Sierra National Forest
Chapter 1: Assessing Terrestrial Ecosystems, Aquatic Ecosystems, and Watersheds

Figures

Figure 1.1 Ecological sections of California showing context for Sierra National Forest
Figure 1.2 Ecological Subsections from Miles and Goudey (1997) overlain with the Sierra National Forest and the county boundaries
Figure 1.3 West facing foothill woodland dominated by blue oak and interior live oak above Big Creek, Fresno County, CA on April 5, 2009. (Sacate Ridge Research Natural Area, High Sierra Ranger District)
Figure 1.4 Montane mixed conifer forest near Nelder Grove; this stand is in a population of the Forest Service Sensitive lady’s slipper orchid (Cypripedium californicum)
Figure 1.5 Illustration of different habitats with subalpine habitat around portal lake in the foreground, alpine habitat on the ridge in the background. Photo by J. Clines
Figure 1.6 Subalpine meadow near Alstot Lake, Madera County. John Muir Wilderness. Photo J. Clines
Figure 1.7 Departure of the average Fire Return Interval (FRI) as compared with an average historical condition for Sierra National Forest, in percent
Figure 1.8 Wilderness areas within Sierra National Forest
Figure 1.9 Sierra National Forest wildlife habitats defined by the California Wildlife Habitat Relationship (CWHR) system
Figure 1.10 Vegetation canopy cover density in Sierra National Forest based on the California Wildlife Habitat Relationship (CWHR) habitat types
Figure 1.11 Vegetation size distribution in Sierra National Forest based on the California Wildlife Habitat Relationships (CWHR) habitat types

Tables

Table 1.1 Summary of ecological sections in the SNF. Displays subsections along with the designations of Miles and Goudey (1997) and identifies the characteristics of the vegetation of these broad zones, with special attention to features unique to the SNF
Table 1.2 Federally listed threatened, endangered, proposed and candidate wildlife species and Forest Service Sensitive species that are known to occur, or have the potential to occur within the Sierra National Forest
Table 1.3 Current Sierra National Forest wildlife habitats as defined by the California Wildlife Habitat Relationships (CWHR)
Table 1.4 Channel sensitivity and stability data

Landscape Setting


Overview

The Sierra National Forest encompasses 1.3 million acres (precisely 1,275,152 acres) of land and waters, with about 42 percent (528,000 acres) designated as Wilderness. The Forest is located along the west slope of the central-southern Sierra Nevada. Elevations range from 900 feet at Pine Flat Reservoir to nearly 14,000 feet at the summit of Mount Humphreys (13,986 feet) along the Sierra Crest. Climate generally consists of warm, dry summers and cool, moist winters at the lower elevations, with harsher winters as elevation increases. Mean annual precipitation is 20 to 60 inches with most falling as snow above about 5,000 feet elevation.
The enormous elevation span of over 12,000 feet, combined with the variability in aspect and slope created by three deep river canyons, a variety of geology and soils, and precipitation primarily as rain at low elevations and snow at high elevations, combine to create an extremely high diversity of ecosystems across the Forest. Indeed, the Sierra National Forest is inhabited by over 1400 taxa (species, subspecies, varieties), of vascular plants, about 300 species of bryophytes (mosses, hornworts, and liverworts), several hundred species each of lichens and fungi; and approximately 346 species of fish and wildlife: 31 fish species, 13 amphibian species, 198 bird species, 82 mammal species and 22 reptile species.

The Sierra National Forest’s geomorphic foundation primarily consists of an uplifted, westward-titled Sierra Nevada block that has been deeply incised by large rivers, such as the Merced, San Joaquin and Kings Rivers, as well as their tributaries. Bedrock is primarily granite, along with limited metamorphic and volcanic presence, as well as glacial deposition in the lower river valleys. Terrain is dominated by steep slopes and rocky canyons intermixed with low slopes and flat areas. Some areas of the Forest contain unusual rock types like limestone/marble and gabbro that create unique soil chemistry that support unique plant communities and often harbor rare plant species. For example, there is a relatively large vein of limestone in the Kaiser Wilderness in Fresno County, where unique plant species such as the rare moonwort ferns (Botrychium ascendens, B. crenulatum) are found at meadow edges. The metamorphic rock type (phyllite) found in the Merced River drainage contains the entire world distribution for two plant species: Congdon’s woolly sunflower (Eriophyllum congdonii)and the Merced clarkia (Clarkia lingulata).

Influences of Past Management

The Sierra National Forest has been largely affected by fire suppression for almost a century. As a result, live and dead fuels have increased to abnormally high levels of abundance, greater than the natural range of variability. However, it is important to keep in mind that forest areas that have missed the largest number of fire return intervals in California are burning predominantly at low/moderate-severity levels, and are not experiencing higher fire severity than areas that have missed fewer fire return intervals (Odion and Hanson, 2006, 2008, van Wagtendonk et al. 2012).

Historical logging, livestock grazing and residential development also have influenced current ecological conditions and management across the landscape. For example, prior to the mid-1900s, and to a less extent from the mid-1900s to the early-1990s, logging in Sierra National Forest, primarily within the lower and mid-slope areas (3,000 to 7,000 ft.), typically consisted of removing many of the largest overstory trees. This was particularly significant in what is now the Bass Lake Ranger District, as a result of extensive railroad logging between the late 1880s through the 1930s. These actions resulted in substantial reductions of sugar, ponderosa and Jeffery pine forests.

Late 19th century and early 20th century descriptions of the pre-European settlement mixed conifer and pine stands in the Sierra Nevada indicate that forest structures were dominated by uneven-aged tree distribution (Dunning, 1923; Show and Kotok, 1924). Dunning and Reineke (1933) remark, “In relatively few sections of this large region are the stands uniform in age…. Stands are usually made up of small even-aged groups, the ages of the groups differing by periods of 10 to 20 years.” The results of this past work in the early 1900s has shown that the historical forest, prior to the era of fire suppression, was composed of multiple age/size classes distributed in patches of varying sizes and shapes across the landscape (North et al. 2012). Research also shows that the historical forest was more open and comprised of widely spaced, large diameter trees (Sudworth, 1900; Stephens, 2001; Stephens and Elliott-Fisk, 1998; Stephenson and Calcarone, 1999). A majority of these trees were pine species with fewer shade tolerant, fire sensitive species, such as white fir and incense cedar found in stands subject to frequent fire (Minnich et al. 1995; Barbour et al. 2002). Reconstruction of historical forests in the Sierra Nevada showed that trees greater than 24 inches diameter at breast height (dbh) dominated Sierra Nevada forests (Taylor 2003). Reconstruction of ponderosa pine forests in the intermountain west (Arno and Scott 1995) also confirmed that large trees dominated those forests. Leiberg (1902), however, in addition to reporting that some areas were open and park-like (and dominated by ponderosa pine, Jeffrey pine, and sugar pine), also reported that other areas were dominated by white fir, incense-cedar, and Douglas-fir, especially on north-facing slopes and on lower slopes of subwatersheds; such areas were predominantly described as dense, often with “heavy underbrush” from past mixed-severity fire. (Leiberg 1902). Similarly, USDA Timber Survey Field Notes from 1910-1912 show that historic ponderosa pine and mixed-conifer forests of the central/southern Sierra Nevada [western slope] varied widely in stand density and composition; open and park-like pine-dominated stands comprised a significant portion of the lower montane and foothill zones, but dense stands dominated by fir and cedar, and by small/medium-sized trees, dominated much of the middle montane zone (it should be noted that the old-growth forests chosen for study by Scholl and Taylor 2010 and Collins et al. 2011 comprised only a very small portion of the 1910-1912 Stanislaus data set). (USDA 1910-1912).

The research on historic stand structure and composition supports the idea that selective logging and fire suppression have reduced the number of large trees, increased the density of smaller trees, and shifted composition toward shade tolerant fir and cedar. These past cumulative factors, combined with fire suppression since the 1920s, have reduced landscape-level ecosystem heterogeneity, as well as created abnormally high levels of fuel loads. This is particularly evident in current conditions with extensive areas dominated by shade-tolerant conifers, especially white fir and incense cedar. The extensive fire suppression, as well as limitations for mechanical forest restoration work during recent decades, also has reduced some meadow, oak and shrub habitat as a result of high coniferous tree density and tree encroachment. Overall, this loss of vegetation heterogeneity has detrimentally affected wildlife habitat diversity, as well as reducing ecosystem resilience affected by stressors, such as climate change. In particular, in regard to heterogeneity, there is likely a deficit of complex early seral forest on the landscape due to fire suppression, past and recent salvage logging, past and recent post-fire reforestation efforts, and past and recent mechanical treatments designed to prevent high-severity fires. Such early seral forest is created primarily by mixed-severity fire but even when such fire occurs, complex early seral forest will only exist when a) the pre-fire area contained elements necessary to create complex early-seral forest (e.g., dense mature forest versus plantations), and b) the post-fire area is not i) salvage logged or ii) reforested via human intervention. (See Chapter 1, Bioregion, "Complex Early Seral Forest").

During the last two decades, Sierra National Forest has made progress in improving and sustaining ecological heterogeneity within the natural range of variability. Some major actions include integrating more wildfire back into fire adapted ecosystems, retaining and developing large live and dead tree structures, and conducting tree thinning to develop and maintain forest heterogeneity, including forest canopy gaps and reducing tree encroachment into meadows and shrub patches (North et al. 2009, North ed. 2012). Although current management in the Sierra National Forest has made important strides toward integrating and sustaining ecological heterogeneity, additional restoration actions, adaptive management and research are needed to fully meet these ecosystem restoration goals.
Ecological Burning in the Sierra Nevada: Actions to Achieve Restoration

Terrestrial Ecosystems


Vegetation

The 12,000 foot elevation range of the forest is reflected in the high diversity of the vegetation. Broad vegetation zones can be seen going from west to east: foothill woodland and foothill chaparral in the low elevations at the western edge of the Forest (and extending up the river canyons) to ponderosa pine and mixed conifer forest at mid-elevations, to red fir/lodgepole pine forests even higher, to subalpine forests and treeless alpine vegetation at the highest elevations. Massive areas of rock outcrops (mostly granitic) occur throughout all of these vegetation types, as well as shrublands (chaparral) dominated by various species of oak, manzanita, and Ceanothus, and meadows, fens and riparian vegetation where moist conditions prevail. Herbaceous plant species contribute the most to species richness, either as understory species or as dominant members of plant communities such as meadows or grasslands. This existing condition description will use the Ecological Subregions of California, Section and Subsection Descriptions as a broad context for understanding the pattern of distribution of vegetation types in the Sierra National Forest (Miles and Goudey, 1997). Map 1 shows the Sections within California: the Sierra NF falls into Sections M261F and M261E. The Subsections will be shown and described next.

