7. MANAGEMENT PRIORITIES FOR PLANT COMMUNITIES

The purpose of gap analysis is to identify land-cover types and vertebrate species in need of additional protection before they become critically threatened. The gap analysis approach uses management intent expressed in legislation, designation, or plans as indicators of the kinds of activities that may be permitted and hence of the potential impact on biodiversity. The previous two chapters summarized the management status of California's land-cover types, wildlife habitats, and vertebrate species. Here we identify the highest p riority elements based in part on management status and partly on other factors such as their rarity and endemism, their condition, the historical loss estimated to have occurred, and additional information about the kinds of activities that are likely to occur in each type. Table 7-1 lists the highest priority plant communities, organized into seven categories, from the statewide assessment and the vulnerable communities in the ten Jepson regions of California (Hickman 1993; see Appendix for details on regional assessments).

Within the set of plant communities, we distinguish seven categories. The first two categories include all those rated as rare by the NHD (S1 or S2 in Table 5-2). Of these, the highest priority (Group A in Table 7-1) is for rare communities with less than 20% level of status 1 and 2 management, while the second priority types have more than 20% (Group B).

For widespread community types, priorities were set based on a combination of two factors: percentage of status 1 and 2 lands and an index of threat. The threat index was calculated as a sum of roadedness (Chapter 4) and projected population growth (Chapter 5), normalized by their mean values, and rescaled so that absence of threat is equal to zero as shown in Figure 7-1. The first group (Group C) of common communities was characterized by a threat index > 3.75, indicating a relatively high degree of either past disturbance or future loss. Note that this threshold level was selected as a natural break in the set of plant communities, not on any a priori or theoretical basis. It had the further advantage of allowing us to divide communities into approximately equal-sized groups. Virtually all Group C community types were also relatively under-represented (< 20% status 1 and 2). The remaining four groups all appear relatively less threatened by roads or future development (threat index < 3.75) and were categorized based on their level of protection into roughly equal numbers of types in each group. We used the same break points as shown in Table 5-2, i.e., 10%, 20%, and 50%, in decreasing order of priority. Five exceptions were made to these general rules. Four types that were rated as rare by NHD were mapped over extensive areas by CA-GAP, perhaps due to differences in interpretation. We therefore chose to assign Mojave Mixed Steppe, Upland Redwood Forest, Westside Ponderosa Pine Forest, and Eastside Ponderosa Pine Forest to groups G, E, E, and D respectively, as if they were not rare types. Also, we assigned Tamarisk Scrub to group G because it is not a native community type and in fact is generally considered a pest species. The remaining urban, agricultural, and non-vegetated land cover types were assigned to group H that has no conservation priority for its vegetation values. There may still be important habitats and other ecosystem values, however, in the non-vegetated types (e.g., water bodies, sand dunes, rock outcrops, etc.).

Figure 7-1. Vulnerability groups of widespread plant communities from the statewide gap analysis based on a combination of current protection and threat.

Table 7-1. Statewide and regional conservation priorities of plant community types based on gap analysis. Bullets indicate occurrence of the type in the region >25 km², a plus sign '+' indicates <25 km². Shading in the cell indicates the type is considered vulnerable within that region (see regional gap analysis summaries in the appendix for details). An asterisk after the community name indicates a type described for CA-GAP. Priorities decrease alphabetically; that is, "A" is highest priority and "G" is lowest.

Priority Level

CNDDB Code

CNDDB Community Name (Holland 1986)

