Water balance and the role of precipitation in estimate growth potential of sand dunes in desert areas (Case study: Sabzevar regoin)

Sand dunes of Iran with more than 4. 5 million hectare area as a feather of desert regions are important from different aspects. Sand dunes with special hydrologic characteristics، in addition to conserving humidity temporary suitable releasing it، capable to converting as a shrub lands or crop lands. Therefore، it is necessary to study water balance on sand dunes. In order to surveying on sand dunes vegetation capability in Sabzerar region using water balance، Dovlat-Abad sand dunes was selected as a fixed site for measuring of effective factors on water balance. Then، considering morphology of sand dunes، sampling and measurements were concentrated on two kinds of sand dunes (fixed & semi-active sand dunes). Continently، with attention to measuring moisture directly on reservoir horizon by TDR، soil profiles were distributed fitly on different slopes of sand dune. Then with recording monthly moisture and temperature data during 1381-1384 years and collecting meteorological data including precipitation & evapotranspiration using equation of water balance، sand dune was classified from hydrological view. Results showed that Dovlat-Abad sand dunes classified as Un–infiltrative sand dunes group. On this group، Gravitational infiltration is negative and nutrition of underground waters is impossible. So، at these sand dunes، precipitation is the major resource for requirement water of plants and the role of under ground waters isn، t important. Optimal exploiting of reserved moisture on sand dunes related on knowing range volume of it that studies indicated on sand dune situation in Dovlat-Abad، extra reservation of moisture nearly field capacity was occurred in winter season. With beginning of dry period، moisture was infiltrated deep layers. So، temporary date of seed or plantlet culturing with concentration of moisture on surface layers، provide conditions that minimum requirement water of plants was released and irrigation was restricted consequently water use of efficiency was increased.