Figure 1.1—Ecological sections of California showing context for Sierra National Forest
Ch1_Sierra_Fig01.1.png
Figure 1.1—Ecological sections of California showing context for Sierra National Forest


The species diversity and number of different plant communities in the Sierra National Forest are both remarkably high, reflecting the variety of growing conditions resulting from differences in elevation, geology, moisture, temperature, soils, sunlight, slope, aspect, and disturbance regimes such as fire, avalanches, floods, and human activities. The native vegetation is also relatively intact compared to other parts of California (e.g. the central Valley, Southern California), with few to no non-native species at higher elevations.

Non-native plants make up a smaller proportion of all species in each major vegetation zone as elevation increases. An example from adjacent Yosemite National Park is given by Botti (2001), who wrote that 23 percent of plant species were non-native in the lower elevation chaparral/oak woodland zone of the Park, 13 percent of species in the mixed conifer zone were non-native, 5 percent of species in the upper montane zone were non-native, and only 0.5 percent were non-native in the subalpine zone. The alpine zone had no non-native species documented. This pattern appears true for neighboring lands in the Sierra National Forest as well. Extensive surveys of the high elevation wilderness over the past few decades have revealed very few non-native plants in the subalpine zone and no non-native species in the alpine zone.

As mentioned above, over 1400 vascular plant taxa have been documented to occur within the Sierra National Forest. Approximately 25 % of these are not native, and about 100 are so aggressive and damaging to ecosystems that they are classified as noxious weeds or invasive non-native plants (see Chapter 3). About 50 are so rare or face enough threats that they are maintained on the Regional Forester’s Sensitive Plant list, and one, the Mariposa pussypaws (Calyptridium pulchellum) is listed by the US Fish and Wildlife Service as Threatened. The Region 5 Sensitive Plant List is being revised in 2013, resulting in over 50 species being maintained as Forest Service Sensitive and about three species being removed from the list as they were found to be more common than previously thought. Chapter 5 provides details on these species at risk.

Figure 1.2—Ecological Subsections from Miles and Goudey (1997) overlain with the Sierra National Forest and the county boundaries
Ch1_Sierra_Fig01.2s.png
Figure 1.2—Ecological Subsections from Miles and Goudey (1997) overlain with the Sierra National Forest and the county boundaries


Table 1.1—Summary of ecological sections in the SNF. Displays subsections along with the designations of Miles and Goudey (1997) and identifies the characteristics of the vegetation of these broad zones, with special attention to features unique to the SNF

Ecological Section Number and Name (see Map 1)
Subsection Number
Subsection Name (See Map 2)
Unique features within the Sierra NF in this series
M261F – Sierra Nevada Foothills
M261Fc
Lower Granitic Foothills
Contains much of the blue-oak woodland in the Forest, about half of the rare tree anemone populations.
M261E – Sierra Nevada
M261Eg
Upper Foothills Metamorphic Belt
Metamorphic Paleozoic marine sedimentary rocks predominate. No ultramafic on the Forest in this region, though it is abundant adjacent. Chaparral dominated by chamise occurs in this part of the Forest. Knobcone pine occurs only within this belt. Many rare and endemic plants found here, including the Forest endemic Merced clarkia (State listed Threatened).
M261E – Sierra Nevada
M261Ep
Lower Batholith
Contains the remainder of the unique foothill chaparral that is lacking chamise and about half the rare tree anemone populations. Mixed conifer forest prevails at higher elevations. Contains Nelder Grove, one of the Forest’s 2 giant sequoia groves. The southern limit of Douglas fir in the Sierra Nevada occurs near Shaver Lake.
M261E – Sierra Nevada
M261Eq
Upper Batholith
Mixed conifer, upper montane coniferous forest, and subalpine forest, some in designated wilderness. Contains McKinley Grove of giant sequoias; the southernmost limit of douglas fir in the Sierra Nevada. This zone is rich in peatlands (fens) and meadows. The effects of past unregulated timber management, fire exclusion, and overstocking of livestock are particularly evident in this zone.
M261E – Sierra Nevada
M261Eo
Glaciated Batholith
Subalpine and Alpine zone, mostly in wilderness.

Foothill Zone

The foothill zone of the Sierra National Forest captures a small proportion of the western foothill belt which is mostly in private ownership throughout the Sierra Nevada. Because of this, the small amount of this biologically diverse vegetation type that is in public ownership is disproportionately important for long-term conservation (i.e. not subject to habitat loss from commercial and residential development).

This vegetation zone falls within Sierra Nevada Ecological Section M261F – Sierra Nevada Foothills – Subsection M261Fc (Lower Granitic Foothills) in the USDA Forest Service National Hierarchical Framework of Ecological Units and the lower part of Section M261Eg Sierra Nevada – Subsection M261Eg (Upper Foothills Metamorphic Belt) (Miles and Goudey, 1997) – See Table 1 above. Varying from gently rolling hills to nearly vertical, cliff-like slopes, this zone is characterized by a Mediterranean climate with long, hot summers, and cool, wet winters where most precipitation falls as rain (20-40 inches). Within the Sierra National Forest, as is typical for the Sierra foothills, the understory biomass is predominantly comprised of non-native plants while paradoxically native species diversity is higher than non-native species. This is primarily due to the presence of non-native annual grasses imported when Europeans arrived hundreds of years ago such as brome (Bromus spp.), wild barley (Hordeum sp.), wild oats (Avena spp.), and annual fescues (Festuca myuros) that form a continuous understory “blanket” while still allowing many natives to persist.

Tree-dominated plant communities are blue oak (Quercus douglasii) woodland or savannah, with foothill pine (Pinus sabiniana), California buckeye (Aesculus californicus), and interior live oak (Quercus wislizenii) present to varying degrees. Figure 1 shows open, southwest-facing slope with blue oak woodland on the north-facing slopes. Other tree-dominated types in the foothills are foothill pine and valley oak forests.


Figure 1.3—West facing foothill woodland dominated by blue oak and interior live oak above Big Creek, Fresno County, CA on April 5, 2009. (Sacate Ridge Research Natural Area, High Sierra Ranger District)
Ch1_Sierra_Fig01.3s.png
Figure 1.3—West facing foothill woodland dominated by blue oak and interior live oak above Big Creek, Fresno County, CA on April 5, 2009. (Sacate Ridge Research Natural Area, High Sierra Ranger District)


The Lower Granitic Foothills, Subsection M261Fc, is the primary Ecological Subsection of 261F within the Forest. This area of hot and sub humid climate and primarily granitic rocks is found on the Forest, north of the Kings River and encompasses part of the San Joaquin River watershed (Figure 1.1). The mixed chaparral found in this area and in the Lower Batholith (Subsection M261Ep) is unique to the Sierra National Forest: it is a diverse mixture of shrubs notably missing chamise (Adenostoma fasciculatum) which is an extremely common if not dominant shrub in chaparral elsewhere in California. Chamise exhibits an inexplicable gap from around the town of Oakhurst in Madera County south to Tulare County. It is not found in the San Joaquin or Kings River watersheds at all, but resumes its presence in the chaparral of the foothills in the Kaweah River Canyon; and is dominant in Mariposa County to the north in the Merced River Canyon.

The distinctive chaparral of eastern Fresno County is dominated by Mariposa manzanita (Arctostaphylos viscida ssp. mariposa), buckbrush (Ceanothus cuneatus), chaparral whitethorn (C. leucodermis), interior live oak (Quercus wislizenii), birchleaf mountain mahogany (Cercocarpus betuloides), western redbud (Cercis occidentalis), flannelbush (Fremontodendron californicum), and yerba santa (Eriodictyon californicum) with many other species adding to a highly diverse and special type of chaparral found only here. The relictual endemic shrub tree anemone (Carpenteria californica) has its natural range in the Sierra NF in this chaparral type, within about a 225 square mile area.

Montane Zone

The lower and mid-elevation conifer vegetation types fall within M261Eg (Upper Foothills Metamorphic Belt) to the north of the Forest, from roughly Jerseydale and the Chowchilla Mountains northward. The mixed conifer forest in this region of the forest is comprised of the typical species making up Sierran mixed conifer forest: ponderosa pine (Pinus ponderosa), sugar pine (P. lambertiana), incense cedar (Calocedrus decurrens), and white fir (Abies concolor), but there is a higher proportion of Douglas fir (Pseudotsuga menziesii) than is found to the south. Another unique tree of this part of the Forest is knobcone pine (Pinus attenuata); a fire-adapted, closed-cone pine that may form solid stands on the ridge tops leading to the Merced River.

Coniferous forest, varying from almost pure ponderosa pine forest at lower elevations to classic Sierran mixed conifer higher up, to red fir (Abies magnifica) forest with jeffrey pine (Pinus jeffreyi) in the rockier sites even higher fall within Subsection 261Ep (Lower Batholith) throughout much of the rest of the Forest. The Forest Service sensitive plant Rawson’s flaming trumpet (Collomia rawsoniana), which is found only in the SNF, is restricted to stream sides and meadow edges in Madera County within the Lower Batholith.

In wetter sites such as around meadows or where the water table remains high in the summer, pure stands of lodgepole pine (Pinus contorta ssp. murrayana) prevail (e.g. in the vicinity of Clover Meadow in Madera County).

Montane chaparral may cover extensive acreage in this zone, sometimes naturally on thin, rocky soils or in response to natural disturbances such as fire or avalanches; or in many cases shrub-dominated areas prevail in areas that have been logged or otherwise disturbed by Forest management activities.
Granitic outcrops are abundant in this zone as well, with many Forest endemics and other rare plants such as the Shuteye Peak fawn lily (Erythronium pluriflorum), Kellogg’s lewisia (Lewisia kelloggii ssp. kelloggii), and the orange lupine (Lupinus citrinus var. citrinus) growing exclusively on rock outcrops.

Figure 1.4—Montane mixed conifer forest near Nelder Grove; this stand is in a population of the Forest Service Sensitive lady’s slipper orchid (Cypripedium californicum)
Ch1_Sierra_Fig01.4s.png
Figure 1.4—Montane mixed conifer forest near Nelder Grove; this stand is in a population of the Forest Service Sensitive lady’s slipper orchid (Cypripedium californicum)


Subalpine and Alpine Zones
The subalpine zone falls within Ecological Subsection M261Eq, Upper Batholith. Coniferous forest types within this zone are upper coniferous forest dominated by red fir and lodge pole pine, with an increasing component of western white pine (Pinus monticola) and some stands of mountain hemlock (Tsuga mertensiana). Whitebark pine is found in harsh, windswept areas of the alpine zone, and singleleaf pinyon (Pinus monophylla) is present in sparse amounts in the high elevations of the SNF, though it is primarily an east slope species.

