Soil Ecology and Research Group last update October 29, 2002

INVASIVE SPECIES CONTROL AND
NATIVE HABITAT ENHANCEMENT
Veldt Grass and Mustard Sites

NALF SAN CLEMENTE ISLAND

 

Background

Two exotic species have gained a foothold on the island and are in the process of expanding their range at the expense of the surrounding native habitat (Figure 1). The first species, Ehrharta calycina, or veldt grass, is a native of south Africa that has become established at two sites at the north end of the island. The first is a six-acre site on the northeast corner of the island along an access road to a small fuel farm. The second site is located adjacent to the airfield and is approximately four acres in size. The veldt grass is currently spreading at both sites into the undisturbed native maritime desert scrub that is dominated by Lycium californicum (box thorn). The second exotic species, Brassica nigra, or black mustard, has become established along China Canyon Road on the southern end of the island. It has quickly spread into the adjacent native grasslands, becoming nearly a monoculture, and currently covers an area approximately twenty-five acres in size.

Methods

To prevent the continued spread of exotic species in both these areas, the veldt grass and black mustard need to be removed and replaced with appropriate native species. Since both areas have developed into nearly monocultures, each area will be sprayed with a herbicide by appropriately licensed personnel and the soil treated with a pre-emergent. This will not only remove the current growth but prevent the reestablishment of the exotic species from the large weed seedbank that is no doubt currently located in the soil. Appropriate native species for both grassland and maritime desert scrub habitats will be grown at the San Clemente Island Native Plant Nursery from locally collected seed. Local soil from adjacent undisturbed habitat will be used to inoculate the seedlings with necessary mycorrhizal fungi during their germination and early growth.

Once each site has been prepared as described above, approximately 400 seedlings per acre will be out-planted during the wet winter season to take advantage of natural precipitation (Table 1). A temporary drip irrigation system will be established for the maritime desert scrub seedlings at the veldt grass site to assist them through the first hot dry summer. This will also allow supplemental water to be directly applied to each seedling, decreasing the germination of weedy species that is prevalent with overhead or flood irrigation. This system will be removed after the first year. No supplemental irrigation system will be used for the grassland site since the grass seedlings will become established much quicker than the maritime desert shrubs.

Both sites will be maintained and monitored during the first year for additional weed control, if necessary, and seedling survival and growth. Two 100 meter long transects at

Figure 1. Location of restoration sites.

the veldt grass site and five 100 meter long transects at the black mustard site will be established upon completion of planting. These will be used in conjunction with a modified California Native Plant Society (CNPS) sampling protocol to analyze restoration success through the determination of species diversity and cover. Photo documentation will be accomplished for all phases of the project from initial seed collection through final monitoring.

Table 1.
Species and quantities to be planted at restoration sites.

Scheduling and Site Access
A schedule of tasks is presented in Table 2. Some flexibility may be required to accommodate weather conditions and military training requirements. The mustard site is located within the Shore Bombardment Area (SHOBA) and will require scheduled access with the Southern California Offshore Range (SCORE) operator. Veldt Grass Site A is located adjacent to a Naval Space and Warfare Command (SPAWAR) facility and will require coordination with the SPAWAR Operations Manager. Access to these sites will be coordinated through the Natural Resources Office Deputy Director of Operations at San Clemente Island.

Table 2.
Schedule of completion dates for products