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Cation-Exchange Capacity (CEC-7)-San Miguel Area, Colorado, Parts of 'J-Bird Mine Site <br />Dolores, Montrose, and San Miguel Counties <br />The aggregation method Dominant Component' returns the attribute value <br />associated with the component with the highest percent composition in the map <br />unit. If more than one component shares the highest percent composition, the <br />corresponding "tie-break" rule determines which value should be returned. The "tie- <br />break" rule indicates whether the lower or higher attribute value should be returned <br />in the case of a percent composition tie. <br />The result returned by this aggregation method may or may not represent the <br />dominant condition throughout the map unit. <br />Component Percent Cutoff.- None Specified <br />Components whose percent composition is below the cutoff value will not be <br />considered. If no cutoff value is specified, all components in the database will be <br />considered. The data for some contrasting soils of minor extent may not be in the <br />database, and therefore are not considered. <br />Tie-break Rule: Higher <br />The tie-break rule indicates which value should be selected from a set of multiple <br />candidate values, or which value should be selected in the event of a percent <br />composition tie. <br />Interpret Nulls as Zero: No <br />This option indicates if a null value for a component should be converted to zero <br />before aggregation occurs. This will be done only if a map unit has at least one <br />component where this value is not null. <br />Layer Options: All Layers <br />For an attribute of a soil horizon, a depth qualification must be specified. In most <br />cases it is probably most appropriate to specify a fixed depth range, either in <br />centimeters or inches. The Bottom Depth must be greater than the Top Depth, and <br />the Top Depth can be greater than zero. The choice of "inches" or "centimeters" <br />only applies to the depth of soil to be evaluated. It has no influence on the units of <br />measure the data are presented in. <br />When "Surface Layer" is specified as the depth qualifier, only the surface layer or <br />horizon is considered when deriving a value for a component, but keep in mind that <br />the thickness of the surface layer varies from component to component. <br />When "All Layers" is specified as the depth qualifier, all layers recorded for a <br />component are considered when deriving the value for that component. <br />Whenever more than one layer or horizon is considered when deriving a value for <br />a component, and the attribute being aggregated is a numeric attribute, a weighted <br />average value is returned, where the weighting factor is the layer or horizon <br />thickness. <br />Natural Resources Web Soil Survey 2.1 12/24/2008 <br />Conservation Service National Cooperative Soil Survey Page 4 of 4