Soil Ecology and Research Group last update February 18, 2003

COASTAL SAGE SCRUB RESTORATION FOR
GNATCATHER MITIGATION ON WEAPONS
SUPPORT FACILITY SEAL BEACH, FALLBROOK
DETACHMENT

Fourth Annual Report

Exexutive Summary
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 that caused removal of 0.6 acres of coastal sage scrub inhabited by the coastal California gnatcatcher, the Navy was required to restore disturbed coastal sage scrub habitat at a ratio of 2:1. In September 1998, the United States Navy signed 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 while two 50 m by 50 m plots remained bare as a control. In order to protect the site from grazing cattle, a 300 m barbed wire perimeter 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. All seedlings were irrigated during the summer 2001 and will not require supplemental water for the remainder of the project.

Soil analyses and vegetation surveys were conducted in Spring 2000, 2001, and 2002 and 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 also appears to be beneficial to weed species establishment, so extra effort is required for weed control.

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 and has continued through the 2001-2002 rainy season appears to be slowing the recovery of the restoration site both in terms of soil health and plant establishment. However, there is hope that the 2002-2003 winter season will bring more rain to the site. Although recovery is slow at the moment, none of the results of the vegetation and soil surveys raise concern over the general health of the restoration site, so remedial action is not necessary at this time.

Introduction
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. This 7,800-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 endangered 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 neighboring Camp Pendleton Marine Corps Base and by the United States Fish and Wildlife Service. In compliance, the Department of the United States Navy signed a Letter of Agreement on 30 September 1998 with the Soil Ecology and Restoration Group (SERG) at San Diego State University (SDSU) which states that SERG will restore the required 1.2 acres while conducting research on native plant restoration techniques. Research and restoration will continue through September 2003.

During the first year of the project (October 1998-September 1999), efforts focused on creating experimental topsoil plots. Topsoil excavated from the holding yard construction site was transported to the restoration site 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 with a tractor blade.

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, the growth of exotic species in the experimental areas increased as well, so weed control is vital a 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.

During this, the fourth year of the project, work on the restoration site included weed control and soil and vegetation monitoring.

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 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 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.

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

(Figure 2)
Figure 2. Aerial photo of restoration site.

Methods
Tables 1 and 2 list the dates of visits to the restoration site and the personnel involved.

Table 1
Dates of visits to the restoration site.

Table 2
Names of personnel involved in the field and the greenhouse.

October 2001 marked the final month of irrigation for the transplanted seedlings at the restoration site. However, due to the terrorist attacks of September 11, 2001, civilian access to the station was not permitted and the trip was cancelled.

In February and April 2002, a total of 21 gallons of a 2% concentration solution of Round Up Pro herbicide was applied to exotic weed species on the site. Weeds in all plots consisted primarily of Brassica nigra and Erodium botrys, but E. botrys in the bare plots was not growing large enough to be considered a threat to the health of native species and was therefore not sprayed with herbicide.

Also in April, ten soil samples were 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.

In June 2002, the annual vegetation monitoring took place. This included counting all surviving transplants, calculating percent survival, and surveying vegetation cover and density according to a revised version of the California Native Plant Society’s (CNPS) field sampling protocol. Percent cover of native shrubs and herbs was measured using two 100-meter transects with points every one meter on the restoration site. Native shrub species density was measured by counting shrubs within a five-meter wide corridor centered on both transects. 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.

Results
In 2002, phosphorus, total nitrogen, pH, and percent organic matter were very similar at all three sample locations while nitrate was higher in the topsoil addition plots than in the bare and undisturbed areas (Figure 3).

Figure 3. Results for soil analyses of samples collected in December 1998 and April 1999, 2000, 2001, and 2002.

Hyphal length extraction results (Figure 4) revealed that the amounts of fungal hyphae found in both the topsoil and bare (control) plots in 2002 were similar to 2001 levels. However, levels at the undisturbed site fell sharply between 2001 and 2002 and were lower than both treatments within the restoration site. The europium staining results for bacteria (Figure 5) in 2002 were very similar among all three sample locations.

Figure 4. Fungal hyphae length in soil samples taken from topsoil addition and bare (control) plots at the restoration site and one undisturbed area.

Figure 5. Bacterial numbers in soil samples taken from topsoil addition and bare (control) plots at the restoration site and one undisturbed area.

Percent survival of transplanted seedlings in 2002 was 79 percent (Table 3), nine percent higher than the 70 percent survival required by the success criteria.

Table 3
Container plants originally planted and surviving in 2002.

Native vegetation cover on the restoration site in 2002 consisted of nine percent shrubs and 7.5 percent herbs and grasses (Table 4) for a total of 16.5 percent cover. This is lower than the 30% required by success criteria and lower than the 36.5 percent cover found within the undisturbed reference site.

