Ecology and management of gulf cordgrass [Spartina spartinae (Trin.) Hitchc.] on the Texas Coastal Prairie

Abstract

Gulf cordgrass occupied intermediate elevations between hydric species at lower elevations and more mesic species at high elevations on the Welder Wildlife Refuge. Botanical composition shifted apparently because of season at higher elevations and season and inundation at lower elevation, but areas supporting gulf cordgrass did not fluctuate greatly in botanical composition. There was no apparent correlation between physical and chemical properties of soils and gulf cordgrass abundance within the community on the Welder Wildlife Refuge. Presence of the species appeared to be related to elevation and period of inundation. Gulf cordgrass plants were relatively static once they matured, and production of inflorescences was the only observed morphological change. Growth of plants occurred from margins of the usually circular clones by basal budding. Temperature, wind and relative humidity were buffered within the dense gulf cordgrass canopy so that extremes never approached those above the canopy. Gulf cordgrass caryopses were fully imbibed after 18 hr at 20°C. germination was enhanced by chilling caryopses or adding gibberellic acid to the germination media. Scarification and high temperatures reduced germination compared to untreated caryopsis. Caryopses tolerated high salinity but were highly sensitive to moisture stress, and germinated within only a narrow temperature range. Germination did not require light although caryopses germinated in alternating light produced more vigorous seedlings than those germinated in the dark. Seedlings from caryopses germinated in the dark then grown in continuous dark did not survive after 21 days while those germinated and grown in alternating light had high survival rates. Caryopses were nonviable after submergement for longer than 3 months in distilled water. Maximum emergence of seedlings occurred when caryopses were barely covered with soil compared to other tested seedling depths. Height and weight of seedlings grown in clay soils were greater than those grown in sandy loam or loam soils...