9. Bishop Creek Ponderosa Pine
(Merced River)
(Talley 1979)
Location
The Bishop Creek Ponderosa Pine candidate RNA lies
within the Mariposa Ranger District in the NW. part of
the Sierra National Forest. It is 10 miles (16 km) SW. of
Yosemite Valley, bordered on the N. by Bishop Creek, on
the SW. by S. Fork Merced River, and on the E. by
Yosemite National Park in Mariposa County. The cRNA
comprises portions of sects. 1, 12, and 13 in T4S, R20E,
and sects. 5, 8, and 17 T4S, R21E SBM, (37°34'N.,
119°41'W.), USGS Yosemite SW 7.5' quad (fig. 18).
Ecological subsection – Lower Batholith (M261Ep).
Target Element
Pacific Ponderosa Pine (Pinus ponderosa)
Distinctive Feature
Figure 18—Biship
Creek Ponderosa
Pine cRNA
This cRNA contains typical stands of the Pacific
ponderosa pine forest type. Undisturbed samples of this
type are extremely rare in the S. Sierra Nevada. This area
also contains extensive stands of scrub forest that form
ecotones between conifer forest and the chaparral, mixed evergreen forest, and
oak woodland communities occurring at lower elevation.
Physical Characteristics
Dashed line = Ecological
study area; Solid gray line = The ecological survey area covers 1764 acres (714 ha), including the area N. of
the cRNA (1140 acres [461 ha]). Elevations are 3200-4700 ft (975-1432 m).
RNA Boundary
Topographically, two basic types occur within the area: steep slopes rising from
the S. Fork Merced River on the W. and a gently sloping terrace on a ridge
separating the Bishop Creek and Alder Creek watersheds.
Information on geology, soil, and climate is not available.
Association Types
Vegetation was field mapped according to dominant species. Representative
stands of forest types were sampled using 75- by 100-ft (0.07-ha) plots to produce
an importance value. Three types were delineated.
Chaparral (37510, 37520): 116 acres (47 ha). Chaparral occurs on S. to SW.
exposures between 3480 and 5410 ft (1060-1650 m), mostly in the N. third of the
survey area. Slope at chaparral sites is usually 20-35°. Cercocarpus betuloides is
dominant, accounting for approximately 45 percent of combined herb and shrub
stratum cover. Ceanothus cuneatus contributes another 25 percent cover. Another 5-10
percent cover may be contributed by Arctostaphylos viscida, A. mariposa, and annual
grasses (mostly Bromus tectorum). Other associated species are Pinus sabiniana,
Eriodictyon californica, Fremontia californica, and Rhamnus crocea var. ilicifolia.
Scrub Forest (71322): 57 percent of the study area, 1013 acres (410 ha), consists of
steep to moderate W., SW., and SE. exposures and less-steep S. exposures vegetated
by a scrub forest. Scrub forest forms a transitional community between chaparral
and pon-derosa pine forest with dominants coming from chaparral (Ceanothus cuneatus,
Arctostaphylos viscida, Cercocarpus betuloides), oak wood-land (Aesculus californica, Pinus
sabiniana, Quercus wislizenii), mixed evergreen forest (Quercus chrysolepis and Q.
kelloggii), and ponderosa
pine
forest
(Pinus
ponderosa and Quercus
kelloggii) (fig. 19). At one
site, hybrids between
Quercus wislizenii and Q.
kelloggii (Q. x morehus)
also occur. Abundance of
sprout clusters of Q.
chrysolepis and Q. kelloggii
(44 acres [18 ha]) within
the scrub forest suggest
that large areas might
develop into mixed
evergreen
forest
if
disturbance, presumably
by fire, was less frequent.
The
transition
from
chaparral to scrub forest is
usually manifest as a
gradual increase in sprout
clusters of oak (Q.
wislizenii, Q. chrysolepis, Q. kelloggii) or Pinus sabiniana, or both, accompanied by a decrease
in dominance of Cercocarpus betuloides and Ceanothus cuneatus. Conversely, the
transition from scrub forest to mixed conifer forest is usually well defined, as
along the crests of ridges with scrub forest predominant on S. to W.
exposures and ponderosa pine dominant on relatively level terrain on N.- to
W.-facing exposures. Within the mixed conifer forest, local areas with S.
exposure and rocky soil support patches of scrub forest despite the existence
of ponderosa pine on nearby slopes that are tall enough to cast shade onto
these regions.
