• Journal of Korean Society of Forest Science
• /
• v.89 no.2
• /
• pp.198-207
• /
• 2000

The diurnal and seasonal changes of water potential and stomatal diffusive resistance were investigated with the effects of shade treatment to elucidate the water relations of the one year old seedlings of Betula platyphylla var. japonica, Zelkova serrata, Acer mono, and Prunus sargentii subjected to five levels of artificial shade treatments from full sun to nearly full shading of 2-6% relative light transmittance. Stomatal diffusive resistance measured in the four deciduous hardwood species studied changed variously by growing season and by species with the five shade treatments in the ranges of 1.7~25.1s/cm in 9 a.m., 2.3~33.3s/cm in 1 p.m., and 1.1~36.8s/cm in 5 p.m.. The measurements of stomatal diffusive resistance increased with increasing the shading, and were higher in September than in June or July in most of the species studied. The stomatal diffusive resistance measured in Zelkova serrata, Acer mono, and Prunus sargentii seemed to be approximately 3~4 times higher in nearly full shading treatment than in full sun. Water potential also changed variously by growing season and by species with five different shade treatments in the ranges of -0.17~-1.20MPa in 9 a. m., -0.30~-2.03MPa in 1 p. m., and -0.18~-1.34MPa in 5 p.m., respectively. On the reverse of stomatal diffusive resistance, the measurements of water potential were lower in September than in June or July in most of the species studied, and the seasonal differences were especially greater in Zelkova serrata comparing with the other species. The water potential seemed to be higher of approximately 2~3 times in nearly full shading treatment than in full sun in all of the species studied, but the differences among the shading treatments were less in water potential than in stomatal diffusive resistance. The differences of water potential following the gradient of five shading treatment seemed to be less in Betula platyphylla var. japonica than in the other species. In Acer mono and Prunus sargentii being some shade tolerant species, the water potential increased rapidly through about noontime with raising the shading level from full sun to the intermediate shading level of 22-28% relative light transmittance, but slowly with closing to full shading. In Betula platyphylla var. japonica and Zelkova serrata being shade intolerant species, the water potential increased gradually throughout the shading levels and the increment ranges were greater in Zelkova serrata than in Betula platyphylla var. japonica.