PARENT SESSION
Poster Session 7: Grasslands
Tuesday, August 9, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Do plant-soil feedbacks increase the resilience of invaded California grasslands?
Grman, Emily*,1, Suding, Katharine2, Hayes, Erin2, 1 Department of Plant Biology, East Lansing, MI, USA2 Department of Ecology and Evolutionary Biology, Irvine, CA, USA
ABSTRACT- The resilience of Southern California coastal annual grasslands to restoration has prompted the hypothesis that native- and exotic-dominated communities represent alternative stable states. According to theory, strong positive and stabilizing feedbacks are required to maintain these alternative states. We conducted a pot experiment to examine whether soil feedbacks and priority effects may maintain California grasslands in an exotic annual-dominated state. We used two different plant mixtures to culture the soil community: natives (Nassella, Eschscholzia, Lasthenia), and exotics (Bromus, Brassica, Erodium). We also established pots without a culturing plant community. After 5 weeks, we removed the culturing plants in half of the pots. We then added "invaders," either the native or exotic 3-species mixture, into all possible combinations of the culturing community (native, exotic, none) and live plant biomass (removed, not removed) treatments. This design allowed us to compare 1) the effects of the culturing plant community mediated purely through the soil and 2) the effects caused by both soil culturing and competitors' 5-week head start. In the absence of competition from established plants, exotic species grew faster in exotic-cultured soil and native species grew faster in native-cultured soil. However, when established plants were present, neither community type resisted invasion by the other, suggesting that live plant priority effects may negate soil-mediated feedbacks. Understanding how these priority effects and feedbacks interact to contribute to exotic dominance may be essential to restore native California perennial grasslands.
Key words: alternative stable states, California grasslands, positive feedbacks, priority effects