Soil Ecology and Research Group last update December 02, 2001

Coastal Sage Scrub Restoration for Gnatcatcher Mitigation on Weapons Support Facility Seal Beach , Fallbrook Detachment

Second Annual Report

During the first year of the project, 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. Erosion control was not installed because there were no signs of sediment loss during the 1998/1999 winter rainy season. Because of the presence of grazing cattle in and around the site, a 300 m barbed wire perimeter fence was constructed on 4 February 1999 to prevent cattle from entering the area and destroying restoration efforts. Monitoring of the plots, including chemical soil analysis, soil bacterial numbers, soil fungal biomass, and vegetation surveys, began in May 1999 and will continue until 2003. Seed collected at Fallbrook beginning in October 1998 was used to grow coastal sage scrub seedlings in the greenhouse at SDSU.

In February of this, the second year of the project, 478 container seedlings were planted on the site. Monitoring and maintenance activities continued (Tables 1 and 2) and will continue in much the same way for the three remaining years of the project.

Table 1
Dates of site visits on the Station.

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

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 rebens (Red brome) and Erodium cicutarium (Red-stem filaree). Fauna observed on the site through visual sightings or tracks 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.

Figure 1. Coastal sage restoration site located on Weapons Support Facility Seal Beach, Fallbrook Detachment.
(click on image for larger view)

Figure 2. Aerial photo of restoration site.
(click on image for larger view)

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
Planting
A total of 478 coastal sage scrub seedlings were planted on the restoration site in February 2000 (Table 3). Planting holes were dug by hand or with a gas-powered auger (Figure 3). Holes were pre-watered and plants immediately installed and post-watered. Basins approximately two feet in diameter wer constructed around each plant as a means of conserving water during irrigation. Each plant was given either a TreePee of Tubex plant shelter (Figure 4) 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 were not planted on the site, as they were not mature at the time of planting.

Table 3
Container plant species planted on the restoration site.

Figure 3. Digging plant holes with an auger and by hand.

Figure 4. Seedling shelters installed.

Maintenance
After planting, seedlings were hand watered one to two times per month through September 2000 when seasonal rains began. Plants received approximately ½ gallons per watering. Basins were filled by hoses hooked up to a 180-gallon watertank 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.

Monitoring
In April 2000, a total of ten soil samples were taken; four from the topsoil on the site, four from the bare (control) areas on the site, 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. Additional soils collected in June 2000 were analyzed for bacterial numbers and fungal biomass at San Diego State University using the europium staining method (Morris et al., 1997). The use of europium staining allows the determination of both active fungal hyphae and bacteria since europium stains only the DNA of active living cells. Thus, used over an extended period of time, a relative comparison of activity, both fungal and bacterial, can be obtained through the use of europium staining. This will allow us to determine if the below ground activity occuring in the restoration site is moving toward or away from the levels found in the undisturbed reference site.

Vegetation on the restoration site and the surrounding undisturbed area was surveyed on 13 April 2000 according to a revised version of the California Native Plant Society (CNPS) field sampling protocol. Percent scrub cover was measured using two 100-meter transects with points every one meter on the restoration site. Percent cover of herbs and grasses were measured using three one-meter square quadrats (Figure 5) on the restoration site. Scrub species density was measured by counting shrubs within a 2.5 meter wide corridor on each side of the 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. Finally, container plant survival was determined. Documentary photos of the site and transects were taken during the summer 2000.

Figure 5. Sampling quadrat in topsoil addition plot.

Results
This year, phosphorus, nitrate, total nitrogen, and percent organic matter increased at both bare (control) and topsoil addition sections of the restoration site as well as in the undisturbed area (Figure 6). Soil pH leveled off and is approximately the same at all three locations. Levels of phosphorus and nitrate were highest at the topsoil addition plots while percent organic matter and total nitrogen were highest at the undisturbed site.

This year's euporium staining results (Figure 7) revealed that the amounts of active fungal hyphae found in both the topsoil and bare (control) plots is only slightly lower than that found in the undisturbed reference site. However, the number of bacteria found in both the topsoil and control plots is significantly lower than that found in the undisturbed reference site.

Native vegetation cover on the restoration site this year consisted of ten percent shrubs and three percent herbs and grasses (Table 4). Cover is higher than the required five percent listed in the success criteria for the second year of the project, but it is still lower than the 23.5 percent shrub and 13 percent herbs and grasses cover found in the

Figure 6. Results for soil analysis of samples collected in December 1998, April 1999, and April 2000.

Figure 7. Fungal hyphae length and bacterial numbers in soil samples taken from topsoil addition and bare (control) plots at the restoration site and one undisturbed area.
(click on image for larger view)

Table 4
Results of vegetation surveys on the restoration and undisturbed sites.

surrounding undisturbed area. Native shrub density on the restoration site was 5,320 shrubs per hectare, much higher than the 2,200 shrubs per hectare found in the undisturbed area and higher than the 1,000 shrubs pers hectare required for the second year.

California sagebrush and Flat top buckwheat seedlings continue to thrive in the topsoil plots, but none have germinated in the control plots (Table 5 and Figure 8). Weed species have germinated in large numbers in both plots. Overall container plant survival at the restoration site is 94% (Table 6), slightly less than the 100% survival required for the second year.

