Photosynthetic light environments in a young Betula ermanii plantation and a B. maximowicziana one

Abstract

Measurements of photosynthetic photon flux density (PPFD) within two young birch stands were compared. Measurements were made during early August under clear and slightly cloudy conditions. Frequency distribution of the relative PPFD showed a L-shape. Relative PPFD in the understory was estimated at 6.1-6.7% of Betula ermanii stand and at 10.7-12.1% of B. maximowicziana one. The average duration of sunfleck and the mean maximum PPFD of Betula ermanii plantation and B. maximowicziana one were 6.7 sec., 179.2μE・m^<-2>・s^<-1> and 10.3 sec., 271.3μE・m^<-2>・s^<-1>, respectively. The light conditions in a stand that were contributed by sunfleck were 34% for Betula ermanii plantation and 43% for B. maximowicziana one. The above mentioned results imply that the photosynthetic light environments within the Betula maximowicziana plantation was better than that in the B. ermanii one.