Soil Ecology and Research Group last update March 9, 2004

Coastal Sage Scrub Site Restoration for the Ordnance Truck Class Holding Yard, Naval Weapons Station Seal Beach, Detachment Fallbrook

Final Report
1 October 1998 – 30 July 2003

Executive Summary

Naval Weapons Station Seal Beach, Detachment Fallbrook (referred here after as Detachment) is located in northern San Diego County, bordered to the east by the community of Fallbrook and to the west by Marine Corps Base Camp Pendleton (MCBCP). Creation of suitable habitat for coastal California gnatcatcher was restored for the construction of a paved ordnance truck class holding yard that caused removal of 0.6 acres of coastal sage scrub. The Navy was required to restore disturbed coastal sage scrub habitat at a ratio of 2:1. In September 1998, at the request of the Detachment, Southwest Division, Naval Facilities Engineering Command entered into a Cooperative 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 meter by 50 meter plots on the restoration site while two 50 meter by 50 meter plots remained bare as a control. In order to protect the site from grazing cattle, a 300 meter barbed wire fence was constructed in February 1999. In February 2000, 478 coastal sage scrub seedlings grown in the SERG greenhouse at SDSU were transplanted to the site. Only a few of these seedlings were planted in the plots covered by the salvaged topsoil because numerous volunteer seedlings had germinated and more were expected to grow. Transplants were irrigated twice each month throughout the summer of 2000. In March 2001, 34 additional seedlings that were not ready in February 2000 were transplanted to the site. Initial irrigation for all seedlings occurred during summer 2001 and no further irrigation was needed for the remainder of the contract.

Soil analyses and vegetation surveys were conducted in Spring 2000, 2001, 2002, and 2003. Results were compared to baseline data collected in 1999. In 2001, surveys comparing species density in the experimental topsoil plots and the bare plots showed that the 400 seedlings per acre that are usually planted for a coastal sage scrub restoration site can be decreased in areas covered with salvaged topsoil because it appears that volunteer seedlings significantly increase density. The addition of tilled topsoil appears to be beneficial to weed species establishment. Additional weed control measures were recommended.

In 2002, weeds were controlled through the use of herbicide and this appears to have been effective. Vegetation and soil surveys conducted in 2002 showed a slight decrease in soil health and percent cover of native species was lower than the required success criteria. The drought that began in 2000 continued through the 2001-2002 rainy season and slowed the recovery of the restoration site both in terms of soil health and plant establishment.

Above average precipitation amounts fell in the 2002-2003 rain year creating conditions favorable for plant establishment and improving soil health. Above ground parameters were met and exceeded all established success criterion. Below ground parameters, while not held to strict success criteria, show a shift in nutrients in disturbed areas similar to those in undisturbed areas. This trend in underground parameters toward baseline conditions in undisturbed areas was one goal of the restoration project. The use of topsoil salvaged from surrounding habitats appears successful and can reduce the amount of transplanted seedlings needed in coastal sage scrub restoration. Weed control continued throughout 2002-2003, and it is recommended that exotic species continue to be monitored in the future. Overall, site conditions continue to improve and the Navy’s restoration of the habitat is a success. SERG believes the no further expertise is needed.

Introduction

Naval Weapons Station Seal Beach, Detachment Fallbrook, located in northern San Diego County, is bordered to the west by Marine Corps Base Camp Pendleton and to the east by the community of Fallbrook. This 8,850-acre facility is used for weapons storage by the United States Navy and Marine Corps. In November 1998, construction began on a paved ordinance truck class holding yard located in the northeast section of the facility. The construction of this holding yard required the removal of 0.6 acres of coastal sage scrub vegetation that was inhabited by the federally-listed threatened coastal California gnatcatcher (Polioptila californica californica). As compensation for this loss of 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 neighboring Camp Pendleton Marine Corps Base and by the United States Fish and Wildlife Service. At the request of the Detachment, Southwest Division, Naval Facilities Engineering Command entered into a Cooperative Letter of Agreement with the Soil Ecology and Restoration Group (SERG) at San Diego State University (SDSU) to provide expertise to the Navy in the restoration of the damaged habitat. Research and restoration continued through September 2003, the end of the five-year agreement.

During the first year of the project (October 1998-September 1999), initial site treatment efforts focused on creating experimental topsoil plots and relocation of vegetation from the impacted holding yard footprint. Topsoil excavated from the holding yard construction site was transported to the restoration site using on 30 November 1998 and placed in two 50 m by 50 m plots to a depth of 25 to 40 cm. Vegetation removed from the holding yard site was also added to the plots and crushed by the weight of the tractor.

