Shallow-rooted grasses and deep-rooted shrubs dominate arid ecosystems where nitrogen is concentrated in the upper layers of the soil and water is distributed throughout. Analysis of mineral nitrogen and absorption patterns using a tracer indicated that shrubs in Patagonia absorbed nutrients from the lower, relatively nutrient-poor layers of the soil. Are they, consequently, at a competitive di...

The dromedary camel is a multipurpose animal adapted to the harsh environments of semiarid and arid zones, essentially kept for milk and meat production and transportation. It is also a financial reserve (asset) and security (drought-prone risk management) for pastoralists and plays an important role in social prestige and wealth (8, 19). Because of the increasing desertification and recurrence...

Meteorological satellite data from 1982 to 1990 were used to identify areas of significant association between tropical Pacific sea surface temperature (SST) and remotely sensed normalized difference vegetation index (NDVI) anomalies, here taken as a surrogate for rainfall anomalies. During this period, large areas of arid and semi-arid Africa, Australia and South America experienced NDVI anoma...

Our objective was to determine if long-term increases in precipitation can maintain grasslands susceptible to desertification, and initiate a reversal of historic regime shifts on desertified shrublands. Perennial grass production and species richness in a multi-year wet period were hypothesized to be greater than expected based on precipitation in a sequence of dry years. These responses were ...

[1] Significant variations in interannual and decadal recharge rates are likely in alluvial basins of the semiarid southwestern United States on the basis of decadal variations in climate and precipitation and correlation of El Niño with high rates of winter precipitation and streamflow. A better understanding of the magnitude of recharge variations in semiarid and arid regions would reduce wat...

Agaves can grow in marginal arid and semiarid lands where their special ecological and physiological adaptations to environmental conditions give them the potential to produce substantial biomass. Agave americana was the first agave species shown to be a Crassulacean Acid Metabolism plant, with CO2 uptake occurring primarily at night and with high wateruse efficiency (photosynthesis/transpirati...

The geometry of foreland basins is controlled by a dynamic balance between thrust-belt migration, fl exural subsidence, and fl uvial deposition. To improve our ability to quantify the relationships between tectonics, climate, and foreland basin geometry, I developed analytic solutions for basin topography and stratigraphy using a classic two-dimensional mathematical model of foreland basin evol...

abstract alluvial fans are the most striking phenomena o fluvial geomorphology . these forms are found in frount of mountains and pediments of arid and semiarid zones . alluvial fans are affected by climate changes and tectonics . occurring of tectonic events lead to reaction of alluvial fans . some of these reactions appear on dissection of alluvial fans and displacement of depocenters on allu...