons and again at

11 years after planting.

All natural vegetation was measured and remeasured at the end of the

growing season on five randomly selected, seedling-centered, square milacre

subplots in each plot. Each milacre contained 0.001 acre or 43.56 ft

2

. Stem density,

stem height, and foliar cover were quantified for several species and categories

of vegetation. More specifically, density was the number of stems per species or

category, counted on each milacre, and presented on a per-acre basis. Foliar

cover, recorded for ponderosa pine seedlings and other vegetation, was estimated

to the nearest square foot and also recorded as a per-acre value. If less than 0.5

square foot, foliar cover was denoted as a trace (T). Height was calculated as the

average of the three tallest stems per species or category in the milacre subplots.

To study rhizome elongation, two 10-foot long permanent transects with 11

evenly spaced metal pins were installed in a randomly selected, site-prepared

area within the study area in fall 1986. Both transects were located in the middle
USDA Forest Service Research Note. PSW-RN-423. 1999. 3

Table 1—Natural vegetation in study plots, Amador

Ranger District, 1986-1996.

Species 1986 1987 1988 1989 1990 1996

Trees

Libocedrus decurrens - - - - XX

Shrubs

Arctostaphylos viscida X X X X XX

Ceanothus integerrimus X X X X XX

Chamaebatia foliolosa X X X X XX

Ribes roezlii X X X X XX

Chrysothamnus spp. - - - - XX

Forbs

Cirsium vulgare XXXXX-

 Dichelostemma congestum - - - XX-

 Fritillaria spp. X - - - --

Galium bolanderi X X X X XX

 Lotus purshianus -X- - --

 Madia qracilis - XXXX-

 Montia parvifolia X- - - --

 Polygala cornuta X X X X XX

 Vicia americana X X X X XX

 Viola purpurea X X X X XX

Grasses

Achnatherum spp. - - - - XX

 Bromus diandrus - - - -X-

 Bromus tectorum X X X X XX

 Vulpia bromoides - - - X XX

Total 12 12 11 13 17 13

of an area of bare ground with a patch of bearclover at least 3 feet away. On one

transect, the bearclover grew uphill toward the transect; on the other, downhill.

The slope was about 12 percent in both instances. No vegetation or roots of

vegetation other than bearclover was present, and no trace of bearclover stems

was noted in the bare area. After each growing season, a pin was placed on the

bearclover stem nearest the corresponding metal pin on the transect. The 11

distances from transect pin to the pin on the bearclover were averaged each

season to arrive at the amount of annual rhizome elongation.

Results

Plant Diversity

Twenty naturally-established plant species were found on study plots during the

1986 to 1996 period and ranged from 11 to 17 species in a given year (table 1).

Their number was primarily governed by the high density and foliar cover of the

bearclover. When the study began, no tree seedlings, four shrubs, seven forbs,

and one grass were present; when it ended, one tree seedling, five shrubs, four

forbs and three grasses were present.

Ponderosa Pine

Planted ponderosa pine seedlings also were affected by the bearclover. Survival at

the end of the study was 69 percent. Mortality was recorded from 1987 through 1996

with more seedlings dying in 1989, 1990, and 1996 than in other years. Competition/

suppression was the primary cause of death. Foliar cover ranged from a trace in 1986

to 12,193 ft2 per acre in 1996, and height averaged 0.52 foot at the beginning of the

study and 16.67 feet at the end of the study (table 2).
USDA Forest Service Research Note. PSW-RN-423. 1999. 4

Table 2—Average density, foliar cover, and height with standard

errors (SE) of pine, bearclover, whiteleaf manzanita, forbs, and grasses,

Amador Ranger District, 1986-1996.

