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Forest Peatland Drainage and Subsidence Affect Soil Water Retention and Transport Properties in an Alberta Peatland

Silins, Uldis, Rothwell, Richard L.
Soil Science Society of America journal 1998 v.62 no.4 pp. 1048-1056
peatlands, forests, drainage, subsidence, peat, bulk density, peat soils, soil water retention, saturated hydraulic conductivity, unsaturated hydraulic conductivity, Alberta
Water table level control by drainage improves forested peatland sites for tree growth, but can also result in subsidence of the peatland surface. The purpose of this study was to investigate the effects of changes to peat bulk density associated with postdrainage subsidence on peat hydrologic properties at a peatland drained for forestry in north-central Alberta, Canada. Peat hydrologic functions were determined by inverse techniques developed for multistep outflow experiments (MULSTP). Seven years after drainage, mean peat bulk density (0–40-cm depth) was 63% greater and mean soil water retention (−5 to −15000 cm pressure head) was 66% greater than peat from the nearby undrained control area. Subsidence after drainage was associated with loss of pores >600-µm diam. with concurrent increases in 3- to 30-mm-diam. pore-size classes. Mean saturated hydraulic conductivity was 1.69 and 14.46 cm h⁻¹, while mean unsaturated hydraulic conductivity (−5 to −15000 cm pressure head) was 0.014 and 0.004 cm h⁻¹ in peat from drained and undrained areas, respectively. Changes in water transport characteristics and in the pool of “plant-available” soil water will probably be beneficial to tree growth in the drained area.