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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 kmē, a plus sign '+' indicates <25 kmē. 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)

SW

CW

NW

GV

CAS

MOD

ESN

SN

MOJ

SON

A

21210

Northern Foredunes

 

+

+

             

A

21310

Northern Dune Scrub

   

·

             

B

21320

Central Dune Scrub

 

+

               

F

22000

Desert Dunes

               

·

·

B

23300

Monvero Residual Dunes

     

+

           

B

31100

Northern Coastal Bluff Scrub

 

·

               

A

31200

Southern Coastal Bluff Scrub

+

                 

C

32100

Northern (Franciscan) Coastal Scrub

 

·

·

             

C

32200

Central (Lucian) Coastal Scrub

 

·

               

C

32300

Venturan Coastal Sage Scrub

·

·

               

C

32500

Diegan Coastal Sage Scrub

·

                 

D

32600

Diablan Sage Scrub

 

·

 

·

           

C

32700

Riversidian Sage Scrub

·

                 

F

33100

Sonoran Creosote Bush Scrub

               

·

·

F

33200

Sonoran Desert Mixed Scrub

                 

·

F

34100

Mojave Creosote Bush Scrub

·

         

·

+

· west only

·

G

34210

Mojave Mixed Woody Scrub

           

·

·

·

·

G

34220

Mojave Mixed Steppe

               

·

 

G

34240

Mojave Mixed Woody and Succulent Scrub

               

·

·

G

34300

Blackbush Scrub

           

·

·

·

 

D

35100

Great Basin Mixed Scrub

·

     

·

·

·

·

   

G

35110

Salvia dorri/ Chamaebatiaria scrub *

         

·

       

F

35210

Big Sagebrush Scrub

·

+

+

 

·

·

·

·

·

 

D

35211

Low Sagebrush Scrub *

       

+

·

·

·

   

D

35212

Silver Sagebrush Scrub *

         

·

 

·

   

G

35213

Black Sagebrush Scrub *

               

+

 

E

35220

Subalpine Sagebrush Scrub

       

·

   

·

   

D

35400

Rabbitbrush Scrub

     

+

+

·

+

·

·

 

E

35500

Cercocarpus ledifolius Woodland *

+

     

·

·

·

·

   

C

36110

Desert Saltbush Scrub

         

·

·

 

· west only

·

F

36120

Desert Sink Scrub

           

·

 

· west only

+

D

36130

Desert Greasewood Scrub

         

·

·

 

+

 

G

36140

Shadscale Scrub

           

·

 

·

 

G

36150

Desert Holly Scrub *

               

·

 

A

36210

Valley Sink Scrub

     

·

           

A

36220

Valley Saltbush Scrub

 

+

 

·

           

A

36320

Interior Coast Range Saltbush Scrub

     

·

           

C

37110

Northern Mixed Chaparral

·

+

·

 

·

   

·

   

C

37120

Southern Mixed Chaparral

·

                 

E

37200

Chamise Chaparral

·

·

·

+

     

·

·

 

C

37300

Red Shank Chaparral

·

+

               

E

37400

Semi-Desert Chaparral

·

·

 

·

     

·

·

·

F

37510

Mixed Montane Chaparral

·

+

·

 

·

   

·

   

E

37520

Montane Manzanita Chaparral

+

+

·

 

·

·

 

·

   

E

37530

Montane Ceanothus Chaparral

·

+

·

 

·

·

 

·

   

E

37541

Shin Oak Brush

   

·

 

·

   

·

   

F

37542

Huckleberry Oak Chaparral

   

·

       

·

   

E

37550

Bush Chinquapin Chaparral

   

+

 

·

   

·

   

A

37610

Mixed Serpentine Chaparral

 

·

·

             

E

37620

Leather Oak Chaparral

 

·

         

+

   

E

37810

Buck Brush Chaparral

·

·

·

 

·

·

 

·

   

E

37820

Blue Brush Chaparral

 

·

+

             

C

37830

Ceanothus crassifolius Chaparral

·

+

               

C

37840

Ceanothus megacarpus Chaparral

·

+

               

F

37900

Scrub Oak Chaparral

·

·

+

+

     

·

   

F

37A00

Interior Live Oak Chaparral

·

·

 

·

·

   

·

·

 

F

37B00

Upper Sonoran Manzanita Chaparral

·

·

         

·

   

A

37C10

Northern Maritime Chaparral

 

+

               

A

37C20

Central Maritime Chaparral

 

·

               

A

37D00

Ione Chaparral

             

+

   

F

37E00

Mesic North Slope Chaparral

+

·

·

 

+

   

·

   

C

37G00

Coastal Sage-Chaparral Scrub

·

·

               

F

39000

Upper Sonoran Subshrub Scrub

 

·

 

·

     

