and the processes of soil development start. This continues as long as 

 protection from the sea is provided. However, from the standpoint of 

 stabilization, the plant cover on the typical intermediate zone affords 

 less protection against wind and water erosion than does the cover on a 

 well-vegetated foredune in the pioneer zone. Many intermediate zone 

 plants cannot withstand sand burial and the thin, open ground cover is 

 less resistant to wind and water erosion. 



Where continued protection is required and especially where over- 

 topping by storm tides is a threat, it may be desirable to delay the 

 ecological succession and retain a protective cover of vigorous pio- 

 neer zone plants. Although the reasons for the decline in vigor of 

 pioneer species as sand accumulation decreases are not well understood, 

 nutrient supply associated with the fresh sand can be a major factor. 

 Some sand-starved, declining stands of both American beachgrass {Ammophila 

 breviligulita) and sea oats {Uniola paniculatd) have been revived through 

 the application of fertilizers (Woodhouse and Hanes, 1967). Fertiliza- 

 tion has been reported as useful in maintaining plant vigor in diverse 

 regions (Atlantic coast, Oregon, Texas, and Europe). 



(3) Forest Zone . Forests form on dunes only after a substan- 

 tial period of soil development and only on sites with considerable pro- 

 tection from salt spray and flooding. The vegetation varies from the 

 dense thickets of trees, shrubs, and vines of the maritime forests of 

 the South Atlantic and gulf coasts to the coniferous, hardwood, and 

 mixed open tree forests of the Great Lakes dunes. 



After dune stabilization with pioneer and intermediate zone species, 

 trees have been planted successfully to convert large mobile dunes and 

 dune fields to forests (Lehotsky, 1941; McLaughlin and Brown, 1942). 

 However, trees are not planted in the barrier dune environment, and 

 are not desirable where the dune protects the backshore. Trees will 

 shade out the pioneer and intermediate species and leave the dune im- 

 protected and unable to regenerate cover quickly following a severe 

 disease, insect outbreak, or fire. Fire was probably a major factor 

 in the initiation of large mobile dunes in the Pacific Northwest. 



The major pioneer species extend over much wider ranges, geograph- 

 ically and climatically, than do the plants of the intermediate and 

 forest zones. However, the number of species is usually much greater 

 in the more stable areas. 



c. Coastal Regions . The coasts of the continental United States 

 should be divided into regions for planting purposes. These regions 

 deviate from those drawn along climatic boundaries. Climatic effects 

 become somewhat blurred and distorted in the narrow band near the water 

 where barrier dunes occur. The localized maritime influence on fog, 

 humidity, frost, temperature fluctuations, etc., enables some foredime 

 species to range across a variety of climatic zones. Divisions along 

 species adaptation lines are more useful in dealing with those plants. 



28 



