Bishop Creek Ponderosa Pine

The ecological survey area covers 1764 acres (714 ha), including the area north of the cRNA (1140 acres [461 ha]). Elevations are 3200-4700 ft (975-1432 m). Topographically, two basic types occur within the area: steep slopes rising from the South Fork Merced River on the west and a gently sloping terrace on a ridge separating the Bishop Creek and Alder Creek watersheds. 

This cRNA contains typical stands of the Pacific ponderosa pine forest type. Undisturbed samples of this type are extremely rare in the southern 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.  

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 south to southwest exposures between 3480 and 5410 ft (1060-1650 m), mostly in the northern 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 west, southwest, and southeast exposures and less-steep southern exposures vegetated by a scrub forest. Scrub forest forms a transitional community between chaparral and ponderosa pine forest with dominants coming from chaparral (Ceanothus cuneatus, Arctostaphylos viscida, Cercocarpus betuloides), oak woodland (Aesculus californica, Pinus sabiniana, Quercus wislizenii), mixed evergreen forest (Quercus chrysolepis and Q. kelloggii), and ponderosa pine forest (Pinus ponderosa and Quercus kelloggii). 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 southern to western exposures and ponderosa pine dominant on relatively level terrain on north- to west-facing exposures. Within the mixed conifer forest, local areas with southern 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 incense-cedar (Libocedrus decurrens).

Forests on gently sloping terrain (6°-19°) between 4000 and 4800 ft (1220-1465 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.

Below 3600 ft (1100 m) incense-cedar is rare except on steep north-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 eliminate much of the canopy of the best-developed terrace ponderosa-pine-California black oak forest. Fire/fuel management plan need to be developed to maintain the target element.