Editing Soil formation (section)

===Climate===
The principal climatic variables influencing soil formation are effective [[precipitation]] (i.e., precipitation minus [[evapotranspiration]]) and temperature, both of which affect the rates of chemical, physical, and biological processes.<ref>{{cite journal |last=Mosier |first=Arvin R. |year=1998 |title=Soil processes and global change |journal=Biology and Fertility of Soils |volume=27 |issue=3 |pages=221–29 |url=https://link.springer.com/content/pdf/10.1007/s003740050424.pdf |doi=10.1007/s003740050424 |bibcode=1998BioFS..27..221M |s2cid=44244791 |access-date=28 November 2021 }}</ref> Temperature and moisture both influence the organic matter content of soil through their effects on the balance between [[primary production]] and [[decomposition]]: the colder or drier the climate the lesser atmospheric carbon is fixed as organic matter while the lesser organic matter is decomposed.<ref>{{cite journal |last1=Epstein |first1=Howard E. |last2=Burke |first2=Ingrid C. |author-link2=Ingrid Burke |last3=Lauenroth |first3=William K. |year=2002 |title=Regional patterns of decomposition and primary production rates in the U.S. Great Plains |journal=[[Ecology (journal)|Ecology]] |volume=83 |issue=2 |pages=320–27 |url=https://www.researchgate.net/publication/233379719 |doi=10.2307/2680016 |jstor=2680016 |access-date=28 November 2021 }}</ref> Climate also indirectly influences soil formation through the effects of vegetation cover and biological activity, which modify the rates of chemical reactions in the soil.<ref>{{cite journal |last=Lucas |first=Yves |year=2001 |title=The role of plants in controlling rates and products of weathering: importance of biological pumping |url=https://www.researchgate.net/publication/228608786 |journal=[[Annual Review of Earth and Planetary Sciences]] |volume=29 |pages=135–63 |bibcode=2001AREPS..29..135L |doi=10.1146/annurev.earth.29.1.135 |access-date=5 December 2021}}</ref>

Climate is the dominant factor in soil formation, and soils show the distinctive characteristics of the [[climate zone]]s in which they form, with a feedback to climate through transfer of carbon stocked in soil horizons back to the atmosphere.<ref name="Davidson">{{cite journal |last1=Davidson |first1=Eric A. |last2=Janssens |first2=Ivan A. |journal=[[Nature (journal)|Nature]] |volume=440 |title=Temperature sensitivity of soil carbon decomposition and feedbacks to climate change |year=2006 |issue=7081 |pages=165‒73 |doi=10.1038/nature04514 |pmid=16525463|bibcode=2006Natur.440..165D |s2cid=4404915 |doi-access=free }}</ref> If warm temperatures and abundant water are present in the profile at the same time, the processes of weathering, [[Leaching (agriculture)|leaching]], and [[Plant development|plant growth]] will be maximized. According to the climatic determination of [[biomes]], humid climates favor the growth of trees. In contrast, grasses are the dominant native vegetation in [[Subhumid temperate climate|subhumid]] and [[Semi-arid climate|semiarid]] regions, while shrubs and brush of various kinds dominate in [[Desert climate|arid]] areas.<ref>{{cite journal |last1=Woodward |first1=F. Ian |last2=Lomas |first2=Mark R. |last3=Kelly |first3=Colleen K. |year=2004 |title=Global climate and the distribution of plant biomes |journal=[[Philosophical Transactions of the Royal Society B|Philosophical Transactions of the Royal Society of London, Series B]] |volume=359 |issue=1450 |pages=1465–76 |doi=10.1098/rstb.2004.1525 |pmc=1693431 |pmid=15519965 |url=https://www.researchgate.net/publication/8200458 |access-date=28 November 2021 }}</ref>

