Soil Ecology and Research Group
last update June 3, 2002
COASTAL SAGE SCRUB RESTORATION FOR GNATCATHER MITIGATION ON WEAPONS SUPPORT FACILITY SEAL BEACH, FALLBROOK DETACHMENT
Weapons Support Facility Seal Beach, Fallbrook Detachment is located in northern San Diego County, bordered to the east by Fallbrook and to the west by Camp Pendleton Marine Corps Base. As mitigation for the construction of a paved ordinance truck class holding yard, which removed 0.6 acres of coastal sage scrub inhabited by the coastal California gnatcatcher, the Navy was required to restore disturbed coastal sage scrub at a ratio of 2:1. In September 1998, the United States Navy formed a Letter of Agreement with the Soil Ecology and Restoration Group (SERG) at San Diego State University (SDSU) to perform native plant restoration research on a 1.2 acre area of disturbed coastal sage scrub adjacent to the holding yard construction area. Initial work on the site began with the installation of experimental topsoil plots using soil removed from the construction area. Soil was placed in two 50 m by 50 m plots on the restoration site and two 50 m by 50 m plots remained bare as a control. Vegetation and soil characteristics in the plots will be monitored over a five year period. To protect the site from grazing cattle, a 300 m barbed wire perimeter fence was constructed in February 1999. Seed was also collected in Fallbrook and 500 coastal sage scrub seedlings are being grown in the greenhouse at San Diego State University. An initial vegetation survey on the site and surrounding undisturbed area was conducted in May 1999. Soil samples were also collected for analysis of phosphate, nitrate, total nitrogen, pH, texture and percent organic matter. Approximately 500 coastal sage scrub seedlings will be planted in the Fall 1999/ Spring 2000. Maintenance in the form of temporary irrigation, removal of plant protection and trash removal will continue next year. Monitoring of the seedlings, on site vegetation and soil nutrients will continue through the year 2004.
Weapons Support Facility Seal Beach, Fallbrook Detachment, located in northern San Diego County, is bordered to the west by Camp Pendleton Marine Corps Base and to the east by the city of Fallbrook immediately east of Interstate 15. The facility, situated on 7,800 acres, is used as a storage facility for weapons by the United States Navy and Marine Corps. In November 1998, construction began on a paved ordinance truck class holding yard located on the northeast section of the facility. The construction of this facility included removing 0.6 acres of coastal sage scrub vegetation community inhabited by the coastal California gnatcatcher (Polioptila californica californica). As mitigation for this loss of valuable habitat, enhancement or creation of new coastal sage scrub habitat at a ratio of 2:1 was required by the draft Programmatic Uplands Biological Assessment for the neighboring Marine Corps Base, Camp Pendleton and the United States Fish and Wild life Service. As compliance, the Department of the United States Navy formed a Letter of Agreement on 30 September 1998 with the Soil Ecology and Restoration Group (SERG) at San Diego State University (SDSU) to conduct native plant restoration research. The agreement encompasses restoration, monitoring and maintenance of a 1.2 acre coastal sage scrub restoration site through September 2004. During the first year, efforts focused on creating experimental topsoil plots using soil and vegetation removed from the holding yard construction area. Monitoring on the plots began in May 1999 and will continue for 5 years. A barbed wire cattle fence was constructed around the site to prevent cattle from entering the area and destroying restoration efforts. Seed was collected from the facility and coastal sage seedlings were grown in the greenhouse at SDSU. The following year's work will consist of planting 500 seedlings on the restoration site in the Winter 1999/Spring 2000 and continued monitoring and maintenance.