Table 4
Percent cover of native shrubs and herbs on the restoration site.

Native shrub density (Table 5) on the restoration site in 2002 was 3,170 plants per hectare, higher than the 1,100 plants per hectare found in the undisturbed reference area and higher than the 700 plants per hectare required by the 2002 success criteria.

Table 5
Density of native species on the restoration site.

According to the percent cover estimate of herbs and grasses as measured by the quadrat method, the only species found within the topsoil addition plots was the native A. psilostachya and the only species within the bare plots was the exotic B. nigra (Table 6). Visual observation of exotic species revealed that the topsoil addition plots contained a higher density of weeds than the bare plots.

Table 6
Comparison of relative percent cover of herbs and grasses in the topsoil plots and bare (control) plots.

Discussion
Work in 2001/2002 focused on weed control and continuing to collect data on transplant success, soil health, and the potential benefits of using salvaged topsoil to restore coastal sage scrub habitat. Results of soil analyses were used to determine whether levels in the restoration plots are, as a sign of recovery, beginning to follow the same trends as those in the undisturbed reference site. All soil nutrient levels except for nitrate were similar at the three sampling locations. The high average nitrate content measured within the topsoil addition plots is likely due to two of the four collected soil samples having unusually high nitrate levels. The levels in these two samples were much higher than any sample collected from the topsoil plots in the previous four years. They are therefore not likely to be representative of the average nitrate levels within the topsoil plots. If the two anomalous soil samples are removed, the nitrate level drops to 36 which is both more similar to samples taken from the undisturbed and bare areas and to levels measured in previous years. The results of the soil nutrient analyses therefore do not indicate a need for soil remediation at the restoration site.

Fungal length and bacterial numbers dropped within both treatments of the restoration site. Fungal hyphae length at the undisturbed site also dropped but bacterial numbers remained constant. Both fungi and bacteria are moisture dependent, fungal more so than bacteria. Steady or rising fungal and bacterial activity is a sign of stable or improving soil health. The 2002 results indicate a slight decline in soil health at all three areas and it may be due to the dry 2001-2002 rainy season. The lack of rain has led to a decrease in vegetation cover and also appears to have had a detrimental affect on soil health.

Fungal hyphae length within the topsoil addition plots and the bare plots were similar, but the length at the undisturbed site was much lower than in the restoration plots. Fungal length at the undisturbed site is expected to remain somewhat constant since the area is not undergoing recovery. Therefore, this dramatic drop in fungal activity must be ignored as a spatial anomally.

As expected, bacterial levels were similar in the topsoil addition plots and at the undisturbed reference site. Also as expected, the levels in the bare plots were slightly lower than at the other two locations. The reason for this is that the bare plots are the most disturbed of the three areas. Although there were fewer bacteria in the bare plots, levels were similar to the less disturbed locations and this can be seen as a sign of recovery.

The percent cover of native species at the restoration site did not meet the required success criterion for 2002. A potential explanation for this is, again, the dry 2001-2002 rainy season. Lack of rain resulted in fewer annuals germinating in 2002 than in previous years and the death of many seemingly well-established perennials. In addition, those perennials that survived did not grow as much as they would have during a wet year. However, even though percent native cover fell short this year, no additional seedlings will be planted during the 2002-2003 rainy season. Percent survival of the original transplants and native species density both exceeded the requirements of the success criteria and the next rainy season is likely to improve percent cover.

The quadrat method used to compare the composition of herbs and grasses within the topsoil addition plots and the bare plots revealed an overall reduction in the number of exotic species between 2001 (four species) and 2002 (one species). However, the number of native species found was reduced by the same amount. This reduction is likely due, once again, to the lack of rainfall, but may also be due to the weed control efforts that took place in February and April 2002. Because of the low germination of annuals in 2002, the species composition comparison reveals little, if anything, about the topsoil and bare plots. Visual observation, however, again revealed the higher density of exotic species within the topsoil plots. This high density is likely due to the less compacted nature of the added topsoil.

Conclusion and Management Implications
The drought that began in 2000 and has continued through the 2001-2002 rainy season appears to be slowing the recovery of the restoration site both in terms of soil health and plant establishment. However, there is hope that the 2002-2003 winter season will bring more rain to the site. Although recovery is slow at the moment, none of the results of the vegetation and soil surveys raise concern over the general health of the restoration site. There is, therefore, no need for any corrective action.

The site will continue to be monitored and maintained in 2003. Work will include continued weed control, a final vegetation and soil survey in May 2003, and the removal of any remaining seedling shelters.

First Annual Report (June 3, 2002)

Second Annual Report (December 2, 2001)

Third Annual Report (February 18, 2003)

Final Report (March 9, 2004)