The chemistry of pedogenic thresholds

Oliver A. Chadwick, Jon Chorover

Research output: Contribution to journalArticle

248 Citations (Scopus)

Abstract

Pedogenesis can be slow or fast depending on the internal chemical response to environmental forcing factors. When a shift in the external environment does not produce any pedogenic change even though one is expected, the soil is said to be in a state of pedogenic inertia. In contrast, soil properties sometimes change suddenly and irreversibly in a threshold response to external stimuli or internal change in soil processes. Significant progress has been made in understanding the thermodynamics and kinetics of soil-property change. Even in the open soil system, the direction of change can be determined from measures of disequilibrium. Favorable reactions may proceed in parallel, but the most prevalent and rapid ones have the greatest impact on product formation. Simultaneous acid-base, ion exchange, redox and mineral-transformation reactions interact to determine the direction and rate of change. The nature of the governing reactions is such that soils are well buffered to pH change in the alkaline and strongly acid regions but far less so in the neutral to slightly acid zones. Organic matter inputs may drive oxidation-reduction processes through a stepwise consumption of electron acceptors (thereby producing thresholds) but disequilibrium among redox couples and regeneration of redox buffer capacity may attenuate this response. Synthesis of secondary minerals, ranging from carbonates and smectites to kaolinite and oxides, forms a basis for many of the reported cases of pedogenic inertia and thresholds. Mineralogical change tends to occur in a serial, irreversible fashion that, under favorable environmental conditions, can lead to large accumulations of specific minerals whose crystallinity evolves over time. These accumulations and associated "ripening" processes can channel soil processes along existing pathways or they can force thresholds by causing changes in water flux and kinetic pathways.

Original languageEnglish (US)
Pages (from-to)321-353
Number of pages33
JournalGeoderma
Volume100
Issue number3-4
DOIs
StatePublished - 2001
Externally publishedYes

Fingerprint

chemistry
inertia
disequilibrium
soil
acid
soil property
minerals
acids
soil properties
kinetics
ripening
pedogenesis
secondary mineral
mineral
crystallinity
smectite
kaolinite
soil formation
ion exchange
regeneration

Keywords

  • Inertia
  • Pedogenesis
  • Threshold

ASJC Scopus subject areas

  • Soil Science
  • Earth-Surface Processes

Cite this

The chemistry of pedogenic thresholds. / Chadwick, Oliver A.; Chorover, Jon.

In: Geoderma, Vol. 100, No. 3-4, 2001, p. 321-353.

Research output: Contribution to journalArticle

Chadwick, Oliver A. ; Chorover, Jon. / The chemistry of pedogenic thresholds. In: Geoderma. 2001 ; Vol. 100, No. 3-4. pp. 321-353.
@article{2f71dcde952241418e20fc8945ca9028,
title = "The chemistry of pedogenic thresholds",
abstract = "Pedogenesis can be slow or fast depending on the internal chemical response to environmental forcing factors. When a shift in the external environment does not produce any pedogenic change even though one is expected, the soil is said to be in a state of pedogenic inertia. In contrast, soil properties sometimes change suddenly and irreversibly in a threshold response to external stimuli or internal change in soil processes. Significant progress has been made in understanding the thermodynamics and kinetics of soil-property change. Even in the open soil system, the direction of change can be determined from measures of disequilibrium. Favorable reactions may proceed in parallel, but the most prevalent and rapid ones have the greatest impact on product formation. Simultaneous acid-base, ion exchange, redox and mineral-transformation reactions interact to determine the direction and rate of change. The nature of the governing reactions is such that soils are well buffered to pH change in the alkaline and strongly acid regions but far less so in the neutral to slightly acid zones. Organic matter inputs may drive oxidation-reduction processes through a stepwise consumption of electron acceptors (thereby producing thresholds) but disequilibrium among redox couples and regeneration of redox buffer capacity may attenuate this response. Synthesis of secondary minerals, ranging from carbonates and smectites to kaolinite and oxides, forms a basis for many of the reported cases of pedogenic inertia and thresholds. Mineralogical change tends to occur in a serial, irreversible fashion that, under favorable environmental conditions, can lead to large accumulations of specific minerals whose crystallinity evolves over time. These accumulations and associated {"}ripening{"} processes can channel soil processes along existing pathways or they can force thresholds by causing changes in water flux and kinetic pathways.",
keywords = "Inertia, Pedogenesis, Threshold",
author = "Chadwick, {Oliver A.} and Jon Chorover",
year = "2001",
doi = "10.1016/S0016-7061(01)00027-1",
language = "English (US)",
volume = "100",
pages = "321--353",
journal = "Geoderma",
issn = "0016-7061",
publisher = "Elsevier",
number = "3-4",

}

TY - JOUR

T1 - The chemistry of pedogenic thresholds

AU - Chadwick, Oliver A.