The 1.2 acre study area is located east of ..directly across from the ordinance truck class holding yard and is sloped approximately 8 degrees with a southeast aspect (Figure 1 and 2). The area was selected as the mitigation site due to its close proximity to the disturbance site, nearby undisturbed coastal sage scrub habitat inhabited by the California coastal Gnatcatcher, scarce existing native vegetation and easy vehicle access. Existing vegetation on the site consists of a few Artemisia californica (California sagebrush), Nassella pulchra (Purple needlegrass), Eremocarpus setigerus (Dove weed) and non native species such as Bromus rubens (Red brome) and Erodium cicutarium (Red-stem filaree). Fauna observed on the site through visual sightings or tracks include rabbit and squirrel. Disturbance on this site and the surrounding area was probably due to the installation of a now abandoned railroad to the east of the site. The site is also in the area used for cattle grazing during the spring each year, adding to the previous disturbance.
The construction company, contracted by the .., excavated topsoil from the holding yard construction site and placed it in two 50 m by 50 m plots to a depth of 25 to 40 cm on 30 November 1998 (Figure 3). Vegetation removed from the holding yard site was also added to the plots and crushed with a tractor blade. Five piles of topsoil, left on the western portion of the site by the construction company, were spread with hand tools in the plots by SERG personnel in March 1999.
Topsoil plots were monitored for signs of erosion during the winter 1998/ Spring 1999. There was no sign of sediment loss from the topsoil; therefore, biodegradable erosion control was not necessary.
A 300 m barbed wire perimeter fence was constructed around the restoration site on 4 February 1999 by Frontier Fence Company of Vista, California to prevent cattle from entering the site (Figure 4). Specifications used in the construction of the fence are in Appendix I.
Figure 1. Location of mitigation site on Weapons Station Seal Beach, Fallbrook.
Figure 2. Location of mitigation site on aerial photograph taken
Figure 3. Topsoil plots (foreground) on the restoration site in December 1998.
Figure 4. Barbed wire cattle fence (northeast corner) installed by Frontier Fence in February 1999.
Seed Collection and Container Planting
Seed collection for the 500 coastal sage scrub seedlings to be planted on the restoration site began in October 1998 and will continue to be collected in October 1999. All seed, with the exception of Rhus integrifolia (Lemonadeberry) and Nassella pulchra (Purple needlegrass), was collected on the Weapons Station. Seed for lemonadeberry was collected on the Point Loma Peninsula and for purple needlegrass on Camp Pendleton, both in San Diego county. A total of 393 of the 500 seedlings are ready for planting (Table 1). Seed collected from Baccharis sarothroides (Broom baccharis) and Salvia mellifera (Black sage) in the fall 1998 did not germinate and additional seed is currently being collected in the fall 1999.
Table 1. Container plant species to be planted on the restoration site between November 1999 and March 2000 and number ready for planting as of 30 September 1999.
Two soil samples, each to a depth of ten to twelve cm, were collected in December 1998 from the bare soil plots on the site, the top soil addition plot on the site and the surrounding undisturbed coastal sage scrub for a total of six soil samples. The area to the east of the site, known to be home territory of the California coastal gnatcatchers, was used as the undisturbed reference area. In April 1999, three soil samples were collected from the top soil plot, three from the bare (control) area and two from the surrounding undisturbed area. All samples were sent to A&L Agricultural Laboratories to be analyzed for nitrate, total nitrogen, phosphorus, pH and organic matter. 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). Bacterial numbers and fungal biomass were analyzed at San Diego State University using the Europium staining method (Morris et al., 1997). Vegetation on the restoration site and the surrounding undisturbed area was surveyed on 28 April 1999. Percent shrub cover of was measured using two 100 meter transects with points every one meter on both the restoration site and undisturbed area. Density was measured by counting shrubs within 2.5 m each side of the transect. Native and non native herbs and grasses were measured using three, one meter square quadrats in both areas. A comparison of the vegetation in the topsoil plots and the bare (control) plots was made by using three one meter square quadrats in each of the plots for a total of 12 quadrats. Documentary photos of the site and transects were taken in December 1998, March, May and September 1999 (CD ROM included).
