PARENT SESSION
Oral Session # 60: Invasive Species V: Genetics; Chemical Cycling Effects.
Presiding: S Miao
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 204.

Interactions between the invasive forb, Centaurea maculosa, and soil nitrogen cycling.

Thorpe, Andrea^*,1, Callaway, Ragan¹, ¹ University of Montana, Missoula, Montana, USA

ABSTRACT- Positive feedback with soil microbes appears to play an important role in the success of invasive plants. This feedback effect has been attributed to invasive plants escaping species-specific soil pathogens and taking advantage of generalist mutualists such as AM fungi. Our research suggests that feedback between the invasive forb, Centaurea maculosa Lam. (Asteraceae) and soil microbes may also involve the soil nitrogen cycle. Microbial communities in soil collected from C. maculosa rhizospheres were significantly different than those collected from native grass rhizospheres and there is evidence that such microbial effects may drive positive feedback between C. maculosa and the soil community in Montana. Furthermore, soil ammonium and nitrate are reduced in C. maculosa -invaded communities compared to adjacent, uninvaded communities. Nitrate was approximately 75% higher in native communities than invaded communities (P < 0.0005). These patterns may be due simply to different uptake rates; however, growing evidence suggests that an anti-microbial root exudate produced by C. maculosa, (+)-catechin alters the activity of nitrifying bacteria and changes the nitrogen cycle in ways that benefit C. maculosa. Our results indicate that the invasive success of C. maculosa may be due in part to complex interactions with microbial components of the soil ecosystem.

Key words: feedback, nitrogen, invasive plant, Centaurea maculosa