PARENT SESSION
Tuesday, August 8, 8:00-11:30 am
COS 16 - Disturbance ecology
L-2, Lobby Level, Cook Convention Center
Presiders: S Pathikonda and S Riffell

Modeling responses of wetland plant populations to salinity stress.

Pathikonda, Sharmila^*,1, Ackleh, Azmy¹, Mopper, Susan¹, ¹ University of Louisiana at Lafayette, Lafayette, LA, USA

ABSTRACT- Southeastern United States wetlands have evolved with natural floods, sea level change, and hurricanes. But the intensity of these events has risen recently, possibly due to global climate change. Severe hurricanes such as Katrina and Rita have accelerated salinization of freshwater marsh, in addition to causing extensive damage to flora and fauna. We are developing quantitative models to predict long-term effects of salinity stress on wetland plant populations. These models are parameterized using field studies and common garden experiments investigating native Iris hexagona populations, which inhabit freshwater and brackish coastal wetlands. Empirical data indicate that salinity has non-linear effects on sexual reproduction. Low concentrations of salt promote seed production compared to freshwater conditions, but higher levels inhibit fertility. In contrast, all levels of salinity reduce clonal reproduction by suppressing rhizome growth. Our models subdivide the life history of I. hexagona into two main categories: aboveground structures consisting of 1) seeds, 2) juveniles, 3) non-reproductive, and 4) sexually reproductive plants, and belowground structures consisting of 5) rhizomes. Initial simulations predict that despite elevated seed numbers, long-term survival declines in iris exposed to salinity compared to freshwater populations. These results indicate that clonal tissues (rhizomes) may have stronger effects on population persistence than seeds.

Key words: hurricane, Iris hexagona, rhizomes