Water is essential for all the major chemical weathering reactions. To be effective in soil formation, water must penetrate the [[regolith]]. The seasonal rainfall distribution, evaporative losses, site [[topography]], and [[soil permeability]] interact to determine how effectively precipitation can influence soil formation. The greater the depth of water penetration, the greater the depth of weathering of the soil and its development.<ref>{{cite journal |last1=Graham |first1=Robert C. |last2=Rossi |first2=Ann M. |last3=Hubbert |first3=Kenneth R. |year=2010 |title=Rock to regolith conversion: producing hospitable substrates for terrestrial ecosystems |journal=[[Geological Society of America|GSA Today]] |volume=20 |issue=2 |pages=4–9 |doi=10.1130/GSAT57A.1 |url=https://www.geosociety.org/gsatoday/archive/20/2/pdf/i1052-5173-20-2-4.pdf |access-date=28 November 2021 }}</ref> Surplus water percolating through the soil profile transports soluble and suspended materials from the upper layers ([[eluviation]]) to the lower layers ([[illuviation]]), including clay particles<ref>{{cite journal |last=Fedoroff |first=Nicolas |year=1997 |title=Clay illuviation in Red Mediterranean soils |url=https://art1lib.org/book/17953836/4309d5 |journal=Catena |volume=28 |issue=3–4 |pages=171–89 |doi=10.1016/S0341-8162(96)00036-7 |bibcode=1997Caten..28..171F |access-date=5 December 2021 }}</ref> and [[dissolved organic matter]].<ref>{{cite journal |last1=Michalzik |first1=Beate |last2=Kalbitz |first2=Karsten |last3=Park |first3=Ji-Hyung |last4=Solinger |first4=Stephan |last5=Matzner |first5=Egbert |year=2001 |title=Fluxes and concentrations of dissolved organic carbon and nitrogen: a synthesis for temperate forests |journal=Biogeochemistry |volume=52 |issue=2 |pages=173–205 |url=https://www.researchgate.net/publication/226356840 |doi=10.1023/A:1006441620810 |bibcode=2001Biogc..52..173M |s2cid=97298438 |access-date=5 December 2021 }}</ref> It may also carry away soluble materials in the surface [[drainage]] waters. Thus, percolating water stimulates weathering reactions and helps differentiate soil horizons. 

Likewise, a deficiency of water is a major factor in determining the characteristics of soils of dry regions. Soluble salts are not leached from these soils, and in some cases they build up to levels that curtail plant<ref>{{cite journal |last=Bernstein |first=Leon |year=1975 |title=Effects of salinity and sodicity on plant growth |url=https://art1lib.org/book/15512677/2cdb0b |journal=[[Annual Review of Phytopathology]] |volume=13 |issue=1 |pages=295–312 |doi=10.1146/annurev.py.13.090175.001455  |bibcode=1975AnRvP..13..295B |access-date=5 December 2021 }}</ref> and microbial growth.<ref>{{cite journal |last1=Yuan |first1=Bing-Cheng |last2=Li |first2=Zi-Zhen |last3=Liu |first3=Hua |last4=Gao |first4=Meng |last5=Zhang |first5=Yan-Yu |year=2007 |title=Microbial biomass and activity in salt affected soils under arid conditions |journal=Applied Soil Ecology |volume=35 |issue=2 |pages=319–28 |url=https://art1lib.org/book/16525751/aa5578 |doi=10.1016/j.apsoil.2006.07.004 |bibcode=2007AppSE..35..319Y |access-date=5 December 2021 }}</ref> Soil profiles in arid and semi-arid regions are also apt to accumulate carbonates and certain types of expansive clays ([[calcrete]] or [[caliche]] horizons).<ref>{{cite journal |last=Schlesinger |first=William H. |year=1982 |title=Carbon storage in the caliche of arid soils: a case study from Arizona |journal=Soil Science |volume=133 |issue=4 |pages=247–55 |doi=10.1097/00010694-198204000-00008 |bibcode=1982SoilS.133..247S |s2cid=97632160 |url=https://www.researchgate.net/publication/249345714 |archive-url=https://web.archive.org/web/20180304054729/http://alliance.la.asu.edu/temporary/students/Phil/ArizonaCarbonStorage.pdf |url-status=live |archive-date=4 March 2018 |access-date=5 December 2021 }}</ref><ref>{{cite journal |last1=Nalbantoglu |first1=Zalihe |last2=Gucbilmez |first2=Emin |year=2001 |title=Improvement of calcareous expansive soils in semi-arid environments  |url=https://coek.info/pdf-improvement-of-calcareous-expansive-soils-in-semi-arid-environments-.html |journal=[[Journal of Arid Environments]] |volume=47 |issue=4 |pages=453–63 |doi=10.1006/jare.2000.0726 |bibcode=2001JArEn..47..453N  |access-date=5 December 2021 }}</ref> In tropical soils, when the soil has been deprived of vegetation (e.g. by [[deforestation]]) and thereby is submitted to intense evaporation, the upward [[Capillary action|capillary]] movement of water, which has dissolved iron and aluminum salts, is responsible for the formation of a superficial hard pan of [[laterite]] or [[bauxite]], respectively, which is improper for cultivation, a known case of irreversible [[soil degradation]].<ref>{{cite journal |last=Retallack |first=Gregory J. |year=2010 |title=Lateritization and bauxitization events |journal=[[Economic Geology (journal)|Economic Geology]] |volume=105 |issue=3 |pages=655–67 |url=https://www.researchgate.net/publication/247864948 |doi=10.2113/gsecongeo.105.3.655 |bibcode=2010EcGeo.105..655R |access-date=5 December 2021 }}</ref>

