Soil Ecology and Restoration Group

Coastal sage scrub restoration

 

Continued research on CSS revegetation and restoration has provided further understanding of plant production, planting, irrigation, and maintenance requirements for CSS. The more complete challenge or recreating CSS ecosystems on degraded sites is still a study in progress. As read et at. (1996) note CSS restoration cannot be treated simply as a landscaping project. The goal is to create or repair a complex community that includes soil fungi, bacteria, insects, algae, mosses, lichen, mammals, birds and plants. This community still is not well understood despite extensive work by Westman (1981) and others, see Eliason (1995). Unfortunately more money has been spent on failed restoration projects than on basic research to understand the "patchy" community, which has been heavily disturbed in most of its range. Some have even argued that it is a product of disturbance, an anthropogenic community (Vogl, 1976; Axedlrod, 1978).

Our work has tested the value of desert planting approaches in the CSS community. These have been successful, but the deeper containers desirable in the desert have not been required along the coast where summer fog reduces plant moisture stress. A brief summary of results from several of our CSS shrub replanting projects is included after a very brief description of the CSS community. This is followed by the description of a general approach for dealing with CSS revegetation. The specifics for a given site will depend on the nature and level of disturbance, remnant plant populations, the condition of adjacent lands, and the time and constraints on repair work. More work has been done on perennial plants than annuals, a remaining challenge that may be critical for a butterfly habitat repair and mitigation.

 

What is CSS?
CSS is found at low elevation in the maritime climate zone of Southern California. CSS shrubs are generally low growing and predominantly drought-deciduous. Plants of the CSS community are adapted to the limited rainfall and cope by being: 1) evergreen, with relatively small often resinous or waxy leaves, 2) drought deciduous, or 3) drought avoiding. CSS has been severely affected by urbanization, overgrazing, and agriculture. Much of the work in CSS has been driven by the need to improve habitat for the California Gnatcatcher, Polopptila californica. Key components in CSS for the Gnatcatcher include: California Sagebrush, Artemisia californica, California buckwheat, Eriogonum fasciculatum, with a few scattered perching shrubs, such as Laural sumac (Malosma laurina). Future challenges may include habitat repair for endangered butterflies.

Moisture differences between north and south facing slopes lead to dramatic changes in CSS community structure and function. Plants on south facing slopes tend to be small and drought tolerant with succulents, while north facing slopes and moister areas may have large evergreen shrubs and trees. Mesa tops and other areas may include species from both communities, as well as scattered vernal pools.

The most visible parts of the CSS community include California Encelia californica, with bright yellow flowers and drought deciduous light-green foliage; Black sage, Salvia mellifiera, with blackish square stems and narrow dark-green lance-shaped leaves with white flowers on long stalks. Monkey flowers, Mimulus sp., provide a bright spring show with creamy yellow to dark red blossoms favored by hummingbirds and chaparral Mallow, Malacotham nusfasciculatu, provides showy pink flowers for many weeks.

Many succulents are found in CSS and the related Maritime Succulent Shrub, including barrelcacuts, Ferocactus sp., Beavertail cactus Opuntia basilaris, chollas, Opuntia parryi v. serpentina, and prickly pears, Opuntia littoralis. Dudleya edulis, Lady Fingers, and Dudleya lanceolata, Coastal Dudleya. Our Lord's Candle, Yucca whipplei and Yucca schidegera are more rare. A range of grasses may be found under shrubs and between shrubs including the Stipas, Nassella lepida and Nassella pulchra, Mellicas, and many others. Less disturbed areas are often carpeted with the light gray to gray green Mesa club moss, (also known as gray spike moss of ashy spike moss), Selaginella cinerascens. Flowering bulbs were once probably much more common. These include several lily species, Calachortus sp., Blue Dicks, Dichlostemma puchellum, and wild onions, Allium sp. That provided important food for the native people. Othe common flowers include Blue Eyed Grass, Sisyrinch bellum, lupines, Lupinus sp., gentians, goldfields, everlastings, and poppies. In less disturbed moist areas, Shooting stars, Dodecathon clevelandii, may be encountered.

The plants growing in moist areas and on north-facing slopes and more commonly evergreen with larger leaves and extensive roots. These include Toyon, Heteromeles arbutifolia, Laural sumac, Malosma laurina, Lemonade berry, Rhus integrifolia, and Fuchsia-flowered gooseberry, Ribes speciosum. Several species of Ceanothus may also be found, including Ceanothus verrucosus, the Warty-stemmed Ceanothus.

Oaks were probably once more common in CSS communities where they are now absent. A few appropriate oaks Coast Live (Q. agrifolia) or Scrub oaks (Q. berbidifolia) may add value to a CSS site. These were rapidly removed for fuelwood, construction materials and other purposes in the 1700s and 1800s. Early accounts often describe magnificent oaks in areas where they are no longer found.

