TEXTURAL AND MINERALOGICAL MODIFICATIONS OF A SOIL PROFILE AS A RESULT OF FIRE

The degree of soil heating during a fire event will influence modifications to soil texture and mineralogy. Typically, the upper 5-8cm of soil will experience the most intense heat and have significant alterations as a result of fire. Sub-surface soils are less affected by the soil heating. Intense heat is usually attributed to high severity fires or burning of large fuel loads such as logs, brush, or slash piles. Intense heat can increase the sand fraction and decrease the silt and clay fractions. This is attributed to fusing of silt and clay particles into larger sand sized particles. There is also indication for the reverse effect, whereby intense heating may physically weather sand particles, resulting in decreased coarse fragments and increased fine sands, silts, and clays. It may also structurally alter clay minerals. These alterations may persist with time.

It is un-clear as to the fate of altered surface soils resulting from intense soil heating due to fire. This study aims to investigate the potential for translocation as time persists from the most recent burn event. Soil was sampled in increments of 5, 10, and 20cm following a prescribed burn event in north-western NJ from the area underneath and adjacent to a burned brush pile using a soil corer. Sampling occurred prior to the burn event, one month, and three months post burn.

Preliminary laser-particle size analyses indicate non-significant modifications to percentages of clay, silt, and sand as a result of burning in the upper 5cm of soil. This is contrary to the anticipated result as the location underneath the brush pile was chosen as a likely area of intense soil heating. Determination of fine vs. coarse clay and fine vs. coarse sand percentages in surface and sub-surface soil will later be determined. Preliminary X-ray diffraction (XRD) data indicate the presence of kaolinite and chlorite. XRD analysis will be utilized to investigate clay mineral structural alterations. Thin section microscopy will be utilized to examine clay films on mineral grains, an indicator of translocation.