Steppe

R. S. Michalski, R. E. Stepp. Learning from Observation Ganceptual Clustering, in Machine Learning An Artificial Intelligence Approach, R.S. Michalski, f.G. CarboneU, T.M. Mitchell (Eds.), Morgan Kauffmatm, San Mateo, GA, 1983, pp. 331-363. 

Plate 3 shows a map of dominant soil orders for the entire world. Although this map necessarily lacks detail due to its scale, the relationship between soils and the biosphere is evident. Different terrestrial ecosystems are correlated with climatic conditions and different soils are correlated with both. For example, Mollisols are common in areas where there are prairies or steppes a result of grasses as the dominant vegetation and low, seasonal rainfall. Spodosols occur where coniferous forests dominate and the climate is cold and wet. Comparing Fig. 8-5 and Plate 3 carefully will show how strong this correlation is for the entire Earth. 

Bocherens, H., Pacaud, G., Lazarev, P. and Mariotti, A. 1996 Stable isotope abundances ( C, N) in collagen and soft tissues from Pleistocene mammals from Yakutia. Implications for the paleobiology of the mammoth steppe. Palaeogeography, Palaeoclimatolology, Palaeoecology 126 31. ... 

Mediterranean sites in Chile and the steppe ecotone of Argentina, and a second gronp from mesic sites in the Argentinean lakes area and Chilean rain forest. The latter gronp was distinguished on the basis of their 20-carbon unsaturated acids. 

K. L. Chase, R. S. Bryant, T. E. Burchfield, K. M. Bertus, and A. K. Stepp. Investigations of microbial mechanisms for oil mobilization in porous media. In E. C. Donaldson, editor. Microbial enhancement of oil recovery Recent advances Proceedings of the 1990 International Conference on Microbial Enhancement of Oil Recovery, volume 31 of Developments in Petroleum Science, pages 79-94. Elsevier Science Ltd, 1991. 

Damaskin V.I. Gigienicheskoye obosnovaniye profilakticheskikh meropriyatiy v svyazi s primenyeniyem pestitsidov v stepnoy zone yuga Ukrainy (Health Implications for Preventive Measures Connected With Pesticide Use in the Steppe Region of Southern Ukraine) Dis.. ..Candidate of Medical Sciences. Kiev, 1979. 24 pp. 

Semi-arid regions with a precipitation sum of 250 to 500 mm/year and a steppe savannah/prairie/pampa vegetation. 

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)... 

Where the aridity index (Ia) is equal to the mean annual precipitation in mm (Pmm) divided by the mean annual temperature in °C plus 10. According to this index, values below 5 characterize true deserts, values of approximately 10 define dry steppes, values of about 20 represent prairies, and values above 30 typify forest. 

Thus, the Martonne aridity index defines not only climatic parameters but also vegetational ones. Seasonality of precipitation is another climatic factor that affects desert and steppe boundaries. For a given mean annual temperature, the boundary of a steppe will extend into wetter climates if its precipitation falls mainly in the summer. This is because summer evapotranspiration depletes soil moisture more thoroughly than winter evapotranspiration. For similar reasons, the size of a desert will be larger if its precipitation falls in the summer rather than in the winter (Monger et al., 2004). 

Steppes and steppic regions (pampas, prairies) receive between 250 and 500 mm of precipitation annually, i.e. more than twice the quantity that falls in true desert areas where rainfall is insufficient to support a vegetation that could protect the land from erosion. 

Dunes and sand plains form where strong winds carry sand grains in saltation over short distances. Particles finer than sand are transported in suspension and over greater distances until they settle as loess , predominantly in the steppe regions adjacent to the desert zone. 

During the Late Pleniglacial, between 20,000 and 13,000 BP, some 25% of the land surface became covered with continental ice sheets (versus some 10% today). With so much water stored in ice sheets, the sea level dropped to about 120 meters below the present level and large parts of the world became extremely arid. The Amazon rain forest dwindled to isolated refugia, European forests disappeared but for small sheltered areas, and large parts of the globe turned to tundra, steppe, savannah or desert. 

