Sensitivity of thermal analysis and calorimetry to assess the impact of forest management on soils

Abstract

Thermal analysis and calorimetry are useful tools for soil research providing different indices enriching the understanding of soil processes. In this work, we test their sensitivity to study the impact on soil of macroscopic forestry managements applied to eucalypt forest in the northwest of Spain: clearing scrub and thinning. Their impact on soil is assessed by differentiating the thermal properties of the organic matter and the biodecomposition. Thermal properties yield the percentage of soil organic matter, the heat of combustion and the degree of reduction of the organic matter. Calorimetry provide the biodecomposition rates as the heat rate and the respiration rate by a calorespirometric procedure. These properties were determined to soils from different depths and tracked from young to mature forest stands under management and compared to their respective references. All of them were sensitive to the different forestry practices. Clearing and thinning caused losses of SOM due to enhanced microbial respiration in soils from sites, where the organic matter evolves to a more oxidized state from young to adult stands. These methods also allowed us discerning mechanisms making the organic matter to evolve to a more reduced or to a more oxidized state with time and with depth, suggesting that natural evolution of the soil organic matter can depend on external factors like the land use and land use changes.