The subalpine meadows of the SNF are also rich in peatlands (fens) and many are inhabited by Sphagnum moss, which was formerly thought to be rare in the High Sierra. Meadows of the subalpine zone in areas with non-granitic geology are prime habitat for rare moonworts, Botrychium spp., and more of these unusual ferns are being found in the central Sierra each year. The alpine zone is generally referred to as “above timberline” but may have stunted or krummholz or stunted trees, especially of whitebark pine.

Figure 1.5—Illustration of different habitats with subalpine habitat around portal lake in the foreground, alpine habitat on the ridge in the background. Photo by J. Clines.
Ch1_Sierra_Fig01.5.png

Figure 1.6—Subalpine meadow near Alstot Lake, Madera County. John Muir Wilderness. Photo J. Clines.Ch1_Sierra_Fig01.6.png

Riparian ecosystems

Riparian vegetation is found along streams and in meadows, springs, and seeps. Riparian vegetation along streams varies considerably within the Forest, ranging from clearly defined bands of riparian forest dominated by white alder (Alnus rhombifolia), willow (Salix spp)., and Oregon ash (Fraxinus latifolia) to simply a strip of herbaceous riparian plants with upland forest trees growing next to the stream throughout much of the conifer forest belt. Meadows are defined as openings in forests which generally have high water tables and are dominated by herbaceous vegetation that is adapted to wet conditions. Meadows are typically heterogeneous, containing patches of different plant assemblages in response to variations in moisture, drainage, elevation, etc. Overall, meadows can be classified as dry, moist, or wet; and montane, subalpine, or alpine (Ratliff, 1985). Some meadows contain areas of peat soils called fens. Fens are areas of perennial saturation where peat soils form because accumulation of organic matter exceeds decomposition (Cooper and Wolf, 2006). Fens are of significance because of their contribution to hydrologic function in meadows and because they provide habitat for several rare plant species.

Fens

Fens, also called peatlands, are perennially saturated areas, usually within meadows, dominated by mosses and herbaceous wetland vegetation. Fens are important because of their function in meadow water storage, and their role in maintaining water quality and hydrologic integrity in meadows. In addition, several sensitive plant species are found primarily in fen habitats. Fens are defined by having at least 40 cm of organic soil within the top 80 cm that has formed in place and where peat-forming vegetation (generally certain species of sedges and mosses) occurs and is entirely rooted within the peat body (Cooper and Wolf, 2006). In the Sierra Nevada, the type of peatland is termed a fen rather than a bog, because the primary source of water is groundwater, although precipitation contributes water as well (Cooper and Wolf, 2006). Inventories of Sierra Nevada fens began in 2003, and are ongoing. The extent to which livestock grazing and trampling affect fens has been investigated in a preliminary study by Cooper et al. (2006), and will continue to be studied in an attempt to determine the amount of such use fen ecosystems can sustain.

The Sierra National Forest provides a diverse range of aquatic and riparian habitat types, ranging from low elevation ponds in chaparral woodland to glacial tarns near granitic alpine ridgelines. The large elevation range from 900 to nearly 14,000 feet results in a huge diversity of habitats and microclimates for a wide variety of aquatic/riparian species. The SNF also provides a variety of riparian habitats associated with streams (both perennial and seasonal), meadows, springs and lakes. Riparian areas are high in biodiversity due to the water, relative humidity, cooler temperatures and complex cover provided. They also serve as important corridors for species dispersal. There are an estimated 15,750 acres of meadow on the Forest and 465,000 acres of Riparian Conservation Areas (RCA) (USDA-FS 2001 and 2004), associated with streams, meadows, springs and lakes.

Riparian areas in the drier southern Sierra Nevada Mountains provide important habitat diversity and habitat for plants/animals. Riparian areas/habitats encompass everything from rivers and creeks, to meadows and springs. The Sierra National Forest has some very large rivers (such as the San Joaquin and Kings) and numerous small and mid-size creeks as well. Meadows range from extremely large to tiny meadows around springs. Large diverse meadow complexes are found in the wetter areas of the Forest and also the drier portions, because of persistent snowpack and extensive shallow groundwater systems.

The riparian areas of the Sierra National Forest can be divided into four broad categories dominated by: forest/woodland; scrub-shrub vegetation; forb (herbaceous) vegetation or meadow; and graminoid (grasses and grass-like) vegetation or meadow. Riparian forest woodlands can be dominated by a variety of coniferous trees, such as pines, firs and incense cedar), and to a less extent deciduous trees, such as black oaks, white alder, Oregon ash, and cottonwood. Having tall shading cover and a large source of organic matter dead-fall (leaves/needles) provides excellent habitat for a diversity of plants and animals. Scrub-Scrub riparian areas are usually dominated by a diversity of shrub habitats. These types of riparian areas provide a rich dense humid habitat for plants, amphibians, and small birds. Forb/herbaceous riparian areas can be found along small creeks and within dry or wet meadows. These areas are usually dominated with wild onion, lupine, bistort, senecio, or corn lilies. Graminoid dominated riparian areas can also be found along small creeks and within wet meadows. These habitats usually have close to 100 percent cover of sedges, grasses, and rushes (graminoid).

Wildlife


Species Overview

The Sierra National Forest is inhabited by approximately 302 species of terrestrial wildlife: 198 bird species, 82 mammal species and 22 reptile species. Four of those species are classified as federal threatened, endangered, proposed or candidate species under the Endangered Species Act (ESA) (Table 1.2). One of those species, the Valley elderberry longhorn bettle is currently in the process of being delisted by the U.S. Fish and Wildlife Service. An additional 11 species are classified as Forest Service sensitive species known to occur, or have the potential to occur, within Sierra National Forest (Table 1.2). Federally designated critical habitat for terrestrial wildlife species is not present on Sierra National Forest. Additional information pertaining to the federally listed, proposed and candidate species, as well as Species of Conservation Concern (SCC), is provided in the Chapter 5: At-Risk Species of the Bioregional Assessment.

Table 1.2—Federally listed threatened, endangered, proposed and candidate wildlife species and Forest Service Sensitive species that are known to occur, or have the potential to occur within the Sierra National Forest
Common Name
Scientific Name
Status
Sierra Nevada bighorn sheep
Ovis canadensis californiana
Endangered
California condor
Gymnogyps californianus
Endangered
Valley elderberry longhorn beetle
Desmocerus californicus dimporphus
Threatened
Pacific fisher
Martes pennanti pacifica
Candidate, FS Sensitive
Bald eagle
Haliaeetus leucocephalus
FS Sensitive
California spotted owl
Strix occidentalis occidentalis
FS Sensitive
American marten
Martes americana
FS Sensitive
Wolverine
Gulo gulo luteus
FS Sensitive
Sierra Nevada red fox
Vulpes vulpes necator
FS Sensitive
Northern goshawk
Accipter gentiles
FS Sensitive
Great gray owl
Strix nebulosa
FS Sensitive
Willow flycatcher
Empidonax traillii
FS Sensitive
Western red bat
Lasiurus blossevillii
FS Sensitive
Pallid bat
Antrozous pallidus
FS Sensitive
Townsend’s big-eared bat
Corynorhinus townsendii
FS Sensitive

The forests of the montane zone are inhabited by some of the most vulnerable at-risk species of Sierra National Forest, principally the California condor and Pacific fisher. California condors, federally listed as endangered, have only recently been reported flying over the furthest southern portion of the Forest, and none have been reported nesting or perching there. Pacific fisher, a candidate for federal listing, as well as the California spotted owl, which is a Forest Service Sensitive Species and a Species of Conservation Concern, are montane forest species with some of the greatest levels of management concern due to their use of large live and dead tree structures for denning, resting, nesting and perching, as well as their need for areas of high forest canopy cover within portions of their home ranges.

The alpine and subalpine zone of the Sierra National Forest is inhabited by one federally listed species, the Sierra Nevada bighorn sheep. This species, however is rarely sighted in the Forest and primarily limited to the highest elevations at the Sierra Nevada crest, in the John Muir Wilderness Area. The core population of this species is found on the east-side of the Sierra Nevada, within Inyo National Forest and the Sequoia Kings Canyon National Park. Two other species, the wolverine and the Sierra Nevada red fox also historically were found in Sierra National Forest and both are Forest Sensitive Species and Species of Conservation Concern. Both of these species were recently petitioned for federal listing, and they are currently under further review by the U.S. Fish and Wildlife Service. Additional details of these and other at-risk species are provided in Chapter 5 of the Bioregional Assessment.

Habitat Overview

Environment and Past Management

The 1.3 million acres of Sierra National Forest contain a high level of wildlife habitat diversity due to the high diversity of elevations, topography and moisture conditions. Specifically, the Forest has an elevation span of over 12,000 feet extending from the highest elevations of alpine habitats at nearly 14,000 ft. elevation to the lowest elevations with oak woodland and chaparral habitats at about 2,000 ft. elevation. Precipitation primarily occurs during the winter season, and it predominately occurs as rain in low elevations and snow at high elevations.

In addition to the diverse environmental conditions present in the Forest, past management has helped cumulatively create the current conditions of wildlife habitats that we have today. One of the most significant past management influences has been fire suppression beginning during the early 1900s. As a result, live and dead fuels have increased to abnormally high levels of abundance, greater than the natural range of variability. These abnormal conditions are represented by Figure 1.7, which shows the difference between the current average Fire Return Interval (FRI) as compared with the reference condition, which is primarily based on the historic conditions. The higher percentages shown in Figure 1.7 represents the higher divergence from those average reference conditions. It is important to keep in mind, however, that missed fire returns does not equate with higher-severity fire -- forest areas that have missed the largest number of fire return intervals in California are burning predominantly at low/moderate-severity levels, and are not experiencing higher fire severity than areas that have missed fewer fire return intervals (Odion and Hanson, 2006, 2008, van Wagtendonk et al. 2012).

Other management, besides fire suppression, also has affected the current conditions of wildlife habitats. Clear cutting through the 1990s created plantations of trees that are often uniform and lack structural attributes such as large down wood and snags. Further, logging prior to 1992 removed significant numbers of large conifers and often focused on the removal of pines. This homogenized stands and removed important seed sources for pine regeneration. Designated areas, such as wilderness, represent different styles of management. Wilderness Areas make up approximately 42 percent (528,000 acres) of the Forest (Figure 1.8), and these areas typically have not been influenced by active management other than by various degrees of fire suppression. In contrast, areas outside Wilderness Areas, which are generally below the 9,000-10,000 foot elevation, have experienced a wide variety of management as a result of historical logging, livestock grazing and residential development.

Prior to the mid-1900s, and to a less extent from the mid-1900s to the early-1990s, logging in Sierra National Forest, primarily within the lower and mid-slope areas (3,000 to 7,000 ft.), typically consisted of removing many of the largest overstory trees. This was particularly significant in what is now the Bass Lake Ranger District, as a result of extensive railroad logging between the late 1880s through the 1930s.

