Physiological Integration among Clonal Ramets during Invasion of Disturbance Patches in a New England Salt Marsh

Abstract

Resource sharing between ramets growing across environmental resource gradients may have important consequences for clonal plant populations and community dynamics. As the clonal salt marsh grasses, Spartina patens and Distichlis spicata, vegetatively colonize disturbance-generated bare patches, they span steep gradients in soil salinity and available sunlight. Examination of water relations and carbon translocation in the field and greenhouse revealed that connected ramets of these marsh grasses share water and carbon in response to gradients in resource availability. Ramets colonizing disturbance patches rely upon physiological integration with connected parent ramets to overcome water stress associated with hypersaline patch environments. In addition, upon establishment inside a bare patch, daughter ramets may translocate carbon back to shaded parent ramets in the surrounding vegetation outside of patches. Physiological integration of ramets colonizing disturbance-generated bare patches and parent ramets outside of patches may explain the predominance of vegetative invasion over sexual recruitment in marsh succession. Hypersaline soil conditions, which inhibit seedling recruitment into patches, have little effect on the success of clonal colonizers that can import water from parent ramets. This success appears to be due to the ability of clonal marsh grasses to translocate water and carbon products between ramets growing across opposing gradients in resource availability.