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Soil biogeochemical processes, atmos...

Ewing, Stephanie Alice.

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Soil biogeochemical processes, atmospheric deposition, and in-soil transport in the hyperarid Atacama Desert, Chile.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Soil biogeochemical processes, atmospheric deposition, and in-soil transport in the hyperarid Atacama Desert, Chile./
作者:	Ewing, Stephanie Alice.
面頁冊數:	281 p.
附註:	Adviser: Ronald Amundson.
Contained By:	Dissertation Abstracts International68-08B.
標題:	Agriculture, Soil Science. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3275410
ISBN:	9780549167525

Soil biogeochemical processes, atmospheric deposition, and in-soil transport in the hyperarid Atacama Desert, Chile.
Ewing, Stephanie Alice.

Soil biogeochemical processes, atmospheric deposition, and in-soil transport in the hyperarid Atacama Desert, Chile. - 281 p.

Adviser: Ronald Amundson.

Thesis (Ph.D.)--University of California, Berkeley, 2007.

In the Atacama Desert of northern Chile, ancient (&sim;2My) soils along an arid to hyperarid rainfall gradient (21 to <2 mm rain y-1) reveal a transformation of pedogenesis and biogeochemical cycling. In the most hyperarid zone, soils acquire mass through atmospheric deposition and physically expand as they form (Chapter 1). Biological cycling of N is virtually halted (Chapter 2), organic C turnover is unusually slow (Chapters 2 and 3), and soluble Ca isotopes record transient fractionation effects of limited long-term downward transport by small amounts of water (Chapter 4). This work explores how decreasing rainfall leads to these unusual circumstances, and provides an analog for predicting likely surficial geochemistry on Mars.

ISBN: 9780549167525Subjects--Topical Terms:

1017824
Agriculture, Soil Science.

Soil biogeochemical processes, atmospheric deposition, and in-soil transport in the hyperarid Atacama Desert, Chile.
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100 1 $a Ewing, Stephanie Alice. $3 1285798
245 1 0 $a Soil biogeochemical processes, atmospheric deposition, and in-soil transport in the hyperarid Atacama Desert, Chile.
300 $a 281 p.
500 $a Adviser: Ronald Amundson.
500 $a Source: Dissertation Abstracts International, Volume: 68-08, Section: B, page: 5081.
502 $a Thesis (Ph.D.)--University of California, Berkeley, 2007.
520 $a In the Atacama Desert of northern Chile, ancient (&sim;2My) soils along an arid to hyperarid rainfall gradient (21 to <2 mm rain y-1) reveal a transformation of pedogenesis and biogeochemical cycling. In the most hyperarid zone, soils acquire mass through atmospheric deposition and physically expand as they form (Chapter 1). Biological cycling of N is virtually halted (Chapter 2), organic C turnover is unusually slow (Chapters 2 and 3), and soluble Ca isotopes record transient fractionation effects of limited long-term downward transport by small amounts of water (Chapter 4). This work explores how decreasing rainfall leads to these unusual circumstances, and provides an analog for predicting likely surficial geochemistry on Mars.
520 $a Chapter 1 evaluates the age, morphology and soluble geochemistry of these soils. A mass balance analysis quantifies the accumulation of atmospheric solutes and physical expansion over time. Ages of the arid and intermediate sites are >2My, while the age of the driest site is well constrained at &sim;2.1 My. This allows for calculation of long-term deposition rates based on the inventories of the driest soil, and these are comparable to directly measured deposition rates. Soil salts become increasingly soluble with decreasing rainfall, and solubility generally increases with depth at a given site. A pedogenic threshold is crossed: from net mass loss and volumetric collapse at wetter sites, to mass gain and volumetric expansion as a function of atmospheric deposition in the driest soil.
520 $a In Chapter 2, the effect of the arid-hyperarid transition on N cycling is quantified using N speciation, stable isotopes of N and O in soil nitrate, and radiocarbon. With increasing aridity, total soil N increases, and is increasingly dominated by inorganic N, while biological activity and organic C decrease. Triple O isotopes in soils and deposition show that as nitrate increases with decreasing rainfall, it is increasingly atmospheric, with 80% of the large nitrate inventory at the driest site preserved unaltered as a result of 2 My of atmospheric deposition.
520 $a In Chapter 3, radiocarbon and delta13C values in soil organic C reveal a transition away from more typical C cycling as aridity increases. At the and site, surface cycling is patchy, and plant inputs dominate above and below ground. At the driest site where roots are absent, organic C is transported below ground along preferential flowpaths, and cycling is uniformly slow. Variation in delta13C and OC/ON values in the upper horizons of the driest soil suggests that photolysis may be a significant means of abiotic OC transformation in this environment, making OC more available for turnover by the small microbial population in the shallow subsurface.
520 $a Chapter 4 focuses on stable isotopes of sulfate- and carbonate-associated Ca at the driest site. delta44/40Ca values increase substantially with depth below the surface horizon, resulting in a range that would suggest biological activity in wetter environments. Inverse correlation with S and O isotopes in sulfate, along with multiple indicators of consistent inputs over time, indicates that isotopic fractionation is a function of incremental downward transport and precipitation. A numerical simulation shows that the depth trend in Ca, S and O isotopes may reflect the scale and frequency of recurring wetting events.
520 $a This work shows that in the driest parts of the Atacama Desert, extreme aridity transforms dominant soil processes. In wetter places, the ongoing deposition of atmospheric particles may be overlooked or at least difficult to observe. In the Atacama over millions of years, this process contributes a major portion of the "parent material" that is retained and transformed by soil formation. Under these circumstances, soil formation occurs by transformation and vertical redistribution of atmospherically derived salts within the chemically unweathered silicate matrix of the original landform.
590 $a School code: 0028.
650 4 $a Agriculture, Soil Science. $3 1017824
650 4 $a Biogeochemistry. $3 545717
690 $a 0425
690 $a 0481
710 2 $a University of California, Berkeley. $3 687832
773 0 $t Dissertation Abstracts International $g 68-08B.
790 $a 0028
790 1 0 $a Amundson, Ronald, $e advisor
791 $a Ph.D.
792 $a 2007
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3275410