Vegetation and sediment characteristics of created and natural Spartina alterniflora marshes in Lower Galveston Bay, Texas

Abstract

Five natural and ten created Spartina altemiflora marshes in the Lower Galveston Bay System, Texas, were compared to determine if there were significantly different vegetative and sediment characteristics associated with each marsh type. Vegetative and sediment parameters were compared on the basis of marsh type, age, habitat zone and microhabitat type. Created marshes were characterized by consistently taller stems and greater live plant biomass, but lower densities of live and dead stems and lower biomass of dead plant material than natural marshes. Percent cover was the same in both marsh types, while created marshes had fewer but taller stems and greater biomass than natural marshes. Young created marshes also had fewer but taller and more robust stems, and equal to greater biomass than natural marshes. Older created marshes had comparable stem densities and heights, but greater biomass than natural marshes. Belowground biomass and organic matter were lower in created marshes than natural marshes, and belowground biomass was concentrated in the upper 5 cm of soil. Belowground biomass appeared to increase with increasing marsh age, but organic matter did not. Belowground biomass was evenly distributed in natural marshes, but concentrated beneath clumps of vegetation in created marshes. Soil organic matter was evenly distributed across the surface of both natural and created marshes. Sediments in created marshes consisted of approximately 66% sand and 33% silt and clay. Natural marsh soils consisted of nearly equal proportions of sand, silt, and clay particles.