PARENT SESSION
Contributed Oral Session 135: Invasive Species: Plant - Soil Feedbacks; Invasion Success
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 518 A, Level 5, Palais des congrès de Montréal

The role of plant-soil feedbacks in native coastal sage shrub recolonization of exotic annual grasslands.

Yelenik, Stephanie^*,1, Levine, Jonathan^*,1, ¹ Department of Ecology, Evolution, and Marine Biology, Santa Barbara, CA, USA

ABSTRACT- Understanding the processes that contribute to plant species invasiveness is important for protecting agricultural and unmanaged lands from the harmful effects of exotic plant invasions. Exotic plants that alter soil microbial communities or nutrient cycling in ways that favor their own growth, spread, and impact are predicted to be particularly pernicious invaders. The research presented here focuses on how these plant-soil feedbacks constrain native shrub reestablishment in exotic annual grasslands of the California Channel Islands. Although the grazers that initially converted the islands from shrubland to grassland have been removed, native shrubs, such as Artemisia californica and Eriogonum arborescens , have been slow to recolonize into grasslands dominated by the annual exotic Avena fatua . To study the role of plant-soil feedbacks in regulating this dynamic, we examined how exotic grass effects on nutrient cycling differ from those of the native shrubs, and how these differences feedback to alter plant performance using a greenhouse experiment in which Artemisia , Eriogonum, and Avena were each grown on their own and on each others soils. In the greenhouse experiment, Avena grew best on Artemisia soil. Soils on which Artemisia seedlings had grown, in turn, contained higher levels of phosphorus, irrespective of soil origin. Because Avena seedlings contained lower nitrogen concentrations than the other two species, we suggest that the exotic grass may be phosphorus limited on field soils, but is released from this constraint when grown on Artemisia soil. Potentially, therefore, elevated growth of exotic annual grass on phosphorus enriched soils near Artemisia may slow shrub recruitment due to higher competition in areas where shrub seed are most likely to fall.

Key words: plant-soil feedback, invasive plants, coastal sage scrub, grassland