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Dendroecological techniques were used to study the dynamics and species recruitment patterns, spanning nearly four centuries, for a mesic, montane, old-growth forest in Hokkaido, northern Japan. The forest is dominated by Abies sachalinensis (Masters), Acer palmatum (Thunb.),Quercus mongolica var. grosseserrata (Rehd.), and Cercidiphyllum japonicum (Sieb.). From 1620 to 1750 and 1820 to 1840, Q. mongolica exhibited continuous recruitment into the overstory. A lack of recruitment for all tree species from 1750 to 1820 followed a 1739 volcanic eruption 200 km from the study area. Release events for individual trees occurred almost every decade of the stand history, indicating that frequent small-scale disturbances coupled with infrequent large-scale disturbances, impact tree growth and species recruitment. From 1870 to 1950, canopy recruitment of Abies and Acer dominated the forest, while recruitment of Quercus ceased. These later successional species appeared to be replacing Quercus, suggesting that the syndrome of declining oak dominance is an increasingly global phenomenon. However, successional patterns in the forest are difficult to predict because intensive deer browsing has recently prevented canopy recruitment of all tree species and the possibility of future large-scale disturbances, such as fire and volcanic eruption.

Morphological plasticity in terms of asymmetric display of crowns was compared between Piceaabies (L.) Karst. and Betulamaximowicziana Regel. To evaluate crown asymmetry in relation to local environment, a model that predicts crown asymmetry from topography and configuration of neighbors was applied to data derived from a mixed forest in Hokkaido, northern Japan. Betulamaximowicziana had greater crown asymmetry than P. abies in absolute value. However, observed crown asymmetry of both species was determined by local environment to similar degrees. Some other differences were found between the two species. Crowns of P. abies were more influenced by neighbors than topography, while crowns of B. maximowicziana were more influenced by topography than neighbors. Crowns of P. abies were influenced mainly by larger neighbors, while crowns of B. maximowicziana were influenced by large and by relatively small neighbors.

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The mean labor time of a leaf (hour/day -1 ) is defined as the ratio of mean daily photosynthetic rate of a leaf (D a ; mol m -2 day -1 ) to the mean value of potential hourly photosynthetic rate (60 ◊ 60A max mol m -2 h -1 ) of the leaf. A model was proposed to estimate mean labor time of leaves. Mean labor time was obtained as the product of 24 (hours/day -1 ) and the four effects, each of which reduces production of a leaf: diel change in light (Diel Effect), reduction in light during cloudy and rainy days (Cloudy Effect), shading on the focal leaves (Shading Effect), and midday and afternoon depression in photosynthesis (Depression Effect). These four effects were estimated for open grown saplings of alder ( Alnus sieboldiana ), by measuring instantaneous photosynthetic rate and photon flux density above each leaf. The potential daily photosynthetic rate calculated from diel light condition in a clear day was 46.5% of hypothetical daily photosynthetic rate where maximum instantaneous photosynthetic rate was assumed to last throughout the life of the leaf (Diel Effect). The average of the daily photosynthetic rate considering clear, cloudy and rainy days was 79.7% of the clear day (Cloudy Effect). The photosynthetic rate estimated from light condition on the leaf was 85.6% of that in the open site (Shading Effect). Midday depression reduced the daily photosynthetic rate to 72.1% of the potential daily photosynthetic rate (Depression Effect). The product of the four effects multiplied by 24 h gave the estimate of mean labor time of leaves to be approximately 5.5 (h/day -1 ).