Table 5
Results of comparison between topsoil plots and bare (control) plots.

View of topsoil addition plot (foreground) adjacent ro relatively bare control plot.

Table 6
Container plant survival as of April 2000.

Discussion
This year's work focused on planting seedlings, irrigating through the dry summer months, and continuing to collect data on soil health, transplant success, 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. Soil analysis revealed that phosphorus levels increased significantly in the topsoil addition plots while levels in the bare (control) plots and undisturbed area rose at the same rate and are nearly the same. The dramatic rise in phosphorus in the topsoil plots is misleading, however, sinve one of the four topsoil plot samples tested extremely high for phosphorus. Whatever the cause of this result, it is likely a localized anomaly and is not representative of the entire topsoil area. Remedial measures will therefore not be taken unless soil analyses in April 2001 reveal whether or not this is a trend.

Although total nitrogen levels for all three plots were higher in April 2000 than they were the previous year, levels at the undisturbed site rose at a significantly faster rate. This is an unusual result since we would expect samples taken at the same time of year in an area not subject to disturbances to remain largely unchanged (Allen, 1996). April 2001 soil analyses will reveal whether this result is a site trend or simply a localized occurrence. Nitrate levels also rose slightly at the undisturbed ad bare locations. The topsoil plot levels rose slightly at the undisturbed and bare locations. The topsoil plot levels rose as well, but much faster. This result is not unusual because when topsoil was spread at the site, mature plants that were originally growing in it were crushed and mixed into the soil. This debris was then broken down into nitrates by soil microorganisms that then remained in the soil. Nitrates did not increase as quickly in the bare and undisturbed areas because no crushed vegetation was ever added to the soil.

Percent organic matter in the bare and topsoil plots is not significantly different from and is following the same rising trend as the undisturbed area. Soil pH levels in all three sampling areas are the same and are slightly acidic which is characteristic of coastal sage scrub habitat soils. All of these results indicate that there is no need for soil remediation at this time.

It appears that fungal activity at the restoration site, for both topsoil and control plots, is currently similar to that found at the undisturbed reference site. This similarity was expected for the topsoil plots but not for the bare control plots. Below ground activity, however, is extremely variable, both temporally and spatially, and for this reason individual sample results are not as important as the trend that appears over several years of sampling. This same premise also applies to the bacteria results where low bacteria counts were expected in the bare control plots but not in the topsoil plots. A truer picture of below ground activity will be formulated after several years of sampling have occurred.

This year, percent cover of native shrubs increased dramatically. This is partly because of container planting in the bare restoration site plots, but much of it is due to the surprising number of native seedlings that germinated from the salvaged topsoil that was added to the site. The comparison of percent cover between the two types of plots illustrates this fact as the topsoil plots contain nearly six times as many California sagebrush and Flat top buckwheat individuals as the bare plots. These results are even more dramatic when considering the fact that more seedlings were planted in the bare plots then were added to the topsoil plots. Overall, percent shrub cover is increasing toward the 23.5 percent cover found in the undisturbed area and it meets the success criterion for this second year of the project. Percent cover of native herbs fell this year, but this is likely due to the increase in shrub cover. Density of native shrubs at the restoration site is much higher than the undisturbed reference site and it far surpasses the success criterion. This result is caused by the large number of volunteer seedlings that germinated from the salvaged topsoil. Percent survival of container seedlings was slightly less than the required 100%, but not enough to require additional planting at this time.

Conclusion and Recommendations
Results of soil analyses have so far produced no cause for concern. Samples will continue to be collected in April of every year through 2003 and if trends indicative of poor soil health appear, corrective soil amendments will be applied.

Results of fungal hyphae and bacteria sampling for 2000 have provided a starting point upon which the next several years of sampling will build. Soil samples were also collected and stained in 1999 but have proven to be improperly stained and are therefore unreadable. After sampling finishes in 2003, we will have four years of data that will give us a more complete picture of below activity and remedial actions, if deemed necessary at that time, can then be accomplished.

The germination of seedlings from the salvaged topsoil addition plots had far surpassed expectations. In the future, sites with native topsoil additions may be planted with fewer than the 400 container plants per acre that are generally installed at coastal sage scrub restoration sites. Because of the high percent cover and density at this site, the 22 B. sarathroides seedlings that were not ready for planting in February 2000 will not be planted at this time. In the event that percent survival of container seedlings falls below the 80% required at sampling time in April 2001, then some of the B. sarathroides will be used for replacement planting.

Comparisons between the topsoil addition and bare plots revealed that California sagebrush and Flat top buckwheat benefited the most from this trial. During the next vegetation survey, we will measure species diversity at the two types of plots and compare it to the undisturbed site in order to determine if topsoil addition alone is sufficient for restoration or if topsoil should still be supplemented with container planting. Next year's work will also include hand weeding on an as-needed basis, removal of Tubex and TreePee shelters as seedlings outgrow these protective devices, soil analysis and vegetation surveys in April, and irrigating once per month from May through October.

First Annual Report (June 3, 2002)

Third Annual Report (February 18, 2003)

Fourth Annual Report (February 18, 2003)

Final Report (March 9, 2004)