The effects of fire events on soil geochemistry in semi-arid grasslands

Abstract

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. Our research investigates the effects of fire events on selected soil characteristics (pH, NO₃^-, PO₄^-3, 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, post-burn results indicate geology is the most important variable for soil pH, NO₃^-, and PO₄^-3. 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 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 role geology plays in grassland ecosystems.

Parent Publication

• Connecting mountain islands and desert seas: Biodiversity and management of the Madrean Archipelago II

Citation

Biggs, Thomas H.; Florkowski, Lisa N.; Pearthree, Philip A.; Shaner, Pei-Jen L. 2005. The effects of fire events on soil geochemistry in semi-arid grasslands. Gottfried, Gerald J.; Gebow, Brooke S.; Eskew, Lane G.; Edminster, Carleton B., comps. Connecting mountain islands and desert seas: biodiversity and management of the Madrean Archipelago II. Proc. RMRS-P-36. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 503-507