Looking for hydric soil indicators in volcanic ash-derived soil

Many of the soils in Southcentral Alaska, west of Cook Inlet, are derived from volcanic ash parent material. Development projects in the region will rely upon wetland delineation for permitting, but evidence of observed soil characteristics that meet the regulatory standards for wetland soils (those with anaerobic conditions) may not be readily measurable or observable in soils of volcanic ash-derived parent material. These soils, when saturated, frequently present few or no observable hydric soil features as described in the USACE Alaska Supplement of the Wetland Delineation Manual. In these cases, in-situ monitoring may be used to establish the presence or absence of anaerobic conditions. We will install IRIS tubes along with Pt electrodes and peizometers to measure redox potential and document the presence of reduced condition.

While it is generally believed that soils formed in tephra may be slower to develop redoximorphic features or that development of these features may be entirely inhibited, there is little documentation on this subject. This study will increase the understanding of how hydric soil indicators develop in andic soils by correlating the soil chemical properties with the presence or absence of redox feature development as detected by instrumentation.