Changes in Soil Structure and Hydraulic Properties in a Wooded-Shrubland Ecosystem following a Prescribed Fire
- Karletta Chief *a,
- Michael H. Youngb and
- David S. Shaferc
- a Dep. of Soil, Water, and Environmental Sciences Univ. of Arizona 1177 E. Fourth St. Shantz Bldg. Rm. 429 Tucson, AZ 85721
b Bureau of Economic Geology Jackson School of Geosciences Univ. of Texas at Austin Austin, TX 78713-8924
c DOE Office of Legacy Management 2597 Legacy Way Grand Junction, CO 81503
Pre- and post-fire measurements were made for a low-intensity prescribed fire in a semiarid, shrub-woodland transition zone, and objectives were to: (i) determine changes in near-saturated hydraulic conductivity (Kf measured with a tension infiltrometer), air permeability (ka measured with an air permeameter), and soil physical properties at shrub undercanopy and interspace microsites immediately before and after a fall burn and for a 13-mo period; and (ii) quantify the importance and effect of post-fire soil structure on hydraulic properties using pre- and post-fire measurements. At undercanopy microsites, structure deteriorated from a moderate to a weak subangular blocky structure after the fire that broke down to a structureless soil 10 mo later. At interspace microsites, post-fire soil structure deteriorated from a moderate-strong subangular blocky structure with hard dry consistency to a weak subangular blocky structure with soft dry consistency. After 10 mo, the intercanopy maintained a weak-moderate soil structure that became structureless-weak after 13 mo. Immediately after the fire, at both microsites, there was incomplete organic combustion, a decrease in bulk density, and an increase in ka; however, at undercanopy microsites, there was no significant change in Kf even though there was a slight to moderate hydrophobicity, whereas at interspace microsites where no water repellency existed, Kf increased. These changes may be a result of expansion of vaporized water through soil pores that broke up aggregates, deteriorating soil structure. Thus, mechanisms that contributed to changes immediately and after the first year post-fire were different for low-intensity burns than for higher intensity burns.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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