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This content will become publicly available on May 18, 2019

Title: Ecohydrologic processes and soil thickness feedbacks control limestone-weathering rates in a karst landscape

Here, chemical weathering of bedrock plays an essential role in the formation and evolution of Earth's critical zone. Over geologic time, the negative feedback between temperature and chemical weathering rates contributes to the regulation of Earth climate. The challenge of understanding weathering rates and the resulting evolution of critical zone structures lies in complicated interactions and feedbacks among environmental variables, local ecohydrologic processes, and soil thickness, the relative importance of which remains unresolved. We investigate these interactions using a reactive-transport kinetics model, focusing on a low-relief, wetland-dominated karst landscape (Big Cypress National Preserve, South Florida, USA) as a case study. Across a broad range of environmental variables, model simulations highlight primary controls of climate and soil biological respiration, where soil thickness both supplies and limits transport of biologically derived acidity. Consequently, the weathering rate maximum occurs at intermediate soil thickness. The value of the maximum weathering rate and the precise soil thickness at which it occurs depend on several environmental variables, including precipitation regime, soil inundation, vegetation characteristics, and rate of groundwater drainage. Simulations for environmental conditions specific to Big Cypress suggest that wetland depressions in this landscape began to form around beginning of the Holocene with gradual dissolution ofmore » limestone bedrock and attendant soil development, highlighting large influence of age-varying soil thickness on weathering rates and consequent landscape development. While climatic variables are often considered most important for chemical weathering, our results indicate that soil thickness and biotic activity are equally important. Weathering rates reflect complex interactions among soil thickness, climate, and local hydrologic and biotic processes, which jointly shape the supply and delivery of chemical reactants, and the resulting trajectories of critical zone and karst landscape development.« less
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [1] ;  [4] ;  [2] ;  [1]
  1. Duke Univ., Durham, NC (United States)
  2. Univ. of Florida, Gainesville, FL (United States)
  3. Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
  4. Univ. of Florida, Gainesville, FL (United States); Pacific Northwest National Lab. (PNNL), Sequim, WA (United States)
Publication Date:
Report Number(s):
PNNL-SA-132178
Journal ID: ISSN 0009-2541; PII: S0009254118302419
Grant/Contract Number:
DEB#1354783; AC05-76RL01830
Type:
Accepted Manuscript
Journal Name:
Chemical Geology
Additional Journal Information:
Journal Name: Chemical Geology; Journal ID: ISSN 0009-2541
Publisher:
Elsevier
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; Chemical weathering; Critical zone; Feedbacks; Patterned landscape
OSTI Identifier:
1439093