Seeding native plants to restore desert farmland and mitigate fugitive dust and PM10

Windblown fugitive dust contributes to violations of air quality standards for particulate matter <10 mu m aerodynamic diameter (PM10). In the western Mojave Desert of California, approximately 1070 ha of previously tilled or over-grazed land impacted downwind metropolitan areas by wind-driven emissions of dust. A protocol of furrowing across the wind and direct seeding of three native perennial shrubs and a bunch grass helped reduce fugitive dust emissions in this area by more than 95%. Seeded species varied from 35 to 97% of Living plant cover in individual years, reflecting rainfall patterns. In areas of deep sand, Indian ricegrass (Achnatherum hymenoides Roemer & Shultes) outperformed the shrubs, while fourwing saltbush [Atriplex canescens (Pursh) Nutt.] exhibited the most widespread establishment. This revegetation was achieved in an anomalous year with above average and late rainfall that eliminated early competition from annual species and later fostered abundant shrub growth. This success was not reproducible in more normal years, when minimal disturbance protocols such as broadcasting of seed on the untilled soil surface were as effective and less costly. We conclude: (i) direct seeding can lead to plant establishment in favorable years, but is likely to fail in any given year, (ii) direct seeding should be implemented with little soil disturbance, (iii) the native fourwing saltbush is the most likely species to become established in this environment, and (iv) unpredictable rainfall and temperature require that direct seeding be backed up with alternative strategies to achieve reliable dust and PM10 mitigation in arid environments.