Clearly, aeolian processes were much more important at that time than at present. Large parts of the present temperate zone, from the cover sands of the Netherlands to the sand dunes in north-east Siberia are Ice Age (aeolian) sands. South and east of this cover sand belt lies a belt of loess deposits, extending from France, across Belgium, the southern Netherlands, Germany and large parts of Eastern Europe into the vast steppes of Russia, and further east to Siberia and China. A similar east-west loess belt exists in the USA and less extensive areas occur on the Southern Hemisphere, e.g. in the Argentinean pampas. 

Loess settles when dust-laden winds slow down to speeds between 7 (on dry surfaces) to 14 meters per second (on moist surfaces). The pore distribution of loess lets it quickly be retained by capillary forces if it lands on a moist surface. The presence of a vegetation cover may also enhance the rate of loess deposition, and many authors maintain that the northern limit of loess deposition coincides with the northernmost extent of grass steppes during arid periods in the Pleistocene. 

The vast loess and till plains are now colonized by grasses and/or forest. They are the home of some of the best soils of the world the black earths . Deep, black Chernozems occupy the central parts of the Eurasian and North American steppe zones. Brown Kastanozems are typical of the drier parts of the steppe zone and border on arid and semi-arid lands. Dusky red Phaeozems occur in slightly more humid areas such as the American prairies and pampas. 

The semi-arid areas receiving somewhat higher rainfall are covered by a steppe-like fairly continuous vegetative cover of Xerophilous shrubs and grasses. In the Central Asian Plains, east of the Caspian Sea, wind erosion and transport are the dominant features. Sand dunes dominate the landscape for hundreds of kilometers. 

In chernozems formed on serpentinite diluvium, Co content is in the range of 10-30 mg/kg, while in chestnut and chestnut vertic soils, Co concentrations vary from 3-15 and 15-45 mg/kg, respectively. Soils on basalt, andesite and gabbro contain 15-68 mg/kg total Cu. Total Mn in chernozems is in the range of 520-850 mg/kg. Chestnut soils have 42-106 mg/kg Zn content. Total Zn in saline alkali soils is in the range of 40-60 mg/kg Zn. Bioavailable Zn (ammonium acetate-extractable Zn) in chernozems, chestnut soils and saline alkali soils of the steppe zones varies from trace amounts to 3.8 mg/kg (1-8.3% of total Zn). In chernozems of Northern Bulgaria, total B is in the range of 25-53 mg/kg. Boron increases in saline soils and saline alkali soils. 

Levine, M. A. (1999) Origins of horse husbandry. In Late Prehistoric Exploitation of the Eurasian Steppe (Eds Levine, M. A., Rassamakin, Y., Kislenko A. and Tatarintseva, N.), McDonald Institute for Archaeological Research, Cambridge, pp. 5 58. 

Phyletic links of apparent endemic species of the central Ebro valley with easternmost species were revealed after studying the insect communities at the Monegros region. These have a pre-Pleistocene origin of their relict distributions, associated with the persistence of steppe habitats over gypsiferous soils in the area since the Late Tertiary. Distributions of phytophages and their parasitoids on plants such as Krascheninnikovia ceratoides or Juniperus thurifera supported the continuity of their presence in the central Ebro valley through the Quaternary [14]. 

Ribera I, Blasco-Zumeta J (1998) Biogeographical links between steppe insects in the Monegros region (Aragon, NE Spain), the eastern Mediterranean, and central Asia. J Biogeogr 25 969-986... 

Wagener KB, Brzezinska K, Anderson JD, Younkin TR, Steppe K, DeBoer W (1997) Macromolecules 30 7363... 

Anderson (2007) reports encouraging results obtained with field crops in the semi-arid steppe of the USA through the adoption of no-till in a dualistic approach of prevention and control which permitted to reduce to about 50% the amount of herbicides. 

Taiga Meadow-Steppe Planosols Central Yakutian 10.0 0.35 3.5... 

Forest Meadow Steppe Euvic Carpathian-North Caucasian 1.2 0.75 0.9... 

South American Meadow Steppe Chernozems, Vertisols Eastern Pampa 0.8 0.95 0.8... 

Steppe Chernozems, Kastanozems Solonetzes European Kazakhstan 0.7 0.57 0.4... 

Desert-Steppe and Desert Xerosols, Regosols, Arenosols, Yermosols, Central Asian 0.4 0.70 0.3... 

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