FOREST FIRE'S ROLE AS A CATALYST FOR CLAY MINERAL ALTERATION IN SOIL AND ITS EFFECT ON CATION EXCHANGE CAPACITY

The cation exchange capacity (CEC) of soils is dependant on several factors, including the clay mineralogical soil component. Clay minerals act as a type of storage facility for available cations in the soil by holding cations on their surface edges as well as along interlayer surfaces. However, what happens when the structural integrity of the clay mineral is compromised? Will this significantly affect the CEC of the soil? One way in which the structure of a clay mineral may be impacted is through heat, more specifically, through soil heating during forest fires. Fire can impact the clay mineral structure by degrading, collapsing, or completely destroying it as well as increasing the proportion of clay sized minerals. This typically occurs within the uppermost soil horizon, in the top several centimeters of soil, where heat is most intense.

This study will determine changes in clay mineral structure, soil CEC, and the particle size distribution of the upper 5cm of the soil profile due to forest fire. The study area is located in the fire prone ecosystem of the New Jersey Pine Barrens. Structural variations in the clay minerals were determined using X-ray Diffraction and results indicate structural variability in the vermiculite component with little change in the kaolin component. CEC values will be determined using the ammonia chloride method with optical ICP. Results of the particle size distribution analysis, as well as preliminary CEC testing, indicate a possible soil formation dynamic equilibrium. This trend shows a general decrease in sand sized particles as well as CEC values as the fire frequency decreases (i.e. from every 2-73 years) but then begins to increase again, finally reaching a point similar to the starting point. Further analysis is required to determine if the dominant factor affecting the CEC values is interlayer attraction, surface edge attraction, or another variable such as organic matter component.