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