Determining Vigor of Natural and Planted Stands of Sea Oats on the Texas Gulf Coast

Abstract

Natural vegetation of the foredune complex of coastal barrier islands is an impor- tant factor in sand stabilization. Sea oats (Uniola paniculata), a dominant grass on fore-dunes, traps and accumulates fresh beach sand to provide a natural barrier against storm-generated waves. Sea oats relies on salt spray, accumulating fresh beach sand, and decaying organic matter for min- eral nutrition. The objective of this study was to investigate sea oats at three natural dune loca- tions, identifying vegetative characteristics that would relate to differences in vigor, and to com- pare natural dunes with fertilized, sprigged stands planted in an island nursery and on the beach in an overwash area of the main dune line. For the natural dune locations, the fore-dune complex was divided into fore-dune, mid-dune, and hind-dune areas. The growth form of sea oats on the fore-dune was that of a single culm, while several culms emerged from each crown on the mid- and hind-dune areas. Dry weight per culm and flowering culm weight (dry wt/culm by number of flowering culms/plant) were considered the most important variables in determining plant vigor. Based on these measurements there were no differences in vigor among fore-dune, mid-dune, and hind-dune plants. However, fertilized sea oats in the beach planting and in the island nursery were more vigorous than those growing in the natural, unfertilized dunes. Barrier islands on the Texas Gulf Coast are large, sandy shoreline forms, built through time by natural processes of marine transport and sand depo- sition. Their dune ridges, which run parallel to the beach, protect the main- land from storm surges and hurricane-generated waves (Bascom, 1964).