Soil Ecology Restoration Group

last update January 13, 2001

COASTAL SAGE SCRUB RESTORATION ON 0.6 ACRE MITIGATION SITE ON MARINE CORPS AIR STATION MIRAMAR FIRST YEAR ANNUAL REPORT 1999

Introduction
Marine Corps Air Station Miramar, hereinafter referred to as the "Station", is located in San Diego County, California four miles east of the Pacific Ocean and 13 miles north of downtown San Diego. Road expansion work in November 1998 on Vega Road just east of Kearny Villa Road and on the east end of Ammo Road Road extended into a total of 0.3 acres of undisturbed coastal sage scrub habitat. This area is known to support populations of the federally threatened coastal California gnatcatcher (Polioptila californica californica). Mitigation for this project required restoration of a 0.6 acre area. In September 1998, a Cooperative Letter of Agreement was signed between Southwest Division , Naval Facilities Engineering Command and the Soil Ecology and Restoration Group (SERG) at United States International University (USIU) to locate and prepare a document describing potential 0.6 acre restoration sites, prepare a restoration plan for the selected site and restore the site to coastal sage scrub vegetation. In November 1998, seven sites were selected for potential restoration and described in the document, Proposed Restoration Sites for 0.6 Acre Native Plant Restoration on Marine Corps Air Station Miramar, San Diego, California dated 20 November 1998. Site number four was selected from this document and approved by MCAS Miramar, Public Works Department in March 1999 and approved by MCAS Miramar in March 1999. Soil strength measurements on the site showed a high degree of compaction on the dirt road bisecting the site. One-half of the road was rototilled to test the effects of soil compaction on seedling survival. In April 1999, 300 coastal sage scrub seedlings grown in the SERG greenhouse were planted on the site. Vegetation on the site was surveyed in May 1999 and compared to the surrounding area. Maintenance in the form of irrigation, weeding and removal of plant protection and trash occurred through September 1999. Vegetation monitoring and soil analysis will be conducted annually for three years beginning in May 2000.

Study Site
The site is located approximately 30 meters (m) west of Austin Avenue and 100 meters northwest of the South Gate off Harris Plant Road (Figure 1). This site was selected over the other sites primarily because no future Public Works projects were scheduled that would affect this site. The area requiring restoration is approximately 2.5 acres in size; however, restoration is being conducted on 0.6 acres, in order to fulfill the mitigation requirement. The remaining area is accessable through disturbed areas to the south of the restoration site. Native vegetation on the site mainly consisted of Laurel sumac (Malosma laurina), Flat-top buckwheat (Eriogonum fasciculatum), Foothill needle grass (Nassella pulchra) and Tarweed (Hemizonia fasciculata). Exotic vegetation on the site included Avena and Bromus exotic grass species and Red filaree (Erodium cicutarium). Soil was mildly compacted with signs of disturbance caused by off road vehicle activity. Fauna on the site through visual sightings and tracks consists of coyotes, rabbits and rattlesnakes. The site is situated just east of San Clemente Canyon. San Clemente Canyon is composed of a coastal sage scrub community dominated by Laurel sumac, Toyon (Heteromeles arbutifolia), California sagebrush (Artemisia californica), Flat-top buckwheat and Yerba santa (Eriodictyon crassifolium). Initial disturbance appears to have been caused by the construction of a graded dirt road through the site.

Site Preparation
Soil compaction on the site and the surrounding undisturbed area was measured using a penetrometer. Penetrometer measurements were made using a five foot metal pin with a 2 kilogram weight attached. The weight was dropped along the pin for two feet until it hit a stopper, forcing the pin into the soil. The distance traveled was measured for each hit. This process was repeated until the pin no will no longer sink into the soil or until 20 hits were achieved. Seven points on the site were measured; three on the dirt road and four on the remainder of the site. Three points were measured in the surrounding undisturbed area and one on the service dirt road running parallel to Altair Road (Figure 2). The dirt road on the site was significantly more compacted in comparison to the rest of the site. To determine the effects of soil compaction on container seedling

Figure 1. Location of restoration site on Marine Corps Air Station Miramar.

survival, an experiment was designed and implemented creating two 25 m by 25 m plots on the dirt.

