TREES BRING RAIN in DESERTS

Massachusetts Institute of Technology scientists have found that trees in a dense forest of Oman have an unusual way to water themselves by extracting moisture from low-lying clouds. Professor Elfatih A.B. Eltahir of civil and environmental engineering have found that the trees have preserved an ecological niche in an area characterized mostly by desert. The plants exploit a wispy thin source of water that occurs seasonally. The forest could be driven to extinction if camel continue to graze frequently. As the forest disappears, the trees will lose the ability to pull water from the mist and recharge underground reservoirs.

All but the most arid desert lands support life that is frequently abundant and well adapted to the scarcity of water and the daytime heat.
Desert plants have evolved ways of conserving and efficiently using the water available to them. Some flowering desert plants are ephemeral; they live for a few days at most. Their seeds lie dormant in the soil, sometimes for years, until a soaking rain enables them to germinate and quickly bloom. Woody desert plants either have long root systems that reach deep water sources or have spreading shallow roots that are able to take up surface moisture quickly from heavy dews and occasional rains. Desert plants usually have small leaves. This conserves water by reducing surface area from which transpiration can take place. Other plants drop their leaves during the dry period. The process of photosynthesis-by which sunlight is converted to energy and usually conducted primarily in leaves-is taken over in the desert by the stems. A number of desert plants are succulents, storing water in leaves, stems, and roots. Thorns, which are modified leaves, serve to guard the water from animal invaders. These plants may take in and store carbon dioxide only at night; during the day their stomata, or pores, are closed to prevent evaporation. Desert plants growing on saline soils may concentrate salt in their sap and then secrete the salt through their leaves.
Burning and overgrazing of semiarid lands on the periphery of deserts can irreversibly damage the plants that concentrate moisture and hold the soil together, thus enabling deserts to encroach on arable land. This encroachment, a serious world problem, is called desertification. A 1984 report of a desertification study made for the United Nations stated that 35 percent of the earth's land surface was at least threatened by such processes.
Massachusetts Institute of Technology (MIT), one of the world's leading research universities, in Cambridge, Massachusetts. In 1865 the school was opened in Boston by geologist William Barton Rogers, who became its first president.