So we've killed it, now what? Quantitative and qualitative synthesis of native plant restoration projects after invasive Tamarix removal

Background/Question/Methods Invasive plants often are the source of habitat degradation and are therefore the focus of restoration, however repairing ecosystems usually requires much more than weed removal. Recent attention to the Tamarix (tamarisk, saltcedar) infestations across the western US has meant vast resources spent on herbicide, mechanical removal, and most recently, biological control. In many cases, revegetation is critical for restoring ecosystem function and services, however information is lacking and failures plentiful. In response to this problem, we have been collecting quantitative (i.e. biotic and environmental variables) and qualitative (land manager interview) data across the American West to identify which conditions and management practices cause Tamarix-dominated watersheds to be restored to a desirable condition. The most recent of these studies has been a survey of restoration projects in the Upper Colorado River watershed; arguably one of the most challenging areas to do revegetation work. We interviewed over 50 land managers and measured vegetation and soil characters at all sites where Tamarix had been removed and revegetation attempted. The vast majority of projects had done no active revegetation, and those that had were met with varying degrees of success.

Results/Conclusions Preliminary analysis reveals that degree and type of initial invasion combined with water availability may be the most important features to predict resulting plant communities, suggesting that site selection is a key component of restoration success. The results of this information synthesis will be used to create a best management practices handbook, and may reveal why this particular area has shown different invasion patterns than other watersheds, particularly the Rio Grande. Observing ecosystems post weed control can reveal much about causes of invasion and the underlying management issues that may be at play.