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The responses of radial and height growth, plant architecture, and the probability of mortality of saplings to varying light levels were quantified for six tree species in temperate conifer forests of the Bhutan Himalayas. Increases in growth with increasing light were comparable with those of high latitude tree species but lower than those of tropical tree species and temperate species in North America. The shade-tolerant species Tsuga dumosa (D. Don.) Eichler showed the strongest increase in radial growth at low light and reached asymptotic growth early. It had the deepest crowns in low light and a low decrease of leader growth with decreasing light. It represents a continuous growth type, which invests in height rather than lateral growth under low light conditions. Betula utilis D. Don. showed greater increases in radial growth and a higher mortality at low light than the more shade-tolerant Abies densa Griff., in keeping with the trade-off between survivorship and growth at low light. Picea spinulosa Griff, Larix griffithiana Carriére, and Pinus wallichiana A.B. Jackson showed small increases in growth at low light levels. The latter two species showed no capacity to adapt their morphology in response to changing light levels, which resulted in higher probabilities of mortality at lower light levels. Differences in the probability of mortality at different light levels were more pronounced than differences in the light-growth response, underlining the importance of survivorship at low light for successional dynamics.Résumé : Les effets de différents niveaux de lumière sur la croissance radiale et la croissance en hauteur, sur l'architecture des arbres et sur les chances de survie des jeunes tiges ont été quantifiés chez six espèces d'arbres dans les forêts tempérées de conifères de la zone himalayenne du Bhoutan. Les augmentations de croissance dues à un niveau de lumière plus élevé étaient comparables à celles qu'on observe chez les espèces d'arbres des latitudes élevées mais infé-rieures à celles des espèces tropicales ou tempérées d'Amérique du Nord. L'espèce tolérante Tsuga dumosa (D. Don.) Eichler a connu la plus forte augmentation de croissance radiale sous une faible intensité lumineuse et a rapidement atteint une croissance asymptotique. Cette espèce avait la cime la plus profonde sous faible intensité lumineuse et subissait une légère diminution de croissance apicale avec la réduction du niveau de lumière. Cette essence est typique du type à croissance continue qui investit dans la croissance en hauteur plutôt que latérale sous faible intensité lumineuse. Betula utilis D. Don. a connu une plus forte augmentation de croissance radiale et de mortalité sous faible intensité lumineuse qu'Abies densa Griff., une espèce plus tolérante, conformément au compromis entre survie et croissance sous faible intensité lumineuse. Picea spinulosa Griff., Larix griffithiana Carriére et Pinus wallichiana A.B. Jackson ont connu de faibles augmentations de croissance sous faible intensité lumineuse. Les deux dernières e...

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Bamboo plantations in two locations in eastern Thailand differed in their biomass yield by an order of magnitude as a result of site productivity and plantation management. The biomass yield of Bambusa beecheyana and Dendrocalamus membranaceus was comparable, but the moisture content of culms of B. beecheyana was considerably higher as compared to D. membranaceus. With D. membranaceus, internodes had higher moisture content, as compared to nodes. The moisture content decreased with increasing height along culms with both species, but this gradient was stronger with D. membranaceus. The moisture content of culms of B. beecheyana declined with increasing culm age, indicating that older culms are more suitable for energetic utilization. While general feedstock characteristics of the two species were comparable, the calorific content of D. membranaceus was significantly higher than of B. beecheyana. Primarily the upper sections and nodes of older culms of both species are attractive options as bioenergy feedstock, but plantations established on marginal sites without proper plantation management will result in very low yields.