species is a sedge, Fimbristylis castanea. The difference may be due to the soil surface on 

 south Padre that is paved with large shells and shell fragments from previous surge overwash; 

 on north Padre the surface is mostly fine sand. The large shells allow the surface layer to dry 

 out quickly on south Padre and may inhibit seedling establishment of many species 

 occurring on north Padre. Leeward of the 1,200-foot sea oats dune, the most common 

 species is water-hyssop (Bacopa Monnieri), a prostrate mat-forming forb not found in dry 

 sand. 



VI. SUMMARY AND CONCLUSIONS 



1. Best Adapted Species. 



Bitter panicum (Panicum amarum Ell.) and sea oats (Uniola particulate. L.) are the two 

 best adapted species, both for planting on the backshore for dune building, and for 

 stabilizing existing dunes on the Texas gulf coast. Other native dune species, such as 

 saltmeadow cordgrass and seashore dropseed, were tested and rejected due to poor survival, 

 lack of vigor, or poor sandtrapping ability. Fifteen exotic species tested for potential use in 

 beach plantings were either total or near -total failures. 



2. Seeding. 



Establishment by seed of sea oats on the backshore or on barren dunes is not 

 recommended due to low germination rates and slow seedling growth. Bitter panicum seed is 

 sterile, and must be established vegetatively. 



3. Mixed Planting. 



Bitter panicum usually is more successfully transplanted than sea oats and is easier to 

 procure and handle. However, a mixed planting of bitter panicum and sea oats is 

 recommended, since this reduces the chance of total stand failure, creates a more desirable 

 polyspecific community, and uses the seed-reproduction capability of sea oats for natural 

 recolonization of contiguous areas. 



4. Sand-Trapping Capability. 



Foredunes were most easily and successfully established by planting sea oats and bitter 

 panicum directly on the barren backshore with a tobacco transplanter, and allowing the 

 growing plants £o trap and stabilize accumulating sand. Five years after planting with sea 

 oats, a beach site had grown to a dune 11.4 feet high (15.4 feet above MSL), which 

 contained 24 cubic yards of sand per linear foot of beach. Two years after planting, a bitter 

 panicum dune was 7.4 feet high (12.6 feet above MSL) and contained 10.2 cubic yards per 

 linear foot of beach. Average annual sand accumulation on all experimental sites was from 

 3.3 to 5.2 cubic yards per linear foot of beach, with a mean of 4.3 cubic yards per linear 

 foot of beach. The main limitation of dune growth was not the trapping capacity of the 

 plants, but the amount of blowing sand available. 



5. Hurricane Washover Channels. 



Vegetation could not be established on the original surface of two hurricane washover 

 channels due to high soil salinity and surge wave action. The planting surface then was raised 



170 



