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San Marcos Highlands Habitat Restoration Implementation

Quick Facts:

  • Development Size: 80 acres
  • Location: San Marcos, CA (North San Diego County)
  • Client: KB Home

Project Summary:

Great Ecology is implementing a Habitat Mitigation and Monitoring Plan (HMMP) to offset impacts from an 80-acre development project in San Marcos, California. Mitigation measures involve the restoration and enhancement of approximately seven acres of disturbed riparian habitat and twelve acres of Diegan coastal sage scrub. Great Ecology’s restoration activities will include site clearing and preparation, removing non-native vegetation, protecting existing native habitat, salvaging and transplanting native onsite vegetation, and installing native seeds, shrubs, and trees.

Ongoing/Completed Activities:

- Collected soil from a restoration area under a eucalyptus grove, to test for the presence of allelopathic chemicals in the soil. These chemicals, found in the foliage of eucalyptus and some other trees, “poison” the soil beneath them, rendering it inhospitable to survival of other plants. Soil testing tells us how deep to remove and replace the soil layer to ensure successful plantings where the eucalyptus grove once stood.

- Flagged native plants that are locally adapted for salvage. Sourcing existing plants can promote the rapid spread of target species and ensure restoration success. Transplants are also a source of mycorrhizae for the receiving site may enhance growth of surrounding coastal sage scrub seedlings. Salvaged plants include typical Diegan coastal sage scrub and southern riparian species like:

  • California sage brush (Artemisia californica)
  • Black sage (Salvia mellifera)
  • White sage (Salvia apiana)
  • Red and arroyo willow (Salix sp.)
  • Mule fat (Baccharis salicifolia)

- Collected, transported, and stored the salvaged plants in a designated laydown area. Smaller, younger shrubs are the best candidates for salvage, since they are more portable than larger, dense shrubs. They do not have deep roots, do not require additional trimming, and have a higher likelihood of establishment once replanted. Once the plants arrive at the laydown area they are repotted with high quality soil and watered as they await restoration. Woody species like mule fat and willows are transplanted via cuttings (called whips) and require less intensive storage and watering than the salvaged shrubs.

Planned Activities:

- Ordering seed mixes of riparian and sage scrub plants - these seeds will supplement the salvaged local plants in the restoration areas. Some plants are too large to successfully uproot and replant, or will grow better from seed. Transplants can also help the seeds grow and successfully establish by providing shade, soil stabilization, and protection from predators.

- Incorporating recovered litter layer (called duff) into the soil for Diegan coastal sage scrub restoration. Duff is composed of accumulated materials like woody debris, leaf litter, and organic material that builds up below the sage scrub community. Using duff for restoration will provide cover for the seeds to establish and mimic natural conditions for the salvaged plants to thrive. The duff is collected by scraping a thin (three to six inch) soil layer using a backhoe or bulldozer. This material is then crushed, cut, or shredded, then stockpiled at the construction site for our future restoration.

Field Blogs:

San Marcos, CA