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Decomposition subsystems have an essential role in forest dynamics but few studies demonstrate the effect of microbial decay traits on seedling regeneration. In the present study, we focused on seedling regeneration on coarse woody material (CWM), which is an important regeneration site for forest tree species, and the effects of wood decay type according to fungal decay preference for wood structural components on seedling colonization. Effects of log properties including wood decay type and other environmental variables on seedling density were evaluated by ordination methods and generalized linear models. In total, 22 woody species were recorded as seedlings on Pinus densiflora logs. By ordination analysis, white rot in heartwood and brown rot in sapwood, as well as canopy openness and log diameter, showed significant association with seedling communities. The factors selected for a generalized linear model for explaining seedling densities of the two dominant seedling species Cryptomeria japonica and P. densiflora included brown rot in sapwood and white rot in heartwood, but the effects were different: a positive effect of brown rot on C. japonica and a negative effect of white rot on P. densiflora. These results suggested that wood decay type could induce niche separation between dominant tree species regenerating on CWM. Key words: forest regeneration, log, rot type, seedling colonization, wood decay fungi. Les sous-systemes de decomposition jouent un role essentiel dans la dynamique forestiere mais peu d'etudes demontrent l'effet des caracteristiques de la decomposition microbienne sur la regeneration des semis. Dans cette etude, nous mettons l'accent sur la regeneration des semis sur le materiel ligneux grossier (MLG), qui constitue un important site de regeneration pour les especes forestieres arbustives, et sur les effets du type de carie dubois, d'apres les preferences des champignons de carie pour les composantes structurales du bois, sur la colonisation des semis. Les effets des proprietes des billes, incluant le type de carie, et des autres variables environnementales sur la densite des semis ont ete evalues avec des methodes d'ordination et des modeles lineaires generalises. Au total, les semis de 22 especes ligneuses ont ete trouves sur les billes du Pinus densiflora. Selon l'analyse par ordination, la carie blanche dans le bois de creur et la carie brune dans le bois d'aubier ainsi que l'ouverture du couvert forestier et le diametre des billes etaient significativement associes a des communautes de semis. Les facteurs retenus pour construire un modele lineaire generalise en vue d'expliquer la densite des semis des deux especes dominantes de semis, soit Cryptomeria japonica et P. densiflora, incluaient la carie brune dans lebois d'aubier et la carie blanche dans lebois de creur mais leur effet etait different: la carie brune avait un effet positif sur C. japonica et la carie blanche avait un effet negatif sur P. densiflora. Ces resultats indiquent que le type de carie du bois pourrait provoquer une differenciation des niches parmi les especes d'arbres dominantes qui se regenerent sur les MLG. [Traduit par la Redaction] Mots-cles: regeneration de la foret, bille, type de carie, colonisation des semis, champignons responsables de la carie du bois., 1. Introduction Environmental heterogeneity created by ecosystem engineers has large impacts on biotic communities and the ecosystem processes (Odling-Smee et al. 2003). Microbes of the decomposition subsystems such as fungi [...]

A particle tracking velocimetry (PTV) system has been developed to obtain instantaneous two velocity components on several sections in three-dimensional space. The flow visualization is conducted by means of parallel laser-light sheets created by a scanning laser beam and the visualized particle images are taken by a high-speed video system synchronized with the scanning. In order to obtain higher accuracy in velocity measurements than usual PTV, some improvements are made on the analyzing procedures: the extraction of particle images, the determination of their center points, the derivation of velocity components and others. The present PTV was applied to the transient flows in a cylindrical tank with a rotating disk. As a result, two-dimensional transient flow patterns with large scale disturbances are continuously captured in three-dimensional space.

A cylindrical vessel reveals internal standing waves which exhibit a near-wall behavior in the area of an adiabatic cylinder found at the middle of the vessel. A low-Reynolds-number erratic model induces the development of internal standing waves and their near-wall characteristics. The attenuation and phase movements under varying temperatures distinguish the waves. Statistical data, standard internal wave movements and flow patterns are used to accurately predict the results of the experiment. The results reflect the boundary layer attenuation effects on the temperature.

This paper describes an investigation on a numerical prediction method to estimate local scour due to the cooling-water jets discharged from power stations. The method presented simulates the unsteady convection and diffusion of the warmed jets with a two-equation turbulence model within the calculation area being deformed by the local scour. The profile of the scoured sand bed is predicted by computing the amount of both the bed load and the suspended load in parallel with the simulation of the flow itself. The prediction method was applied to three kinds of experiments: a three-dimensional warm-jet experiment above a fixed bed, and two local-scour experiments carried out under two- and three-dimensional flows. The validity of the numerical prediction method was reasonably confirmed by these comparisons of results.