CAS

MOD

ESN

MOJ

SON

21210

Northern Foredunes

21310

Northern Dune Scrub

21320

Central Dune Scrub

22000

Desert Dunes

23300

Monvero Residual Dunes

31100

Northern Coastal Bluff Scrub

31200

Southern Coastal Bluff Scrub

32100

Northern (Franciscan) Coastal Scrub

32200

Central (Lucian) Coastal Scrub

32300

Venturan Coastal Sage Scrub

32500

Diegan Coastal Sage Scrub

32600

Diablan Sage Scrub

32700

Riversidian Sage Scrub

33100

Sonoran Creosote Bush Scrub

33200

Sonoran Desert Mixed Scrub

34100

Mojave Creosote Bush Scrub

· west only

34210

Mojave Mixed Woody Scrub

34220

Mojave Mixed Steppe

34240

Mojave Mixed Woody and Succulent Scrub

34300

Blackbush Scrub

35100

Great Basin Mixed Scrub

35110

Salvia dorri/ Chamaebatiaria scrub *

35210

Big Sagebrush Scrub

35211

Low Sagebrush Scrub *

35212

Silver Sagebrush Scrub *

35213

Black Sagebrush Scrub *

35220

Subalpine Sagebrush Scrub

35400

Rabbitbrush Scrub

35500

Cercocarpus ledifolius Woodland *

36110

Desert Saltbush Scrub

· west only

36120

Desert Sink Scrub

· west only

36130

Desert Greasewood Scrub

36140

Shadscale Scrub

36150

Desert Holly Scrub *

36210

Valley Sink Scrub

36220

Valley Saltbush Scrub

36320

Interior Coast Range Saltbush Scrub

37110

Northern Mixed Chaparral

37120

Southern Mixed Chaparral

37200

Chamise Chaparral

37300

Red Shank Chaparral

37400

Semi-Desert Chaparral

37510

Mixed Montane Chaparral

37520

Montane Manzanita Chaparral

37530

Montane Ceanothus Chaparral

37541

Shin Oak Brush

37542

Huckleberry Oak Chaparral

37550

Bush Chinquapin Chaparral

37610

Mixed Serpentine Chaparral

37620

Leather Oak Chaparral

37810

Buck Brush Chaparral

37820

Blue Brush Chaparral

37830

Ceanothus crassifolius Chaparral

37840

Ceanothus megacarpus Chaparral

37900

Scrub Oak Chaparral

37A00

Interior Live Oak Chaparral

37B00

Upper Sonoran Manzanita Chaparral

37C10

Northern Maritime Chaparral

37C20

Central Maritime Chaparral

37D00

Ione Chaparral

37E00

Mesic North Slope Chaparral

37G00

Coastal Sage-Chaparral Scrub

39000

Upper Sonoran Subshrub Scrub

41000

Coastal Prairie

42110

Valley Needlegrass Grassland

42120

Valley Sacaton Grassland

42160

Desert Native Grassland *

42200

Non-Native Grassland

42300

Wildflower Field

43000

Great Basin Grassland

44110

Northern Hardpan Vernal Pool

44120

Northern Claypan Vernal Pool

44131

Northern Basalt Flow Vernal Pool

45100

Montane Meadow

45200

Subalpine or Alpine Meadow

45310

Alkali Meadow

45500

Great Basin Wet Meadow *

46000

Alkali Playa

· west only

47000

Pavement Plain

51110

Sphagnum Bog

52110

Northern Coastal Salt Marsh

52120

Southern Coastal Salt Marsh

52200

Coastal Brackish Marsh

52310

Cismontane Alkali Marsh

52320

Transmontane Alkali Marsh

52410

Coastal and Valley Freshwater Marsh

52420

Transmontane Freshwater Marsh

61110

North Coast Black Cottonwood Riparian Forest

61130

Red Alder Riparian Forest

61210

Central Coast Cottonwood-Sycamore Riparian Forest

61220

Central Coast Live Oak Riparian Forest

61230

Central Coast Arroyo Willow Riparian Forest

61310

Southern Coast Live Oak Riparian Forest

61320

Southern Arroyo Willow Riparian Forest

61330

Southern Cottonwood-Willow Riparian Forest

61410

Great Valley Cottonwood Riparian Forest

61420

Great Valley Mixed Riparian Forest

61430

Great Valley Valley Oak Riparian Forest

61510

White Alder Riparian Forest

61520

Aspen Riparian Forest

61530

Montane Black Cottonwood Riparian Forest

61610

Modoc-Great Basin Cottonwood-Willow Riparian Forest

61700

Mojave Riparian Forest

61810

Sonoran Cottonwood-Willow Riparian Forest

61820

Mesquite Bosque

· west only

62100

Sycamore Alluvial Woodland

62200

Desert Dry Wash Woodland

62400

Southern Sycamore-Alder Riparian Woodland

63100

North Coast Riparian Scrub

63200

Central Coast Riparian Scrub

63310

Mule Fat Scrub

63320

Southern Willow Scrub

63330

Southern Alluvial Fan Scrub *

63410

Great Valley Willow Scrub

63420

Great Valley Mesquite Scrub

63500

Montane Riparian Scrub

63600

Modoc-Great Basin Riparian Scrub

63700

Mojave Desert Wash Scrub

63810

Tamarisk Scrub

63820

Arrowweed Scrub

71110

Oregon Oak Woodland

71120

Black Oak Woodland

71130

Valley Oak Woodland

71140

Blue Oak Woodland

71150

Interior Live Oak Woodland

71160

Coast Live Oak Woodland

71170

Alvord Oak Woodland

71182

Dense Engelmann Oak Woodland

71210

California Walnut Woodland

71310

Open Foothill Pine Woodland

71321

Serpentine Foothill Pine-Chaparral Woodland

71322

Non-Serpentine Foothill Pine Woodland

71410

Foothill Pine-Oak Woodland

71420

Mixed North Slope Cismontane Woodland

71430

Juniper-Oak Cismontane Woodland

71600

Oak-Piñon Woodland *

72100

Great Basin Woodlands

72200

Mojavean Pinyon and Juniper Woodlands

72300

Peninsular Pinyon and Juniper Woodlands

72400

Cismontane Juniper Woodland and Scrub

73000

Joshua Tree Woodland

81100

Mixed Evergreen Forest

81200

California Bay Forest

81310

Coast Live Oak Forest

81320

Canyon Live Oak Forest

81330

Interior Live Oak Forest

81340

Black Oak Forest

81400

Tan-Oak Forest

81B00

Aspen Forest

82100

Sitka Spruce-Grand Fir Forest

82310

Alluvial Redwood Forest

82320

Upland Redwood Forest

82410

Coastal Douglas-Fir-Western Hemlock Forest

82420

Upland Douglas-Fir Forest

82500

Port Orford Cedar Forest

83110

Beach Pine Forest

83120

Bishop Pine Forest

83130

Monterey Pine Forest

83161

Mendocino Pygmy Cypress Forest

83210

Knobcone Pine Forest

83220

