Soil Ecology and Restoration Group

NATIVE PLANT RESTORATION ON R33

COASTAL SAGE SCRUB MITIGATION SITE

ON MARINE CORPS AIR STATION MIRAMAR,

SAN DIEGO, CALIFORNIA

Executive Summary
In August 1998, a 3.16 acre area on the Marine Corps Air Station Miramar (MCAS) was cleared during fuel break and fire road maintenance. The area cleared was covered with coastal sage scrub used as a home range for the endangered Polioptila californica californica (California coastal gnatcatcher). To repair damage to the area, the United States Navy signed a cooperative letter of agreement with the Soil Ecology and Restoration Group (SERG) to install temporary erosion control, revegetate and conduct native plant restoration research on the site. In November 1999, SERG installed biodegradable straw flake dams to serve as erosion control. Since then, sediment loss on the slope has been monitored with aluminum erosion control monitoring pins. Only a negligible amount of sediment has been lost from the site. In the spring of 2000, 1558 coastal sage scrub seedlings grown in the SERG greenhouse at San Diego State University and the SERG shadehouse at United States International University were outplanted. Seedlings were irrigated throughout the summer. Vegetation surveys continued for the second year and results for species percent cover and density were compared to those from the reference site. The success criteria for this year was five percent total species cover, a total species density of 1268 plants per hectare, and 100% container plant survival. The restoration site met the criteria for cover and was an insignificant 2% behind on survival. The site also fell slightly short of the required species density. We will wait until the results of next year's survey to determine if action needs to be taken to increase density. Results of soil analyses show that nutrient levels are beginning to return to levels in the undisturbed areas. Next year, seedlings will be irrigated throughout the summer months and monitoring of vegetation, soil nutrients, and erosion will continue.

Introduction
Marine Corps Air Station Miramar, hereinafter referred to as the "Station", is located on approximately 23,116 acres of land in San Diego County, California four miles east of the Pacific Ocean and thirteen miles north of downtown San Diego (Figure 1). In August 1998, a 3.16 acre area of undisturbed Diegan coastal sage scrub inhabited by the California coastal gnatcatcher (Polioptila californica californica) was removed by Station personnel during fuel break and fire road maintenance. In September 1998, a cooperative letter of agreement with Southwest Division, Naval Facilities Engineering Command and the Soil Ecology and Restoration Group located at United States International University (USIU), was signed to allow USIU to restore the impacted area and conduct native plant restoration. The letter of agreement includes erosion control, weeding, container planting, monitoring, and maintenance continuing through September 2002.

The focus of the project during the first year was on installing temporary, biodegradable erosion control, collecting seed, growing plants, and collecting initial vegetation and soil data for future reference. Signs designating the site closed to all forms of traffic were posted. Erosion control in the form of 39 straw flake dams was installed. Dams run perpendicularly to the road and are evenly spaced along the two sides of the slope. In addition to these activities, two small populations of Selaginella cinerascens (ashy spike-moss) were salvaged from the road widening construction area along Vega Drive in November 1998 and immediately transported to the R33 restoration site for replanting. Seven sections of ashy spike-moss, 20-30 cm long by 10-15 cm wide, were placed on the south section of the site and six on the north section. Each section was marked by a red flag. Two California sagebrush removed from the construction site were also transplanted on the R33 site.

In this, the second year of the project, over 1500 container seedlings were planted on site. Monitoring and maintenance activities continued (Tables 1 and 2) and will continue in much the same way for the two remaining years of the project.

Figure 1. Coastal sage scrub restoration site located on Marine Corps Air Station Miramar.

Table 1
Dates of site visits on the Station.

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

Site Description
The 3.16 acre site is located in the southeast corner of the Station on both the north and south sides of fire road R33. The site is sloped approximately 20° to the southeast and is bordered to the east by a dirt road running north and south along a riverbed. Disturbance to the site was due to the clearing of vegetation via a chain pulled behind a vehicle in August 1999. In September 1999, vegetation remaining on the site consisted of a few Opuntia littoralis (prickly pear cactus) and Eriogonum fasciculatum (flat-topped buckwheat). Vegetation in the surrounding undisturbed area included Eriogonum fasciculatum (flat-top buckwheat), Artemisia californica (California sagebrush), Malosma laurina (laurel sumac), Salvia mellifera (Black sage), Baccharis sarothroides (broom baccharis), Mimulus aurantiacus (monkey flower) and exotic grasses such as Avena barbata (slender wild oat). The site is in the home range of Polioptila californica californica (California coastal gnatcatcher). Additional wildlife found on the site through visual sightings or tracks include deer, rabbit, rattlesnake and coyote. The road on the site is used by station personnel during security checks and occasionally by unauthorized off road vehicle activity.

