Chemical Characteristics of Serpentinitic Soils of Clear Creek Management Area, California.

 The Clear Creek Management Area in San Benito County, California is dominated by soils developed from serpentinite rock in a xeric soil moisture regime. Seven pedons were described and sampled in support of an ongoing soil survey. These soils represent the range of parent materials, elevation and vegetation that occur in the area. Existing vegetation included bigberry manzanita, buckbrush, chamise, and Coulter pine. Two pedons did not have serpentinite parent material. Pedons formed in serpentinite rock had magnesic family mineralogy. Two of the pedons from serpentinite rock had sparse vegetation. Total analysis and aqueous extracts with NH₄OAc and the Mehlich 3 extractant were used to measure the elemental content of the soils. The Ca/Mg ratios ranged from 0.003 to 0.5, 0.01 to 0.88, and 0.01 to 0.61 for total analysis, Mehlich 3, and NH₄OAc, respectively. The concentration ranking of the top 10 elements for all soils, by Mehlich 3, was Mg>Si>Fe>Ca>Al>Mn>Ni>K>Cr>Ba. The concentration ranged from 1900 to 6 mg/kg. The concentration ranking of the top 10 elements, by Mehlich 3, for soils with sparse vegetation was Mg>Fe>Si>Ni>Ca>Al>Cr>Mn>K>Co. The concentration ranged from 3110 to 2 mg/kg. Soils with sparse vegetation had a average Cr, by Mehlich 3, concentration of 47 mg/kg compared to 2 mg/kg for soils with abundant vegetation. Soluble elements and Fe by Mehlich 3 were also higher in the soils with sparse vegetation. The higher Cr content and soluble elements may contribute to the sparse vegetation.