[152 meters) (Fig. 22). The sand volume values (Table 5) show 

 this; the longitudinal figure is just graphic verification. The 

 poorer initial stands of the south 600 feet of both the 1,100- 

 and 1,200- foot bitter panicum dunes are readily apparent from the 

 less uniform profiles and the deep cuts through the dunes (Figs. 

 19 and 23). Such profiles also provide an instant evaluation of 

 the effectiveness of the overall dune-building research. Although 

 some of the deep canyons through the dunes begin to heal in time, 

 the canyons are mostly quite persistent and will probably require 

 mechanical repair to completely heal them; e.g., most deep cuts 

 present in March 1975 were still very much in evidence in August 

 1976. How to repair these obvious "leaks" is an area that 

 should be further researched. Perhaps, stacking bales of hay in 

 the cuts and tying the bales to the canyon walls with netting 

 to reduce the wind velocity would allow healing. Such treatment 

 would probably be relatively inexpensive yet effective. 



2. Vegetative Transects . 



Vegetation on Experimental Dunes . Sea oats and bitter 

 panicum have laterally spread slowly on Padre Island. From a 50- 

 foot planting width in March 1969, the sea oats has spread 

 seaward 5.25 feet (1.6 meters) per year (Table 7). 



While the bitter panicum has spread slightly faster since 

 planting than the sea oats, it is doubtful that one will actually 

 spread any faster than the other. Note that for August 1975 

 to August 1976, the sea oats spread more than the bitter panicum 

 (Table 7). 



If it is assumed that a 125-foot base is needed for a restored 

 foredune, it is apparent that attaining such a base from a 

 single 50-foot-wide planting will take about 15 years with either 

 species. If a wide base is desired in as short a period as possible, 

 the technique of following an initial 50-foot planting with a 

 second 50-foot planting on the beach side in 4 years appears to 

 be the better method. The best method will be known once these 

 study dunes are subjected to direct hurricane attack. 



(1) Extension of Planted Species . In reviewing the 

 species reported for transects measured in 1971 and 1973 (Dahl, 

 et al . , 1975), the species commonly found in 1975 and 1976 tran- 

 sects were the same and little change in relative composition 

 occurred except a tendency for increased proportion of grasses. 

 Basic differences in the 1975 and 1976 surveys were largely in 

 percent cover and frequency of occurrence. Apparently, growing 

 conditions were better in 1976 than in 1975 as ground cover was 

 often 100 percent greater (Table 8). Generally, sea oats 

 tended to increase, occurring more frequently on almost all 

 transects. Bitter panicum tended to remain more stable with only 



45 



