Saltcedar management following a summer wildfire at Lake Meredith National Recreation Area

Saltcedar (Tamarix spp.) has been a problem invasive plant species in the US since its introduction in the 1800's and subsequent escape and naturalization in the 1850's. Saltcedar is a riparian species but has been able to exploit upland sites when adequate moisture conditions occur for seedling establishment. Saltcedar is a perennial shrub that can reach heights of 7.6 m (25 ft), and has a life span of about 100 years. It tolerates extremely saline soil conditions and increases the salt content of the upper soil crust. It is a prolific seed producer with an affinity for disturbed sites in proximity to water. Saltcedar will spread by seeds or vegetatively by stems or roots. It often occurs in tightly habitated monocultures resulting in a closed canopy.

Studies were conducted near Fritch, Texas at Lake Meredith National Recreation Area. Total nonstructural carbohydrate (TNC) trends, invasion patterns, plant response to fire and rollerchopping, and plant response to triclopyr and imazapyr were monitored. These studies were conducted from January 1999 through October 2000. Trees treated with triclopyr and imazapyr during the dormant season of early winter of 1999 and late winter of 2000 were evaluated after the 2000 growing season. The objectives of this study were to: (1) determine seasonal TNC trends in saltcedar, (2) determine 1>JC differences in burned verses non-burned saltcedar, (3) determine mortality of saltcedar following summer wildfire, rollerchopping, and herbicidal treatment, (4) monitor invasion capabilities of saltcedar, and (5) develop economical, practical, and sound recommendations for saltcedar management.

TNC trends indicate that saltcedar has the lowest TNC concentrations in the spring of the year as it initiates budbreak in May. TNC trends increase and then stabilize during the growing season until after the first hard freeze. After the first freeze until budbreak there is a gradual decline in TNC due to plant metabolism in the absence of vegetative material. Results indicate that the time to optimize saltcedar mortalit) with mechanical treatment would be during May. This research indicates that there is a slight difference in TNC concentration between burned and non-burned saltcedar for one growing season after burning. Due to the ability of saltcedar to rapidly acquire new vegetative material and its extensive root system and reserves, the difference will only occur during the first growing season after fire.

Triclopyr is an effective herbicidal control of burned, resprouting saltcedar with individual plant basal bark treatments. Lower concentrations (15%) of triclopyr were as lethal as higher concentrations (25%) with JLB oil alone providing no mortalit). Triclopyr was effective in all seasons of treatment. Imazapyr was not an effective herbicidal control of burned, resprouting saltcedar with individual plant basal bark treatments. Imazapyr altered the growth form of the saltcedar leaves and might have caused mortality of saltcedar if more than one growing season was allowed before assessment of treatment.

The following thesis is arranged in four chapters as follows: Chapter I is a review of the literature, Chapter II is invasion monitoring. Chapter III pertains to seasonal TNC trends in burned and non-burned saltcedar, and Chapter IV discusses saltcedar response to fire, rollerchopping, and herbicides. Chapters II, III, and IV were written in journal format for submission for publication as refereed journal articles. The following appendices provide a GIS map of Alibates Creek, data and forms used to record data, and procedures.