12.2 Biological Crusts of Arid Regions ............................. 346 12.2.1 Characteristic Species ................................................... 346 12.2.2 Taxonomic Problems in Describing Crust Cyanobacteria ...................................................... 347 12.2.3 Environmental Factors .................................................. 348 12.2.3.1 Light .......................

forest canopy rainfall interception loss (i), canopy water storage (s), and the ratio of mean evaporation to mean rainfall intensity () are important components of the water balance in arid and semi-arid climate zones. the goal of this project was to quantify i and s and to evaluate the gash interception model for rainfall interception in a mature semi-arid pinus eldarica medw afforestation pla...

one of the characteristics in iranian model of desertification potential assessment (imdpa) is vegetation. sincevegetation is very important factor in the degradation of land, so some indices were determined for this item in order toevaluate desertification potential of arid, semi arid and arid sub humid areas of iran. the indices included vegetationcondition, exploit and revegetation. to calib...

introduction: evaporation and evapotranspiration are two major components of hydrological cycle which are very important for agricultural studies as well as water resources management. so far, various methods have been addressed for the estimation of daily reference crop evapotranspiration (et0). among them, fao penman-montieth 56 (pmf-56) (allen et al., 1998) is widely used as a standard metho...

Stomatal regulation of leaf gas exchange with the atmosphere is a key process in plant adaptation to the environment, particularly in semi-arid regions with high atmospheric evaporative demand. Development of stomata, integrating internal signaling and environmental cues sets the limit for maximum diffusive capacity of stomata, through size and density and is under a complex genetic control, th...

Aeolian processes are tightly linked to soil and vegetation change in arid and semi-arid systems at multiple spatial and temporal scales. Wind influences patterns of vegetation and soil within the landscape, and these patterns control wind erosion at patch to landscape scales. Aggregated at larger scales, patterns in soil and vegetation distributions influence global distributions of dust and i...

On July 17, 2003, the National Bureau of Economic Research announced that the United States economy had troughed in November 2001 following the peak in March 2001. This makes the 2001 recession one of the shortest in U.S. history being only eight months in length. Whereas business cycles are defined in terms of the overall economies the authors of this paper investigate whether this national re...