Mixed Conifer Forest (84210): This type occurs over approximately 568 acres
(230 ha). At least three phases of mixed conifer forest occur within the area:
Open Pinus ponderosa-Quercus kelloggii forest with a dense understory of
Chamaebatia foliolosa, closed Pinus ponderosa-Quercus kelloggii forest with a
sparsely vegetated understory, and riparian conifer forest dominated by incensecedar (Libocedrus decurrens).
Forests on gently sloping terrain (6°-19°) between 4000 and 4800 ft (12201465 m) are typically open stands of Pinus ponderosa with occasional Quercus
kelloggii and incense-cedar. Except for sites dominated by young trees, the forest
understory possesses well-developed populations of Chamaebatia foliolosa
penetrated by clusters of Arctostaphylos mariposa, A. viscida, and increasingly, by
saplings of incense-cedar and Pinus ponderosa. Localized xeric areas within the
open Pinus ponderosa-Quercus kelloggii forest that are not exposed or rocky
enough, or both, to support scrub forest are vegetated by stands of scrubby Q.
kelloggii with understories of Arctostaphylos mariposa and Chamaebatia foliolosa.
Riparian mixed conifer forest occurs above 4000 ft (1220 m) on level to
gently sloping topography along Bishop Creek. Here incense-cedars occur
among mature specimens of Pinus ponderosa, Quercus kelloggii, Alnus rhombifolia,
Abies concolor, Corylus cornuta, and Cornus nuttallii. Dominant incense-cedars at
these sites all appear to be the same age. Large Pinus ponderosa and Quercus
kelloggii are present, but neither species has vigorous specimens in the
understory. Incense-cedar saplings, however, appear to be maintaining a steady
growth rate.
Figure 19—Bishop
Creek Ponderosa
Pine, looking south
up the South Fork
Merced River from
approximately 4265 ft.
(1300 m) elevation.
Vegetation in the foreground is scrub forest,
a mixture of chaparral,
oak woodland, mixed
evergreen forest, and
mixed conifer forest
species, which dominates warm-xeric
slopes below the ponderosa pine phase of
mixed conifer forest.
(1979)
Below 3600 ft (1100 m) incense-cedar is rare except on steep N.-facing slopes
and along streams. Besides an occasional Pseudotsuga menziesii or Pinus sabiniana,
Pinus ponderosa is the only conifer present in the lower-elevation mixed conifer
forests. Tree stratum cover of Quercus kelloggii increases such that the forest
canopy is now continuous, and the herb stratum can support only a
discontinued cover of Chamaebatia foliolosa. Examples of woody species present
in closed Pinus ponderosa-Quercus kelloggii forest, but rare or absent in open Pinus
ponderosa-Quercus kelloggii forests at higher elevation, are Umbellularia californica,
Aesculus californica, Toxicodendron diversiloba, and Ceanothus thyrsiflorus. Quercus
chrysolepis is infrequent in both open and closed canopy Pinus ponderosa-Quercus
kelloggii forests except along the bottoms of small ravines.
Fire/Insect: Some trees show fire scars from fires that occurred before 1930. Fire
suppression in the area started in the 1920s. A fire interval of 5 to 15 years in the
area is estimated for the century before approximately 1870. Bark beetle activities
prevailed in the 1970s. Mortality rate of ponderosa pine caused by the insects
was about 5 percent during 1978 and 1979.
Plant Diversity
A list of plant species in the area was not provided.
Conflicting Impacts
No major conflicts in land use have been identified.
Under current conditions, uncontrolled fire entering the area could
eliminiate much of the canopy of the best-developed terrace ponderosa-pineCalifornia black oak forest. Fire/fuel management plan need to be developed to
maintain the target element.