Seasonal Dynamics of Surface Soil Bulk Density in a Forested Catchment.

Bulk density is a commonly measured soil property during field investigations of soils. Accurate and reliable bulk density measurements are critical for assessing soil productivity and soil degradation, as well as for converting mass-based measurements to volume-based values (e.g., calculating mass C per mass of soil to mass C per volume of soil). In forested soils, measurement of bulk density is complicated by the presence of rock fragments, the presence of macroscopic vegetal materials, and the generally shallow depths of surface O and A horizons. It is recognized that bulk density is variable both spatially and temporally. However, most attempts to quantify the dynamic nature of bulk density have focused on agricultural fields and the effects of tillage operations. Our objective was to determine if there are significant seasonal changes to the measured bulk density of surface soil horizons (O and A) in a forested ecosystem. The frame method was used to measure bulk density at monthly intervals for 12 months at 10 locations within a forested catchment selected using a generalized random tessellation stratified spatial sample. We will report results on the effects of seasonality on measured differences in bulk density.