Downward Movement of Partly Degraded Materials in Dyked Marsh Soils
1987
Dinel, H. | Mathur, S.P. | Levesque, M. P.
Comparisons were made between organic depth layers of a virgin area (site A) and two fields, cultivated for 6 and 30 yr (sites B and C), all on the Keswick Marsh in the active delta of the Holland (Schomberg) River and Simcoe Lake, Ontario, Canada. Contrary to current concepts and earlier observations for other peat landforms, physical changes in the marsh soils extended beyond the initial period of cultivation while biochemical oxidation appeared to pervade the subsurface layers. Also, an increase in the extent of oxidation with the period of cultivation was clearly evident in the subsurface layers at sites B and C, but not so much in the more aerated and tilled surface layers. These anomalies could be explained if the products of biochemical oxidation were assumed to have moved downwards from the surface zone in these organic soils. This is feasible because these soils are drained rapidly by energetic pumping rather than by gravity alone. This conclusion was supported by variation of particle-size distribution with depth, increase of pollen concentrations in the subsurface, and inversion of ¹⁴C dates in certain depth layers of the cultivated fields. The data indicate that measures for controlling the long-term subsidence of cultivated Histosols should be aimed at the surface layer as that is where most of the biochemical oxidation occurs.
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