Desert arid environments

In arid environments, where the soluble products of weathering are not completely removed from the soil, saline solutions may circulate in the soil as well as in rock fractures. If upon evaporation the salt concentration increases above its saturation point, salt crystals form and grow (Goudie et al, 1970). The growth of salt crystals in crevices can force open fractures. Salt weathering occurs in cold or hot deserts or areas where salts accumulate. Boulders, blocks. 

Brown G, Schoknecht N (2001) Off-road vehicles and vegetation patterning in a degraded desert ecosystem in Kuwait. J Arid Environ 49 413-427... 

Webb RH, WHshire HG (1980) Recovery of soils and vegetation in a Mojave Desert ghost town, Nevada, U.S.A. J Arid Environ 3 291-303... 

Gntterman Y (1997) Spring and snmmer daily snbsnrface temperatnres in three microhabitats in a flat natnral loess area in the Negev desert, Israel. J Arid Environ 36 225-235... 

An important problem which remains to be elucidated is the evolution of CAM. Is it truly an example of convergent evolution The occurrence of CAM in the gymnosperm Welwitschia and in ferns suggests a positive answer to that question. If so, are the specific metabolic details of CAM in each family similar or are there distinctive differences which are representative of the taxonomic categories In this context, did these plants with the CAM photosynthetic pathway actually all develop in the tropics and then move into arid environments of the subtropics and deserts of the world ... 

Riddle, B.R. and Hafner, D.J. (2006a) A step-wise approach to integrating phylogeographic and phylogenetic biogeographic perspectives on the history of a core North American warm deserts biota. Journal of Arid Environments, 66 435 61. 

Schmidt, R.H., Jr. (1989) The arid zones of Mexico Climatic extremes and conceptualization of the Sonoran Desert. Journal of Arid Environments, 16 241-256. 

Castillo, S., Moreno, T., Querol, X., Alastuey, A., Cuevas, E., Herrmann, L., Mounkaila, M., and Gibbons, W. 2008. Trace element variation in size-fractionated African desert dusts. Journal of Arid Environments 72(6) 1034-1045. 

Thompson, A.E., Dierig, D.A., Johnson, E.R., 1989. Yield potential of Lesquerella fendleri L. (gray) Wats., a desert plant resource for hydroxyl fatty acids. J. Arid. Environ. 16, 331-336. 

Numerous theories exist as to how the Chilean deposits formed and survived. It has been postulated that the unique nitrate-rich caUche deposits of northern Chile owe their existence to an environment favorable to accumulation and preservation of the deposits, rather than to any unusual source of the saline materials (2). The essential conditions are an extremely arid climate similar to that of the Atacama desert in the 1990s, slow accumulation during the late Tertiary and Quaternary periods, and a paucity of nitrate-utilizing plants and soil microorganisms. 

On die other hand, the measure of the afforestation is also classified into no-regrettable one from the viewpoint of environment. Furthermore, most of desert area is said to be formed by partly somewhat human activities. The activities of afforestation of arid land without crop production are also a no-regrettable measure [14-17]. 

Figure 1.1. (a) Climate categories based on mean annual precipitation (b) Desert and steppe boundaries as a function of both mean annual precipitation and temperature according to the Koeppen system arrows show how boundaries shift according to whether precipitation falls mainly in in the summer or winter (after Monger et al., 2004. Reprinted from Encyclopedia of Soils in the Environment, D. Hillel, Tropical soils Arid and Semi-arid, p 183, Copyright (2004), with permission from Elsevier)... 

Wang, X., Wen, X., Ye, R., LiuZ., Sun, B., Zhao, S., Shi, S., Wei, H. 2007. Vertical variation and dispersion of elements in arid desert regolith a case study from the Jinwozi gold deposit, northwestern China. Geochemistry Exploration, Environment, Analysis, 7, 163-171. 

The possibility of using superabsorbent hydrogels as water managing materials for the renewal of arid and desert environments has attracted great attention [135]. These materials can reduce irrigation... 

---