The plot on the eastern portion of the dirt road on the site was rototilled to a depth of 15 to 20 cm (Figure 3).

Figure 2. Penetrometer measurements on Altair Road site and surrounding area.

Figure 3. Rototilling experimental decompaction plot on dirt road.

Seed collection and Container Planting
Three hundred seedlings were grown in the greenhouse at San Diego State University (SDSU) and the shadehouse at USIU for the restoration site. Seed was collected on the Station when possible; however, due to the short period of time between the signing of the Letter of Agreement and planting, it was necessary to collect additional seed from other areas in San Diego County (Table 1). While at the greenhouse, seedlings were initially watered three times a week and fertilized monthly. Water and fertilizer were reduced one month prior to planting and the plants were removed from under shade cloth. Seedlings were planted in April 1999 by creating holes for plants using either a power auger or a shovel. Plant protection in the form of Treepees, cone shaped plastic coverings one to two feet tall with a one foot wide base, or tubex, cylinder shaped plastic coverings 15 to 20 cm tall, were placed over each seedling to reduce herbivory. All exotic vegetation was removed to a radius of 18 cm around each plant. Of the 300 seedlings, 100 were planted in the experimental plots on the dirt road: 50 in the rototilled plot and 50 in the untreated plot.

Table 1. Species and seed source for container seedlings planted on the 0.6 acre Altair Road site.

Monitoring
On 3 June 1999, both vegetation and soil surface substrate were surveyed using two 50 meter transects on the restoration site and two 50 meter transects in the undisturbed vegetation to the west. Herbs and forbs were measured using three, one meter quadrats on the site and three, one meter square quadrats in the undisturbed areas. The zero meter mark for the transects on the site were marked with a one meter stake painted red for future surveys. Transect one on the site faces east at 80 degrees from the zero point; transect two on the site faces east at 100 degrees; transect three in the undisturbed area faces southeast at 126 degrees; and transect four in the undisturbed area faces northeast at 48 degrees. Documentary photos were taken of the quadrats and the site. Percent survival by species of container planted seedling was determined in June 1999 and September 1999. Percent survival of seedlings planted in the rototilled plot and control plot were also measured.

Three soil samples were taken from both the site the undisturbed area and were analyzed for ammonium, nitrate, available phosphorus and pH by A&L Laboratories in Modesto, California. Texture was measured at SDSU using the Hydrometer method (Gee and Bauder, 1986). Bulk density was determined using the excavation method by taking an eight to ten cm core of soil and then filling the hole with a measured amount of sand (Blake and Hartage, 1986).

Maintenance
Installation of a temporary irrigation system in the form of ½" irrigation tubing and 2 gallon per hour drip emitters was completed in May 1999. Seedlings were watered twice each month, May through September 1999, using water mechanically pumped onto the site from a 180 gallon water tank in the bed of a pickup truck. However, the irrigation system was continuously damaged by coyotes in search of water and needed to be repaired in June and July. Cayenne pepper wax, purchased from Garden Suppliers Inc., was sprayed on the ½" tubing in June 1999 in an attempt to repel the coyotes, but proved unsuccessful. In August, the damage was too extensive to repair and the majority of the ½" irrigation system was no longer used. In August and September each seedling was irrigated using water pumped onto the site through 50 meters of ½" polyvinyl tubing attached to ¾" garden hoses. Treepees and tubex shelters were removed from seedlings as they outgrew the plant protection.

Results
Overall plant survival in June 1999 was 88 percent, but dropped to 76 percent by September 1999 (Table 2). Survival of the seedlings planted in the rototilled plots (96 and 90 percent) was higher than in the nonrototilled plots (80 and 50 percent) in both June and September 1999 (Figure 4).

