Chaparral Restoration

Chaparral, among the most stable and resilient vegetation types in California, has shown signs of degradation by altered fire frequency, drought, non-native species, recreation, urban development, and possibly anthropogenic nitrogen deposition in southern California. Restoration has been practiced less frequently in chaparral than other, more extensively disturbed vegetation types, but recent degradation suggests that restoration may be important for the maintenance of ecosystem services such as slope stabilization, carbon sequestration, biodiversity conservation, and scenic beauty. Most chaparral restoration has primarily been " passive restoration", the removal of disturbance stressors or management of fire frequency to promote natural successional processes for plant, animal, and soil recovery. However, areas that have suffered severe disturbance, such as topsoil removal and extensive plant invasions, seldom recover passively or at best may be colonized by early successional shrubs. Active restoration, which can include weeding, planting, seeding, treatments to break seed dormancy, and/ or stabilizing soil treatments, may be needed in many cases. We review current knowledge of chaparral stressors and dynamics that relate to restoration as well as restoration methods. The -limited information on restoration projects to date indicates that early successional, deciduous shrub species, which are common to sage scrub and have low seed dormancy, are most successful in establishment. These may accomplish some restoration objectives, such as soil stabilization and ability to recover from fire, but fall short in biodiversity goals. Application of techniques to establish evergreen chaparral species, such as -large-scale dormancy breaking treatments or facilitation by early successional shrubs, is needed. We also discuss plant traits that might be used to guide restoration toward -persistent communities under frequent fire. Our aim is to describe knowledge gaps about chaparral restoration and inspire restoration research, planning, and practice.