Appendix SN. The Sierra Nevada Region

Contributing Authors: Frank Davis and David Stoms

Regional Character
Land Stewardship
Plant Community Types

The Sierra Nevada Region encompasses 63,118 km² extending from Tejon Pass at the southern end to the North Fork of the Feather River at the north (Figure SN-1). Because of the size and biological heterogeneity of the Sierra Nevada, we conducted gap analyses for a northern versus a central/southern subregion divided at the Stanislaus River. In The Jepson Manual the Stanislaus River divides the northern from the central and southern Sierra Nevada.

Figure SN-1. Shaded relief image of the Sierra Nevada Region and the two subregions.

The following digital geospatial data were compiled for this analysis:

topography (100 m grid)
vegetation (classified to Holland types using a 100 ha minimum mapping unit [MMU]. The MMU is the nominal extent of the smallest mapped feature).
dominant plant species (100 ha MMU)
land ownership and administrative designation in terms of conservation (200 ha MMU)
U.S. Forest Service grazing allotment boundaries (1 ha grid)
USFS land suitability classes (1 ha grid)

These data were analyzed to address the following specific questions:

1. How do land ownership and land management vary among elevation zones?

2. What are the sizes and locations of existing parks, wilderness areas, and reserves?

3. How is each terrestrial plant community type distributed with respect to land ownership and conservation management?

4. Which major terrestrial plant community types may be vulnerable to degradation of habitat and which types appear to be relatively well protected based on their current management profile?

Land Stewardship

GAP classifies land ownership and management into four categories intended to capture the degree to which the land is managed to maintain biodiversity (Scott et al. 1993). We depart slightly from the GAP categories by distinguishing lands based on permitted use. We assume that the most pervasive land uses affecting the status and trends of terrestrial biodiversity in the Sierra Nevada are grazing, fire suppression, timber harvest, and urban, residential, and agricultural development. Other activities such as recreation, trapping, and mining, are certainly important but more localized and/or less readily mapped. Thus we have distinguished five ownership/management classes based on fire policy and on potential for development, timber harvest, or grazing.

Class 1: Public or private land formally designated for conservation of native biodiversity and within which economic activities such as development, grazing, and timber harvest are precluded. Natural disturbance events are generally allowed to proceed without interference or are mimicked through management. The areas may be used for primitive recreational activities. Examples include national parks, national monuments, ungrazed lands within USFS wilderness areas, USFS research natural areas, USFS wild and scenic rivers, Blue Ridge National Wildlife Refuge, The Nature Conservancy preserves, and state parks and ecological reserves.

Class 2: national forest land that is generally managed for its natural values but is not formally designated for conservation of native biodiversity. Development and grazing are excluded, and timber harvest is generally excluded because it conflicts with other multiple-use objectives. Wildfires are generally suppressed. The distribution of recreational activities on Class 2 lands is unknown, but a small fraction of the land is developed for recreational facilities.

Class 3: public land that is generally managed for its natural values, is treated in existing management plans as unsuitable for timber harvest, and may be grazed. Wildfires may be actively suppressed. Examples include grazing allotments within USFS wilderness areas, grazing allotments on national forest lands classified as unsuitable for timber harvest, the San Joaquin Experimental Range, Bureau of Land Management (BLM) areas of critical environmental concern, and BLM wilderness areas.

Class 4: Other public lands not included in Classes 1 through 3, mainly multiple-use federal lands managed by the Bureau of Indian Affairs (BIA), Bureau of Reclamation, BLM, and USFS. National forest lands in this category include areas that are classified in existing plans as suitable for timber harvest. These USFS areas can also be within existing grazing allotments. Wildfires are actively suppressed.

Class 5: private lands other than those in Class 1. In the absence of more detailed zoning data, we assume that these lands are potentially available for development, timber harvest, and grazing and that wildfires are actively suppressed.

The base map for land ownership/management is 1:100,000 BLM surface management status maps. A statewide digital coverage was provided by the Teale Data Center. This map was updated and enhanced to include boundaries of managed areas such as wilderness areas and research natural areas that do not coincide with ownership boundaries. To do this, we consulted national forest maps and digital databases and U.S. Geological Survey (USGS) topographic maps. We obtained additional maps and information from many agencies, conservation organizations, and land trusts. All managed areas in the resulting regional map of land ownership/management were described in an associated database containing fields for the managing agency, the management level with respect to biodiversity conservation, and a managed area code assigned by the California Department of Fish and Game Natural Heritage Division.

Figure SN-2. Management classes of lands in the Sierra Nevada Region. See text for definitions of management classes.

The map of land management levels was converted to a 1 ha grid and intersected with 1 ha grids of USFS land suitability class maps and grazing allotments. Digital land suitability class maps were obtained directly from the USFS. Digital grazing allotment data were obtained from the USFS for all of the national forests except Lassen, Modoc, and the Lake Tahoe Basin. We digitized the grazing allotment boundaries on these forests from paper maps provided by USFS range conservation staff.