Residential and other structures are present in limited areas that are in and around the Forest, but primarily within mid-elevation areas between about 3,000 and 7,000 ft. elevation. These developments occur on leased Forest Service land, such as in the Huntington Lake community, as well as on nearby private lands, such as the Sugar Pine and Shaver Lake communities. The locations of these structures have influenced current ecological conditions to some degree as a result of past management designed to reduce and prevent forest fires.

These past cumulative factors, combined with nearly a century of fire suppression, have contributed to reducing overall landscape-level ecosystem heterogeneity and to some extent wildlife habitat diversity. This is particularly evident with abnormally high levels of fuel loads, such as extensive areas dominated by shade-tolerant conifers, especially white fir and incense cedar. The past fire suppression, as well as limitations for mechanical and fire restoration work during recent decades, has reduced meadow, shrub, and black oak habitat, due to high tree density and tree encroachment. Overall, this loss of vegetation heterogeneity can detrimentally affect wildlife habitat diversity, as well as reducing ecosystem resilience to stressors, such as climate change and abnormally high levels of tree disease and pest infestations.

Figure 1.7—Departure of the average Fire Return Interval (FRI) as compared with an average historical condition for Sierra National Forest, in percent
Ch1_Sierra_Fig01.8.png
Figure 1.7—Departure of the average Fire Return Interval (FRI) as compared with an average historical condition for Sierra National Forest, in percent.

Figure 1.8. Wilderness Areas in Sierra National Forest.
WildernessMap3.jpg
Figure 1.8. Wilderness areas in Sierra National Forest.


Habitat Characteristics

Broad-scale Characteristics
Wildlife habitats are identified by using a variety of methods, and an important classification system for California is the California Wildlife Habitat Relationships (CWHR) system - Ver. 8.2 (CDFG 2008). This comprehensive system is used throughout California’s National Forests, and it is the system we use here to provide an overview, or broad-scale filter, of habitats within the Sierra National Forest.

The Sierra National Forest contains 30 terrestrial vegetation types, as well as two aquatic habitat types (riverine and lacustrine), as defined by CWHR (Figure 1.9, Table 1.3). Canopy cover density and size classes of those cover types also are shown in Figures 1.10 and 1.11, respectively. A large percentage of those vegetation types are montane forests, such as mixed-conifer, ponderosa pine, hardwood-conifer, white fir, and at the higher elevations, red fir and lodgepole pine. Subalpine and alpine habitats also cover large areas of the Forest in the Wilderness Areas, such as subalpine conifer, lodgepole pine, tundra (grassland) and rock. Meadow and riparian habitats cover relatively fewer acres, however they also tend to have greater species numbers and diversity per unit area, as compared with most other types of habitats.

Table 1.3—Current Sierra National Forest vegetation types as defined by the California Wildlife Habitat Relationships (CWHR).

Habitat Type (CWHR)
Acres
Alpine Dwarf-Shrub
42,503
Annual Grassland
19,473
Aspen
569
Barren
141,884
Blue Oak Woodland
29,893
Blue Oak-Foothill Pine
6,018
Chamise-Redshank Chaparral
4,906
Closed-Cone Pine-Cypress
379
Cropland
146
Deciduous Orchard
4
Jeffrey Pine
28,585
Juniper
155
Lacustrine
22,489
Lodgepole Pine
32,168
Low Sage
423
Mixed Chaparral
50,657
Montane Chaparral
83,724
Montane Hardwood
148,049
Montane Hardwood-Conifer
77,455
Montane Riparian
3,823
Perennial Grassland
392
Ponderosa Pine
73,574
Red fir
141,303
Riverine
810
Sagebrush
619
Sierran Mixed Conifer
269,921
Subalpine Conifer
179,348
Urban
26
Valley Foothill Riparian
251
Valley Oak Woodland
32,067
Wet Meadow
19,355
White fir
2,556

Figure 1.9—Sierra National Forest vegetation types defined by the California Wildlife Habitat Relationship (CWHR) system
Ch1_Sierra_Fig01.9.png

Figure 1.10—Canopy cover density in Sierra National Forest, based on the California Wildlife Habitat Relationship (CWHR) habitat types.
Ch1_Sierra_Fig01.10.png

Figure 1.11—Vegetation size in Sierra National Forest, based on the California Wildlife Habitat Relationships (CWHR) habitat types.
Ch1_Sierra_Fig01.11.png

Habitats are further classified by combining the three CWHR criteria: vegetation type, size and canopy cover to create primary habitat types, such as those shown in Table 1.4 and Figure 1.12. According to the most recent mapping, the largest habitat coverage in Sierra National Forest are the: mid seral coniferous forests (19.9 percent); hardwood and mixed hardwood /conifer forests (15.1 percent); late seral, closed canopy coniferous forests (11.5 percent); and shrublands (9.7 percent).

Table 1.4. Habitat types of Sierra National Forest using 2010 mapping based on 2007 satellite imagery.





2010 Acreage b
Habitat Type
CWHR Habitat Classes a




Acres
%
Lacustrine (Lakes) and Riverine (Streams, Rivers)
Lacustrine (LAC) and riverine (RIV)
23,115
1.7%
West-slope Shrublands (Chaparral types)
Montane chaparral (MCP), mixed chaparral (MCH), chamise-redshank chaparral (CRC)
134,932
9.7%
Sagebrush
Sagebrush (SGB)
620
0.0%
Oak-associated Hardwoods and Hardwood/Conifers
Montane hardwood (MHW), montane hardwood-conifer (MHC)
209,852
15.1%
Wet Meadow
Wet meadow (WTM), freshwater emergent wetland (FEW)
19,356
1.4%
Coniferous Forest,
Early Seral
Ponderosa pine (PPN), Sierran mixed conifer (SMC), white fir (WFR), red fir (RFR), tree sizes 0-11 inches dbh, all canopy closures
47,153
3.4%
Coniferous Forest,
Mid Seral
Ponderosa pine (PPN), Sierran mixed conifer (SMC), white fir (WFR), red fir (RFR), tree size 11 – 24 inches dbh, all canopy closures
275,854
19.9%
Coniferous Forest,
Late Seral, Open Canopy
Ponderosa pine (PPN), Sierran mixed conifer (SMC), white fir (WFR), red fir (RFR), tree size >24 inches dbh, canopy closure 10-39 percent
2,709
0.2%
Coniferous Forest, Late Seral, Closed Canopy
Ponderosa pine (PPN), Sierran mixed conifer (SMC), white fir (WFR), red fir (RFR), tree size > 24 inches dbh, canopy closure > 40 percent
159,865
11.5%
Other land cover
Rock, snow, urban and other vegetation not included in the above cover types, such as grassland and tundra.
514,813
37%
Total

1,388,269
100.0%
a Dbh – Diameter at breast height.
b The 2010 vegetation mapping was created using 2007 LANDSAT satellite imagery to map Ecological Groupings based on CALVEG at a scale of 1:24,000.


Figure 1.12. CWHR habitats in Sierra National Forest.
CWHR_Mar 25.JPG

Aquatic Ecosystems


Species

Fish

The Sierra National Forest is within the Sacramento-San Joaquin zoogeographic province as described by Moyle (2002). Nine of the fish species currently occurring in the Forest are native, with most Forest waters barren of fish prior to man's transplanting activities starting in the late 19th Century. Moyle (1996, 2002) identifies much of the west slope of the Sierra Nevada range above 5,000 feet as being historically fishless due to glaciation during the Pleistocene and steep topography. However, it is noted that trout may have occurred up to 7,200 feet in the Middle Fork of the Kings River (Moyle et al 1996). The fish communities represented on the SNF include the “rainbow trout” and “pikeminnow-hardhead-sucker” assemblages for the zoogeographic province described by Moyle (2002). Elevations on the Forest above approximately 2,500 feet are within the rainbow trout (O. mykiss) assemblage. Habitats are characterized as having more riffle than pools, with water temperatures seldom exceeding 70 degrees Fahrenheit (21° Celsius). Elevations less than 2,500 feet are generally part of the pikeminnow-hardhead-sucker assemblage described by Moyle (2002) as occurring within Sierra Nevada foothill streams. Water temperatures within this transitional area may exceed 70° Fahrenheit (21° Celsius) during the summer, especially during “dry and critically dry” water years. Trout species may persist within these areas, but water temperatures limit the populations and introduced centrarchids (sunfish family) are better adapted to these habitat conditions.

The Sierra National Forest was occupied by eleven native fish species prior to 1850: Kern brook lamprey (Lamptera hubbs); Chinook salmon (Oncorhynchus tshawytscha); rainbow trout (resident rainbow and steelhead)(O. mykiss); Sacramento hitch (Lavinia exilicauda exilicauda); San Joaquin roach (L. symmetricus Ssp.); hardhead (Mylopharodon conocephalus); Sacramento pikeminnow (Ptychocheilus grandis); Sacramento sucker (Catostomus occidentalis occidentalis); prickly sculpin (Cottus asper); and riffle sculpin (C. gulosus).

Three fish species have been identified by the Forest Service as At-Risk species. At-risk species are those currently listed as threatened or endangered, or proposed for listing or candidates for listing under the Endangered Species Act (ESA). These are: Lahontan (O. clarkii henshawii) and Paiute (O. c. seleniris) cutthroat trout. Neither fish is native to the Sierra National Forest, but the species are listed as endangered under the Endangered Species Act and covered under Recovery Plans.

Occupied habitat for the two cutthroat species are within Critical Aquatic Refuges (CARs) (USDA – Forest Service 2001; 2004). CARs are subwatersheds with known locations of threatened, endangered, or sensitive species; highly vulnerable populations of native plant or animal species; or localized populations of rare native aquatic- or riparian-dependent plant or animal species. The primary role of CARs is to preserve, enhance, restore or connect habitats for these species at the local level and to ensure the viability of aquatic or riparian dependent species.

Historically the Forest provided spawning and rearing habitat for anadromous Chinook salmon and steelhead trout. Native fish distribution was limited following the glaciation that occurred during the Pleistocene and the steep topography of the streams tributary to the major rivers. It is estimated that native fish occurred within approximately 100 miles of streams within the Forest (Map 1) (Yoshiyama and Moyle 1996, USDI – NMFS 2010). Of the 11 species native to the Forest, five are considered stable or expanding; one noted as stable; one noted as declining; two noted as species of special concern; and two are extirpated from the Forest (Moyle et. al 1996). Hardhead minnow is listed as a sensitive species by the Forest Service, and Kern Brook lamprey may be designated as sensitive in the near future. Dams downstream of the Forest have extirpated Chinook salmon and steelhead from the Forest.

Salmon accumulate most of their body mass during their years at sea. Their return to freshwater systems represents a source of marine derived protein to predators, and nutrients to aquatic and riparian systems. Marine derived nutrients such as nitrogen and phosphorus are found at higher levels in streams and riparian zones associated with salmon, compared to those streams where salmon did not occur (Naiman et. al 2002; Schindler et. al 2003; Bilby et. al 2003). The loss of Chinook salmon eliminated marine derived nutrients for those portions of the Forest where spawning runs historically occurred.

