@article {51458, title = {Quantitative modeling of soil forming processes in deserts: the CALDEP and CALGYP models}, year = {1994}, note = {//NMSU//LTER III//ProCite field[6]: In}, month = {1994}, pages = {129-145}, institution = {Soil Science Society of America}, address = {Madison, Wisconsin}, abstract = {

Many models have been developed to simulate CaC03 (calcite) formation in soils. Mechanistic models that focus primarily on the long-term formation of CaC03 are summarized in Table 8-1. These models differ with respect to: (i) the mechanism of CaC03 formation, (ii) Ca sources, (iii) the inclusion of chemical kinetics, (iv) spatial and temporal variability in pH and CO2, (v) the type of rainfall model, and (vi) the inclusion of other minerals in the model.

}, keywords = {book, books, calcite, also SEE , calcite, formation model, calcium carbonate, also SEE , chapter, chapters, gypsum, formation model, model, calcite formation, model, CALDEP, model, CALGYP, report, reports, soil chemistry, soil, paleo-processes}, isbn = {SSSA Special Publication 39}, url = {files/bibliography/JRN00178.pdf}, author = {G. M. Marion and W. H. Schlesinger} } @article {51539, title = {Alkalinity measurements in water extracts of calcareous soils}, journal = {Soil Science Society of America Journal}, volume = {56}, year = {1992}, note = {//NMSU//LTER II//Listed in LTER3 proposal as citing LTER2 support//}, month = {1992}, pages = {598-600}, abstract = {

In soil carbonate solubility studies, it is usually assumed that total alkalinity is equal to inorganic-C alkalinity. Recent studies have raised questions about the validity of this assumption. This study reexamined previously published soil data from grass-oak (Quercus spp.) woodlands and deserts to test the hypothesis that total alkalinity is equal to inorganic-C alkalinity. Total alkalinity was measured with strong-acid titration, while inorganic-C alkalinity was calculated from pH and the partial pressure of CO2 (pCO2) measurements. Within the limits of error, calculated inorganic C alkalinity (Y) was equal to measured total alkalinity (X) (Y = 0.01 + 0.998X, r2 = 0.97). A recommendation was made for overdetermining the state of experimental systems in solubility studies; this allows one to check the internal consistency of experimental measurements, equilibrium constants, and model assumptions.

}, keywords = {alkalinity, calcareous soil, article, articles, calcareous soil,alkalinity, journal, journals, soil, calcareous}, doi = {10.2136/sssaj1992.03615995005600020042x}, url = {files/bibliography/JRN00150.pdf}, author = {G. M. Marion and W. H. Schlesinger and P. J. Fonteyn} } @article {51622, title = {Spatial variability of CaCO3 solubility in a Chihuahuan Desert soil}, journal = {Arid Soil Research and Rehabilitation}, volume = {4}, year = {1990}, note = {//NMSU//LTER II//Listed in LTER3 proposal as citing LTER2 support//}, month = {1990}, pages = {181-191}, abstract = {

Spatial variability in CaCO3 solubility is an important factor in parameterizing simulation models and designing experiments. The objective of this study was to quantify the spatial variability, both horizontal and vertical, in CaCO3 solubility in a Chihuahuan Desert soil. CaCO3 solubilities were estimated in 1:5 soil:water suspensions. Soil horizon extracts were generally supersaturated with respect to calcite. The mean (+- 1 SE) pIAP(CaCO3) for the A, Bk1, and Bk2 horizons were 8.03 (0.055), 8.19 (0.019), and 8.26 (0.15), respectively. The differences in pIAP between the A and B horizons (vertical variability) were statistically significant; these differences could be due to organic matter inhibition of calcite precipitation. Supersaturation with respect to calcite and vertical variability in CaCO3 solubility needs to be explicitly considered in simulation models. The standard errors in pIAP (horizontal variability) were greatest for the A horizons and decreased with increasing soil depth. Given the inherent variability in CaCO3 solubility, a large sample size is necessary to detect small differences in CaCO3 solubility for this Chihuahuan Desert soil.

}, keywords = {article, articles, calcium carbonate, solubility, calcium carbonate, spatial variability, caliche, also SEE , journal, journals, simulation modelling, SEE , soil chemistry, soil, also SEE }, doi = {10.1080/15324989009381247}, url = {files/bibliography/JRN00131.pdf}, author = {G. M. Marion and W. H. Schlesinger and P. J. Fonteyn} } @article {51890, title = {CALDEP: a regional model for CaCO3 (caliche) deposition in southwestern deserts}, journal = {Soil Science}, volume = {139}, number = {5}, year = {1985}, note = {//NMSU//LTER I//}, month = {1985}, pages = {468-481}, abstract = {

Our objective was to develop and validate a regional model for CaCO3 deposition in desert soils of the southwestern United States. There were five major components in the simulation model, an evportranspiration model, chemical thermodynamic relationships, soil parameterization, and a soil water and CaCO3 flux model.

For the present climate, a cold-dry Pleistocene climate, and a cool-wet (summer) Pleistocene climate, the model predicted a shallower depth for the calcic horizon than was found in field soils. However, the model was compatible with field soils if one assumed that most pedogenic carbonate formed during a cool-wet (winter) Pleistocene climate. The model was highly sensitive to the frequency of extreme precipitation events and to soil water-holding capacity. The biotic factor played an important role in CaCO3 deposition through its control of soil CO2 concentrations and evapotranspiration rates. The range in predicted CaCO3 deposition rates agreed with the rates for most field studies (1 to 5 g/m2/yr); also, the model predicted an increasing rate of CaCO3 deposition with increasing precipitation, which agreed with field studies. The model is a valuable research tool for evaluating the role of state factors on soil CaCO3 deposition.

}, keywords = {article, articles, calcium carbonate,deposition model, caliche, deposition model, journal, journals, model, calcium carbonate deposition, model, CALDEP, model,regional}, doi = {10.1097/00010694-198505000-00014}, author = {G. M. Marion and W. H. Schlesinger and P. J. Fonteyn} }