In March 1971, the Arizona Bureau of Mines—predecessor of today’s Arizona Geological Survey—published the first issue of Fieldnotes. For nearly 40 years, Fieldnotes, and its successor, Arizona Geology, showcased all things geologic in Arizona. From the onset, the quarterly magazine printed topical pieces on Arizona’s mineral resources, energy potential, and environmental geology. In Fall 1988, Fieldnotes became Arizona Geology, and the newsletter was retailored to meet the needs of Arizona’s exploding population. There was increased focus on articles describing geologic phenomena—flash floods and regional floods, earthquakes, landslides, volcanism, swelling and shrinking soils, earth fissures, and more—with the most immediate and adverse impact on the lives and properties of our fellow Arizonans. But that was then and this is now! As print publication costs rise through the stratosphere, we simply can no longer afford to print and mail 4100 copies of Arizona Geology quarterly. Arizona Geology is going digital. We are suspending the print publication immediately and we are moving from a quarterly schedule to three times annually.

This white paper has been created by Arizona Land Subsidence Group to help educate stakeholders and decision makers by describing the geological features and processes of land subsidence and earth fissures, and the hazards they create. This paper presents the current and future technical needs that exist in terms of basic knowledge, available data, and the state of professional practice.

Throughout the southwestern United States, vegetation in what historically was grassland has changed to a mixture of trees and shrubs; exotic grass species and undesirable shrubs have also invaded the grasslands at the expense of native grasses. The availability and amount of soil nutrients influence the relative success of plants, but few studies have examined fire effects on soil characteristics in a temporal, spatial, and species group-specific fashion. Likewise, few studies have tied fire effects and ecological aspects to the underlying geology. Our research investigates the effects of fire events on selected soil characteristics pH, nitrate (NO3-), plant-available phosphorus (PO4-3), and total organic carbon (TOC) on native grass-, exotic grass-, and mixed grass-dominated plots distributed on four different geological surfaces. Treated and control plots were sampled prior to burn treatment and at intervals after the burns. In addition to new geologic mapping of the study areas, results indicate the geologic substrate is the most important variable for explaining pH, NO3- and PO4-3 values in the soils. Dominant grass type – native, non-native, or mixed – had little effect on the response of soil geochemistry to fire events: post-burn results indicate vegetation was a significant factor only for TOC. Recovery to pre-burn levels varies with characteristic: there were no significant initial differences between vegetation types, but significant differences in NO3-, PO4-3, and TOC amounts occur as a result of fire events, geological characteristics, and time. The research helps identify the soil response to fire and the recovery times of soil characteristics, further defines which fire frequency is optimal as a management strategy to maximize soil macronutrient contents, and illustrates the important role geology plays in grassland ecosystems.