Forest waters less than 2500 feet in elevation are considered “transitional” or “warmwater” fisheries and are more likely to be occupied by fish from the bass/sunfish and catfish families, although stocked Chinook salmon may be caught on Pine Flat Reservoir, along with occasional brown or rainbow trout at other sites below 2500 feet. Angler experience and success may be affected by the time of year since stream and lake levels may be influenced by spring runoff of snowmelt; low summer/fall flows; drought; or drawdown of hydroelectric/flood control reservoirs in the fall.

Reservoir fisheries exist where dams established as part of hydroelectric power development or flood control has created lakes. Kokanee salmon (O. nerka) are popular at several large reservoirs above this elevation. However, both Bass and Shaver Lakes develop temperature thermoclines over the course of the summer, which provides temperatures suitable for species from the bass/sunfish (centrarchid) and catfish families.

There were approximately 100 miles of streams on the Forest occupied by fish through the 1850s. There are now currently more than 1500 miles of stream occupied by fish species, 11 large reservoirs (greater 150 acres), and 21,550 acres of lakes distributed across the Sierra National Forest, with 31 species of fish now present.

Streams and lakes above approximately 2500 feet elevation are generally considered “coldwater” (water temperatures less than 70°F) fisheries, where anglers may catch rainbow (Oncorhynchus mykiss), golden (O. aquabonita), brown (Salmo trutta), or eastern brook trout (Salvelinus fontinalis). The distribution of fish across the Forest has been greatly expanded (Map 1), and most of the waters on the Forest are currently occupied by non-native fishes as described by Moyle and others (1996).

Amphibians

Jennings (1996) noted that 12 of the 14 frogs and toads native to the Sierra Nevada were in need of some type of protection. Three native amphibians with habitat within or adjacent to the Forest have been identified as At-Risk Species by the Forest Service: California red-legged frog (Rana aurora draytonii), mountain yellow-legged frog (R. sierrae), and Yosemite toad (Anaxyrus (=Bufo) canorus).

California red-legged, which occupied habitats adjacent to the Forest, is listed under the ESA (1996) and possibly extirpated from the Forest. Two native amphibians on the Forest (Yosemite toad and mountain-yellow-legged frog) are currently candidates for listing under the Endangered Species Act, while three others are designated as sensitive by the Forest Service (foothill yellow-legged frog (R. boylii), limestone salamander (Hydromantes brunus), and relictual slender salamander (Batrachoseps relictus (regius)). Jennings (1996) notes the declines of some amphibian species within the introduction of a suite of exotic species (especially fishes) partially as the result of increased distribution of fish across the Forest.

Introduction of non-native fish has provided a predator in aquatic system that has disrupted the connectivity of habitat for amphibian species in particular. Mountain yellow-legged frog (see amphibian declines) populations have become increasingly isolated in part by introduced salmonids. While aquatic habitat remains connected at higher elevations across the Forest, the presence of predatory fish within that habitat limits the ability of mountain yellow-legged frog to disperse.

Non-native bullfrog (R. catesbeiana) has become widely dispersed across the Forest at elevations less than 5500 feet. Bullfrogs are larger than native frogs and may be both a competitor for habitat and a predator. Much of the potential habitat for California red-legged frog and foothill yellow-legged frog is not occupied by bullfrog, however its range is expanding into the lower elevational distribution of mountain yellow-legged frog.

Aquatic invertebrates

Erman (1996) notes that “Aquatic invertebrates are a major source of food for birds, mammals, amphibians, reptiles, fish, and other invertebrates in both aquatic and terrestrial habitats. Changes in a food source of such importance as aquatic invertebrates can have repercussions in many parts of the food web. The life cycles of aquatic invertebrates are intricately connected to land as well as water, and the majority of aquatic invertebrates spend part of their life cycle in terrestrial habitats. Aquatic invertebrates are affected by human caused activities on land as well as activities in the water”.

Knapp (1996) indicates that introduction of non-native fish has effected both zooplankton and benthic macroinvertebrate communities. The zooplankton communities in lakes have shifted from large bodied species to those species with smaller bodies (Bradford et. al 1994). A similar pattern exists for benthic macroinvertebrates in lakes, with many species with free-swimming larvae being absent or reduced in lakes occupied with introduced fish (Bradford 1994). There is limited information on benthic aquatic community on the Forest. Review of 40 benthic macroinvertebrate datasets during the Forest Watershed Condition Assessment indicated 29 samples represented Functioning Properly; 9 indicated Functioning at Risk; and two indicated Impaired aquatic systems.

As previously identified, there are approximately 155 miles of stream on the Forest subject to minimum instream flows downstream of hydroelectric dams. In review of data collected as part of the relicensing of hydroelectric projects (including data from the Forest), Rehn (2009) indicated that benthic macroinvertebrates were most affected by altered hydrologic regime. While the relationships between flow parameters and biotic integrity scores were based on limited data points, it was indicated that lower scores were associated with artificially reduced flows below dams.

Knapp (1996) suggests multiple trophic level consequences of fish introductions, several community-wide effects of trout introductions for aquatic ecosystems in the Sierra Nevada. The effects from introduced trout on native aquatic biota extend beyond interaction at two trophic levels (e.g., trout preying on amphibians, trout preying on zooplankton). Changes in one trophic level due to trout introductions may result in cascading effects to the food web. This was suggested by Jennings and others (1992) through declines in garter snake (Thamnophis elegans), that utilize frog tadpoles as prey. Knapp (1996) also notes that “because introduced trout are likely to be one of the causal factors leading to the decline of at least one Sierran amphibian (Bradford 1989; Bradford et al. 1993), trout may also indirectly cause the decline of T. elegans.” Further, the loss of tadpoles would impact trophic levels, since tadpoles feed on algae resulting in a reduction in algal biomass and altering lake nutrient cycling.

Habitat


The Sierra National Forest provides a diverse range of habitats for amphibians, fish and other aquatic biota. Aquatic habitat types range from low elevation streams in chaparral and oak woodland to glacial tarns near granitic alpine ridgelines. Elevations on the Forest range from about 1,000 to nearly 14,000 feet in elevation, and this topography creates distinct seasonal variation in precipitation.

Approximately 1,300,000 acres drain to the San Joaquin River system via the Merced, Chowchilla, Fresno and Kings Rivers, along with the mainstem San Joaquin River. Aquatic habitat includes an estimated 2,000 miles of perennial streams and rivers, along with 21,550 acres of lakes and ponds. The Sierra National Forest aquatic systems provide habitat for 31 species of fish, with approximately 1,580 miles of stream occupied by fish (USDA-FS 1992). Perennial waters also provide potential habitat for a variety of amphibian and reptile species, as well as benthic macroinvertebrates. Additionally, there are 8,200 miles of intermittent or seasonal streams, some of which also provide habitat for fish, benthic macroinvertebrates and amphibians.

There are more than 1500 miles of stream occupied by fish species, 11 large reservoirs (greater 150 acres), and 7500 acres of lakes distributed across the Sierra National Forest providing a variety of angling opportunities for some 30 species of fish. The Forest provides reservoir fisheries; high mountain lake fisheries; as well as both warm and coldwater fisheries. Streams and lakes above approximately 2500 feet elevation are generally considered “coldwater” (water temperatures less than 70°F) fisheries, where anglers may catch rainbow (Oncorhynchus mykiss), golden (O. aquabonita), brown (Salmo trutta), or eastern brook trout (Salvelinus fontinalis). Reservoir fisheries exist where dams established as part of hydroelectric power development or flood control has created lakes. Kokanee salmon (O. nerka) are popular at several large reservoirs above this elevation. However, both Bass and Shaver Lakes develop temperature thermoclines over the course of the summer, which provides temperatures suitable for species from the bass/sunfish (centrarchid) families. Forest waters less than 2500 feet in elevation are considered “transitional” or “warmwater” fisheries and are more likely to be occupied by fish from the bass/sunfish and catfish families, although stocked Chinook salmon may be caught on Pine Flat Reservoir, along with occasional brown or rainbow trout at other sites below 2500 feet. Angler experience and success may be affected by the time of year since stream and lake levels may be influenced by spring runoff of snowmelt; low summer/fall flows; drought; or drawdown of hydroelectric reservoirs in the fall.

Aquatic species viability may be limited by the ability of species to access partners for breeding. Sierran systems were naturally limited by post-glaciation, which resulted in limited occupancy by fishes. However, aquatic/riparian species capable of moving through the terrestrial environment (such as herpetofauna or insects with terrestrial life stages) were able to utilize habitat across the Forest.

Most of the waters on the Forest are currently occupied by non-native fishes as described by Moyle and others (1996), thus the distribution of fish across the Forest has been greatly expanded. Additionally, two stream segments located within or adjacent to the Forest are listed as impaired by the State Water Resources Control Board (SWRCB 2008). Finally, sediment accumulation in pools and riffles has reduced the quality of aquatic habitat on some stream segments within the Forest.

Dams/Diversions and Habitat Connectivity

As described under the Sierra Nevada Ecosystem Project (SNEP 1996), connectivity of aquatic habitat on the Sierra National Forest has been altered by dams, diversions, and road crossings. Some native fish species have declined or been extirpated from the Forest. Introduction of non-native fish have greatly expanded the distribution of fish across the Forest. Distribution of native frogs and toads has declined. Alteration of fire regime and climate change has also contributed to alteration of Aquatic/Riparian Habitat.

There are 50 dams and diversions on the Forest, which have been built for flood control, generation of hydroelectric power, and water rights. Dam and diversions may contribute to aquatic habitat alteration through flooding, removal of water, alteration of flow regime, blocking fish movement or migration, and contribute to species isolation (Moyle et. al 1996). Water temperatures downstream of dams are affected by volume of flow and temperature of the upstream reservoir. Dams and diversions affect flow over approximately 220 miles of streams on the Forest. Several streams receive enhanced flows as a result of flow diversion however a majority are subject to less flow than if the diversion was not present. There are approximately 155 stream miles on the Forest subject to flow regulation under licenses from the Federal Energy Regulatory Commission (FERC). Streams under FERC licenses have conditions for providing minimum instream flows (MIF).

Culverts on road crossings can also disrupt habitat connectivity by restricting upstream movement by species. Culverts may represent a total barrier to fish upstream movements, or force amphibians and reptiles to attempt road crossings that my subject them to mortality. Fish passage success is dependent on the swimming capability of the fish, lifestage of concern, stream discharge, and the relationship of fish movement with stream discharge. It is estimated there are more than 14,700 crossings on the Sierra National Forest, with more than 1,500 of these crossings on perennial streams. The percentage of the culverts that provide for upstream passage is not known. However, in a limited analysis of perennial crossings on the Forest during 2011, 88 of 121 crossings evaluated would not provide upstream passage for adult rainbow trout.

