aesthetically, and tends to be self-repairing when damaged. A vegeta- 

 tive cover is the only practical means of long-term stabilization of 

 sand dunes, except for certain specialized methods such as covering 

 with crushed stone or asphalt. 



Where both sand fence and vegetation are to be used to build a 

 barrier dune, planting should begin as early in the process as feasible. 

 The higher the dune grows, the more difficult and expensive planting 

 becomes. Large fence-built dunes usually can be planted only by hand; 

 machine planting is often possible on low dunes at an earlier stage. 

 For example, one or two "half- fences" (60 centimeters high, obtained by 

 cutting rolls of standard 1.2-meter fence in half) can be very effective 

 in building a low ridge that is still amenable to machine planting but 

 substantial enough to reduce the hazard of storm tides. Half-fences 

 also may be installed in new plantings to speed up sand trapping tempo- 

 rarily but not accumulate enough sand to smother the plants. 



Dune plants are especially effective in stopping and holding wind- 

 borne sand. Their growth produces a surface roughness which decreases 

 wind velocity near the ground, thereby reducing the ability of the wind 

 to move sand. Equally important, the plant stems and leaves above the 

 sand surface strongly interfere with sand movement by saltation and sur- 

 face creep. Consequently, penetration of windblown sand in a stand of 

 dune grass is usually limited to 1 meter or less along the leading edge. 

 As the grass fills and becomes buried, sand spills farther and farther 

 into the interior of the stand. In addition, a cover of foredune plants 

 tends to regenerate trapping capacity by growth even as it fills because 

 the plants are stimulated to grow by the deposition of sand around them. 



Once sand grains enter the dune grass stand, they are protected from 

 the wind by the surrounding growth as long as sufficient vegetation pro- 

 trudes above the surface. Observations following storms suggest that 

 vegetative growth is far more important in protecting dunes against both 

 wind and water erosion than root growth. An adequate vegetative mat pro- 

 tects the dune surface from scouring by wave and current action and actu- 

 ally promotes sand deposition, as well as shielding the surface from wave 

 action. 



The beach environment is generally harsh for plant growth. Success 

 requires a combination of special adaptations by the species grown there. 

 This is especially true of the more active zone of barrier dune systems 

 where, for example, plants must be able to tolerate rapid sand accumula- 

 tion, flooding, salt spray, sandblast, wind and water erosion, wide tem- 

 perature fluctuations, drought, and low nutrient levels. 



In spite of the severe limits these requirements place on the plant 

 species, plants capable of stabilizing coastal dunes do occur in most 

 coastal regions with enough rainfall to support plant growth. This in- 

 cludes a wide range of climates — from humid to semiarid and from cold to 

 tropical. 



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