Year Density SE Cover SE Height SE

stems/acre ft2/acre ft

Ponderosa Pine

1986 - - T1 - 0.52 0.03

1987 - - 467 176 0.96 0.09

1988 - - 1,067 333 1.73 0.29

1989 - - 2,200 902 2.68 0.58

1990 - - 3,667 1,568 4.03 0.93

1996 - - 12,193 139 16.67 0.29

Bearclover

1986 152,200 38,504 8,667 1,288 0.59 0.03

1987 200,330 24,420 11,867 1,462 0.66 0.04

1988 224,533 24,195 17,067 2,293 0.75 0.02

1989 190,667 16,170 22,067 546 0.83 0.02

1990 152,333 32,119 24,867 1,110 0.82 0.05

1996 117,200 21,803 15,700 5,701 1.44 0.08

Whiteleaf Manzanita

1986 600 305 T T 0.24 0.03

1987 867 92 T T 0.34 0.01

1988 800 231 67 67 0.49 0.01

1989 1,067 67 200 36 0.85 0.41

1990 1,067 67 467 177 1.30 0.01

1996 1,100 100 2,200 1,800 4.25 0.04

Forbs

1986 - - - - - -

1987 867 553 400 231 0.71 0.40

1988 2,067 1,157 800 416 1.00 0.50

1989 1,667 1,182 600 305 1.25 0.60

1990 7,333 481 467 240 1.60 0.20

1996 - - - - - -

Grasses

1986 - - - - - -

1987 133 133 T T 0.76 0.17

1988 2,699 1,858 67 67 0.90 0.06

1989 133 90 67 67 2.60 0.76

1990 438,400 73,302 2,400 305 1.30 0.42

1996 37,600 25,204 600 600 1.88 1.21

1T=trace

Table 3—Average bearclover rhizome elongation along an uphill and downhill transect,

with standard errors (SE), Amador Ranger

District, 1987-1989.

Year Uphill Downhill

_____________________________________________________________________________

Mean SE Mean SE

- - - - - - - - - - inches - - - - - - - - - -

1987 6.82 1.87 4.60 1.41

1988 22.27 3.96 5.00 0.81

1989 0.64 0.30 0.00 -

Total 29.73 9.60
USDA Forest Service Research Note. PSW-RN-423. 1999. 5

Bearclover

Bearclover was checked for sprout or seedling status by gently pulling on the stems.

All appeared to be connected below ground, which indicated vegetative

reproduction. Although vigorously searched for, no seedlings were found. The

initial density, foliar cover, and height values for bearclover (152,200 stems per acre,

8,667 ft2 per acre, and 0.59 foot) reflect this species strong resurgence soon after

disturbance (table 2). Mean bearclover density peaked in 1988 with 224,533 stems per

acre; foliar cover was best in 1990 at 24,867 ft2 per acre, and height peaked in 1996 at

1.44 feet. At the end of the study, both average density (117,200 stems per acre) and

foliar cover (15,700 ft2 per acre) had decreased from peak values.

After three successive growing seasons, bearclover rhizome extension, as

denoted by above-ground stems, was 29.7 inches if growing uphill and 9.6 inches

if extending downhill (table 3). Growth was best the second year and virtually

nonexistent the third growing season. During the fourth season, tiny new

bearclover plants appeared within the bare area. Pulling on them revealed that

they originated from deep in the soil, apparently from structures deeper than the

rhizomes whose elongation we were quantifying. The transect part of the study

ended at this point.

Whiteleaf Manzanita

In this study, manzanita can best be characterized as starting weak and finishing

strong. It was almost nonexistent at the beginning of the study with only 600

plants per acre, a trace of foliar cover, and a mean height of 0.24 foot (table 2). By

the end of the study, however, average density had increased to 1,100 plants per

acre, foliar cover to 2,200 ft2 per acre, and height to 4.25 feet.

Forbs

The most common forbs, present throughout the study period, were Galium

bolanderi A. Gray, Polygola cornuta Kellogg, and Vicia americana Willd. Although

present in 1986, these and other forbs were few, poorly distributed, and

consequently not quantified. In 1987, average forb density was 867 plants per

acre, foliar cover was 400 ft2 per acre, and height was 0.71 foot (table 2). In 1990,

forb density had increased to 7,333 plants per acre, foliar cover to 467 ft2 per acre,

and height to 1.6 feet. Because few forbs were present in 1996, they were not

quantified.