Sediment/Water Quality

Segments of Forest streams have been surveyed for stream channel characteristics and stability between 1989 and 2008. Channels and riparian areas were evaluated using various methodologies, including Rosgen channel typing and Pfankuch channel stability ratings.

Rosgen Channel Typing

Channel reach types (Rosgen 1996) were determined based on channel attributes such as width/depth ratio; gradient; sinuosity; and substrate, along with sediment and transport characteristics. Approximately 465 miles of perennial stream channel have been evaluated across the Forest. Stream reaches with low sensitivity are bedrock/boulder (Rosgen channel types A1-2, B1-3, C1-2, F1-2 and G1-2) and represent approximately 60 percent of the streams evaluated. These channel types are considered inherently stable and are not significantly influenced by land management activities. However, sediment build-up can occur in these channels if upstream stream channels degrade. Effects to aquatic habitat would be likely on those Rosgen channel types considered as sensitive, degraded or unstable (sensitivity of moderate and high in Table 1.6).

Pfankuch channel stability ratings

The Pfankuch channel stability rating (USDA-FS 1975) developed to evaluate the stream channel condition and stability from within the floodplain and stream channel. This method utilizes observation of attributes from the upper banks, lower banks and channel bottom. Channels are categorized into three ratings of poor, fair or good. Table 1.5 indicates the Modified Pfankuch streambank stability condition. Channel types were evaluated in terms of sensitivity to disturbance as presented by Rosgen (1996), which varies by channel gradient and size of substrate. The Modifications proposed by Rosgen evaluate each channel type separately in terms of vegetative bank cover, stream bank cutting, channel bottom deposition, channel bottom scour and deposition and percent stable material. Under Rosgen’s (1996) modified approach, channels are evaluated considering sensitivity to disturbance, recognizing channel characteristics rather than evaluating all channels against a common metric.

While approximately 90 percent of the naturally unstable channel types had at least Fair channel stability, 54 percent of the moderately sensitive channels were indicated to have Poor channel stability under the Modified Pfankuch approach. Table 1.5 displays the channel stability conditions for sensitive, degraded or naturally unstable within the analysis units.

Table 1.5—Channel sensitivity and stability data
Rosgen Sensitivity (mi)
Modified Pfankuch Ratings Moderate sensitivity reaches (mi)
Modified Pfankuch Ratings High sensitivity reaches (mi)
Low
Moderate
High
Good
Fair
Poor
Good
Fair
Poor
274.5
71.4
117.4
13.0
19.5
38.8
75.6
29.4
12.4

The Sierra Nevada Ecosystem Project (SNEP) (1996) identified both excessive sediment yield and water quality impacts as stressors of aquatic systems. Erosion and sedimentation are probably the most common water quality issues related to forest management. Unfortunately, very few records of annual sediment loads are available for streams on or near NFS lands in the Sierra Nevada. Roads are a documented source of disturbance in managed watersheds (Trombulak and Frissell 2000; Switalski et. al 2004). Roads and cattle grazing represent sediment source mentioned in SNEP (1996).

Sediment

Sediment studies have identified roads producing more sediment than other forest management practices (Robichaud et al 2010). Roads can also affect meadows and wetlands directly by encroachment and indirectly by altering surface and subsurface flow paths. Alteration of the hydrologic flow paths can indirectly affect meadow and wetland function, with the effects extending far beyond the area road itself. The effects can include erosion and/or lowering of the water table.

The potential for water to run down roads or trails is termed ‘diversion potential’. When this occurs, stream flow diversions can be a major cause of road-related erosion (Furniss et al 1997). When roads concentrate surface flow and deliver it to streams via surface flow paths, they are termed ‘hydrologically connected’ and they functionally increase the drainage density (Wemple and others 1996). In a study of forest road segments on the Eldorado NF, Coe (2006) found that 25 percent of the road segments surveyed were hydrologically connected. A local study in the Kings River Experimental Watershed (KREW) area found that 13 percent of the road length in the study area was hydrologically connected (Korte and MacDonald 2005). Robichaud and others (2010) note that studies in the western U.S. have found between 23 and 75 percent hydrologic connectivity of roads. The Forest works at the project scale to identify and reduce instances of roads being connected.

The majority of the Forest includes cattle grazing under permits. Numerous effects on aquatic habitat and species have been attributed to prolonged use of riparian areas by cattle. Literature suggests potential effects from cattle grazing such as altering channel function, which reduces natural processes, habitat diversity and habitat complexity for aquatic or riparian animals (Clary and Webster 1989; EPA 1991; Meehan et. al. 1991; Belsky et. al. 1999). Animal wastes could directly impair water quality through bacterial contamination and increasing nutrient levels (EPA 1991; Derlet et al. 2006; 2008; 2010), although Campbell and Allen-Diaz (1997) and Allen-Diaz and others (2010) reported no significant differences in nitrate, orthophosphate, dissolved oxygen, temperature, or pH in a study evaluating grazing effects to water quality. While these factors could result in negative effects to aquatic/riparian habitat, quantifying effects related to continued cattle grazing and recovery from past effects has proved difficult to evaluate due to absence of reference sites that have never been grazed by livestock (Kattelmann 1996).

Many of the effects described in literature are noted as resulting from “heavy” or “overgrazing”. Cattle grazing permits are administered under U.S. Forest Service, which include compliance with standards and guidelines from the Sierra National Forest Land and Resources Management Plan (USDA – Forest Service 1992; 2001; 2004). Grazing permits are subject to NEPA analysis where identified negative effects can be mitigated. It is expected that cattle grazing continues to result in exposed streambanks and erosion on a local basis.

Water quality

Water quality across the Forest is managed under the Central Valley Basin Plan for the San Joaquin and Sacramento River Basins (Central Valley Regional Water Quality Control Board 2007), and the Tulare Lake Basin (CVRWQCB 2004). These plans designate the beneficial uses to be protected, water quality objectives, and an implementation program for achieving objectives. Beneficial uses identified in the plans include: Municipal and Domestic Supply; Hydropower Generation; Water Contact Recreation; Non-contact Water Recreation; Rare, Threatened, or Endangered Species; Warm Freshwater Habitat; Cold Freshwater Habitat; Migration of Aquatic Organisms; Spawning, Reproduction, and/or Early Development; Freshwater Replenishment; and Wildlife.

Summer water temperature monitoring has been implemented by the Forest, and as part of the relicensing for hydroelectric projects. Data from approximately 200 sites suggests that the transitional zone between cold and warm-water habitat may be influenced by minimum instream flows and that smaller streams above 3000 feet elevation currently meet Moyle’s (2002) description of the rainbow trout zone (<21° Celsius). Water temperatures in larger streams may be influenced by limited riparian shading, especially in streams flowing through bedrock canyons.

Several drainages are listed as having impaired water quality by the Central Valley Regional Water Quality Control Board (CVRWQCB). A water body or segment of a water body (e.g., a fresh stream, river or lake) that does not meet (or is not expected to meet) water quality standards may be considered a “Water Quality Limited Segment” (WQLS). WQLS are added biennially by the CVRWQCB to the Clean Water Act Section 303(d) list of impaired waters.

A segment of Willow Creek was added to the 303(d) list in 2006 for failing to meet the water temperature objective. The listed segment is 6.2 miles long and is located downstream of the confluence of the North and South Forks of Willow Creek. The source of impairment is restricted (regulated) flow and excess fine sediment causing an increase in stream temperature. The Total Maximum Daily Loads (TMDLs) is scheduled to be completed by 2019.

The Fresno River (downstream of the SNF) was added to the 2008 303(d) list for failing to meet the dissolved oxygen (DO) objective. The listed segment is 30 miles long and is located between the confluence of Lewis Fork and Nelder Creeks and the Hensley Reservoir. The source of the impairment is unknown. Dissolved oxygen levels in the Fresno River could be influenced by the water quality (particularly sediment, turbidity, nutrients and temperature) of contributing waters from Miami, Lewis Fork, and Nelder Creeks. The TMDL is scheduled to be completed by 2021.

Watershed Condition Assessment

The Forest completed a Watershed Condition Assessment (WCA)(USDA –Forest Service 2010). The WCA represents a systematic, flexible means of classifying watersheds based on a core set of national watershed condition indicators. It included professional judgment exercised by Forest interdisciplinary teams, GIS data and national databases to the extent they were available and written rule sets and criteria for indicators that describe proper function, functioning-at-risk, and impaired conditions. The WCA evaluated 65 12th field Hydrologic Unit Code (HUC) watersheds that are located within or partially within the Forest. Watersheds were evaluated as being in Good (Properly Functioning); Fair (Functional at Risk); or Poor (Impaired Function) considering both aquatic (physical and biological conditions) and terrestrial (physical and biological) data.

Watershed condition refers to the state of the physical and biological characteristics, along with the processes within a watershed that affect the hydrologic and soil functions supporting aquatic ecosystems. Watershed condition reflects a range of variability from natural pristine (properly functioning) to degraded (severely altered state or impaired). Watersheds in properly functioning condition have terrestrial, riparian, and aquatic ecosystems that capture, store, and release water, sediment, wood, and nutrients within their range of natural variability for these processes. Properly functioning watershed conditions create and sustain functional terrestrial, riparian, aquatic, and wetland habitats that are capable of supporting diverse populations of native aquatic- and riparian-dependent species.

In general, the greater the departure from the natural pristine state, the more impaired the watershed condition is likely to be. Properly functioning watersheds provide for high biotic integrity; are resilient and recover rapidly from natural and human disturbances; exhibit a high degree of connectivity; provide important ecosystem services such as high quality water, recharge of streams and aquifers; and maintain long-term soil productivity. The results of the WCA for the Forest indicate that 25 watersheds would be classified as being in Good (43% of Forest drainage), 33 watersheds would be classified as being in Fair (52% of Forest drainage), and 7 watersheds would be classified as being in Poor Condition (5% of Forest drainage). The Upper Big Creek and Willow Creek watersheds were identified as Forest priorities for restoration treatments. Habitat fragmentation, flow alteration, exotic species, road density, and road proximity to water were the most common stressors affecting watersheds in less than Good condition.

Drivers and Stressors


Disturbances have occurred for millennia, and plant species and communities have evolved and adapted to them over time. Disturbances perform important functions within the Sierran ecosystem, such as insect outbreaks that modify species composition and structure by thinning individual and groups of trees and creating openings. This and other types of disturbance also create spatial diversity across the landscape which can provide opportunities for shrubs, forbs, and other low vegetation to maintain species diversity through time. Because of these types of interactions and disturbances cannot be viewed as necessarily destructive or damaging. They are major processes that develop resources for use by other components of the ecosystem and established system structure. However, major drivers and stressors of ecosystems can also be abnormal outside the desired or reference range of ecosystem variability, thus potentially resulting in severe disruptions to ecosystems. The following is an overview of some key drivers and stressors for terrestrial and aquatic ecosystems including those created by humans. Chapter 3 of the assessment provides additional details of the most wide-spread and influential drivers and stressors, such as fire and climate change.

