[in Japanese]

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[in Japanese]

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To clarify the relationship between hydrochemical variables and community gradients in poor fen under nutrient and mineral loading via groundwater, we set up loaded and control sites in poor fen and investigated plant community and pH, electrical conductivity (EC) and inorganic ions of peat water in both sites. Poor fen consists of mosaic topographies with raised hummocks and depressed hollows and non-mosaic topographies without hummocks and hollows. We expected that groundwater (saturated peat water) would have different effects on plants growing in each topography, because the distance from the water table to the surface of each topography is different. In this study, as a result of the plant community analysis in different topographical spaces, two community gradients were extracted from the mosaic-non-mosaic and one community gradient from the hummock, and one end of each community gradient consisted of a community type dominated by Sphagnum species. These three community gradients were accompanied by changes in concentrations of inorganic ions. On the other hand, no community gradient was extracted from the hollow along changes in concentrations of inorganic ions. As a result of comparing peat water in hummocks (unsaturated peat water) and hollows (saturated peat water) between loaded site and control site, concentration of most inorganic ions was generally higher in loaded site for both hummocks and hollows. From this result, it can be suggested that ion concentrations in hummocks increased due to the loading of nutrients and minerals via groundwater, and reduced in coverage of Sphagnum species, which arose community gradient on hummocks through loaded and control sites.

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This study aimed to investigate the time-activity budgets of wintering Bean geese Anser fabalis middendorffii in Katano-kamoike, which is a Ramsar site in Kaga City, Ishikawa Prefecture. Resting was the dominant activity, followed by foraging; other activities were uncommon. Generalized linear mixed models were constructed to investigate the effects of season (the number of days since December 1st), time of day, water level in Katano-kamoike, air temperature, amount of precipitation, amount of snowfall, snow depth, and wind speed on the number of foraging Bean geese. The number of foraging Bean geese was negatively affected by the water level, snowfall, and season but positively affected by the time of day and snow depth. When the foraging grounds of wintering Bean geese are covered by snow, the value of Katano-kamoike as a foraging site is more important especially when the snow depth is deep. Therefore, for the conservation of wintering Bean geese, appropriate management of the water level in Katano-kamoike is very important.

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We analyzed the effect of groundwater flow direction and velocity on vegetation composition. Because the available hydrological data required to conduct an unsteady flow analysis were insufficient, we conducted our simulations assuming a steady flow. The results indicate that plant communities from the Phragmitetea class developed in areas with high flow velocity, Ulmus davidiana and Betula platyphyla communities developed in areas with upward flow, and communities from the Oxycocco-Sphagnetea class developed in areas with low vertical velocity. Although unsteady hydrological states such as flooding and water level fluctuation are known to have an impact on vegetation composition, our study suggests that steady state simulations can also effectively support the evaluation of vegetation distribution.

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Distribution patterns of two Drosera species (Droseraceae), D. rotundifolia and D. tokaiensis subsp. tokaiensis, are discussed in relation with the soil water conditions studied by continuous observation of soil water content and soil water qualities during the dry and wet seasons in summer in small-scale spring-fed marshes, Kani City, Central Japan. Soil water contents calculated from the electrical permittivity in fields correlated with the distribution pattern of two Drosera species; D. rotundifolia grew in wet areas over 0.4 m³m^-3 water content and D. tokaiensis subsp. tokaiensis in dry areas under 0.1 m³ m^-3 water content. The ion compositions of the water extracted from the soil differed; K⁺ and NH₄⁺ were more abundant in the habitats of D. tokaiensis subsp. tokaiensis than those of D. rotundifolia, perhaps due to the difference in salt concentrations caused by drying off. Judging from the water content of the soil and the diurnal quantitative fluctuation and qualities of soil water, we deduce that, in dry seasons, habitats of D. rotundifolia are recharged by rainfall leaking out from the ground, and those of D. tokaiensis subsp. tokaiensis by sorption from the moister layers under impermeable layers or dewfalls.

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