Methods
In the fall of 1999, a contractor was hired by the Navy to repair the R33 fire road. This work resulted in damage to much of the restoration that had already been completed at the site. Repairs to the road removed most of the straw flake dams installed in November 1999 by SERG on the south side of the road. In the spring of 2000, these dams were reinstalled. Additional repairs were made to erosion gullies that had begun to form on the impacted area. These were filled with straw bales and rocks to prevent further sediment loss.

In addition, the lower southeast portion of the site is now most likely severely compacted as it was used as a staging area and dump for excess gravel (see foreground of Figure 2). No plan was implemented to repair the damage to this area, such as ripping to reduce compaction and removal of the excess gravel, so it was decided that no coastal sage scrub seedlings would be planted in the area since they would be unlikely to grow.

Figure 2. R33 site after planting and installation of seedling shelters.

Planting
Between February and April 2000, a total of 1558 coastal sage scrub seedlings were planted (Table 3). Planting holes were dug by hand and with a gas-powered auger. Holes were pre-watered and plants were 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 to protect seedlings from herbivory and desiccation (Figure 2).

Table 3
Coastal sage scrub seedlings planted in spring 2000.

Maintenance
After planting, seedlings were watered twice each month through September when seasonal rains began. Plants received 1/2 gallon per watering. Basins were filled with hoses from a water tank located in the back of a pickup truck. Water was obtained either from the fire pump located at the intersection of Green's Farm Road and Ammo Road or from the Padre Dam water treatment facility. Selaginella cinerascens patches were also watered. During trips to the site for irrigation, plant protective shelters were removed from plants that had outgrown them and "NO ENTRY" signs that had been removed by road construction contractors and trespassers were replaced (Figure 3).

Figure 3. Installing "NO ENTRY" boundary sign.

In July 2000, in an effort to control weeds, approximately one-third of the seedlings were surrounded by straw mulch to a distance of one foot from the plant stem. Exotic vegetation was not sprayed with herbicide as permission for herbicide use was not obtained until 14 June 2000, but standing weeds were cut down using a gas powered weed trimmer (Figure 4). Cut weeds were bagged and disposed of offsite at the Miramar landfill.

Figure 4. Cutting down weeds with a gas-powered weed trimmer.

Monitoring
Documentary photos were taken throughout each stage of the project. Erosion monitoring pins were checked for accumulated sediment monthly during winter 1999/spring 2000 and after each precipitation event greater than 0.5 inches. In May 2000, ten soil samples, five from the site and five from the surrounding undisturbed area, were collected and analyzed at A&L Western Agricultural Laboratories for nitrate, total nitrogen, phosphorus, pH, and organic matter. On 29 May 2000, estimates of species density and species percent cover were determined as well as ground cover and percent survival of container plants. Vegetation surveys were conducted according to a revised version of the California Native Plant Society (CNPS) field sampling protocol. Percent cover was determined using two 100-meter transects, one on the south section of the site running east/west at an angle of 84° and the second on the north section of the site running east/west at an angle of 268°, with points every 0.5 meters (Figure 5). Species density was measured by counting the number of plants within 2.5 m of each side of the transects. Native and non-native herbs and forbs were measured using five one-meter square quadrats. Selaginella cinerascens transplants were monitored for health and survival.

Figure 5. 100-meter transect on the northern portion of R33 site.

Results
During the 1999/2000 rainy season, erosion monitoring pins were measured only on the north side of the site where straw flake dams had not been damaged by road repair work. Only 1mm of sediment was lost during the season. Deep erosion gullies had formed on the south side of the site where dams had been destroyed.

Results of the chemical soil tests for samples collected on the restoration site and surrounding undisturbed area in November 1998, May 1999, and May 2000 are shown in Figure 6. Soil pH at the disturbed and undisturbed sites are nearly identical. Nitrates increased at both sites while total nitrogen decreased at the undisturbed site but stayed constant at the disturbed site. Available phosphorus increased at the undisturbed site and decreased at the disturbed site. Percent organic matter remained constant at the undisturbed site, but increased slightly at the disturbed site.