The direct influences of climate include:{{sfn|Donahue|Miller|Shickluna|1977|p=35}}
* A shallow accumulation of lime in low rainfall areas as [[caliche]]
* Formation of acid soils in humid areas
* Erosion of soils on steep hillsides
* Deposition of eroded materials downstream
* Very intense chemical weathering, leaching, and erosion in warm and humid regions where soil does not freeze

Climate directly affects the rate of weathering and leaching. Wind moves sand and smaller particles (dust), especially in arid regions where there is little plant cover, depositing it close to<ref>{{cite book |last1=Pye |first1=Kenneth |last2=Tsoar |first2=Haim |year=1987 |chapter=The mechanics and geological implications of dust transport and deposition in deserts with particular reference to loess formation and dune sand diagenesis in the northern Negev, Israel |doi=10.1144/GSL.SP.1987.035.01.10 |title=Desert sediments: ancient and modern |journal=Geological Society of London, Special Publications |volume=35 |issue=1 |editor1-last=Frostick |editor1-first=Lynne |editor2-last=Reid |editor2-first=Ian |pages=139–56 |isbn=978-0-632-01905-2 |chapter-url=https://www.researchgate.net/publication/238424245 |access-date=5 December 2021 |bibcode=1987GSLSP..35..139P |s2cid=128746705 }}</ref> or far from the entrainment source.<ref>{{cite journal |last=Prospero |first=Joseph M. |year=1999 |title=Long-range transport of mineral dust in the global atmosphere: impact of African dust on the environment of the southeastern United States |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |volume=96 |issue=7 |pages=3396–403 |doi=10.1073/pnas.96.7.3396 |pmid=10097049 |bibcode=1999PNAS...96.3396P |pmc=34280 |doi-access=free }}</ref> The type and amount of precipitation influence soil formation by affecting the movement of ions and particles through the soil, and aid in the development of different soil profiles. Soil profiles are more distinct in wet and cool climates, where organic materials may accumulate, than in wet and warm climates, where organic materials are rapidly consumed.<ref>{{cite journal |last1=Post |first1=Wilfred M. |last2=Emanuel |first2=William R. |last3=Zinke |first3=Paul J. |last4=Stangerberger |first4=Alan G. |year=1999 |title=Soil carbon pools and world life zones |url=https://art1lib.org/book/10473904/17cc99 |journal=[[Nature (journal)|Nature]] |volume=298 |issue=5870 |pages=156–59 |doi=10.1038/298156a0 |bibcode=1982Natur.298..156P |s2cid=4311653 |access-date=5 December 2021 }}</ref> The effectiveness of water in weathering parent rock material depends on seasonal and daily temperature fluctuations, which favour [[tensile stress]]es in rock minerals, and thus their mechanical disaggregation, a process called [[thermal fatigue]].<ref>{{cite journal |last1=Gómez-Heras |first1=Miguel |last2=Smith |first2=Bernard J. |last3=Fort |first3=Rafael |year=2006 |title=Surface temperature differences between minerals in crystalline rocks: implications for granular disaggregation of granites through thermal fatigue |url=https://www.academia.edu/52691323 |journal=[[Geomorphology (journal)|Geomorphology]] |volume=78 |issue=3/4 |pages=236–49 |doi=10.1016/j.geomorph.2005.12.013 |bibcode=2006Geomo..78..236G |access-date=5 December 2021 }}</ref> By the same process [[freeze-thaw]] cycles are an effective mechanism which breaks up rocks and other consolidated materials.<ref>{{cite journal |last1=Nicholson |first1=Dawn T. |last2=Nicholson |first2=Frank H. |year=2000 |title=Physical deterioration of sedimentary rocks subjected to experimental freeze–thaw weathering |journal=[[Earth Surface Processes and Landforms]] |volume=25 |issue=12 |pages=1295–307 |doi=10.1002/1096-9837(200011)25:12<1295::AID-ESP138>3.0.CO;2-E |bibcode=2000ESPL...25.1295N |url=https://art1lib.org/book/135323/a787c4 |access-date=5 December 2021 }}</ref>