Regeneration of Scirpus americanus in a Texas coastal marsh following lesser snow goose herbivory
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abstract
Interaction of herbivory by wintering lesser snow geese (Anser caerulescens caenilescens), environmental conditions, and burning were investigated in a mid-Texas coastal marsh dominated by Scirpits americanus (Olney bulrush). Goose grubbing and use of S. americamis rhizomes and roots initially produced a patchwork of denuded and vegetated areas on a recently bumed area. Regrowth occurred by reestablishment of uprooted shoot complexes; regeneration from seed was not observed. Regrowth was dependent on intensity of use and post-herbivory environmental conditions. After three years of varying levels of goose use and environmental conditions, lowest foliar cover and standing crop occurred in areas with a high frequency and intensity of goose use followed by spring drought and high salinities. Greatest growth was associated with low frequency and intensity of use followed by normal spring freshwater inflows and low salinities. Burning did not significantly affect the response of S. americanus. Continued frequent and intense snow goose use, coupled with high salinity and extended periods with water levels below the marsh surface, can produce denuded mudflats subject to accelerated soil erosion. Management strategies to reduce the impact of these combined events could be implemented. Hydroperiod and salinity conditions should be routinely monitored, and goose populations should be temporally and spatially directed to reduce the potential for conversion of marsh to permanent mudflats.
