Leonard F. DeBano

The role of fire and soil heating on water repellency in wildland environments: a review

Abstract This paper describes the heat transfer mechanisms operating as heat moves downward in the soil along steep temperature gradients during both wildfires and prescribed fires. The transfer of heat downward in the upper part of the soil is enhanced by the vaporization and movement of water and organic compounds. Available information on the changes in the chemistry of vaporized organic compounds is summarized and discussed. An operational theory describing the formation of a highly water repellent soil condition during fire is presented. The relationship between the formation of this fire-related watershed condition and subsequent surface runoff and erosion from wildland ecosystems is explored. Worldwide literature describing fire-induced water repellency is reviewed and summarized.

Water repellency in soils: a historical overview.

The purpose of this paper is to document some of the more important highlights of the research and historical aspects concerning soil water-repellency. This effort traces the evolution of interests and concerns in water repellency from basic studies in the nineteenth century to the earlier part of the 20th century and up to our current-day understanding of this subject. The interactions among different scientific disciplines, various manager-scientists efforts, and specific scientific and management concerns are presented chronologically. This growing interest in water repellency generated an earlier conference in 1968 which was devoted exclusively to water repellency and has since initiated productive discussions and debate on water repellency during several peripherally related national and international conferences. The 1968 conference held in Riverside, California (USA), mainly involved scientists from the United States and Australia. Since this early conference, a large body of information has been published in a wide range of scientific disciplines throughout the world. This worldwide attention has produced many recent research findings, which have improved the understanding of water-repellent soils, particularly of the dynamics of the water movement and redistribution in these unique systems. Intermingled with the effort in water repellency is a related, although somewhat separate, body of information dealing with soil aggregation and water harvesting, which are important for improving the productivity of fragile arid ecosystems. A summary is presented of the literature on water repellency, showing changes in subject areas and national interests over time.

Wildland fire in ecosystems: effects of fire on soils and water

This state-of-knowledge review about the effects of fire on soils and water can assist land and fire managers with information on the physical, chemical, and biological effects of fire needed to successfully conduct ecosystem management, and effectively inform others about the role and impacts of wildland fire. Chapter topics include the soil resource, soil physical properties and fire, soil chemistry effects, soil biology responses, the hydrologic cycle and water resources, water quality, aquatic biology, fire effects on wetland and riparian systems, fire effects models, and watershed rehabilitation.

Effects of simulated fire on vesicular-arbuscular mycorrhizae in pinyon-juniper woodland soil

Effects of fire on vesicular-arbuscular mycorrhizal fungi were tested using microcosms constructed from soil, litter, and duff collected beneath canopies of pinyon pine, Utah juniper, and in the open space (interspace). Burning was conducted over wet and dry soils. Soil temperatures were monitored continuously throughout the microcosms during burning. Plants grown in soils burned when dry had a lower VAM colonization than soils burned when wet. Juniper soils demonstrated the greatest reduction, over 95%, compared to their respective controls. Plants grown in interspace soils burned when wet were least affected. There was a positive correlation (r2=0.90) between the decrease in VAM colonization and the soil temperature as a result of the fire. Temperature effects, and associated reductions in VAM, were related to amount of litter burned in each microcosm and the moisture content of the soils.

Potential variation of nitrogen transformations in pinyon-juniper ecosystems resulting from burning

SummaryForest floor litter, duff, and underlying soils were assembled in laboratory microcosms representing pinyon, juniper, and interspace field conditions. Burning removed more than 95% of both N and C from the litter, with losses from the duff dependent on soil moisture conditions. No significant changes in total N or C were noted in the soil. Immediate increases were observed in soil NHinf4sup+, decreasing with depth and related to soil heating. The greatest increases were noted in both the pinyon and juniper soils that were dry at the time of the burn, with interspace soils exhibiting the least changes. Soil NHinf4sup+closely approximated the controls on day 90 after the burns in all treatments. Ninety days after the burn microbial biomass N was highest in the controls, followed by the wet and then the dry-burned soils, in both the pinyon and juniper microcosms. This was inversely related to the levels of accumulated NOinf3sup-. Nitrifying bacteria populations were indirectly correlated to soil temperatures during the burn. Population levels 90 days after the burn showed increases in both the wet- and the dry-burn treatments, with those in the pinyon treatments exceeding those found in the nitial controls of pinyon soils.

The role of fire and soil heating on water repellency

This paper describes the heat transfer mechanisms operating as heat moves downward in the soil along steep temperature gradients during both wildfires and prescribed fires. The transfer of heat downward in the upper part of the soil is enhanced by the vaporization and movement of water and organic compounds. Available information on the changes in the chemistry of vaporized organic compounds is summarized and discussed. An operational theory describing the formation of a highly water repellent soil condition during fire is presented. The relationship between the formation of this fire-related watershed condition and subsequent surface runoff and erosion from wildland ecosystems is explored. Worldwide literature describing fire-induced water repellency is reviewed and summarized. q 2000 Elsevier Science B.V. All rights reserved.

Mesquite removal and mulching impacts on herbage production on a semidesert grass-shrub rangeland

The objectives of our study were to determining the effects of velvet mesquite (Prosopis velutina) removal, control of the resulting basal sprouts, and mulching treatments on herbage production (standing biomass) and selected soil chemicals (nutrients) shown to affect herbage production on the Santa Rita Experimental Range. Mesquite control treatments consisted of overstory removal by chain saw with and without control of the resulting basal sprouts. Mulching treatments were applications of mesquite wood chips, commercial compost, or lopped-and-scattered mesquite branchwood. Mesquite removal resulted in increases for total herbage production and the production of native herbaceous species. Production of the nonnative Lehmann lovegrass (Eragrostis lehmanniana), the dominant herbaceous species, was unchanged. The mulching treatments did not affect herbage production. None of the treatments affected soil chemical properties thought to influence herbage production.