美唄泥炭地における地盤沈下 : 湿原と泥炭農用地の管理(第2報)

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We measured land altitude, surveyed soils and determined the degree of decomposition of peat of marshland, windbreak forests and arable lands in Bibai, central Hokkaido. Marshland and arable land including peat layers and tephra layers showed a difference in subsidence of more than 3m over 40y. The subsidence resulted mainly from compaction, shrinkage and decomposition of the high moor peat layer that mainly consisted of Sphagnum peat. The difference in the annual rate of subsidence between paddy field and upland field was estimated to be 3cm, based on the measurement of the land altitude. A larger surface subsidence for upland field than for paddy field was ascribed to mixing of the sublayer peat with the topdressed mineral soil by deeper plowing and to a larger lowering of the groundwater table than paddy field, both of which may accelerate the decomposition of peat materials. Comparing carbon contents of peat layers at marshland with those at forest land, 80% of organic carbon in the peat layers disappeared after the change of land use from marshland to forest land. Proportional contribution of the decomposition to the whole subsidence and the average annual rate of subsidence over 40y caused by the decomposition were estimated to be 30% and 2cm, respectively.
社団法人日本土壌肥料学会の論文
1995-10-05