In February of the second year of the project (October 1999-September 2000), 478 container seedlings were planted on the site. Site monitoring revealed that the addition of topsoil salvaged from coastal sage scrub habitat and applied to a restoration site dramatically increases the rate of native shrub establishment and reduces the need for container transplants. However, since the growth of exotic species in the experimental areas increased as well, it appears that weed control is vital to any restoration effort that utilizes native topsoil.

In March of the third year (October 2000-September 2001), 34 additional seedlings that were not ready in February 2000 were transplanted to the site. Soil analyses and vegetation surveys were conducted in Spring 2001, as they were in Spring 2000, and results were compared to baseline data collected in 1999. Results of these analyses were sufficient to meet established success criteria as stated in the initial restoration plan (Heffernan 1999, pg 9).

The fourth year of the project (October 2001-September 2002) included weed control and soil and vegetation monitoring. Soil analysis and vegetation surveys were conducted in Spring 2002. Weed control was an ongoing effort using herbicides and hand pulling methods. Results of these analyses were sufficient to meet established success criteria.

The fifth and final year of the project (October 2002-September 2003) concluded with excellent results. Soil analysis and vegetation surveys were completed and showed significant improvement over previous years. Results of these analyses were sufficient to meet established success criteria. Weed control continued involving herbicides, mechanical, and hand weeding methods with special attention on control plots.

Site Description

The 1.2 acre study area is located east of Copperhead Road, directly across from the ordinance truck class holding yard, and is sloped approximately 8 degrees with a southeast aspect (Figures 1 and 2). The area was selected as the mitigation site due to its close proximity to both the disturbance site and to undisturbed coastal sage scrub inhabited by the California coastal gnatcatcher, its near lack of native vegetation and its ease of vehicle access. Existing vegetation on the site consisted of a few Artemisia californica (California sagebrush), Nassella pulchra (Purple needlegrass), Eremocarpus setigerus (Dove weed), and non-native species such as Bromus madritensis (Red brome) and Erodium botrys (Red-stem filaree). Before restoration began, fauna visually observed on the site included rabbits and ground squirrels. Disturbance to this site and the surrounding area was originally due to the installation of a now abandoned railroad to the east of the site. The use of the area for cattle grazing during the spring each year continued to impact the site until it was fenced in on 4 February 1999.

Methods

Site Preparation
Topsoil was excavated from the holding yard construction site and placed in two 50 m by 50 m plots to a depth of 25 to 40 cm on 30 November 1998 (Figure 3) by a front end loader. Vegetation removed from the holding yard site was also added to the plots and crushed by the weight of the tractor. 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 meter barbed wire 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) as directed by Natural Resource personnel.

(Figure 1)
Figure 1. Coastal sage scrub restoration site located on Naval Weapons Station Seal Beach, Detachment Fallbrook

(Figure 2)
Figure 2. Ammunition Road

Figure 3. Topsoil additions in November 1998

Figure 4. Fence construction 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 continued 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. Seed collected from Baccharis sarothroides (Broom baccharis) and Salvia mellifera (Black sage) in the fall 1998 did not germinate and additional seed was collected in the fall 1999. A total of 478 coastal sage scrub seedlings were planted on the restoration site in February 2000. Planting holes were dug by hand or with a gas-powered auger (Figure 5). Holes were pre-watered and plants immediately installed and post-watered. Basins approximately two feet in diameter were constructed around each plant as a means of conserving water during irrigation. Each plant was given either a TreePee or Tubex plant shelter (Figure 6) to protect seedlings from herbivory and desiccation. Due to the successful germination of A. californica and Eriogonum fasciculatum seedlings in the topsoil plots, these two species were not container planted in those areas. In addition, the topsoil plots were planted sparsely in comparison to the remainder of the site. Baccharis sarothroides seedlings were not planted on the site, as they were not mature at the time of planting.

Figure 5. Digging planting holes with an auger and by hand

Figure 6. Plant protectors installed to prevent herbivory

Maintenance
After planting, seedlings were hand watered one to two times each month through September 2000 when seasonal rains began. Plants received approximately 1/2 gallon per watering. Basins were filled by hoses hooked up to a 180-gallon water tank in the back of a pickup truck. Hand weeding occurred at the same time as watering. Treepees and Tubex shelters were removed from seedlings as they outgrew their protective devices. Seedlings that were planted in February 2000 and watered during the summer following planting were not watered from October 2000 through May 2001 because winter rains were sufficient for plant survival and growth. In March 2001, 34 B. pilularis individuals were transplanted and watered twice each month through June 2001. The following month, both the new and the original transplanted seedlings were watered once each month until October 2001 when winter rains provided sufficient amounts of moisture. Weed control encompassed herbicide, mechanical, and hand pull methods. A combination of mechanical and hand pull methods provided sufficient suppression of established exotic species (figures 7 and 8), while herbicides were most effective on early germinates of exotic species.

