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We monitored variation in seasonal and annual net ecosystem production (NEP), gross primary production (GPP), and ecosystem respiration (R E ) based on 7-year eddy covariance measurements above a cool-temperate deciduous broad-leaved forest (Japanese beech forest). The 7-year means (±SD) of annual NEP, GPP, and R E were 312 ± 64, 1250 ± 62, and 938 ± 36 g C m -2 year -1 , respectively. Variation in NEP was much larger than variation in GPP and R E . During the growing season, the main factor controlling carbon balance was air temperature; variation in seasonal integrated NEP was regulated by accumulated air temperature (degree-day) with a significant negative correlation, whereas the seasonal ratio of R E to GPP was correlated positively with accumulated air temperature. Because the deviation of seasonal NEP was also significantly correlated with seasonal R E /GPP, NEP was controlled by R E /GPP, depending on air temperature during the growing season. Seasonal R E in the defoliation and snow seasons was also important for evaluating the annual carbon balance, because the total number of days in the two seasons was quite large owing to a long snowy winter. In the defoliation and snow seasons, we found defoliation season length was a major factor determining seasonal integrated R E , illustrating the positive correlation between R E and defoliation season length. The major factors controlling interannual variations in forest carbon balance are discussed.

In order to clarify the effect of dwarf bamboo Sasa palmata elimination on regeneration of hinoki cypress Chamaecyparis obtusa , changes in the coverages of dwarf bamboo and regenerating trees were examined by aerial photographs taken from 1969 to 2005. Strip logging took place in 1967 1969. In three of six logged strips, the dwarf bamboo was eliminated with herbicide sodium chlorate in 1969, weeded manually every year from 1977 to 1979 and herbicide tetrapion was applied again in 1980. The effect of herbicide which decreased dwarf bamboo was estimated lasting for approximately three years. In the remaining three strips dwarf bamboo was undisturbed control treatment , and the control area has been covered with thick dwarf bamboo till 2005 except for the short term after the logging. In 2005, the regenerating trees covered about 24 of the control area, while they covered more than 70 of the treated area. There was a negative correlation between the coverages of dwarf bamboo in 1979 and regenerated trees in 2005. These results suggest that the elimination treatment of dwarf bamboo promotes the regeneration of hinoki cypress.

We describe observed long-term adaptive responses to light conditions in the morphology of saplings of Thujopsis dolabrata var. hondai Makino, a shade-tolerant conifer species. Under stably bright conditions, the crown shape was slender and conical. In contrast, in stably dark conditions, the crowns had a highly distinctive broad, shallow, bowl-like shape, due to the formation of characteristic orthotropic lateral branches with higher apices than the stem. Leaf display by these branches may reduce self-shading and stem elongation requirements for leaf arrangement in dark conditions, thereby minimizing increases in maintenance costs associated with increasing tree size. Epicormic terminal leaders were frequently present on long branches in the lower part of the crowns. These branches did not show vigorous growth or contribute to crown expansion. However, the low-hanging branches in the lowest quarter of the crown may frequently touch the ground, particularly under snow pressure, and produce adventitious roots under these leaders, thereby increasing numbers of ramets. The snow pressure may also cause stem layering and restrain saplings from increasing their height to more than 1 m. These morphological and reproductive traits of lateral branches may contribute to shade tolerance and improve survival of the saplings.Key words: apical control, epicormic shoot, light intensity, longevity in shade, orthotropic end of a branch, vegetative reproduction. Résumé :Les auteurs décrivent les réponses adaptatives aux conditions de lumière observées à long-terme sur la morphologie des gaules de Thujopsis dolabrata var. hondai Makino, une espèce de conifère tolérante à l'ombre. En condition d'éclairage stable, la taille de la couronne était plus mince et conique. Par contre, en condition de noirceur stable, les couronnes présentaient une forme distinctive large et concave à cause de la formation de branches latérales orthotropes caractéristiques possédant des apex plus hauts que la tige. L'organisation des feuilles sur ces branches pourrait réduire l'auto-ombrage et les exigences relatives à l'allongement des tiges pour l'arrangement des feuilles en condition de noirceur, minimisant ainsi les augmentations de coûts de maintien associés à l'accroissement de la taille de l'arbre. Des pousses apicales épicormiques terminales étaient fréquemment présentes sur les branches longues de la partie inférieure des couronnes. Ces branches ne montraient pas de croissance vigoureuse ou ne contribuaient pas à l'expansion de la couronne. Cependant, les branches basses du quart inférieur de la couronne pouvaient souvent toucher le sol, particulièrement sous la pression de la neige et produire des racines adventices sous ces pousses apicales, augmentant ainsi le nombre de ramets. La pression de la neige pouvait aussi provoquer le marcottage des tiges et restreindre l'augmentation de la hauteur des gaules à plus qu'un mètre. Ces traits morphologiques et reproductifs des branches latérales pourraient contribuer à la tolérance à l'ombre et améliorer ...