Understory

The Lyon Peak/Needle Lake Research Natural Area (LNRNA) is located within the Truckee Ranger District of the Tahoe National Forest. It represents the mountain hemlock (Tsuga mertensiana) target element for the Northern Sierra Nevada Physiographic Province of California. Located just west of Lake Tahoe, the LNRNA also includes other Sierran montane and subalpine communities, aquatic communities, and geologic features.

Babbitt Peak Research Natural Area occupies the highest crests and surrounding slopes of the Bald Mountain Range, one of the most eastward ranges with typical Sierran coniferous vegetation in this part of California. The coniferous vegetation of the RNA not only includes the previously mentioned pure western white pine forest and Washoe pine forest, but also includes extensive stands of white fir-dominated forest and smaller areas of mixed red fir and western white pine forest. Plant communities with Great Basin affinity include several patches of low aspen forest, extensive areas of big sageb...

Sugar Pine Point Research Natural Area consists entirely of a one square mile (2.6 sq. km) area on a south facing slope of the North Fork American River canyon. The RNA is situated on the slopes and peaks south of Sugar Pine Point, a 6325 ft (1928 m) elevation promontory at the southern terminus of the divide between Big Valley Canyon and Little Granite Creek. Most of the RNA consists primarily of a bowl-shaped slope enclosed by descending ridges on the east and west edges of the section. Within this overall form, additional relief is present as small drainages and benches. Topography is gener...

The American Canyon Research Natural Area (ACRNA) is characterized by the presence of Coulter pine forest, northern mixed chaparral, Central Coast live oak riparian forest, and valley needlegrass grassland. Seven plant species found within the area are listed by the California Native Plant Society as rare, threatened, endangered, or of limited distribution; one of these is a forest sensitive species. Most of the vegetation in the ACRNA burned in 1939. The patches left untouched by this fire had burned in previous fires in 1921 and 1926.

The Peavine Point Research Natural Area is distinguished by the presence of old growth westside Ponderosa pine forest. Other plant communities include black oak forest, canyon live oak forest, Sierran mixed conifer forest, and white alder riparian forest. Most of the area lies on the south slope between Peavine Ridge and the South Fork of the American River drainage. Grandiorite underlies most of the unit, while Tertiary volcanic rocks cap Peavine Ridge directly north of the area. Soils are predominantly of the Mariposa and Josephine series.

The Church Dome Research Natural Area (CDRNA) is underlain primarily by granitic basement rocks. However, a small area long the southeastern boundary is Pleistocene basalt flow. This forms the top and sides of Black Mountain. The CDRNA occupies a part of the southeast-flowing Manter Creek drainage. This broad basin (up to 4 miles or 6.4 km wide) is rimmed on the northwest by the Sirretta Peak highlands (approximately 10,000 ft. 3048 m elevation), and the south by the precipitous battlements and spectacular chasms and escarpments of Church Dome.The RNA contains a large portion of the southern M...

The King Creek Research Natural Area (KCRNA) is underlain primarily by gabbroic basement rocks, with small areas of granitic rock in the southern portion. The KCRNA occupies part of the upper drainage of the southwest-flowing King Creek. This is a relatively small drainage heading at the Cuyamaca Peak-Japacha Peak ridge just northeast of the RNA and flowing into Conejos Creek. The western part of the RNA is bounded by the Boulder Creek Road and the southern part by private land. Highest elevations are in the northeast near the summit of Cuyamaca Peak and lowest elevations are along the bottom ...

The Millard Canyon Research Natural Area occupies the eastern side of the Middle Branch of Millard Canyon, a tributary of the San Gorgonio River. Although located within the drainage of the Salton Sink in the southeastern portion of the San Bernardino Mountains, the vegetation is distinctly cismontane with only a small interior-desert influence. Slope aspect is varied with north, south, and west exposures predominating.

Grass Lake Research Natural Area contains the largest sphagnum bog in California. The RNA is a diverse mosaic of wetland communities in a montane valley, on the rim of the Lake Tahoe Basin. Six different terrestrial communities are represented: sphagnum bog, montane meadow, Jeffrey pine forest, red fir forest, lodgepole pine forest, and aspen riparian forest.More than 270 species of vascular plants have been identified from the RNA vicinity. Tree species occurring in the RNA include red fir (Abies magnifica), western white pine (Pinus monticola), lodgepole pine (Pinus contorta var. murrayana) ...

The Agua Tibia Research Natural Area contains three major vegetation types: bigcone Douglas-fir (BCDF) forest, montane manzanita chaparral, and canyon live oak forest. The area contains two Forest sensitive plants, both of which are listed by the California Native Plant Society. Aside from BCDF, it contains six plant species at or near the southern extent of their range.