+

   

A

41000

Coastal Prairie

 

·

·

             

C

42110

Valley Needlegrass Grassland

+

   

+

           

B

42120

Valley Sacaton Grassland

     

+

           

D

42160

Desert Native Grassland *

               

·

 

D

42200

Non-Native Grassland

·

·

·

·

·

·

+

·

·

·

A

42300

Wildflower Field

               

+

 

A

43000

Great Basin Grassland

       

+

·

+

     

D

44110

Northern Hardpan Vernal Pool

     

+

           

B

44120

Northern Claypan Vernal Pool

     

+

           

A

44131

Northern Basalt Flow Vernal Pool

         

+

       

F

45100

Montane Meadow

   

·

 

·

+

·

·

   

F

45200

Subalpine or Alpine Meadow

       

·

 

+

·

   

A

45310

Alkali Meadow

     

·

 

+

·

+

   

E

45500

Great Basin Wet Meadow *

         

·

       

F

46000

Alkali Playa

               

· west only

·

A

47000

Pavement Plain

+

                 

B

51110

Sphagnum Bog

             

+

   

F

52110

Northern Coastal Salt Marsh

 

·

+

             

B

52120

Southern Coastal Salt Marsh

+

                 

A

52200

Coastal Brackish Marsh

+

 

·

·

           

A

52310

Cismontane Alkali Marsh

 

+

 

+

     

+

   

B

52320

Transmontane Alkali Marsh

         

+

+

+

+

 

B

52410

Coastal and Valley Freshwater Marsh

·

+

+

·

           

B

52420

Transmontane Freshwater Marsh

         

·

·

 

+

 

A

61110

North Coast Black Cottonwood Riparian Forest

   

+

             

A

61130

Red Alder Riparian Forest

 

+

+

             

C

61210

Central Coast Cottonwood-Sycamore Riparian Forest

 

·

               

E

61220

Central Coast Live Oak Riparian Forest

 

·

               

C

61230

Central Coast Arroyo Willow Riparian Forest

 

·

               

E

61310

Southern Coast Live Oak Riparian Forest

·

                 

A

61320

Southern Arroyo Willow Riparian Forest

·

                 

C

61330

Southern Cottonwood-Willow Riparian Forest

·

                 

A

61410

Great Valley Cottonwood Riparian Forest

     

·

+

   

+

   

A

61420

Great Valley Mixed Riparian Forest

   

+

·

+

   

+

   

A

61430

Great Valley Valley Oak Riparian Forest

     

·

+

   

+

   

C

61510

White Alder Riparian Forest

+

     

+

   

+

   

D

61520

Aspen Riparian Forest

           

·

+

   

E

61530

Montane Black Cottonwood Riparian Forest

           

+

+

   

A

61610

Modoc-Great Basin Cottonwood-Willow Riparian Forest

       

+

·

+

 

+

 

A

61700

Mojave Riparian Forest

               

·

 

A

61810

Sonoran Cottonwood-Willow Riparian Forest

                 

+

B

61820

Mesquite Bosque

               

· west only

·

A

62100

Sycamore Alluvial Woodland

 

+

 

+

           

F

62200

Desert Dry Wash Woodland

               

·

·

C

62400

Southern Sycamore-Alder Riparian Woodland

+

                 

D

63100

North Coast Riparian Scrub

   

·

             

C

63200

Central Coast Riparian Scrub

 

+

               

C

63310

Mule Fat Scrub

·

·

               

A

63320

Southern Willow Scrub

+

                 

C

63330

Southern Alluvial Fan Scrub *

+

                 

D

63410

Great Valley Willow Scrub

     

+

           

A

63420

Great Valley Mesquite Scrub

     

+

           

F

63500

Montane Riparian Scrub

       

+

 

+

·

   

A

63600

Modoc-Great Basin Riparian Scrub

         

+

·

     

C

63700

Mojave Desert Wash Scrub

               

+

 

G

63810

Tamarisk Scrub

     

·

       

·

 

C

63820

Arrowweed Scrub

     

+

           

D

71110

Oregon Oak Woodland

   

·

 

·

·

 

·

   

D

71120

Black Oak Woodland

 

·

·

 

·

   

·

   

A

71130

Valley Oak Woodland

·

·

·

·

+

   

·

   

D

71140

Blue Oak Woodland

+

·

·

·

·

   

·

   

D

71150

Interior Live Oak Woodland

+

 

·

+

·

 

+

·

   

C

71160

Coast Live Oak Woodland

·

·

·

+

           

A

71170

Alvord Oak Woodland

 

·

               

A

71182

Dense Engelmann Oak Woodland

·

                 

A

71210

California Walnut Woodland

·

                 

E

71310

Open Foothill Pine Woodland

 

·

·

 

