last update January 13, 2001
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. In August 1998, a 3.16 acre area of undisturbed Diegan coastal sage scrub
inhabited by Polioptila californica californica (California coastal gnatcatcher)
was removed by Station personnel during fuelbreak 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. In addition, Selaginella cinerascens (ashy spike-moss)
was salvaged from a construction site and placed on the R33 restoration site.
Next year's work will consist of planting, exotic vegetation control and continued
monitoring.
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 (Figure 1). 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-topped 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 homerange 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.
Site Preparation
A total of 50 signs, supplied by MCAS Miramar and designating the site closed
to foot traffic, were placed every 50 feet along the east and west side of R33
adjacent to the restoration site. Erosion control in the form of straw flake
dams were installed on the site in November and December 1998. The dams were
constructed along the contours of the slope by SERG personnel digging six to
eight inch ditches perpendicular to the road using hand tools. Ten centimeter
thick sections of straw were placed vertically into the ditches and then backfilled.
A total of 39 dams were placed on the slope, 21 on the southern portion and
18 on the northern portion using 100 straw bales (Figure 2). Tire tracks on
the site running parallel to the slope were pitted by hand to prevent the formation
of gullies. Seed from California sagebrush and flat-top buckwheat was collected
from the surrounding area of the site and spread upslope of the straw flake
dams to encourage seed germination. Eight 18 inch aluminum dowels were placed
approximately 12 inches into the ground and notched at ground lever in order
to monitor sediment loss on the slope. The dowels were topped with yellow rubber
caps to mark the pins and avoid injury personnel (Figure 3). Trash in the form
of beverage bottles, cans and food wrappers were removed from the site.
Figure 1. Coastal sage scrub restoration site located on Marine Corps Air Station Miramar, San Diego, California.
Figure 2. Straw flake dams installed on R33 site during the Winter 1999.
Figure 3. Installation of erosion control monitoring pins.
Seed Collection and Growing Plants
Seed for coastal sage scrub plant species grown for the restoration project
(Table 1) was collected October 1998 through August 1999. All seed collection
was conducted on MCAS Miramar (Figure 4) with the exception of Ferocactus viridescens
(San Diego barrel cactus) which was collected from Point Loma, San Diego, California.
Plants were grown at the greenhouse at San Diego State University (SDSU) and
the shadehouse at USIU. A total of 1180 of the 1520 seedlings are growing as
of 31 August 1999. The remainder of the plants will be ready for planting by
December 1999.
Table 1. Container grown seedlings ready for planting as of 31 August 1999 and total number to be planted on the R33 site during winter 1999/ Spring 2000.
|
Species Total |
Common name
|
Available 1180 |
Needed 500 10 200 15 55 25 90 255 20 90 140 120 1520 |
Figure 4. Seed collection sites on MCAS, Miramar for R33 coastal sage restoration project.
Experimental design
Two small populations of Selaginella cinerascens (ashy spike-moss) was salvaged
from the road widening construction area along Vega Drive in November 1998.
The ashy spike-moss was excavated from the ground using the bucket of a skip
loader. Sections of the ashy spike-moss were removed from the bucket by hand
and placed in the bed of a plastic-lined pickup truck and immediately transported
to the R33 restoration site for replanting. Holes were dug (10 to 15 cm deep)
in the shape of the sections of ashy spike-moss and the sections were laid in
the ground and backfilled. 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. In addition, two California
sagebrush removed from the construction site were also transplanted on the R33
site.
Monitoring
Ten soil samples, five from the site and five from the surrounding undisturbed
area, were collected in October 1998 to be used as a baseline reference. The
undisturbed areas used as references are defined as having greater than 50 percent
cover of native coastal sage scrub vegetation species and less than 20 percent
non native vegetation species. An additional ten soil samples were collected
in May 1999. Samples were sent to A&L Western Agricultural Laboratories to be
analyzed for organic matter, phosphorus, pH, nitrate and total nitrogen. Texture
analysis was done at San Diego State University using the … method. Bulk density
was measured by taking an eight to ten cm core of soil and then filling the
hole with a measured amount of sand. The soil was dried in an oven at approximately
85° C overnight and then the dry weight measured to yield grams of soil per
ml.
An initial vegetation survey on the site and on an undisturbed, east facing slope to the south of the site was conducted in November 1998 using the European Relevé method (Mueller-Dombois and Ellenberg 1974). An additional vegetation survey was conducted using a modified California Native Plant Society (CNPS) method in May 1999. One transect was established on the south section of the site running east/west at an angle of 84°. The second transect was on the north section of the site running east/west at an angle of 268°. The 0 m mark for each transect was marked by a 1m stake painted red at the top for future surveys. Percent cover was determined using two 100 meter transects with points every 0.5 m. Density was measured by counting the number of plants within 2.5 m of each side of the transects. Native and nonnative herbs and forbs were measured using five-one meter square quadrats. Four photo points were established, two at the top of the hill and two at the bottom of the hill and documentary photos of the site and surveying taken in October and November 1998, May and August 1999.
The erosion control monitoring pins were checked monthly during the winter/spring and after each precipitation event greater than 0.5 in.
Maintenance
Exotic vegetation on the site was sprayed with Round up Pro in May 1999 and
cut down using a gas powered weed trimmer in June 1999. Trash was removed on
the site during each site visit. Signs removed by trespassers were replaced,
when possible, during site visits.