Maps of timber harvest suitability and grazing allotments were converted back to a vector (polygon) representation and overlaid with land ownership. The derived product was reclassified into the five classes defined above.

Thirty-seven percent of the region is privately owned (Table SN-1). The remainder, in public lands, is largely national forests (47%) and national parks (10%). The Bureau of Land Management administers 5% of the region. Native American tribes, other Department of Interior agencies, and state oversee the remaining 2% of the region's land base.

Table SN-1. Area and percentage of land surface by management status level of the Sierra Nevada Region and two subregions.

Class % in Sierra Nevada % in Northern Subregion % in Central/ Southern Subregion

1 15.4 2.1 25.7

2 6.7 10.1 4.1

3 21.4 16.8 24.9

4 20.0 25.7 15.6

5 36.5 45.3 29.8

Total 100.0 100.0 100.0

We found that 15% of the region is in Class 1 management status (Table SN-1, Figure SN-2). Yosemite and Sequoia/King's Canyon National Parks account for 89% of the Class 1 area. The size distribution of Class 1 areas is strongly skewed toward parcels less than 200 ha (Figure SN-3). These account for nearly half of the Class 1 parcels but contribute less than 1% of the total Class 1 area.

Figure SN-3. Frequency of Class 1 areas by size class (bars) and cumulative area (curve) in the Sierra Nevada region.

An additional 7% of the Sierra Nevada region is in Class 2 lands in national forests. By summing Classes 3, 4, and 5, we estimate that roughly 80% of the region is available for grazing (89% of vegetated lands). Summing Classes 4 and 5, we estimate that 56.5% of the land area (63.3% of vegetated lands) is available for timber harvest, although not all of this land is actually timberland.

Plant Community Types

Vegetation types were classified based on overstory structure, cover, and dominant species composition. The overstory is described by one to three species, each contributing greater than 20% of the relative canopy cover. These species assemblages (Davis et al. 1995) were subsequently reclassified into natural plant community types described by the California Department of Fish and Game Natural Heritage Division (Holland 1986).

Maps of actual vegetation were produced using summer 1990 Landsat Thematic Mapper satellite imagery, 1985-1990 high altitude color infrared photography (1:58,000 scale), draft and published maps of the California vegetation type mapping survey (Wieslander 1946), miscellaneous recent vegetation maps (notably the vegetation databases from the national forests and parks), and ground surveys of selected areas.

Floristic information was derived mainly from published and unpublished maps produced by the vegetation type mapping survey. Where these maps were lacking we relied on USFS soil and vegetation survey notes (alpine and subalpine areas surveyed by R. Taskey), our own 1994/95 field reconnaissance surveys, forest patch type descriptions from the SNEP late seral old growth database (Franklin and Fites-Kaufmann 1996), and the map of foothill woodland types prepared by Pillsbury et al. (1991). Our draft map was extensively updated in timber-producing areas using USFS maps of timber plantations and shrub-dominated timberlands.

The database for the Sierra Nevada Region consists of 7,021 landscape units providing distributional information on 150 dominant species and 77 plant community types. Analysts can query the database to retrieve distribution data on individual species, unique combinations of species, or vegetation types defined by physiognomy and/or composition.

Because source information ranged widely in date and reliability, the current database is uneven in both level of detail and accuracy. We did not have the resources to assess the statistical accuracy of the vegetation map and associated database. However, we have appraised the product using less formal methods that have guided our use of the product. Based on UCSB field surveys in 1994 and 1995 and on comparisons with independent sources of vegetation data, the vegetation map probably overestimates the extent of conifer forest types and underestimates the extent of shrubland and mid-elevation hardwood types. Floristic information is more reliable in the northern and central subregion than in the southern subregion, which was only partially covered by the vegetation type mapping survey. Floristic information is also more reliable on public lands than private lands, and better for the national parks than for the national forests. The data on upland community types and wildlife habitat types are more reliable than information on individual species or on wetland or meadow habitats.

Sierra Nevada Region as a Whole

We mapped the Jepson Sierra Nevada Region over an area of 63,118 km². We classified 56,658 km² (89.7%) of this area as vegetated (Table SN-2). Non-vegetated areas included urban areas, lakes, reservoirs, rock outcrops, and alpine areas with little or no vascular plant cover.

