HR: 1055h
AN: H52B-03    [Abstracts]
TI: Application of a quantitative pedogenic energy model to predict critical zone structure and function
AU: * Rasmussen, C
EM: crasmuss@ag.arizona.edu
AF: Soil, Water and Environmental Science Department, University of Arizona 1177 E. Fourth St. Shantz Bldg., Tucson, AZ 85721, United States
AB: Energy-based pedogenic models present a framework for quantitatively linking pedogenesis and mineral weathering to soil system energy through-flow. This study presents refinement and application of the Quantitative Pedogenic Energy Model (QPEM) at global, watershed, and pedon spatial scales. The QPEM model framework is based an open-system principles and uses rates of effective energy and mass transfer (EEMT; kJ m-2 yr-1) to predict soil development and pedogenic environments. Study objectives included: (i) derivation of a global equation for estimating EEMT; (ii) testing the QPEM framework at the various spatial scales using a combination of global soil datasets and site specific pedon data; (iii) incorporation of EEMT into a soil mass balance model of silicate weathering; and (iv) development of quantitative transfer functions between pedogenic indices and EEMT. We derived a 2-D Gaussian expression for estimating EEMT from mean annual temperature (MAT) and mean annual precipitation (MAP) (R2=0.96) using a global climate dataset. Global EEMT patterns demonstrated distinct latitudinal variation in total EEMT and the percent of EEMT derived from biologic and climatic sources. Pedon data demonstrated significant linear and non-linear functions between EEMT and a variety of pedogenic indices including pedon depth, clay content, subsurface chemical index of alteration, and the ratio of free Fe- oxides to total Fe. Watershed scale stream Si-flux data demonstrated a significant linear relationship to EEMT (r2=0.82), whereas depletion of soil Si relative to bedrock demonstrated a significant exponential rise to maximum function (r2=0.76) with increasing EEMT. At the watershed scale, modeled pedon depth and landscape denudation data indicated a feedback between EEMT, denudation and rates of silicate weathering. Furthermore, at all of the observed scales, significant differences in EEMT were observed amongst soil classes according to U.S. Soil Taxonomy. The presented data analysis indicates the potential for using rates of effective energy and mass transfer in an energy-balance approach to characterize critical zone structure and function.
DE: 0486 Soils/pedology (1865)
DE: 1865 Soils (0486)
SC: Hydrology [H]
MN: 2007 Fall Meeting