Water balance and physiology of hygrophyte in cold regions.

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Vegetation type, water physiology and water/heat balances of hygrophytes community were investigated in the Sarobetsu Mire, North Hokkaido. The results are summarized as follows,a) Diurnal changes of stomatal conductance were measured by a diffusion porometer for six species (Sasa palumata, Moliniopsis japonica, Myrica gale var.tomentosa, Ledum palusire var.diversipilosum, Chamaedaphne calyculata, llex crenata var.paldosa) growing in the Sasa-Hygrophytes mixed community.b) Water potential at a depth of 10cm in the peat soil was closed to zero throughout the summer though the ground water level dropped to 40cm below the surface during dry weather.c) The diameter of the subterranean stem of Myrica gale var. tomentosa were decreased and the length of them were extended with rising ground water level in this site.d) Stomatal conductances of the six species were correlated negatively with daily maximum VPD (vapor pressure deficit). When the daytime VPD was large, stomatal conductance maintained at small values and VPD was the main factor to determine the transpiration.