AU - Chorover, Jon

PY - 2001

Y1 - 2001

N2 - Pedogenesis can be slow or fast depending on the internal chemical response to environmental forcing factors. When a shift in the external environment does not produce any pedogenic change even though one is expected, the soil is said to be in a state of pedogenic inertia. In contrast, soil properties sometimes change suddenly and irreversibly in a threshold response to external stimuli or internal change in soil processes. Significant progress has been made in understanding the thermodynamics and kinetics of soil-property change. Even in the open soil system, the direction of change can be determined from measures of disequilibrium. Favorable reactions may proceed in parallel, but the most prevalent and rapid ones have the greatest impact on product formation. Simultaneous acid-base, ion exchange, redox and mineral-transformation reactions interact to determine the direction and rate of change. The nature of the governing reactions is such that soils are well buffered to pH change in the alkaline and strongly acid regions but far less so in the neutral to slightly acid zones. Organic matter inputs may drive oxidation-reduction processes through a stepwise consumption of electron acceptors (thereby producing thresholds) but disequilibrium among redox couples and regeneration of redox buffer capacity may attenuate this response. Synthesis of secondary minerals, ranging from carbonates and smectites to kaolinite and oxides, forms a basis for many of the reported cases of pedogenic inertia and thresholds. Mineralogical change tends to occur in a serial, irreversible fashion that, under favorable environmental conditions, can lead to large accumulations of specific minerals whose crystallinity evolves over time. These accumulations and associated "ripening" processes can channel soil processes along existing pathways or they can force thresholds by causing changes in water flux and kinetic pathways.

AB - Pedogenesis can be slow or fast depending on the internal chemical response to environmental forcing factors. When a shift in the external environment does not produce any pedogenic change even though one is expected, the soil is said to be in a state of pedogenic inertia. In contrast, soil properties sometimes change suddenly and irreversibly in a threshold response to external stimuli or internal change in soil processes. Significant progress has been made in understanding the thermodynamics and kinetics of soil-property change. Even in the open soil system, the direction of change can be determined from measures of disequilibrium. Favorable reactions may proceed in parallel, but the most prevalent and rapid ones have the greatest impact on product formation. Simultaneous acid-base, ion exchange, redox and mineral-transformation reactions interact to determine the direction and rate of change. The nature of the governing reactions is such that soils are well buffered to pH change in the alkaline and strongly acid regions but far less so in the neutral to slightly acid zones. Organic matter inputs may drive oxidation-reduction processes through a stepwise consumption of electron acceptors (thereby producing thresholds) but disequilibrium among redox couples and regeneration of redox buffer capacity may attenuate this response. Synthesis of secondary minerals, ranging from carbonates and smectites to kaolinite and oxides, forms a basis for many of the reported cases of pedogenic inertia and thresholds. Mineralogical change tends to occur in a serial, irreversible fashion that, under favorable environmental conditions, can lead to large accumulations of specific minerals whose crystallinity evolves over time. These accumulations and associated "ripening" processes can channel soil processes along existing pathways or they can force thresholds by causing changes in water flux and kinetic pathways.

KW - Inertia

KW - Pedogenesis

KW - Threshold

UR - http://www.scopus.com/inward/record.url?scp=0034993748&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0034993748&partnerID=8YFLogxK

U2 - 10.1016/S0016-7061(01)00027-1

DO - 10.1016/S0016-7061(01)00027-1

M3 - Article

AN - SCOPUS:0034993748

VL - 100

SP - 321

EP - 353

JO - Geoderma

JF - Geoderma

SN - 0016-7061

IS - 3-4

ER -