·

   

·

   

D

71321

Serpentine Foothill Pine-Chaparral Woodland

 

·

·

             

D

71322

Non-Serpentine Foothill Pine Woodland

+

+

·

 

·

   

·

   

D

71410

Foothill Pine-Oak Woodland

+

·

·

 

·

+

 

·

+

 

D

71420

Mixed North Slope Cismontane Woodland

   

·

             

D

71430

Juniper-Oak Cismontane Woodland

 

·

 

+

·

         

G

71600

Oak-Piñon Woodland *

             

·

   

E

72100

Great Basin Woodlands

   

·

 

·

·

·

·

   

F

72200

Mojavean Pinyon and Juniper Woodlands

·

+

 

+

   

+

·

·

·

G

72300

Peninsular Pinyon and Juniper Woodlands

+

               

·

A

72400

Cismontane Juniper Woodland and Scrub

 

·

               

G

73000

Joshua Tree Woodland

           

·

·

   

E

81100

Mixed Evergreen Forest

 

·

·

             

D

81200

California Bay Forest

 

+

+

             

D

81310

Coast Live Oak Forest

·

·

·

             

F

81320

Canyon Live Oak Forest

·

·

·

 

·

 

+

·

   

D

81330

Interior Live Oak Forest

·

·

·

 

·

   

·

   

D

81340

Black Oak Forest

·

·

·

 

·

+

 

·

   

D

81400

Tan-Oak Forest

 

·

·

 

+

   

·

   

E

81B00

Aspen Forest

         

·

·

·

   

B

82100

Sitka Spruce-Grand Fir Forest

   

·

             

D

82310

Alluvial Redwood Forest

   

·

             

E

82320

Upland Redwood Forest

 

·

·

             

A

82410

Coastal Douglas-Fir-Western Hemlock Forest

   

·

             

E

82420

Upland Douglas-Fir Forest

 

·

·

             

B

82500

Port Orford Cedar Forest

   

+

             

B

83110

Beach Pine Forest

   

+

             

B

83120

Bishop Pine Forest

 

·

·

             

A

83130

Monterey Pine Forest

 

·

               

A

83161

Mendocino Pygmy Cypress Forest

   

+

             

D

83210

Knobcone Pine Forest

+

+

·

 

·

   

+

   

A

83220

Northern Interior Cypress Forest

 

+

·

   

+

       

A

83330

Southern Interior Cypress Forest

+

           

+

   

E

84110

Coast Range Mixed Coniferous Forest

 

+

·

             

B

84120

Santa Lucia Fir Forest

 

+

               

F

84130

Coast Range Ponderosa Pine Forest

 

·

·

             

F

84140

Coulter Pine Forest

·

·

               

F

84150

Bigcone Spruce-Canyon Oak Forest

·

+

               

G

84160

Ultramafic White Pine Forest

   

+

             

F

84171

Northern Ultramafic Jeffrey Pine Forest

   

·

             

E

84180

Ultramafic Mixed Coniferous Forest

 

·

·

             

E

84210

Westside Ponderosa Pine Forest

·

+

·

 

·

   

·

   

D

84220

Eastside Ponderosa Pine Forest

   

+

 

·

·

 

·

   

D

84230

Sierran Mixed Coniferous Forest

·

 

·

 

·

·

 

·

   

F

84240

Sierran White Fir Forest

   

·

 

·

   

·

   

F

84250

Big Tree Forest

             

·

   

D

84260

Modoc White Fir Forest *

         

·

       

F

85100

Jeffrey Pine Forest

·

+

+

 

·

·

·

·

   

G

85120

Red Fir-Western White Pine Forest *

             

·

   

F

85210

Jeffrey Pine-Fir Forest

·

+

·

 

·

·

+

·

   

F

85310

Red Fir Forest

   

·

 

·

+

 

·

   

F

85320

Southern California White Fir Forest

·

                 

B

85410

Siskyou Enriched Coniferous Forest

   

·

             

B

85420

Salmon-Scott Enriched Coniferous Forest

   

·

             

G

86100

Lodgepole Pine Forest

+

 

+

 

·

·

·

·

   

G

86210

Whitebark Pine-Mountain Hemlock Forest

       

·

   

·

   

G

86220

Whitebark Pine-Lodgepole Pine Forest

         

+

·

·

   

G

86300

Foxtail Pine Forest

             

·

   

B

86400

Bristlecone Pine Forest

           

·

 

+

 

G

86500

Southern California Subalpine Forest

·

                 

G

86600

Whitebark Pine Forest

       

+

 

+

·

   

B

86700

Limber Pine Forest

           

+

+

   

G

91110

Klamath-Cascade Fell-field

   

+

 

·

         

G

91120

Sierra Nevada Fell-field

             

·

   

G

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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