 

Shrub planting success in San Diego
The following tables provide survival data for four sites at Point Loma. The sites range from relatively undisturbed soils at the McClelland Road site, with a healthy soil and good phosphorus to nitrogen ratio, to a moderately disturbed site at the South Tank, to very disturbed sites at the erosion slope and Bayview. Only limited remediation of soil was possible at these sites. Plants were outplanted from a range of container types. These studies showed that standard gallon pots or plant bands were suitable for most species. Plants received treeshelters or cages for protection from herbivory, predominantly from rabbits. Hand watering was typically done twice a month in the summer.

The survival by species suggests which plants may be most appropriate for different disturbance levels. Two of the key species from Gnatcatchers are in bold, California Sagebrush was successful on all sites, but California Buckwheat survival was closely related to site condition. Buckwheat survival dropped from 77% at McClelland Road to 27% on the erosion slope. The survival of California Sagebrush is also an indicator of site condition, dropping from 91% at the least disturbed site to 72% at the very disturbed Bayview site. The more vulnerable Locoweed plants dropped from 100% survival at the McClelland Road site to 11% at the Bayview site and 17% at the erosion slope. The succulent Dudleyas generally did well even on disturbed, compacted sites.

 

Table 1. Percent survival by species of container planted seedlings on McClelland Road, a slightly disturbed site affected by limited road use and utility installation. Flat with some protection from winds by a fence and ground shape.

Species Common name Percent survival
Artemisia californica
Astragalus trichopodus
Ceanothus verrucosus
Ceanothus tomentosus
Cneoridium dumosum
Dudleya edulis
Dudleya lanceolata
Dudleya pulverulenta
Elymus condensatus
Encelia californica
Eriogonum fasciculatum
Euphorbia misera
Hemizonia fasciculata
Heteromeles arbutifolia
Lotus scoparius
Malacothamnus fasciculatus
Malosma laurina
Nassella lepida
Opuntia littoralis
Opuntia parryi v. serpentina
Pinus torreyana
Quercus dumosum
Rhamnus crocea
Rhus integrifolia
Salvia mellifera S
Simmondsia chinensis
California Sagebrush
Locoweed
Wart-stemmed Ceanothus
Ramona Lilac
Spicebush
Lady Fingers
Coastal Dudleya
Chalk Dudleya
Giant Wild Rye
California Encelia
Flat-top Buckwheat
Cliff Spurge
Tarweed
Toyon
Deerweed
Chaparral Mallow
Laurel Sumac
Foothill Needlegrass
Prickly Pear Cactus
Snake Cholla
Torrey Pine
Scrub Oak
Coffeeberry
Lemonade berry
Black Sage
Jojoba
91
100
100
50
40
39
69
22
27
86
77
65
78
61
78
61
77
61
100
95
100
59
21
90
95
44

 

 

Table 2. Percent survival by species of container planted seedlings at the South Tank site, an area affected by construction and formerly covered with acacia trees and ice plant. East facing shallow slope, protected from west winds.

Species Common name Percent survival
Artemisia californica
Astragalus trichopodus
Dudleya edulis
Dudleya lanceolata
Encelia californica
Eriogonum fasciculatum
Euphorbia misera
Heteromeles arbutifolia
Isocoma menziesii
Malacothamnus fasciculatus
Malosma laurina
Nassella lepida
Rhus integrifolia
Salvia mellifera
California Sagebrush
Locoweed
Lady Fingers
Coastal Dudleya
California Encelia
Flat-top Buckwheat
Cliff Spurge
Toyon
Coastal Isocoma
Chaparral Mallow
Laurel Sumac
Foothill Needlegrass
Lemonade berry
Black Sage
83
67
84
100
90
74
86
75
86
79
33
85
88
88

 

 

Table 3. Percent survival by species of container planted seedlings on the Erosion Slope, a pipeline corridor with a land slump exposing subsoil. Steep, east facing, dry and hot in summer.

Species Common name Percent survival
Artemisia californica
Astragalus trichopodus
Cneoridium dumosum
Dudleya edulis
Dudleya lanceolata
Eriogonum fasciculatum
Euphorbia misera
Heteromeles arbutifolia
Isocoma menziesii
Lotus scoparius
Malacothamnus fasciculatus
Malosma laurina
Nassella lepida
Rhus integrifolia
Salvia mellifera
California Sagebrush
Locoweed
Spicebush
Lady Fingers
Coastal Dudleya
Flat-top Buckwheat
Cliff Spurge
Toyon
Coastal Isocoma
Deerweed
Chaparral Mallow
Laurel Sumac
Foothill Needlegrass
Lemonade berry
Black Sage
74
11
19
33
100
27
40
20
25
100
63
50
28
62
3

 

 

Table 4. Percent survival by species of container planted seedlings at Bayview, an area affected by parking lot construction, soil dumping with acacia trees, ice plant, and tumbleweed. East facing, flat to shallow slope but exposed to winds and sun.