Figure 7. Mechanical method of exotic species control

Figure 8. Hand weeding around Artemisia californica volunteer

Monitoring
As part of the original restoration plan, above ground and below ground processes were monitored annually and compared to baseline data taken from an undisturbed location adjacent to the restoration site. Vegetation on the restoration site was surveyed according to a revised version of the California Native Plant Society’s (CNPS) field sampling protocol. Percent shrub cover was measured using two 100-meter transects with points every one meter on the restoration site. Percent cover of herbs and grasses was measured using three one-meter square quadrats. Shrub species density was measured by counting shrubs within a 2.5-meter wide corridor on both sides of each transect. A comparison of the vegetation in the topsoil plots and the bare (control) plots was made using three one-meter square quadrats in each of the plots for a total of 12 quadrats (figure 9).
Soil components were measured by a total of ten soil samples collected on-site; four from the two topsoil-addition plots, four from the two bare (control) plots, and two from the surrounding undisturbed coastal sage scrub. All samples were sent to A&L Western Agricultural Laboratories and analyzed for phosphorus, pH, nitrate, total nitrogen, and percent organic matter. The samples were also analyzed for fungal hyphae length and bacterial content at San Diego State University. Over an extended period of time, a relative comparison of activity, both fungal and bacterial, allows us to determine if the below ground activity occurring in the restoration site is moving toward or away from the levels found in the undisturbed reference site. Fungal hyphae length is determined using a hyphal length extraction technique (Hanssen et al., 1974; Schuepp et al., 1987; Bardgett, 1991; Frey and Ellis, 1997). Bacterial numbers are determined using the europium staining method (Anderson and Westmoreland, 1971; Anderson and Singer, 1975; Trent, 1992; Conners et al., 1994) that stains only the DNA of living cells.

Figure 9. Quadrat sampling method

Results

In 2003, and over the entire five years of the project, below ground processes were similar for phosphorus, total nitrogen, pH, and percent organic matter at all three sample locations. High levels of nitrates found in topsoil plots in 2002, returned to levels equal to bare and undisturbed plots (Figure 10).

Figure 10. Results for annual soil analyses of samples collected over the life of the project

Europium straining results for bacteria (Figure 11) show levels in the undisturbed sample plot sharply declined from the previous year. Overall levels for bare and topsoil plots remained relatively unchanged. Hyphal length extraction results (Figure 12) reveal amounts in all sample locations were up considerably from 2002.

Figure 11. Bacterial numbers in soil samples taken from topsoil addition
and bare(control) plots at the restoration site and one undisturbed area.

Figure 12. Fungal hyphae length in soil samples taken from topsoil addition
and bar (control) plots at the restoration site and one undisturbed area

For referencing success of above ground criteria, Table 1 shows the minimum measurements for percent vegetation cover, percent seedling survival, and species density.

Table 1.
Above ground success criteria

Table 2.
Container plants originally planted and surviving in 2003

Native vegetation cover on the restoration site in 2003 at the end of the five-year project consisted of 27.5% shrubs (Table 3) and 18% herbs and grasses (Table 3), for a total of 45.5% cover. This exceeded the required 40% cover as stated in the success criterion, and is greater than the 36.5% cover found within the undisturbed reference site.

Table 3.
Percent cover of native shrubs and herbs on the restoration site

Native shrub density on the restoration site in 2003 at the end of the five-year project was 5,860 plants per hectare, higher than the 650 plants per hectare required by the success criterion, and greater than the 1,100 plants per hectare found in the undisturbed reference site (Table 4).

Percent cover estimate of herbs and grasses as measured by the quadrat method found

Table 4.
Density of native species on the restoration site

both native and exotic species in topsoil and control plots for 2003 (Table 5). Species diversity increased from 2002, and visual observation revealed a higher density of natives in topsoil plots than control plots.

Table 5.
Comparison of relative percent cover of herbs and
grasses in topsoil plots and control plots

Discussion

Work for habitat enhancement for the federally threatened coastal California gnatcatcher began in 1998. Complete summaries of all work processes are found in the executive summary and introduction sections of this report. Success criterions were established with focuses on above ground and below ground parameters. Above ground criteria was measured by percent vegetation cover, percent seedling survival and species density. Below ground criteria was monitored through phosphates, nitrates, total nitrogen, percent organic matter, and pH and then compared to baseline data collected from two undisturbed reference sites. Aboveground success is dependent upon the recovery of the belowground ecosystem. A successful restoration project will demonstrate a trend of belowground parameters toward the baseline values found at a similar undisturbed site. A shift in nutrient levels on the disturbed site towards nutrient levels of the undisturbed site is the goal.