Grasses

Like the forbs, grasses were few and poorly distributed and not measured in

1986. In 1987 they numbered 133 per acre, had only a trace of foliar cover, and

were 0.17 foot tall (table 2). In 1990, the grass population exploded. Average

density of the three plots was 438,400 plants per acre, foliar cover was 2,400 ft2

per acre, and height was 1.3 feet. By the end of the study in 1996, density had

decreased to 37,600 plants per acre, and foliar cover to 600 ft2 per acre, but height

had increased to almost 1.9 feet.

Discussion

The diversity, density, foliar cover, and height values of the various species and

categories of species in this study portray the dynamic nature of this plant

community and provide an idea of its future composition. The many adaptations

of bearclover, especially its reproductive mode, enabled it to dominate early and

to maintain this status for at least the first 5 years of the study. However, by the

end of the study 6 years later, the planted ponderosa pines were impacting the

bearclover, particularly its foliar cover. Normal development would have been

for bearclover cover to increase during the entire study period, not decrease as it

did in 1996. Thus, by the end of the study, the community was dominated by

both ponderosa pine and bearclover.
USDA Forest Service Research Note. PSW-RN-423. 1999. 6

As components of the plant community, the other species/categories

contributed less during the study. Whiteleaf manzanita was able to begin,

increase, and develop well in an environment of extremely strong competition.

The grasses were enigmatic. Their presence, especially in terms of density, was

slight for the first 4 years, then high, and then modest at the end of the study.

That the grasses became very dense the fifth growing season meant that they had

to do so in an atmosphere of strong and rapidly increasing competition. The

trend of increasing density and development of whiteleaf manzanita, and the

low early density, peak, and decline of the grasses also was noted in a previous

study in the central Sierra Nevada.16 The forbs were the most ephemeral of the

species/categories in this study, but they too had some success (7,333 plants per

acre) in 1990 or during the fifth growing season.

Cheatgrass (Bromus tectorum L.) comprised most of the grass population and

was the species that exploded in 1990. Where it came from is a mystery. It was

not abundant in the surrounding forest, and how it could become abundant

quickly is unknown.

Based on the density and development of the various species/categories in

this study, the composition of the plant community in the near future can be

postulated. Certainly, the main constituents will be ponderosa pine and

bearclover, with whiteleaf manzanita a lesser component. The forbs will be few

and consist of those species that can persist in a shady, competitive environment.

The contribution of the grasses in the near future is more difficult to estimate, but

it is likely that some also will persist in small openings in the bearclover or under

the pines.

McDonald and Everest17 studied the planted ponderosa pine/bearclover/

cheatgass interaction on a similar site on the same USDA Forest Service district.

Results were somewhat similar. Cheatgrass was not present the first year,

invaded the second year, and exhibited a high density the fourth year (130,300

plants per acre), which was the last year of the study. Also after 4 years,

bearclover averaged 282,000 stems per acre, a foliar cover of 27,400 ft2 per acre or

63 percent, and 1.2 feet of height.

That bearclover rhizomes elongated for 2 years after disturbance, developed

very little the third year, and then occupied new territory from deep underground

structures the fourth year, adds to the confusion on when, where, and how

bearclover spreads over the landscape. Numerous observers have noted the

remarkable lack of mature bearclover extension into treated areas, the propensity

of bearclover to sprout in the centers of disturbed areas,18 the lack of extension of

rhizomes from disturbed areas into undisturbed areas, and the sporadic nature

of rooting from nodes of extending rhizomes. Plainly, much more study is

needed.

Extensive literature and numerous observations denote the propensity of

bearclover to produce abundant flowers almost every year. But how much sound

seed is produced by these flowers, and how many plants originate from this seed

is not addressed in the literature. In any case, the proportion of reproductive

tissue in bearclover is very low, with only 0.4 percent of above-ground biomass

allocated to flowers and fruits.7 This supports the finding that sprouting from

underground rhizomes is the primary reproductive mode. Nevertheless, it is

likely that the seed serves the species well. Where bearclover is present,

vegetative propagation keeps the species in place; where bearclover is absent,

the seed allows it to potentially colonize new areas. Of course, disseminators

such as birds, rodents, and perhaps other animals are necessary.

