Plant and bird community response to saltcedar removal along the Virgin River: Considerations for riparian restoration

Background/Question/Methods

Saltcedar or tamarisk (Tamarix spp.), is a shrub or small tree that was deliberately introduced from Eurasia in the late 1800’s to the United States as an ornamental and for erosion prevention. As one of the most successful plant invaders in the western United States, saltcedar has a reputation for influencing ecosystem structure and function. As a first step toward habitat restoration, mechanical (e.g., hand tools, masticators, and bulldozers) removal is widely used where large expanses of saltcedar occur. Obviously such efforts can seriously impact the habitat quality of affected sites, in the short- and long-term.  However, evaluations of the effects or effectiveness of such actions using ecologically meaningful measures are not available.  In response to this information gap, we evaluated the short-term response of vegetation, birds and associated habitat metrics to saltcedar removal at sites along the Virgin River in NV and AZ. We collected information on the plant community response and bird habitat metrics in 120-150 m² plots in treated and non-treated sites in spring 2009.  Concurrently, we conducted spot mapping to capture the bird community response across 60-6.25 ha plots in sites that were mechanically cleared and in nearby non-treated control sites with >60% cover by saltcedar.

Results/Conclusions

In treated sites, saltcedar density was lower while total species richness was higher.  Densities of native perennial grasses and non-native annual grasses were greater in the non-treated sites.  Overall bird abundance was greater in the non-treated site including seven species with species conservation status in the region of the study.  Bird habitat availability and structural complexity was greater in the non-treated sites.    These results demonstrate that the simultaneous consideration of vegetation and bird communities and their habitat has great utility in understanding the short-term ecosystem response for this type of restoration action.  To maintain habitat suitability and bird diversity, careful consideration of post-removal re-vegetation and restoration should be included in any removal operation.