著者

岡田 操

出版者

日本地形学連合

雑誌

地形 (ISSN:03891755)

巻号頁・発行日

vol.29, no.3, pp.281-300, 2008-07-25

被引用文献数

2

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In bog mires, peat formation depends largely on plant growth, the amount of which in turn is influenced by rates of primary production, soil pH, sunlight, and ground, air and water temperatures. Plant growth is also affected by soil saturation and thus groundwater, which in turn are influenced by meteorological factors such as precipitation and evapotranspiration as well as hydrological factors such as inflow, outflow and storage. The flow of groundwater is influenced by peat composition, where a lack of water results in plant death, followed by partial decomposition of plant matter. This accumulates contributing to the upper layers of peat. As time progresses, the plant matter undergoes varying degrees of decomposition and consolidation producing peat of variable density, porosity, and permeability. The model proposed in this paper focuses on groundwater table, the most significant factor in peat formation. The characteristic of this model is the determination of the relationship between plant growth and groundwater table under variable conditions. In a given topographical configuration, if boundary conditions such as the inflow and outflow of rainfall and surface soil are manipulated, unsteady flow calculations reveal changes in water level. If this is iterated for an entire season, vegetation grow and peat will accumulate depending on the mean seasonal water level. This relationship is predicted using the growth function of vegetation, which is determined from growth simulations incorporating actual data from the primary production of specific plants. Iterated over the course of several years the thickness of peat layers gradually changes, giving rise to a conspicuous topography. This model demonstrates that causes of topographical formation, which to date could only be determined qualitatively can now be done quantitatively. Based on the growth processes of bog vegetation, this paper proposes a "Carex Model", which simulates changes in peat layers and thus predicts the formation of the diverse micro-topographies of bog mires.