Change in Particle Density and Other Hydrophysical Properties With Depth in a Northern Boreal Bog Peatland
摘要
Advances in peatland ecohydrological modelling require higher resolution depth profiles of important soil physical properties, which exist as a continuum from Sphagnum-dominated surface cover to highly decomposed peat at depth. We determined the bulk and particle density, porosity, saturated hydraulic conductivity (Ksat ), and von Post score at 5 locations in a northern bog to a depth of ~ 200 cm in 5-cm intervals. The bulk and particle densities and von Post scores increased, and porosity decreased with depth. The particle density had a relatively abrupt shift near ~ 75 cm changing from ~ 0.8 g cm− 3 to a relatively consistent ~ 1.4 g cm− 3. The variability measured was small in the upper ~ 25 cm, larger at depths of ~ 25–125 cm, and became more moderate at depths > ~ 125 cm (but not particle density). The variability of bulk density at the deeper depths results in the observed variability of porosity. The larger variability in physical properties roughly coincides with the abrupt shift in the magnitude of measured properties suggesting that contemporary processes and/or past events (e.g., wildfire, or vegetation succession and peat botanical type) could be responsible for this pattern. Bulk and particle density and porosity exhibited a relationship with the von Post score with a shift in values between von Post scores of 3 and 4. Detailed examination of peatland soil properties, in particular particle densities which are not commonly reported, will improve the robustness and reliability of models and may reveal additional information on the history and processes of formation.