End Notes and References

1

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

California Press; 1,400 p.

2

Little, E.L., Jr. 1979. Checklist of United States trees (native and naturalized). Agric. Handb. 541.

Washington, DC: Forest Service, U.S. Department of Agriculture; 375 p.
USDA Forest Service Research Note. PSW-RN-423. 1999. 7

3

Potter, D.A. 1985. Control of bear clover. In: Proceedings of the 6th annual forest vegetation

management conference; 1984 November 1-2; Redding, CA. Redding, CA: Forest Vegetation

Management Conference; 144-150.

4

Munns, E.N. 1922. Bear clover and forest reproduction. Journal of Forestry 20(7): 745-754.

5

Potter, D.A. 1976. Ecology of bear clover. In: Proceedings of the bear clover conference; 1976 March

17; Sonora, CA; 1-4.

6

Coombes, D.E.; McHenry, W.B. 1984. Bear clover herbicide trials. In: Proceedings of the 5th annual

forest vegetation management conference; 1983 November 2-3; Sacramento, CA. Redding, CA:

Forest Vegetation Management Conference; 135-137.

7

Rundel, P.W.; Baker, G.A.; Parsons, D.J. 1981. Productivity and nutritional responses of

Chamaebatia foliolosa (Rosaceae) to seasonal burning. In: Margaris, N.S.; Mooney, H.A., eds.

Components of productivity of Mediterranean-climate regions—basic and applied aspects. Dr.

W. Junk Publishers, The Hague; 191-196.

8

Lanini, W.T. 1981. Seasonal effectiveness of five herbicides on several Sierran brush species. Davis:

University of California; 92 p. M.S. thesis.

9

Tappeiner, J.C.; Radosevich, S.R. 1982. Effect of bearmat (Chamaebatia foliolosa) on soil moisture

and ponderosa pine (Pinus ponderosa) growth. Weed Science 30: 98-101.

10Heisey, R.M.; Delwiche, C.C.; Virginia, R.A.; Wrona, A.F.; Bryan, B.A. 1980. A new nitrogen-fixing

non-legume: Chamaebatia foliolosa (Rosaceae). American Journal of Botany 67(3): 429-431.

11Furman, T.E. 1959. The structure of the root nodules of Ceanothus sanguineus and Ceanothus

velutinus, with special reference to the endophyte. American Journal of Botany 46: 698-703.

12Newcomb, W.; Heisey, R.M. 1984. Ultrastructure of actinorhizal root nodules of Chamaebatia

foliolosa (Rosaceae). Canadian Journal of Botany 62: 1697-1707.

13Adams, R.S. 1969. How to cure mountain misery. Sacramento: California Division of Forestry; 23 p.

14Gibbens, R.P.; Schultz, A.M. 1963. Brush manipulation on a deer winter range. California Fish and

Game 49(2): 95-117.

15Anderson, M.K. 1997. A study to retrieve the traditional ecological knowledge of Sierran tribes

regarding the former uses, management, and fire ecology of bearclover (Chamaebatia foliolosa).

Unpublished draft supplied by author.

16Potter, D.A. 1997. Results of herbicide trials in low-elevation pine plantations of the Central and

Southern Sierra Nevada. In: Proceedings of the 18th annual forest vegetation management

conference; 1997 January 14-16; Sacramento, CA. Redding, CA: Forest Vegetation Management

Conference; 21-33.

17McDonald, P.M.; Everest, G.A. 1996. Response of young ponderosa pines, shrubs, and grasses to

two release treatments. Res. Note PSW-RN-419. Albany, CA: Pacific Southwest Research Station,

Forest Service, U.S. Department of Agriculture; 7 p.

18Fredrickson, E.A. 1994. Efficiency of forest vegetation control with herbicides. Corvallis: Oregon

State University; 204 p. M.S. thesis.
The Authors

Philip M. McDonald is Research Forester and Gary O. Fiddler is Supervisory

Forester with the Pacific Southwest Research Station’s Western Forests Ecology

and Silviculture Laboratory, 2400 Washington Avenue, Redding, CA 96001.

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