Evaluation of Soil Properties and Hydric Soil Indicators for Vernal Pool Catenas in California

Abstract

Vernal pool soils in California's Mediterranean climate experience extremes in pedogenesis driven by prolonged saturation to extended desiccation. Four northern California vernal pool soil catenas (summit, rim, and basin) were assessed to determine how soil properties and hydric soil indicators vary in response to duration of standing water and landscape position. Each catena had differences in parent material or degree of soil development. Soil properties differed subtly across each microtopographic sequence. In the well‐developed soils, the geochemical signature of horizons overlying the duripans changed sharply compared with horizons below the restrictive layers, suggesting polygenic origins of the soil profiles. The presence and abundance of redoximorphic features (RMFs) in profiles corresponded poorly with the duration of standing water at the four sites. Instead, the abundance of RMFs coincided better with the thickness of the soil above the restrictive horizons in all settings with duripans. Hydric soils were identified in the basin positions of each catena. Most rim positions contained hydric soils and most summit positions had soils that were not hydric. Indicators F8 (redox depressions) and TF2 (test indicator for red parent materials) were most commonly applied. None of the vernal pool catena soils met F9 (vernal pools hydric soil indicator), thus the hydric soil criteria for vernal pools may need to be revised.