Over the life of the project, levels of all measurable soil nutrients have been similar to undisturbed reference areas in both topsoil and bare (control) plots. Unusually high levels of nitrates in topsoil plots in 2002 returned in 2003 to values comparable to bare plots as well as undisturbed areas. This can most probably be attributed first to a buildup of available nitrogen in the soil due to lack of rainfall over 2001/2002 period, and secondly to increased annual vegetation growth, and therefore increased available nitrogen uptake, caused by higher precipitation levels in 2002/2003.

Soil health appears to have improved each year in all three areas, with considerable changes coming in 2002-2003. Levels of bacteria dropped in undisturbed areas, as well as in topsoil addition plots, but increased in control plots. Most importantly, fungal hyphal length significantly increased at all three sample locations. A rise in fungal activity is an important indicator of improving soil health in shrub based communities such as coastal sage scrub.

Percent cover of native species rose this year to 45.5%, an increase of 36.5% from last year, to meet and surpass required success criterion for the final year at the restoration site. The dramatic increase can be linked to higher precipitation levels. Precipitation for 2002-2003 was slightly above average for San Diego County. This increase in precipitation also increased the percent survival of original transplants to 93%, up from 79% in 2002, by invigorating new growth in plants left dormant by several years of
drought. Native species density improved to 5,860 plants per hectare, well above the required 650 plants per hectare. Again, rainfall can be seen as the cause of this increase in density as visual observation revealed high numbers of native seedlings throughout the restoration site.

The comparison of relative percent cover of herbs and grasses, as measured by the quadrat method, demonstrated large increases of natives and exotics alike in the restoration site. Topsoil plots had higher numbers of native herbs than exotics compared to control plots. Control plots, however, had a strong representation of native herbs as well, but due to the nature of higher disturbance on the area as a whole, we can expect exotic species to remain strong.

Weed control efforts over the course of the project have focused strongly on the control areas, but as mentioned above, the large amount of rainfall in the early months of 2003 caused a spike in exotic species germination. Every effort was made to prevent such an occurrence, though after years of drought such an increase in exotics was inevitable. However, the overall weed control program conducted during the past five years has greatly diminished the weed seed bank, thereby providing an environment by which native species can become established, leading to the overall success of the project.

Conclusion and Management Implications

Above average precipitation for 2002-2003 rainfall year produced excellent results for the restoration site as a whole. Previous years of drought had slowed the recovery of the site in terms of soil health and plant establishment. Success criteria for the final year have been met. Remedial measures are not required. Below ground processes, while not held to strict parameters, emulated the levels of the undisturbed reference site during the final monitoring period. All values were similar and followed patterns displayed in successive years of the project. These results point to a shift in nutrient levels on the disturbed site towards nutrient levels of the undisturbed site, therefore demonstrating a trend of belowground parameters moving toward the baseline values found at a similar undisturbed site, one of the goals of the restoration project.

Weed control will remain an issue at the restoration site. While persistent rains of 2002-2003 allowed the dormant seed bank to germinate and subsequently be removed, it is unrealistic to assume exotic species will be absent in the future. Herbicides, mechanical removal and hand pull methods have proven effective on the restoration site for control measures. However, until the restoration site merges with near by mature habitat, fragmentation will continue to pose a problem in weed seed dissemination from the surrounding disturbed habitat. Further monitoring and removal of exotic species is recommended in order to allow regeneration of native species to occur free from competition.

If rains similar to 2002-2003 continue, and the previous years of drought are over, plant establishment and soil health can be expected to continue to improve. Remarkable increases were made during this past year and average to above average yearly rainfall amounts will continue to heighten the recovery rate. Even with less than average rainfall, however, the restoration site has reached a stage where it is self sustaining and will continue to develop and provide necessary habitat for the California gnatcatcher.

In conclusion, SERG believes the restoration effort by the Navy to be a success. With below ground parameters emulating undisturbed reference sites, recruitment of native annuals and shrubs increasing, and continual suppression of exotic species depleting the seed bank it is safe to assume the restored coastal sage scrub habitat will continue to improve.

First Annual Report (June 3, 2002)

Second Annual Report (December 2, 2001)

Third Annual Report (February 18, 2003)

Fourth Annual Report (February 18, 2003)