Date of Award

5-2005

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Earth and Environmental Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Gregory Pope

Committee Member

Matthew Gorring

Committee Member

Huan Feng

Abstract

High intensity forest fires can alter the clay minerals found in soils. These minerals can be degraded, collapsed, as well as completely destroyed. Signatures of these fires may remain for years after the bums. To ascertain the impact of high intensity fire on soil physical properties, samples were collected from the area in and around the 2002 Hayman, Colorado, fire. These included burned samples from several areas within the perimeter of the fire (taken one to four months following the fire), unburned samples near the origin of the fire, as well as samples from areas of historic burns nearby. This series of samples show not only the immediate implications of high intensity forest fires on soil- clay mineralogy, but also the recovery over time of these minerals. Identification of the clay minerals was done using X-ray diffraction of the 5 to 30° 20 range of oriented clay mineral fractions. A series of XRD spectra were obtained for each sample, including air- dried, ethylene glycol saturated, and furnace heated to 400° and 550°C.

The unburned samples contain mixtures of illite, mixed layer illite/smectite and illite/vermiculite, kaolin, mixed layer chlorite, as well as clay-sized quartz, plagioclase and K-feldspar. At depths close to the surface (to 7.7 cm), illite, mixed layer illite/smectite, and kaolin are present. At depths to 13 cm, mixed layer illite/vermiculite as well as clay-sized quartz and plagioclase appear in addition to those found at shallower depths. Eventually (at depths to 27 cm) mixed layer illite/smectite and illite/vermiculite disappear and mixed layer chlorite as well as clay-sized K-feldspar appears.

Comparisons between the recently and historically burned samples to the unburned samples were made to determine the effects of fire on these minerals. The results of these comparisons indicated slight trends in regard to alteration of the clay mineral structures in the upper most portion of the soil. These trends include alteration of the 001 illite peak, the 001 and 002 kaolin peaks, as well as a decrease in the swelling component of mixed layer illite/smectite. These trends indicate that the fire may be impacting the structure of the soil clay minerals.

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