Fire

Fire is a major influence on type, composition and juxtaposition of ecosystems in the Sierra National Forest. Within the Southern Sierra Province, fire occurred at a variety of intervals. "More important than average fire return intervals, the distribution of fire-return intervals can vary substantially among locations in the landscape" (van Wagtendonk and Fites-Kaufman 2006, p. 279). The following graph illustrates the variety of fire return intervals detected in small sample areas and compares mesic and dry sites.

FRI variation.jpg

Along with variation in fire return intervals, the severity within and between fires was variable and related to regional drought and weather conditions (van Wagtendonk and Fites-Kaufman 2006). Low severity fire is often emphasized in discussion about fire regime pine and mixed conifer forest, however, mixed-severity fire, including high-severity fire, is also a natural condition in ponderosa-pine/Jeffrey pine and mixed-conifer forest. Given the fact that fire is a natural part of the ecosystem, one of the most significant changes during the past century has been fire suppression management. At the same time, the length of fire season is extending as a consequence of climate change, thus exacerbating the situation. As a result, live and dead fuels in some parts of the landscape have increased to levels that are greater than the natural range of variability. These conditions are represented by Figure W-1, which depicts the divergence of the current Fire Return Intervals (FRI), as compared with average reference conditions. The following bullets are key concerns pertaining to fire as well as fire suppression.
  • Fire is a key landscape driver in how it contributes to ecological integrity and sustainability, as well as the amount, juxtaposition and quality of wildlife habitats. One such concern is the long-term declining trend of early seral vegetation (e.g., forage habitat) due to fire suppression and lack of any other disturbance that would result in tree mortality. Specific examples of declining habitat for deer and other species include past and current loss of meadow and shrub habitat as a result of tree encroachment. Studies conducted by Longhurst and others (1976) “…concluded that decreased acreage of controlled burns and wildfires in California has contributed to the decline of deer numbers.” In addition, complex early seral forest is important for a whole host of avian species including black-backed woodpeckers as well as shrub dependent birds.
  • Aquatic/riparian affects from fire occurrence and intensity is related to recurrence. Fire suppression activities have resulted in an altered recurrence cycle. That has resulted in an increase in forest density and the abundance of shade-tolerant species. These changes have affected habitat for some aquatic/ riparian species. The USDI-USFWS (2002) identified that “Fire suppression, and changes in fire frequency and hydrology, has probably contributed to the decline of Yosemite toads through habitat loss caused by conifer encroachment on meadows. Under natural conditions, conifers are excluded from meadows by fire and soils too saturated for their survival. But as conifers begin to encroach on a meadow, if they are not occasionally set back by fire, they transpire water out of the meadow, reducing the saturation of the soils, and facilitating further conifer encroachment.
  • A large, high severity fire could disrupt flow regime and alter stream channel dynamics. Soil water storage; base flow; streamflow regime; peak flow; water quality (sediment, temperature, pH, ash slurry); and chemical characteristics can be affected by wildfire (Neary et al. 2005). In an effort to reduce fire intensity and protect communities, more treatments to reduce stand density would be expected in the future. Both wildfire and fuels treatments may result in changes to habitat and potentially direct effects to aquatic/riparian species.

Climate Change

Climate change is a key landscape stressor affecting long-term ecological conditions. It is expected that air temperatures and precipitation patterns may change across the Forest over time. The Forest includes elevational zones characterized as having warm/hot summers (varies by elevation) and cool winters. Most precipitation above 5500 feet falls in the form of snow from fall through spring. Change is expected to be reflected through an increase in daily maximum, minimums, and mean air temperatures, along with altered rainfall patterns. Meyer and Safford (2010) examined fire trends presented in Miller et al. (2009), and incorporated long-term weather stations within or adjacent to the Sierra National Forest to illustrate that mean annual temperature at Huntington Lake has increased by 1.8º F, with a mean minimum (nighttime) increase of 4º F since 1915. Utilizing information projected by Meyer and Safford (ibid), mean annual temperature increases by 0.3 º F; mean annual minimum temperature increases by 0.4 º F; and mean annual maximum temperature increases by 0.19 º F over the 10-year period at Huntington Lake (7000 feet). The following are some key points pertaining to climate change ecosystem stressors.
  • Climate change may facilitate expansion of non-native invasive species. Invasive species have altered terrestrial and aquatic/riparian systems and biodiversity across the Forest.
  • Climate change has been suggested as a contributing agent in the decline of amphibians. Reaser and Blaustein (in Lannoo 2005) summarize that site specific review of amphibian declines indicate possible global changes, and that regional warming, increasing ultraviolet radiation, and diseases are a potential result of global change. California anticipates warmer temperatures, accompanied by altered patterns of precipitation and runoff related to climate change (DWR 2007). Annual runoff in the San Joaquin River basin has declined by 19% over the past 100 years, and projected precipitation alterations could reduce the snowpack by 25% by the year 2050.
  • Thompson (2005) summarizes that direct solar radiation has the greatest influence on water temperature, thus managing to maintain or improve shade is important to reduce heat flux. Precipitation changes would be expected to reflect a great deal of variability. Information from Meyer and Safford (ibid) project an increase in annual precipitation of 2.1 inches at Huntington Lake over the 10-year period, but the projections at Grant Grove in Kings Canyon National Park project no change. Spring runoff is occurring earlier in the year and fraction of runoff occurring in the spring is decreasing. With less snowfall expected to result from elevated air temperatures associated with climate change, it is likely that less water would be available during the late summer and that the water would be warmer than current conditions. An increasing elevation of snow level would reduce the amount of shallow pools during the spring, which provide breeding habitat for Yosemite toad. A similar effect to shallow lakes would reduce the suitability of habitat for mountain yellow-legged frog, which could result in localized extirpations in a species with a high degree of site fidelity.
  • Lind (2008) notes that amphibian and reptile populations respond to changes and variability in air or water temperature, precipitation, and the hydro-period of their environments. Over the short-term (annually), these factors can influence reproductive success rates and survival to metamorphosis. Over the long term, the frequency and duration of extreme temperature and precipitation events can influence the persistence of populations and structure of meta-populations on the landscape. The net effect of less water and higher temperatures would be a reduction in the quantity and quality of aquatic/riparian habitat. Herpetofauna would likely be concentrated at sites where water is available, increasing their susceptibility to predators at these sites. The changing conditions of habitat would provide conditions more favorable for invasion by species currently occurring at lower elevational sites, and possibly an increase in non-native species. It is probable that the range of bullfrog would continue to expand across the Forest.

Invasive Species

The influx of non-native species of animals and plants since the first Europeans arrived in California has changed the ecosystems of the Sierra Nevada and this continues to be a major and increasingly important stressor in the Sierra National Forest.

Land Use and Management


The following are some land use and management activities that can have some degree of stress on the ecosystems.
  • Recent research (Gabriel et al. 2012) has shown that rodenticide poisons, such as those distributed through illegal marijuana growing operations, can have detrimental impacts on species such as mice, rats and squirrels, which in-turn can also detrimentally influence the wellbeing of hunted and non-hunted wildlife populations, as well as potentially negative affects to humans which consume those species.
  • Vegetation and ecosystem management actions can affect the quality and juxtaposition of habitats used by fish, wildlife and rare plant populations, particularly in how conditions diverge from the natural range of variability.
  • Hunting regulations and hunter harvests affect wildlife populations, as well as prey species used by some of those populations.
  • Existing conditions of aquatic/riparian habitat have been influenced by a variety of drivers and stressors, most relating to human disturbance since 1850. Among the findings within the Sierra Nevada Ecosystem Project (SNEP 1996) was that the aquatic/riparian systems were the most altered and impaired habitats of the Sierra Nevada. This finding was based on effects to stream flow (through dams and diversions altering stream-flow patterns and water temperatures); effects to riparian areas damaged by placer mining and grazing; excessive sediment yield into streams; water-quality impacts; introduced aquatic species; amphibian species declines; loss of anadromous fishes (Chinook salmon and steelhead); aquatic invertebrates local degradation of habitat; and due to food chain relationships, impacts to invertebrates have significant cascading effects on other animals.
  • Snowmobiles – which are permitted to travel off designated routes -- put increased stress on wildlife, including ungulates and subnivean species. Snowmobile emissions also contribute to acid pulse during spring runoff which impacts aquatic species. [See, e.g. Ingersoll, G.P., 1998. Effects of Snowmobile Use on Snowpack Chemistry in Yellowstone National Park. J. Ruzycki and J. Lutch, “Impacts of Two-Stroke Engines on Aquatic Resources” 1999 (available at http://beringiasouth.org/impacts-of-two-stroke-engines-on-aquatic-resources.) Jarvinen, J.A., and W. D. Schmid. Snowmobile Use and Winter Mortality of Small Mammals. Pp. 131-141 in M. Chubb (ed.), Proc. of the Snowmobile and Off-Road Vehicle Research Symposium. Michigan State Univ. Tech. Rep. 8, 1971. Severinghaus, C.W. and Tullar, B.F. 1978. Wintering Deer versus OSVs. New York State Department of Environmental Conservation]
  • Snowmobiles may be significant contributors to aquatic and terrestrial pollution in off-road areas. High-speed snowmobile free-play can damage high alpine slopes and meadows. Acid pulse during spring runoff, created by motorized use such as snowmobiles, can harm aquatic species. [Ingersoll, G.P., 1998. Effects of Snowmobile Use on Snowpack Chemistry in Yellowstone National Park. J. Ruzycki and J. Lutch, “Impacts of Two-Stroke Engines on Aquatic Resources” 1999 (available at http://beringiasouth.org/impacts-of-two-stroke-engines-on-aquatic-resources) E. Gage and D.J. Cooper, “Winter Recreation Impacts to Wetlands: A Technical Review”, Mar 2009 (Submitted to Arapaho-Roosevelt National Forests). Shaver, C., Morse, D., and O’Leary, D., 1998. Air Quality In the National Parks. U.S. Department of the Interior, National Park Service, Air Quality Division. Report prepared by Energy and Resource Consultants, Inc., NPS Contract No. CX-0001-4-0054]

Trends

Terrestrial
Species
Trend information pertaining to the At-risk Species is provided in Chapter 5 of the Bioregional Assessment.

Habitat

Introduction

The Sierra National Forest future habitat trends assessed here assume a 10-20 year period with management similar to current conditions. Habitat trends are inherently driven by ecosystem dynamics, such as natural succession, including plant establishment, growth and decay, as well as ecosystem processes and stressors, such as fire and climate change. Key elements of these factors and processes are described in the Science Synthesis, the Bioregional Assessment, and in this and other chapters of this assessment. Habitat trends also are directly and indirectly influenced by past, present and future management actions.