Northern Interior Cypress Forest

83330

Southern Interior Cypress Forest

84110

Coast Range Mixed Coniferous Forest

84120

Santa Lucia Fir Forest

84130

Coast Range Ponderosa Pine Forest

84140

Coulter Pine Forest

84150

Bigcone Spruce-Canyon Oak Forest

84160

Ultramafic White Pine Forest

84171

Northern Ultramafic Jeffrey Pine Forest

84180

Ultramafic Mixed Coniferous Forest

84210

Westside Ponderosa Pine Forest

84220

Eastside Ponderosa Pine Forest

84230

Sierran Mixed Coniferous Forest

84240

Sierran White Fir Forest

84250

Big Tree Forest

84260

Modoc White Fir Forest *

85100

Jeffrey Pine Forest

85120

Red Fir-Western White Pine Forest *

85210

Jeffrey Pine-Fir Forest

85310

Red Fir Forest

85320

Southern California White Fir Forest

85410

Siskyou Enriched Coniferous Forest

85420

Salmon-Scott Enriched Coniferous Forest

86100

Lodgepole Pine Forest

86210

Whitebark Pine-Mountain Hemlock Forest

86220

Whitebark Pine-Lodgepole Pine Forest

86300

Foxtail Pine Forest

86400

Bristlecone Pine Forest

86500

Southern California Subalpine Forest

86600

Whitebark Pine Forest

86700

Limber Pine Forest

91110

Klamath-Cascade Fell-field

91120

Sierra Nevada Fell-field

94000

Alpine Dwarf Scrub

Of the 194 natural community types, we have ranked 41 as highest priority for conservation (Class A), based on their rarity and lack of protection (Table 7-1). Another 20 community types are also rare but have greater than 20% protection. All of these rare types need to be examined in greater detail to determine more their true extent, which was only coarsely estimated by CA-GAP methods, and the actual threats they face. Some of the common types include rare subtypes. Coast Range Ponderosa Pine Forest, for instance, includes a maritime subtype that is restricted to sterile marine sand deposits in Santa Cruz County that may need additional management. These caveats underscore the need to complement the coarse-filter of gap analysis with a fine filter approach to catch these special cases.

The common types were divided into roughly equal-sized priority groups, with between 23 and 31 types in each. Twenty-four types were ranked as Group C, with low protection and relatively high level of threat. Group C types tend to be the coastal scrub, chaparral, and woodland types of southern California where population growth pressures are the greatest. Group D contains communities that are not well-represented in biodiversity management areas but face less threat than Group C according to our simple index. These community types tend to be Great Basin scrub, non-native grassland, oak woodlands, and mixed conifer types, although they all face other forms of threat that our index does not address. Group E is the types with relatively low threat and greater than 10% in status 1 and 2 management areas. This group includes many of the common chaparral types, forests of the coastal mountains, and some Great Basin communities. Types with low threat and moderate protection are in Group F, which consists of many of the desert communities and montane shrub and forest types. Group G has the most well-represented communities, which therefore have the lowest levels of threat. These communities generally are from the desert and subalpine areas, which are the best protected in California.

A few plant community types deserve special mention where the CA-GAP is insufficient to evaluate them adequately. One group of communities that need to be highlighted are those that could not be mapped reliably at the resolution of GAP. Most important of these are the wetland types, such as marshes, vernal pools, riparian scrub, and other aquatic habitats. Joshua Tree Woodland in another example. It was not mapped as a specific plant community in the land-cover database of the Mojave Desert region where it is most common. The presence of Joshua Tree was only recorded as present where known. Frequently the density of Yucca brevifolia is so low (or unknown) that the community was classified as a scrub type. Many of these locations may actually be Joshua Tree Woodland, but our analysis is unable to evaluate its current management status reliably at this time.

Although a statewide assessment is useful for conservation planning at that level, most conservation action occurs at the ecoregional level. The statewide summary can potentially mask regional differences in conservation needs. For example, Mojave Creosote Bush Scrub (34100) at the state level has over 30% in status 1 and 2 managed areas, is relatively unfragmented by roads, and is not threatened with rapid urbanization, and thus is not considered vulnerable by the criteria in CA-GAP. However, in the analysis of the Mojave Desert region, this community was found to be relatively unprotected in the western subregion of the Mojave, is floristically distinct from its counterpart in other regions, and is threatened by continuing urban expansion. Thus our recommendation is this type receive conservation attention in this one subregion of the state. The basis for all the regional ratings is provided in the sections of the appendix discussing individual regions.

Other communities can only be partially evaluated in California because they extend across state lines. There are too many examples to list here, but a few are worth a special note, including Oregon Oak Woodland, Sitka Spruce-Grand Fir, and many of the Great Basin types. Their management status should be evaluated over their entire geographic distributions.

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