SOME OBSERVATIONS OF PHENOLOGY AND ECOPHYSIOLOGY OF DAPHNE KAMTSCHATICA MAXIM. VAR. JEZOENSIS (MAXIM.) OHWI, A SHADE DECIDUOUS SHRUB, IN THE FOREST OF NORTHERN JAPAN

The phenology and leaf traits of Daphne kamtschatica Maxim. var. jezoe nsis (Maxim,) Ohwi, the only summer deciduous shrub (20-40 cm) in the temperate forest of northern Japan, are examined, This plant carries t hrough the winter mature leaves and well formed flower buds, it flower s in early spring during snowmelt and begins photosynthesis under rela tively high irradiance under an open forest canopy, Our results show t hat there is significant carbon gain during the period when new leaves and fruit maturation also take place, Beginning in June, as the fores t canopy closes, leaves on Daphne shoots senesce acropetally and the p lants become completely bare in mid-July. After a period of 20-day dor mancy, the shoots begin to resprout Leaves become mature in early Octo ber and remain on the stem over winter. Leaf traits and photosynthesis measurements suggest as follows. 1) By becoming summer deciduous, D.k amtschatica avoids the cost of maintaining leaves inefficient under de ep shade, 2) The onset and breaking of the summer dormancy is triggere d by photoperiod since plants at the forest edge also become dormant e ven when light remained relatively high, However, the decreased durati on of dormancy with higher light levels suggests that there is a tende ncy towards shorter dormancy where summer shade is absent and this.cou ld eventually lead to an evergreen habit such as that found in the alp ine species Daphne miyabeana.