At the time this study was completed, the growth of nearly 2.5 linear miles of dune line, 

 from 50 to 100 feet wide and from a few months to over 5 years old, was being monitored. 

 This excludes many areas of failure which were replanted once or several times using more 

 refined methods gained through experience. On south Padre, there are five general sites of 

 about 5,800 Linear feet of planted dune line, consisting of beach plantings, hurricane 

 washover-pass plantings with low sand fencing, and two-tiered sand-fence dunes planted 

 after construction. On north Padre, all plantings were on the beach, without sand fencing, 

 and now consists of about 7,000 linear feet. 



V. EXPERIMENTAL RESULTS AND DISCUSSION 



Experimental results are presented by flow diagrams (Figs. 12 through 18) in a sequence 

 of experiments to establish a dune line in various areas. Numbers in the flow diagrams refer 

 to text subsections of this section; the major steps are shown in bold letters. Guidelines and 

 specifications for establishing a dune line are outlined in Appendix A. 

 1. Selection of Species. 



The first phase of this study was to test and select the plants best suited for constructing 

 foredunes. Since this required simulating as closely as possible the natural dune-building 

 process, native Texas barrier island species were given the most consideration. In addition, 

 many exotic (nonnative) species were also tested. 



a. Necessary Attributes. Plant species for foredune construction must possess many 

 adaptations to the harsh barrier island environment. Tolerance of salt spray and of 

 occasional inundations by saltwater are essential attributes. The semiarid climate requires a 

 resistance to low moisture and occasional drought conditions. Adaptations to withstand 

 abrasion by sand particles, smothering by sand drifts, high soil temperatures, and low soil 

 nutrient content, are also essential. 



In addition to being able to survive in the backshore salt-spray zone, the plants must 

 grow through accumulating sand quickly, stabilizing it as the dune builds. A perennial 

 species is essential, especially a grass with a deep, fibrous root system. The ideal plant woidd 

 have the capability of growing through the greatest amount of drifting sand on the 

 backshore without being smothered. 



b. Screening. Four species of grass which occur naturally on the backshore and 

 foredunes initially were thought to possess many or all of these desired attributes. These 

 include sea oats, bitter panicum, saltmeadow cordgrass, and seashore dropseed (Fig. 6). 

 Many other species which occur infrequently to abundantly on the backshore and foredunes 

 were rejected as unsuitable. Some of these, with reasons for rejection, are: (a) railroad vine 

 and beach morning-glory; shallow root system with little ability to grow through drifting 

 sand, and die back almost completely in cold weather; (b) sea purslane; lacks abilitv to form 

 high dunes and easily fragmented by surf action; (c) seacoast bluestem;not resistant to salt 

 spray nor tolerant of drifting sand; and (d) gulfdune paspalum; little sand trapping capacitv 

 and not very tolerant to sand burial. 



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