Results
No sediment loss was measured on the erosion pins during the 1998/1999 rainy
season. In addition, there were no signs of erosion gullies forming on the site.
The ashy-spike moss is slow growing so it is difficult to assess growth. However 12 of the 13 sections appeared healthy as of 24 August 1999. The California sagebrush shrubs transplanted on the R33, one is alive and flowering while the second shrub did not survive.
Results of physical and chemical soil tests for samples collected on the restoration site and surrounding undisturbed area in November 1998 and May 1999 are shown in Figure 5. Percent organic matter in the undisturbed area increased while the disturbed site decreased slightly. Available phosphorus decreased slightly in both areas. Nitrate in the undisturbed area decreased during the spring, while nitrate built up on the disturbed site. The total nitrogen increased in the undisturbed area and decreased on the restoration site. Bulk density on the disturbed site is slightly higher, though the difference in compaction was not significant. Soil texture in the surrounding undisturbed area on the disturbed restoration site are both sandy loam.
Figure 5. Soil test results on R33 restoration site and surrounding undisturbed
area.
Results of the initial vegetation survey of the surrounding undisturbed area using an European relevé are shown in Table 2. The dominant species found in undisturbed area were Eriogonum fasciculatum, Mimulus aurantiacus and Salvia apiana.
Table 2. European Relevé results measured in November 1998.
|
Species Artemisia californica Total Native species * Identification in process. |
% Cover
|
% Cover 1
1 |
The modified CNPS survey conducted in May 1999 resulted in less than 1 percent vegetation cover found on the disturbed site (Table 3).
Table 3. Results of vegetation survey on R33 coastal sage scrub restoration site on 31 May 1999.
|
Species Species
Forbs and Herbs Species |
Percent Cover Density (#/Ha) Percent Cover Percent Cover |
Relative Cover Relative Density |
Discussion
The first years work concentrated on erosion control, collecting initial data
and growing seedlings for planting in the winter/spring 1999/2000. The straw
flake dams, installed as erosion control, were efficient in preventing sediment
loss on the restoration site as no sediment loss or formation of erosion gullies
was observed. Problems associated with the dams was damage due to unauthorized
off road vehicle activity and use of the dams at the top of the slope by deer
as a place to sleep. Security has been notified of the trespassing and efforts
are being made to prevent further damage. All 1520 seedlings will be ready for
planting in winter 1999. Grass seedlings were not started until approximately
two months before planting to prevent seedlings from becoming root bound. The
majority of the ashy-spike moss plugs survived the transplant and will be monitored
over the following three years.
Soil nutrient levels were initially similar in November 1998; however, in a period of six months the lack of vegetation already resulted in a slight difference in organic matter, nitrate, total nitrogen and pH. The organic matter increased in the undisturbed area during the spring growing season, but remained unchanged on the disturbed site. This was probably due to the lack of native vegetation. Nitrate in the undisturbed area decreased as the native plants absorbed it during the spring growing season. On the restoration site, nitrate increased through the high turnover rate inherent in non native grasses. Phosphorus remained relatively unchanged. Bulk density was slightly higher probably from the used of heavy equipment during vegetation removal.
The initial vegetation surveys in the undistured area were used to establish success criteria for the restoration site. Success criteria for May 2000 is five percent cover, 100 percent survival and a density of 507 seedlings per acre. Additional success criteria may be found in the Success Criteria for Native Plant Restoration of R33 Site report (Heffernan, 1998). Ongoing surveys on the disturbed site will be used to measure progress over time.
In addition, SERG is consulting with Station personnel in regards to the to repair of R33, the dirt Road bisecting the site, to minimize the damage to the restoration site during the construction efforts.
Conclusions and Recommendations
Straw flake dams proved to be an effective temporary biodegradable erosion control
method for the restoration site slope. It is recommended that when creating
ditches by hand be done after the first winter rains to allow for easier manipulation
of the soil. Installing temporary fencing around future restoration projects;
partially on the far eastern portion of the Station, may reduce vandalism from
trespassers and possibly reduce damage to the site and plants from deer.
Transplanting and monitoring of the ashy-spike moss will aid in determining the value of salvaging and using it as a ground cover and a possible erosion control method. 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 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. The initial survey of an undisturbed area with a slope and aspect similar to the restoration site will aid in creating habitat similar to the habitat currently used by the California coastal gnatcatchers in the area.
Next year's work will include planting the 1520 container seedlings, all with plant protective devices between November 1999 and March 2000. Maintenance in the form of irrigation, exotic vegetation removal, plant protection removal and monitoring will occur on a regular basis. Further details may be found in the Techniques and Methodology for Native Plant Restoration of R33 site (Heffernan 1998).
References
Mueller-Dombois, D. and Ellenberg, H. 1974. Aims and Methods of Vegetation Ecology.
John Wiley and Sons, Inc. New York.
Heffernan, L. October 1998. Techniques and Methodology for Native Plant Restoration of R33 Site on Marine Corps Air Station, Miramar, San Diego, California. United States International University. San Diego, California.
Heffernan, L. November 1998. Success Criteria for Native Plant Restoration of R33 Site on Marine Corps Air Station Miramar, San Diego, California. United States International University. San Diego, California.
Final Report (February 17, 2003)
