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To clarify the mechanisms underlying the coexistence of Abies mariesii Masters and Abies veitchii Lindl. in a fir-wave forest, we surveyed the population dynamics of the two Abies species throughout stand development on Mount Shimagare, central Japan. We established three belt transects and found that, overall, A. veitchii dominated this fir-wave forest. However, A. mariesii dominated the canopy initially, whereas A. veitchii increased as stand development progressed; thus, dominant A. mariesii was eventually replaced by A. veitchii. This replacement was explained by the presence of an A. mariesii sapling bank that formed under the canopy of a mature stand and by the large A. veitchii seedling bank resulting from greater seed production. For ordinary canopy individuals, which are taller than midcanopy individuals, the increase in height suggested that taller individuals grow faster vertically regardless of species; moreover, height growth did not differ significantly between the two Abies species, which facilitated the growth of A. mariesii into the canopy and the production of seeds for the next generation. We concluded that the persistence of A. mariesii in this fir-wave forest is supported by its shade tolerance. Dans le but de clarifier les mecanismes sous-jacents a la coexistence d'Abies mariesii Masters et d'Abies veitchii Lindl. dans une sapiniere regeneree en vagues, nous avons inventorie la dynamique de population des deux especes d'Abies tout au long du developpement du peuplement sur le mont Shimagare, dans le centre du Japon. Nous avons etabli trois transects en bande et trouve que, globalement, A. veitchii dominait dans cette sapiniere regeneree en vagues. Cependant, A. mariesii dominait initialement dans la canopee tandis que la dominance d'A. veitchii augmentait a mesure que le developpement du peuplement progressait. Par consequent, A. mariesii etait eventuellement remplace par A. veitchii comme essence dominante. Ce remplacement s'expliquait par la presence d'une regeneration preetablie d'A. mariesii qui s'etait installe sous le couvert du peuplement mature et par une importante banque de semis d'A. veitchii qui etait le resultat d'une production plus abondante de graines. Pour les tiges ordinaires dans la canopee, qui sont plus hautes que les tiges du milieu de la canopee, l'accroissement en hauteur indiquait que les tiges les plus hautes croissaient en hauteur plus rapidement peu importe l'espece. De plus, la croissance en hauteur des deux especes d'Abies n'etait pas significativement differente, ce qui facilitait la croissance d'A. mariesii dans la canopee et la production de graines pour la generation suivante. Nous sommes arrives a la conclusion que la persistance d'A. mariesii dans cette sapiniere regeneree en vagues est due a sa tolerance a l'ombre. [Traduit par la Redaction], Introduction Abies mariesii Masters and Abies veitchii Lindl. dominate some subalpine forests in central Japan (Kohyama 1984). Because these fir forests have simple stand structures, they are suitable models for [...]

Investigates the patterns of natural nitrogen abundance in the leaf-to-soil continuum of tropical rain forests differing in nitrogen availability on Mount Kinabalu, Borneo. Enrichment of nitrogen at the litter-topsoil interface; Negative correlation between the magnitude of enrichment with nitrogen depletion in the foliage; Isotopic fractionation during the passage of nitrogen through ectomycorrhizas to plants.

In subalpine fir wave forests, strips of dead and weakened trees occur perpendicular to the slope next to strips of healthy trees. To reveal the transpiration by weakened Abies veitchii trees exposed to increased atmospheric evaporative demand, we investigated the ecophysiological traits closely related to the growth and transpiration, comparing them with those of the healthy trees and saplings in the fir wave of Mt. Shimagare in central Japan. The transpiration rate (E) was investigated using sap flux sensors to measure heat pulse velocity and compared with the surrogate for the needle water demand, which was computed using a multilayered gas and energy transfer model (modeled E, Emod). Weakened trees exhibited smaller diameter growth and narrower sapwood than healthy trees, as well as lower heat pulse velocity compared with healthy saplings. However, needle‐level traits did not differ significantly between weakened and healthy trees. Needle water potential at midday was as negative as the needle turgor loss point, and the measured heat pulse velocity increased linearly with Emod but leveled off above a certain Emod value in weakened trees and healthy saplings, suggesting that trees restricted E to balance the needle water budget. Heat pulse velocity of weakened trees leveled off at Emod lower than that of healthy saplings, probably due to lower capacity for water supply to the needles. Restriction of E would occur less frequently but be necessary for both weakened and healthy A. veitchii on Mt. Shimagare to avoid hydraulic failure, sacrificing photosynthetic carbon assimilation. [ABSTRACT FROM AUTHOR]