Table 2. Percent survival of container plant species in June and September 1999.

Figure 4. Percent survival of seedlings in experimental plots on restoration site.

Results from the vegetation survey conducted in June 1999 showed 18 percent native shrub cover and 2,020 shrubs per hectare on the restoration site (Table 3) and 120 percent native cover and 2,780 shrubs per hectare in the undisturbed area (Table 4). Greater than 100 percent cover resulted from species overlap at survey points.

Soil texture samples taken on the restoration site and the undisturbed area were all sandy loam with the exception of one sample in the rototilled plot which was Sandy Clay Loam. Total nitrogen on the restoration site was significantly higher than in the undisturbed area, but there was no difference in total nitrate between the two areas (Figure 5). The pH was slightly, but not significantly, higher on the restoration site while phosphorus was slightly lower on the restoration site. Percent organic matter was significantly higher in the undisturbed. Bulk density was lowest (least compacted) in the undisturbed area and on the rototilled plot and highest (most compacted) in the control plot.

Table 3. Summary of vegetation cover on restoration site in June 1999.

Table 4. Summary of vegetation cover in undisturbed area west of restoration site in June 1999.

Figure 5. Soil analysis results of samples collected in June 1999.

Discussion
Low container plant survival during the first year was probably due to below average precipitation during a La Niña year and late planting caused by a prolonged approval process by the Station. Although survival was low in June and September, seedlings may resprout as was the case with the deerweed, resulting in an increase in percent survival in September 1999. Rototilling the soil appeared to enhance seedling survival over compacted areas; however, bulk density in the rototilled area was still greater than in the undisturbed area in June 1999. This may have been due to the soil settling and becoming recompacted. The addition of soil amendments might be one method to prevent such recompaction. Bulk density measurements in the future will determine if revegetation of the area decreases the bulk density (compaction) of the soil. Vegetation cover on the site was at 16 percent two months after planting in comparison to the undisturbed area at 120 percent. Although the vegetation density on the site and the surrounding area were similar, percent cover was significantly different due to little cover provided by seedlings recently planted. Also, vegetation diversity was different on the two sites with more grasses and small shrubs; such as deerweed, on the restoration site and larger, well established shrubs in the undisturbed area. Percent cover and density results from the survey in the undisturbed area will be used for future surveys on the site for comparative analysis. Soil analysis showed few significant differences between the site and the undisturbed area. Percent organic matter was probably higher in the undisturbed area due litter from the high percent cover and density of native shrubs.

Conclusions and Recommendations
Seedling survival was low after the first six months, but percent vegetation cover at 16 percent is near the 20 percent requirement for the year 2000 as stated in the restoration plan. During implementation of future restoration projects, it is recommended that container planting should be completed by March to minimize loss from heat stress. Soil decompaction appeared to be beneficial to the seedlings in the rototilled plot. To increase seedling survivorship, it is recommended that decompaction, using a rototiller or ripping bars, should be done on all compacted sites. In addition, experiments incorporating mulch into the soil during decompaction would be beneficial for future projects.

Maintenance on the site will continue with by irrigating seedlings once a month during the period Maythrough September 2000 and removal of treepees and tubex and any trash on the site.

Monitoring, both soil and vegetation, will continue in May each year through 2002. If vegetation percent cover or density does not meet requirements as stated in the restoration plan, additional seedlings will be planted during the following winter.

References
Blake, G.R. and Hartage, K.H. 1986. Bulk density. In: Methods of Soil Analysis Part I, ed. Arnold Klute. Soil Science Society of America. Madison, WI.

Gee, G.W. and J.W. Bauder. 1986. Particle-size Analysis. In: Methods of Soil Analysis Part I, ed. Arnold Klute. Soil Science Society of America. Madison, WI.

Second Annual Report

Final Report (February 17, 2003)