Effects of sap flow in vascular plants on the small change in ground water level in a peat mire.

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Surface ground water in a peat mire is very important for management and land use of the mire. The aim of this study is to make clear the relationship between change of ground water level and water content in the unsaturated subsurface layer and sap flow in the vascular plants growing in the mire. The direction of sap flow was upward in the daytime, and strength of the flow had a good linear relation with solar radiation in the Tukigaumi. The direction of sap flow was downward during the night in several cases. The direction changed to downward just before sunset and changed again to upward the next morning.The effective hourly deviation (EHD) in ground water level, defined as the actual deviation in ground water level minus seepage component, was negative in the day time according to evapotranspiration. Changes in EHD during the daytime roughly corresponded to changes in solar radiation with a time lag of 1-2 hours. The EHD of ground water level became positive during the night in som … More e cases, indicating that ground water was supplied from the upper layer, the unsaturated subsurface layer and/or vegetation layers during the night. The change of EHD to positive during the night occurred simultaneously with downward sap flow in the plant, suggesting that the small rise in ground water level during the is related to the water flow in plants, not only in vascular plants but also in sphagnum. The redistribution of water between the saturated layer and unsaturated layer in a sphagnum peat subsurface layer was found after a rainfall and during the night. This redistribution of water in a peat layer is probably main reason of small rise in ground water level in a high peat mire. A detail profile of C, N, Na, Ca, Si etc. in a Sphagnum peat layer in Sarobetsu Mire showed that the chemical composition distributed evenly from surface to around 4 m in depth. This fact means that the water system in the mire was stable very long time. The redistribution of water in a sphagnum peat might contribute to the stability of the mire. Less