Sandy soil is low in nutrients, and can dry out at the surface, but it is easy to penetrate for the roots that can go very deep until they reach water. Sandy soil also allows air to diffuse deep below the surface, providing oxygen for the roots in places where humidity is high enough for plants to obtain water for transpiration. Nutrient poverty is compensated by profound root penetration, so some plants are perfectly adapted to this environment. A good example is seabuckthorn, it loves sandy dunes near the seaside and produces lots of juicy berries rich in vitamin C and expensive oils for the cosmetic industry, but it does not do very well in loam-based compost rich garden soil (and the berries become bitter).

Sandy soil is low in nutrients, and can dry out at the surface, but it is easy to penetrate for the roots that can go very deep until they reach water. Sandy soil also allows air to diffuse deep below the surface, providing oxygen for the roots in places where humidity is high enough for plants to obtain water for transpiration. Nutrient poverty is compensated by profound root penetration, so some plants are perfectly adapted to this environment. A good example is seabuckthorn, it loves sandy dunes near the seaside and produces lots of juicy berries rich in vitamin C and expensive oils for the cosmetic industry, but it does not do very well in loam-based compost rich garden soil (and the berries become bitter).

Respected Denecke, 

Do you know the characteristics of Ipomoea pes caprae ?

Not really, I have seen them in the dominican republic on the beach quite close to the water so they must be pretty salt tolerant. Check out wikipedia for more info.

http://en.wikipedia.org/wiki/Ipomoea_pes-caprae

The way we survive in harsh academic environment of DJ with adaptation- the same way the species cope in low nutrient level and with extraordinary long root system

Nitrogen fixation is very important for plants that grow on sand or low-nutrient soils. Plants of genera Elaeagnus (silverberries), Hippophae (sea-buckthorns), Shepherdia (buffaloberries), Comptonia (sweetfern), Morella Myrica (bayberries), Cercocarpus (mountain mahoganies),  Chamaebatia (mountain miseries), Dryas, Purshia/ Cowania (bitterbrushes/cliffroses) can accumulate nitrogen and improve soil fertility around roots.

See Dawson, J. O. (2008). "Ecology of actinorhizal plants". Nitrogen-fixing Actinorhizal Symbioses 6. Springer. pp. 199–234.

In our garden, sea-buckthorns plants turned sand into black soil after 15 years of cultivation.

Hairy Grama (Bouteloua hirsuta).--This is a species of very wide range and diverse habit, forming a sod in the more favorable situations but often occurring in isolated clumps. It is even more drought resistant than blue grama, reaching its best development on stable sandy or sandy loam soils. The rhizome habit is conspicuous. The roots spread 1 to 1.5 feet or more just below the soil surface, although this habit varies with soil type and moisture conditions. Roots are abundant, exceedingly Well branched with delicate laterals, and fill the soil more or less completely to depths of at least 2 to 3.5 feet

https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=46&cad=rja&uact=8&ved=0CD0QFjAFOCg&url=http%3A%2F%2Fwww.soilandhealth.org%2F01aglibrary%2F010139fieldcroproots%2F010139ch4.html&ei=zbZiVbrzMKaM7AbhwoLADg&usg=AFQjCNEJVHX97F4yQnW34Ae3f_aEDetFVQ