The current management framework for Sierra National Forest consists of the 1992 Land and Resource Management Plan (LRMP) Record of Decision (ROD) (USDA-FS 1992), as well as amendments. The 2001 Sierra Nevada Forest Plan Amendment (SNFPA) ROD (USDA-FS 2001) included Standards and Guidelines (S&Gs) focusing on fuels treatments, particularly areas within the Wildland Urban Interface/Intermix zones (WUI). In 2004, a Supplemental EIS (USDA-2004a) was written to the SNFPA along with implementing a new ROD (USDA-FS 2004) which replaced the 2001 decision in its entirety.

Beginning in 2004, and with greater refinement over recent years, the Sierra National Forest has emphasized ecosystem management focusing on ecological restoration through initiating or accelerating the recovery of ecosystem health, integrity and sustainability. Ecological restoration is the process of assisting the recovery of resilience and adaptive capacity of ecosystems that have been degraded, damaged, or destroyed. Restoration focuses on establishing the composition, structure, pattern, function and ecological processes necessary to make terrestrial and aquatic ecosystems sustainable, resilient, and healthy under current and future conditions (Forest Service Manual (FSM) 2010). An important aspect of this ecological restoration is restoring forests to a healthy, diverse, fire resilient condition that more closely resembles a range of desired reference conditions. This is partly accomplished by reducing forest stand densities and fuel loads using thinning and underburning, as well as expanding the use of prescribed fire to more often use mixed-severity prescribed fire (as opposed to only using low-severity prescribed fire) and managed wildland fire.

Considerations for Estimating Future Trends

The CWHR habitats previously shown in Table 1.4 provide a broad perspective of key habitats used by a variety of species over a large portion of the Sierra National Forest landscape. These same habitats also are considered for the following trend assessment.

This assessment of future trends also considers past trends that occurred during the same or similar management framework as the projected trends. For this assessment, the best information available to represent these conditions is the vegetation mapping in 2001 and 2010. Habitat changes represented by these two years do not represent a complete template for predicting future trends, yet they do provide an indication of what may occur in the future.

There are two concerns for comparing the habitat mapping in 2001 and 2010: 1) changes in mapping resolution and preciseness, and 2) changes in management. The first concern is clearly evident because the mapping resolution for the 2010 vegetation maps (i.e., 2.5 acres) is approximately twice the resolution of the 2001 mapping. This variation prevents a precise comparison among years however it does provide enough information for general descriptive comparative assessments. These are only draft comparative statements at this time, as further investigations are underway. Of particular note, the comparison between the 2001 and 2010 mapping is not appropriate for fine scale comparisons, yet it has some value when estimating broad-scale trends, such as used here for comparing changes in conifer forests, hardwood forests, as other broad-scale habitat types. Forest Service comparative resolutions and preciseness will continue to improve through time with new imaging and mapping technologies that are supported by funding and expertise.

The second concern for assessing past habitat trends, as well as estimating future trends, is the influence of changed management through time. The current, and projected, management framework was initially implemented in 2004 (USDA-FS 2004), which only partially covers the 2001 to 2010 trend assessment. However, thinning management, primarily focused on smaller tree thinning, occurred throughout the 2001 – 2010 period and even began about five years earlier, in approximately 1995, when management shifted from even-age timber harvesting to individual tree thinning. Thinning management, predominantly smaller tree thinning, became more defined under the 2001 SNFPA and more refined under the 2004 SNFPA. Therefore, the prevalent management throughout the 2001 to 2010 comparative period consisted of individual tree thinning, primarily of smaller trees.

The current management framework, which was adopted in 2004, includes many standards and guidelines, such as retaining live trees greater than 30 inches dbh and snags greater than 15 inches dbh, except for hazard tree considerations. These and other numerous S&Gs can be found in the 2004 SNFPA ROD (2004 SNFPA ROD). In addition to these S&Gs, Sierra National Forest also has been actively implementing design criteria for most projects based on new science and other information. These proactively adapted management criteria include many recommendations from the PSW General Technical Report (GTR) 220: An Ecosystem Management Strategy for the Sierran Mixed-Conifer Forests (North et al. 2009), GTR 237: Managing Sierra Nevada Forests (North et al. 2012), as well as other science and other information, such as conservation measures for the Pacific fisher and other species. Many of these new practices have been adaptively integrated into nearly all forest management projects (e.g., ecosystem restoration projects) by Sierra National Forest since at least 2009. Those practices, along with continued adaptive improvements, are expected to continue in the future, as well as other new management adaptations from new science, technologies and collaboration. Therefore, we cannot know all details of how new adapted management practices will influence future habitat projections, nor can we fully understand the full array of ecosystem changes, particularly as a result of ecosystem stressors such as climate change. However, we do know enough about these past and projected changes to provide broad estimates of change, along with clarifications and caveats.

Past Trends

Broad-scale habitats in the Sierra National Forest have remained relatively stable between 2001 and 2010 (Table 1.6). The management framework during this period also reflects this habitat stability, which has focused on forest sustainability, thinning smaller trees and retaining and growing larger trees. There are, however, some increasing and decreasing trends that are of concern, as noted in Table 1.5. Although the 2001 and 2010 mapping resolution issues do not allow precise details of those trends, considerations of known and projected management and ecosystem drivers and stressors provide further insight into the pace and scale of those trends.

Future Trends

Broad-scale habitats generally are expected to remain relatively stable over the next 20 years (Table 1.6) assuming current management and also considering the relatively slow progression of natural succession. This scenario assumes that the pace and scale of forest treatments, fire suppression, and wildfires would remain similar to the current levels. However, these broad-scale habitat classifications are not intended to assess the finer details of ecosystem health. Nor do they accurately reflect the potential risks of large scale habitat change as a result of ecological stressors, such as climate change and large scale, high intensity fire that is abnormally higher than the natural range of variability. Therefore, some of these key considerations are included in Table 1.5 to provide insight as to their potential effects on future conditions. Supporting details of these ecosystem features, processes, drivers and stressors are provided in a number of the documents associated with this assessment, including the Scientific Synthesis, Bioregional Assessment, and assessments of the natural range of variability, which is currently being drafted.

Table 1.6. Estimated past and future broad-scale habitat trends in Sierra National Forest.
Habitat Type
Current Percent of Sierra National Forest
Estimated Past Trends 2001-2010 a
Estimated Future Trends 2012-2032 b
Lakes and Riverine
1.7
No major change.
No major change expected.
Wet Meadow
1.4
Decreasing trend, potentially due to tree encroachment and climate changes resulting in less water availability.
Decreasing trend expected if: 1) pace and scale of meadow restoration does not increase, such as by reducing tree encroachment, removing roads and trails from meadows that cause a change in hydrology, eliminating grazing impacts that result in drying of meadow systems and cause a change in hydrology; and 2) continued climate changes resulting in less water availability.
Sagebrush
<0.1
No major change.
No major change expected.
Shrublands (Chaparral)
9.7
No major change.
Major change not expected, although large scale, high intensity fire in a warming climate can lead to shifts from forests to shrublands.
Oak-associated Hardwoods and Hardwood/
Conifers
15.1
Declining trend, potentially as the result of succession moving some stands into coniferous forest, possibly due to fire suppression.
Major change not expected however, large scale, high intensity fire in a warming climate can lead to shifts from conifer forests to hardwood dominated forests.
Coniferous Forest,
Early Seral
3.4
Decreasing trend most likely due to fire suppression, salvage logging, and natural succession shifting forests into mid-seral condition.
A continued gradual decreasing trend at the fine scale is projected due to lack of fire. In addition, when openings are created through mechanical thinning or other disturbance, the tree-centric management focus of replanting and limiting or eliminating shrubs and other understory species in the openings limits the development of early seral conditions and speeds up the rate of succession from grass/forbs/shrubs and to conifers. Projected increases in large scale fire that is more severe would favor the development of early seral conditions. However, commonly implemented salvage logging practices would substantially degrade early seral conditions by the simplification of the affected area. Known and projected climate changes may gradually result in lower tree density and patchy tree die-off due drought conditions, thereby creating space for early seral conditions.
Coniferous Forest,
Complex Early Seral
Unknown
Decreasing due to fire suppression, salvage logging, reforestation (by humans), and mechanical thinning.
Continued gradual decreasing trend is estimated due to overall forest management measures. Increased mixed-severity fire could increase this habitat type but only if a) the fires burn areas with the pre-fire conditions necessary to create complex early-seral forest, and b) the areas that burn are not salvage logged and are allowed to regenerate naturally (i.e., no human reforestation).
Also, even aged cutting does not create complex early seral forest.
Coniferous Forest,
Mid Seral
19.9
No substantial change.
Projected gradual decreasing trend as the large amount of mid-seral stands progressively grow into late-seral stands, although somewhat moderated by smaller amounts of early-seral forests progressing into mid-seral forests. Major loses are projected if large scale, high intensity fires occur in these forests due to high fuel loads in many of these forests.
Coniferous Forest, Late Seral, Closed Canopy
11.5
No substantial change.
Projected gradual increasing trend as the large amounts of mid-seral stands progress into late-seral forests. The continued management framework would retain nearly all trees >30 inches dbh, thus increasing the number of stems per acre. Determining if such increases are greater than desired reference conditions requires an analysis of existing conditions, mortality, and growth. Losses to this seral stage also could occur as a result of large scale, high intensity fire, particularly in those areas with fuel loads abnormally higher than the natural range of variability. However, it is important to keep in mind that forest areas that have missed the largest number of fire return intervals in California are burning predominantly at low/moderate-severity levels, and are not experiencing higher fire severity than areas that have missed fewer fire return intervals (Odion and Hanson, 2006, 2008, van Wagtendonk et al. 2012).
Coniferous Forest,
Late Seral, Open Canopy
0.2
Increasing trend, albeit less than 2,000 acres. Trend may be due to small scale wildfire, patchy insect and disease infestations, and smaller-scale timber treatments.
This small amount of habitat is predicted to remain stable although possibly increasing as a result of closed canopy forests shifting into open canopy forests as a result of potentially increased levels of mortality of larger trees due to increased tree stress in a warming climate, including potential increases in disease and pest infestation. The assumed management framework over the next 20 years would not result in a significant increase in forests with less than 40 percent canopy cover due to management limits in place that tend to minimize those conditions.
Other Land Cover
37


Total
100


a This draft 2001 and 2010 comparative assessment is awaiting further analysis.
b dbh – diameter at breast height.

Aquatic

Species
This section will be provided at a later time.
Habitat
This section will be provided at a later time.

References Cited


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[snapshot taken 7/1/2013 @0910]
[snapshot taken 7/2/2013 @0810]