Research

Long-term control of economically and ecologically damaging invasive plants has generally proved unsuccessful in the western U.S.  Integrated pest management (IPM) - which uses a combination of mutually supportive treatments, such as targeted grazing and herbicide - has shown promise. However, the success of IPM approaches for managing particularly noxious invasive annual grasses, are limited. For example, current IPM approaches often do not address more progressive management techniques, including seeding of desired species. Reseeding is a promising IPM component because it creates a barrier to weed establishment; is compatible with forage production; and may increase community resistance to future invasion. At several experimental arid grassland sites, we are testing the utility of seeding functionally similar and functionally dissimilarspecies to reduce dominance of noxious plant invaders, including barb goatgrass (Aegilops triuncialis), medusahead (Taeniatherum caput-medusae), and russian thistle (Salsola spp.).

Strip-seeding is a surprisingly underutilized restoration approach where seeds or plantings are installed in fragmented spatial patterns over an affected area. Because this approach concentrates planting effort and increases the probability of establishment, overall restoration costs are generally reduced. Although practitioners have been employing strip-seeding approaches ad hoc for years, formal tests into the utility of this approach to achieve multiple management goals is essentially absent for grasslands in the western U.S. In a large experiment in Davis, CA, we are testing how strip-seeding can be used to restore multiple ecosystem services such as invasion resistance, forage production, and erosion control. Preliminary data suggests that, after five years, seeding only 60% of a degraded area using a strip-seeding approach would allow a practitioner the ability to enhance multiple ecosystem services equivalent to seeding 100% of a degraded area.

As a result of global change, the intensity and frequency of wildfires occurring in western rangelands are increasing. Policy on most public lands mandate a grazing cessation for three years after fire. However, an understanding of the relationship among fire, grazing, and vegetation community trajectories is not developed for western rangelands. In sites across Arizona and California, we are investigating the interplay among fire, plant community stability, grazing and restoration. At each site, we document how previously grazed plant communities respond to different grazing management techniques after a fire in order to develop effective post-disturbance grazing approaches.