PARENT SESSION
Oral Session #46: Disturbance Ecology.
Presiding: M. Slocum
Tuesday, August 6. 1:00 PM to 4:45 PM. Grand Ballroom East, Radisson.

Soil degradation and plant re-establishment in coastal salt-marshes of the Hudson Bay.

McLaren, Jennie^*,1, Jefferies, Robert¹, Kotanen, Peter¹, ¹ University of Toronto, Toronto, Ontario, Canada

ABSTRACT- Disturbance by herbivores can lead to irreversible plant community changes producing multiple stable states. Increases in goose foraging are changing salt marshes of the Hudson Bay coast into apparently stable bare mudflats largely devoid of vegetation. The loss of vegetation has led to changes in soil conditions, which affect plant re-colonization of disturbed areas. The objective of this study was to examine changes in soil properties as a result of grubbing by snow geese, and to determine impacts of these changes on plant re-establishment. I examined: (a) soil properties in undegraded and degraded areas; (b) the potential for re-establishment of Puccinellia phryganodes(the dominant grass species) in undegraded and degraded areas and; (c) whether soil property changes and plant re-establishment are related to the patch size of the simulated goose grubbing. Results indicate large differences in soil properties between vegetated and degraded areas. Degraded soil has a lower infiltration rate, higher bulk density, higher salinity and lower organic, nitrogen and carbon contents than values for soils where vegetation is intact. Transplants of P. phryganodes established well in vegetated sites, but establishment in degraded sites was highly restricted. Rapid decreases in soil nitrogen and carbon following experimental grubbing indicate the severity of changes in soil properties. Changes in soil physical properties and resource depletion result in salt marshes moving to an apparently stable degraded state (mudflats).

KEY WORDS: disturbance, clonal growth of grasses, sediment patch size, alternate stable states