Table SN-2. Percentage area of each CNDDB community type at each management class level in the Sierra Nevada Region and the northern and southern subregions. * indicates an addition to the standard CNDDB classification (Holland 1986)

CNDDB Code	CNDDB Community Name (Holland 1986)	Class 1			Class 2			Class 3			Class 4			Class 5			Total Mapped Distribution (km²)
		N	S	Total	N	S	Total	N	S	Total	N	S	Total	N	S	Total	N	S	Total

	SCRUB
34100	Mojave creosote bush scrub		0.1	0.1					50.0	50.0					49.9	49.9		7	7
34210	Mojave mixed woody scrub					0.2	0.2		68.4	68.4		3.3	3.3		28.1	28.1		278	278
34300	Blackbush scrub								63.2	63.2		1.9	1.9		34.9	34.9		164	164
35100	Great Basin mixed scrub	0.1	13.3	2.7	1.9	22.0	5.9	20.3	14.0	19.1	32.5	48.5	35.7	45.2	2.2	36.7	243	60	303
35210	Big sagebrush scrub	1.5	4.5	3.3	6.0	2.3	3.8	32.6	45.3	40.3	27.8	17.2	21.3	32.2	30.7	31.3	391	607	998
35211	Low sagebrush scrub *	0.1		0.1	4.3		4.3	30.2		30.2	10.1		10.1	55.4		55.4	77		77
35212	Silver sagebrush scrub *		7.0	5.2		0.3	0.2	9.8	78.3	60.3	7.2	13.7	12.0	83.0	0.7	22.3	11	30	41
35220	Subalpine sagebrush scrub	3.6	0.2	3.5	5.6	39.5	6.6	38.2		37.1	37.9	59.5	38.5	14.7	0.8	14.3	100	3	103
35400	Rabbitbrush scrub	0.9		0.9	3.6		3.6	23.6		23.6	65.0		65.0	7.0		7.0	46		46
35500	Cercocarpus ledifolius woodland *	0.5	42.5	17.7	2.4	40.8	18.2	33.5	7.9	23.0	53.2	7.7	34.5	10.4	1.1	6.6	156	109	264

	CHAPARRAL
37110	Northern mixed chaparral		12.7	11.9	1.7	11.5	10.9	0.9	20.5	19.3	15.4	29.0	28.1	82.0	26.3	29.8	15	219	234
37200	Chamise chaparral	0.1	10.4	5.8	0.8	2.7	1.9	3.4	24.1	14.9	14.4	34.8	25.7	81.3	28.0	51.7	364	457	821
37400	Semi-Desert chaparral		11.8	11.8		1.9	1.9		17.9	17.9		19.1	19.1		49.1	49.1		77	77
37510	Mixed montane chaparral	6.2	31.6	12.6	15.8	13.5	15.2	21.6	33.9	24.7	29.1	13.4	25.1	27.3	7.6	22.4	1,036	345	1,381
37520	Montane manzanita chaparral	0.1	9.0	4.7	9.9	7.6	8.8	8.0	20.5	14.4	19.2	37.3	28.5	62.8	25.6	43.6	229	244	473
37530	Montane ceanothus chaparral	1.2	8.2	1.4	3.7	14.8	4.2	21.3	13.3	21.0	44.5	48.7	44.6	29.4	15.0	28.8	191	8	199
37541	Shin oak brush		36.2	36.2		1.3	1.3		6.3	6.3		3.0	3.0		53.1	53.1		46	46
37542	Huckleberry oak chaparral		42.3	23.0	26.6	0.7	12.5	17.8	45.5	32.9	6.7	11.4	9.2	48.8	0.1	22.3	81	97	178
37550	Bush chinquapin chaparral	4.6	48.9	6.0	5.9		5.7	26.2	48.4	26.9	48.4	2.6	46.9	14.9		14.4	75	3	77
37620	Leather oak chaparral				47.8		47.8				6.8		6.8	45.4		45.4	4	3	6
37810	Buck brush chaparral		1.2	1.1	0.9	17.7	15.3	15.9	50.4	45.6	14.9	16.0	15.8	68.3	14.7	22.1	21	133	155
37900	Scrub oak chaparral				39.8	3.9	6.4	36.6	4.0	6.2	18.8	16.7	16.8	4.9	75.4	70.6	3	45	48
37A00	Interior live oak chaparral		4.4	4.3		7.6	7.5	18.4	8.3	8.5	14.4	9.9	10.0	67.2	69.7	69.7	5	197	202
37B00	Upper Sonoran manzanita chaparral		4.7	4.4	1.5	4.4	4.2	1.1	28.8	27.4	28.9	47.8	46.8	68.5	14.4	17.2	9	172	181
37D00	Ione chaparral										3.8		3.8	96.2		96.2	1		1
37E00	Mesic north slope chaparral		11.5	10.2	8.2	10.1	9.8	6.8	48.9	44.2	8.9	20.7	19.4	76.1	8.8	16.3	15	118	132
39000	Upper Sonoran subshrub scrub								5.1	5.1		15.6	15.6		79.4	79.4		8	8

	HERBACEOUS
42200	Non-native grassland		0.8	0.4	0.3	1.2	0.7	6.0	8.4