Soil formation processes
The climate factor is considered one of the most important factors in determining the properties of soils. On a large scale, this climatic-soil relationship can be seen in correlating soil maps with temperatures and precipitation on a regional scale. Moisture and temperature are the two most important aspects of climate factors in controlling soil properties. Moisture is involved in most of the physical, chemical, and biochemical processes of soil formation. The amount of moisture delivered to the soil profile influence the weathering and leaching conditions with depth. Temperature influences the rates of soil formation processes. The research conducted by our team focuses on studying the formation of mostly irreversible soil properties such as calcic horizons, calcretes, shattered gravels by salts, and gypcrete, using them as proxies for paleoclimate signals mainly in hyperarid and semiarid regions.
Calcic soil is one of the most widespread aridic soil groups, covering an estimated area of about a million square kilometers in arid to semi-arid regions worldwide. A calcic soil is defined as soil that contains a substantial accumulation of secondary (pedogenic) calcium carbonate (CaCO3), generally in the form of the calcic horizon(s). Calcic soils have been identified as sensitive indicators for hydroclimatic variations in water availability and are thus sources of paleoclimatic data. In addition, inorganic carbon within these soils comprises approximately a third of the total carbon pool in soils worldwide, but the precise magnitude of the soil inorganic carbon pool is poorly constrained.
The climatic control on calcium carbonate accumulation in soil has been demonstrated at two different scales: At the pedon scale, the depth of calcic horizon increases with mean annual rainfall, and at a global scale, calcic soils are predominately found in arid to semi-arid regions. However, the quantitative role of specific climatic properties in controlling the formation of pedogenic carbonate is not fully understood.
Calcic-gypsic Reg soil profile in Namibia (Amit et al., 2010)
Publications:
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Crouvi, O., Horowitz, T., Siman-Tov. , L., Morin, E., Rasmussen, C., Pelletier, J., and Rosenzweig, R. (2019). Control of climate characteristics on accumulation of pedogenic carbonate: observations and modeling. INQUA congress, Dublin, Ireland.
Horowitz, T., Morin, E., Crouvi, O., and Rosenzweig, R. (2019). Quantifying the effects of climate properties on soil wetting depth distributions and potential proxies for depth to calcic and gypsic horizons, Israel Geological Society Annual Meeting, Kfar Blum, Israel.
Amit, R., Enzel, Y., Grodek, T., Crouvi, O., Porat, N., Ayalon, A. (2010). The role of rare rainstorms in the formation of calcic soil horizons on alluvial surfaces in extreme deserts. Quaternary Research, 74, 177-187. https://doi.org/10.1016/j.yqres.2010.06.001.
Amit, R., Lekach, J., Ayalon A., Porat, N., Grodek, T. (2007). New insight into pedogenic processes in extremely arid environment and its paleoclimate implication – the Negev, Israel. Quaternary International, 162, 61-75. https://doi.org/10.1016/j.quaint.2006.10.032.
Hyperarid (<80 mm/yr) soils in hot deserts are characterized by accumulations of soluble salts horizons such as halite and gypsum, as a result of limited water availability. Soils with gypsic horizons are estimated to cover about two million square kilometers. In the Negev desert, pedogenic gypsum accumulates in reg soils that develop on stable alluvial fans composed of coarse gravelly alluvium.
In most desert terrains, pedogenic salts are derived from atmospheric dust and soluble ions in rainwater. Therefore, climatic properties such as rainfall amount and distribution, evaporation, and dust flux govern the depth and concentration of pedogenic salts in soil horizons. However, only a few studies quantified the link between climate properties and soluble salts (gypsum and halite) accumulation in the soil, focusing merely on mean annual rainfall. Other factors such as potential evapotranspiration, dust flux, rainwater composition, temporal change in soil hydraulic properties, and annual rainfall distribution, have not been tested for their effect on soluble salts distribution in the soil profile. Quantifying the relations between climate and salts accumulation can improve determining regional mean paleoenvironmental conditions and paleoclimate.
A well developed gypsic horizon in reg soil from Nahal Shehoret, near Elat, Israel (Amit et al., 2017)
Publications:
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Siman-Tov. , L., Morin, E., Crouvi, O., Amit, R., Enzel, Y., Marra, F., Reznik, I. J., and Rosenzweig, R. (2020). Evaluating the long-term climatic-controlled gypsum accumulation in hyperarid alluvial soils using stochastic modeling. Israeli Soil Union Annual Meeting, Israel.
Amit, R., Enzel, Y., Crouvi, O., Ayalon, A., (2017). Aridisols in the southern Levant deserts and their paleoclimate implications, In: Quaternary of the Levant Environment, Climate change and Humans. Eds: Y., Enzel and O., Bar-Yosef, Cambridge University press 521-531p. https://doi.org/10.1017/9781316106754.057.
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