SEEDING NATIVE PLANTS TO RESTORE DESERT FARMLAND AND MITIGATE FUGITIVE DUST AND PM10

Windblown fugitive dust contributes to violations of air quality stand ards for particulate matter <10 mu m aerodynamic diameter (PM10). In t he western Mojave Desert of California, approximately 1070 ha of previ ously tilled or over-grazed land impacted downwind metropolitan areas by wind-driven emissions of dust. A protocol of furrowing across the w ind and direct seeding of three native perennial shrubs and a bunch gr ass helped reduce fugitive dust emissions in this area by more than 95 %. Seeded species varied from 35 to 97% of Living plant cover in indiv idual years, reflecting rainfall patterns. In areas of deep sand, Indi an ricegrass (Achnatherum hymenoides Roemer & Shultes) outperformed th e shrubs, while fourwing saltbush [Atriplex canescens (Pursh) Nutt.] e xhibited the most widespread establishment. This revegetation was achi eved in an anomalous year with above average and late rainfall that el iminated early competition from annual species and later fostered abun dant shrub growth. This success was not reproducible in more normal ye ars, when minimal disturbance protocols such as broadcasting of seed o n the untilled soil surface were as effective and less costly. We conc lude: (i) direct seeding can lead to plant establishment in favorable years, but is likely to fail in any given year, (ii) direct seeding sh ould be implemented with little soil disturbance, (iii) the native fou rwing saltbush is the most likely species to become established in thi s environment, and (iv) unpredictable rainfall and temperature require that direct seeding be backed up with alternative strategies to achie ve reliable dust and PM10 mitigation in arid environments.