Tamarix invasion and management in the northern U.S

Background/Question/Methods

Tamarix is expanding northward in North America but it is unclear if this success is due to adaptation or climate change or both.  This information is important to better predict areas vulnerable to future invasion and aid in targeting resources for early detection and control.  Rapid response with effective treatments is necessary following Tamarix detection but few studies have tested treatment effectiveness on young plants.  We are developing an integrated program that combines research, education, and extension to improve the effectiveness of Tamarix management in northern regions. Specifically, we are (1) examining Tamarix environmental tolerances and genetics to help determine areas at risk of invasion, (2) demonstrating effective methods for controlling young plants, and (3) developing education curriculum and outreach tools to successfully disseminate research findings to maximize community and weed professional involvement in Tamarixmanagement.    

Results/Conclusions

Tamarix establishes near waterways (regulated and unregulated rivers, creeks, and reservoirs) and seasonally wet grassland habitats at northern latitudes.  Recently burned grasslands or areas with little vegetative cover were more vulnerable to Tamarix invasion than intact grassland vegetation, although establishment was possible under grass canopies.  Seeds collected from Tamarix plants at northern latitudes had greater germination following exposure to cold temperatures than seeds produced in more southern locations.  Tamarix genotypes in South Dakota were more similar to T. ramosissima plants sampled in its native range but hybrids with up to 49% relatedness to native T. chinensis were observed.  Fire can be used to successfully control young Tamarix plants in the greenhouse and plants up to 3 years of age in the field in South Dakota.  Students reported that weed science curriculum focused on Tamarix increased their understanding of northern Tamarix invasion and weed management.  Research data suggest that northern grasslands managed with fire or grazing may be vulnerable to Tamarix invasion and support an enhanced tolerance of northern plants to cold.  However, further studies are needed to better understand the relationship between Tamarix genetics and invasion success at northern latitudes.  Education findings suggest that Tamarix can be used as a model for weed management education.