Species Common name Percent survival
Artemisia californica
Astragalus trichopodus
Cneoridium dumosum
Dudleya edulis
Dudleya lanceolata
Eriogonum fasciculatum
Euphorbia misera
Isocoma menziesii
Lotus scoparius
Malacothamnus fasciculatus
Nassella lepida
Rhus integrifolia
Salvia mellifera
California Sagebrush
Locoweed
Spicebush
Lady Fingers
Coastal Dudleya
Flat-top Buckwheat
Cliff Spurge
Coastal Isocoma
Deerweed
Chaparral Mallow
Foothill Needlegrass
Lemonade berry
Black Sage
72
17
22
62
100
35
14
100
77
40
21
64
67

 

 

With good site preparation, well prepared plants, proper planting techniques, plant protection and limited irrigation survival should be between 70-100% for most species. Some species, including spicebush, coffeeberry, and ceanothus were less successful and will require further research.

 

General guidelines for installing CSS
Site evaluation should be completed to determine the level of compaction, rate of infiltration, organic matter, salinity, pH, texture, macronutrients, micronutrients, and fungal hyphae, spores, and bacteria if possible. A site historical review should be done using historical records, old photos and aerial photos to explore past disturbance histories. A community analysis of a less disturbed reference site should be done if possible to plan planting patterns and species composition.

Seed collection should be started as soon as possible from plants on or near the site. Collect seeds from local species for several years if possible. Clean, do germination tests, and store properly. Upgrade seed quality for container production.

Planning is critical, develop a timeline, budget, review regulations and approvals, timing, cooperators, actors etc. Plan plant production carefully. Prepare the site before planting and ensure adequate maintenance.

Site preparation is typically needed to address compaction, infiltration, and nutrient problems. This may include: ripping, spading or pitting, and should leave a rough soil surface. Add organic matter and nutrients as tests indicate. Add compost (beware weed seeds), bark, wood chips (watch seeds if landscaped prunings), sawdust, or straw (esp. vertical straw bundles of native grass or rice straw). Materials with possible weed seeds should be composted thoroughly. High C:N ratio material can help tie up excess nitrogen which encourages weeds. Nitrogen input from atmospheric fallout can exceed 40 kg/ha, most from auto exhaust.

POOR SOIL PREPARATION IS THE PRIMARY CAUSE OF FAILURE.

Weed control can be essential on degraded sites. Solarize, fumigate, or use pre-emergent herbicides, burn, or irrigate and till to minimize weed competition. A large seed bank of weed seeds is almost certain to exist and weed suppression for several years may be needed.

Direct seedling for shrubs rarely works well as many shrubs have long stratification requirements. Hydroseeding rarely works well in this dry environment, but a double spray with seeds in the first mix churned into the soil and then buried with a second spray with wood fiber can be much more effective than a single application. Timing is critical for hydroseeding. Ideally spraying will be done a day before gentle rains begin, or after soaking rains.

Container plants are very effective and the backbone or restoration work in CSS. Plant into prewetted, augered holes. Plants should be root dominated (young, with big roots, small tops) and planted before tops get large (standard 1 gallon pots are ok with appropriate plant management but 5, 10, and 15 gallon pots should be avoided). On large denuded, ice plant or mustard dominated sites inoculation with mycorrhizal fungi may be desirable. A typical mix of containers might include 50% tall ones (6" x 16") or gallons, 50% plant bands (2 x 2 x 14), with smaller containers only for cacti and succulents. Add a ring of large bark mulch or weed mat for each plant if possible. Flat sites may be machine planted from a transplanter.

Plant protection is needed on most sites. Rabbits, pocket gophers, and deer may cause losses without protection. Most areas will require plant protection of treeshelters, cages or fences. In areas with extensive pocket gopher colonies fence may have to be set into the ground to 8 - 12 inches.

Weed control on a continuing basis may be needed if fumigation or solarization could not be done. Competition from fast growing exotic weeds may not kill native shrubs but it does reduce growth. Consider using a blanket wiper, wick, mow or graze weeds. Late spring burns will help where they can be done safely, burn before seed maturity on weeds.

Irrigation is needed in most years. Hand water or install deep pipes or drip systems using emitters in " pvc. Spaghetti tube and even flex tube are usually problematic as a result of animal damage by rabbits and coyotes. Drywater has not been successful. Overhead watering can encourage weeds and be detrimental to native species, but may be successful if timed to mimick natural rain events.

 

Conclusion
CSS can be improved and restored on almost any site. Many of the plants are vigorous and grow rapidly. Costs can range from $1000 acre for a minimal job to more than $20,000 acre. Container planting with plant protection and limited supplemental irrigation is most effective. Direct seeding is limited to sites without weeds, and even there a mix of direct seeding and container plants is likely to provide faster visual and ecological recovery.