Response of a Texas distichlis spicata coastal marsh following lesser snow goose herbivory

Abstract

Mudflat recolonization following lesser snow goose (LSG) ( Anser caerulescens caerulescens (L.)) herbivory was investigated in a Texas Distichlis spicata (L.) Greene (saltgrass) salt marsh. After 6 years of LSG herbivory, large mudflats were produced which contained small (2–4 m 2) islands of vegetation. Island perimeters, that were completely denuded at initiation of this study, had lower vegetation cover and height compared to no use island centers after nearly 3 years of monitoring, even though no LSG use occurred during the evaluation period. Previous level of LSG herbivory and physical disturbance along with summer drought and algal mat accumulations initially delayed the rate of revegetation. With improved hydroperiod, reduced salinity, decreased algal mat and rest from LSG impacts, lateral vegetative growth accelerated. Mean radial expansion was 128 cm after 2.5 years. No regeneration from seeds was observed. Competitive interference during recolonization occurred between D. spicata and Salicornia virginica (L.) (Virginia glasswort). Frequent and severe LSG herbivory can result in unvegetated, eroding mudflats that may become permanent if followed by environmental conditions that retard vegetative recolonization. This may become an increasingly important issue as LSG numbers increase and marsh area declines.