Figure 6. Soil test results on R33 restoration site and surrounding undisturbed area.

The results of this year's vegetation survey are found in Tables 4 and 5. Total species percent cover is 5%, total species density is 1020 plants per hectare, and percent survival of container plantings is 98%. All sections of S. cinerascens still appear alive and healthy. However, they dried out during the summer months, so it remains to be seen if they will green up again after winter rains. One of the two A. californica transplants is also still alive and healthy.

Table 4
Results of vegetation survey on R33 coastal sage scrub restoration site on 29 May 2000.

Table 5
Container plant survival as of May 2000.

Discussion
This year's work focused on planting seedlings, irrigating through the harsh summer months, and continuing to collect data on erosion, soil health, and transplant success. The straw flake dams appear to be effective as a means of erosion control since only 1 mm of sediment was lost from the north side of the site where dams remained intact. In contrast, deep erosion gullies formed on the south side of the site where dams had to be replaced.

Soil nutrient levels were initially similar in November 1998, only a few months after the site had been impacted. In the spring of 1999, the lack of vegetation on site was already having an impact on organic matter, nitrate, total nitrogen and pH. Soil samples analyzed this year were collected only two months after planting, so it was not expected that results would be drastically different than the previous year's results. However, results show that the initial drop in soil pH has reversed and is now virtually the same as at the undisturbed site. Nitrates, too, were falling at the disturbed site, but are now increasing again, just as at the undisturbed site. Total nitrogen levels were originally the same, then rose greatly at the disturbed site, and are now returning to normal levels. A similar path was followed by percent organic matter. Since all of these parameters are either similar to the undisturbed site or show signs of returning to normal levels, there appears to be no need for soil remediation. However, it is still early and a final decision should wait until we see if these trends persist. Phosphorus levels at the undisturbed site have remained fairly steady. However, at the undisturbed site, they are rising. If this trend continues, we will consider adding phosphorus to the disturbed site.

Initial vegetation surveys at the undisturbed site were used to establish success criteria for the restoration site. Success criteria for May 2000 are five percent total species cover, a total species density of 1268 plants per hectare, and 100 percent container plant survival. The restoration site meets the criteria for percent cover and, at 98%, is not significantly off in terms of survival. Vegetation survey results fall short for species density, but numbers are not low enough to cause any great concern. If density has not increased by the next sampling period in May 2001, then additional seedlings will be planted.

Selaginella cinerascens is a very slow-growing species, so it is difficult to assess transplant health by measuring anything more than simple survival. The transplants appear healthy so far and will continue to be monitored through 2002.

Conclusions and Recommendations
Straw flake dams proved to be an effective temporary biodegradable erosion control method for the restoration site slope. For this project, the trenches into which straw flakes were installed were dug by hand. In the future, it is recommended that digging be done after the first winter rains to allow for easier manipulation of the soil. Installing temporary fencing around future restoration projects, particularly those in east Miramar, may reduce vandalism from trespassers and possibly reduce damage to the site and plants from browsing by deer.

Changes seen in soil nutrients so far are short term with more significant changes in soil nutrients likely to appear over time. Future soil samples will be collected in May of each year through 2002 in order to record consistent, comparable results.

Initial surveys of undisturbed areas with characteristics, such as slope and aspect, that are similar to the restoration site is a valuable tool in determining success criteria for the restoration site as areas of coastal sage scrub vary in species composition, percent cover and density. Ensuring that results of yearly monitoring match the success criteria will aid in creating habitat similar to the habitat currently used by the California coastal gnatcatchers in the area.

Selaginella cinerascens appears to respond well to transplanting and may prove to be a useful method of erosion control. However, a longer, more in-depth study than the current one would be required to determine this. The survival of one of the A. californica shrub transplants suggests that it might be worthwhile to study the use of mature plants for coastal sage scrub restoration.

Next year's work will include continued monitoring of erosion, vegetation health and survival, soil nutrients, and Selaginella cinerascens transplant success. Seedlings will be irrigated once each month through the summer and plant protection will be removed as necessary. Approximately 16 Ferocactus viridescens that were not ready for planting during spring 2000 will be planted in the spring of 2001. In addition, since permission has now been received for herbicide application on Station, exotic vegetation will be sprayed with RoundUp Pro approximately twice this year. Further weed control efforts will include mulching around the remaining unmulched seedlings on site and cutting weeds with a weed whacker.

First Annual Report (January 13, 2001)

Final Report (February 17, 2002)