Percent organic matter, pH, total nitrogen, phosphorus and nitrate were the highest in the undisturbed area and lowest on the topsoil plots (Figure 5). Between December 1998 and April 1999, percent organic matter, phosphorus and total nitrogen increased slightly, but not significantly on the restoration site, undisturbed area and topsoil plots. Soil pH remained unchanged. Nitrate in the soil decreased drastically in the undisturbed area, slightly on the restoration site and increased on the topsoil plots.
Figure 5. Results for soil analysis of samples collected in December 1998 and April 1999.
Native vegetation cover on the restoration site consisted of 1.5 percent shrubs and eight percent herbs and grasses (Table 2). In contrast, native vegetation in the surrounding undisturbed area consisted of 23 percent shrubs and 13 percent herbs and grasses (Table 3). Native shrub density on the restoration site was 540 shrubs per hectare as compared to 2200 shrubs per hectare in the undisturbed area. California sagebrush seedlings were sprouting in the topsoil plots, but not in the control plots (Figure 6). In May, Brassica nigra (Mustard) and Avena barbata were sprouting in the bare plots (Table 4); however, in June there appeared to be more Brassica nigra (Mustard) in the topsoil plots than in the bare areas.
Table 2. Results from the vegetation survey on the restoration site.
Table 3. Results from the vegetation survey in the undisturbed
area to the east of the restoration site.
Table 4. Comparison of vegetation cover between top soil
plots and bare (control) plots.
Figure 6. California sagebrush seedlings sprouting in the topsoil plots in May 1999.
All 500 seedlings will be ready to be planted between November 1999 and March 2000. Since seeds from a number of different species such as Black sage and Broom baccharis did not germinate additional seed was collected in September 1999. Those species should be ready for planting by February or March 1999.
Initial soil testing during the first year demonstrated slight differences between the three test areas: the relatively bare restoration site; surrounding undisturbed area; and the top soil plots. The increase in organic matter was greatest in the undisturbed area due to litter additions from plant growth occurring in the spring. There was little change in pH as four months is not enough time to measure significant changes. Total nitrogen increased on all plots possibly due to nitrogen deposition from air pollution (Allen et al., 1996). Phosphorus increased slightly, but not significantly. Nitrate decreased the greatest in the undisturbed area probably from the shrubs utilizing the nitrate in the soil during the spring growing season. It also decreased slightly in the bare areas on the restoration site as annual forbs and grasses also utilized the nitrate. The increase in nitrate in the topsoil plots was probably caused by the buildup of available nitrogen from the mineralization of organic matter and lack of uptake since few plants currently exist in the topsoil plots. Additionally, such an increase in nitrate might also be enhanced by atmospheric deposition.
The vegetation survey in April 1999 reflected a 15 fold increase in vegetation percent cover in the undisturbed area and a 4 fold increase in density in comparison to the undisturbed area. California sagebrush appears to sprout well from salvaged soil will supplement container planting in bringing the vegetation cover up to
Conclusion and Recommendations
Problems encountered with seed germination may have been due to poor seed production by the plants in the fall of 1998 or possible a slight difference in climate between the Facility in Fallbrook and the greenhouse at SDSU. Additional seed is being collected from Fallbrook and stored for possible future projects.
Soil analysis from samples collected during the first year provide an initial profile of the soil for future comparison, but changes observed were probably seasonal. Soil analysis over five years of the project will reflect a more significant comparison between the three areas and changes over time. Initial vegetation data along with the success criteria (Heffernan 1999) will be used as a gauge to evaluate the success of the project over time. The salvage of topsoil from native coastal sage scrub appears to be successful in enhancing California sage seedling germination. Future monitoring of the plots will determine if the restoration site will benefit from the germination of additional species from the topsoil.
The following years work will concentrate on planting the 500 seedlings, supplemental irrigation and monitoring of both vegetation and soil.
Second Annual Report (December 2, 2001)
Third Annual Report (February 18, 2003)
Fourth Annual Report (February 18, 2003)
Final Report (March 9, 2004)