Aspiration of bordered pits in Cryptomeria japonica (L. f.) D. Don was studied in relation to the air permeability in sapwood, transition zone wood, and heartwood. The percentage of aspirated pits relative to the total number of bordered pits with observable tori was determined in samples that were epoxy-embedded and thin sectioned. Air permeability of air-dried and freeze-dried wood samples was measured following the method described by Siau (1984). Pit membrane structure of air-dried and freeze-dried samples was investigated by scanning electron microscopy on split radial surfaces. It is proposed that pit aspiration progresses during heartwood formation as already reported, but the pit aspiration was frequently incomplete and the percentage varied between individuals. The pit aspiration percentage was not obviously related to the sample's initial green moisture content or heartwood color. The results from permeability measurement and SEM observation on air- and freeze-dried samples suggest that pit aspiration occurred in sapwood samples (the initial moisture content of which ranged from 200 to 300%) during air-drying and caused a significant decrease in permeability confirming the pit aspiration mechanism proposed by Hart and Thomas (1967). In the heartwood, encrustation of pit membranes prevented aspiration during air-drying.

Vessels in some species are connected by intervessel pits on the tangential walls of radial multiples, which may allow the radial flow of sap. This network was investigated in Machilus thunbergii Sieb. et Zucc., a diffuse-porous wood with radial multiples extending through growth ring boundaries. Air permeability measurements suggest radial flow paths exist through a growth ring boundary. Flow paths were pressurestained with reduced basic fuchsin solution. Observations of serial cross sections confirmed the flow paths to be via vessels and intervessel pits in radial multiples of vessels on growth ring boundaries. Resin casts of low-density polyethylene, viewed by scanning electron microscopy, showed the vessel network extending through a growth ring boundary as well as the branching of vessels.

To understand the changes in radiocesium (Cs) concentrations in stem woods after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, we investigated Cs concentrations in the bark, sapwood, heartwood, and whole wood of four major tree species at multiple sites with different levels of radiocesium deposition from the FDNPP accident since 2011 (since 2012 at some sites): Japanese cedar at four sites, hinoki cypress and Japanese konara oak at two sites, and Japanese red pine at one site. Our previous report onCs concentrations in bark and whole wood samples collected from 2011 to 2015 suggested that temporal variations were different among sites even within the same species. In the present study, we provided data on bark and whole wood samples in 2016 and separately measured Cs concentrations in sapwood and heartwood samples from 2011 to 2016; we further discussed temporal trends inCs concentrations in each part of tree stems, particularly those in Cs distributions between sapwood and heartwood, in relation to their species and site dependencies. Temporal trends in bark and whole wood samples collected from 2011 to 2016 were consistent with those reported in samples collected from 2011 to 2015. Temporal variations inCs concentrations in barks showed either a decreasing trend or no clear trend, implying that Cs deposition in barks is inhomogeneous and that decontamination is relatively slow in some cases. Temporal trends inCs concentrations in sapwood, heartwood, and whole wood were different among species and also among sites within the same species. Relatively common trends within the same species, which were increasing, were observed in cedar heartwood, and in oak sapwood and whole wood. On the other hand, the ratio of Cs concentration in heartwood to that in sapwood (fresh weight basis) was commonly increased to more than 2 in cedar, although distinct temporal trends were not found in the other species, for which the ratio was around 1 in cypress and pine and below 0.5 in oak, suggesting thatCs transfer from sapwood to heartwood shows species dependency. Consequently, the species dependency of Cs transfer within the tree appears easily, while that from the environment to the trees can be masked by various factors. Thus, prediction ofCs concentrations in stem wood should be carried out carefully as it still requires investigations at multiple sites with a larger sample size and an understanding of the species-specific Cs transfer mechanism.

Summary Changes in the moisture content of green sitka spruce (Picea sitchensis Carr.) during heating in environments of over 100°C and 1 atm were measured. Temperature and weight were measured in a highly accelerated stress test (HAST) chamber. The set temperature and relative humidity ranges were 107–160°C and 75–99%, respectively. The change in the temperature of a specimen was roughly divided into 4 steps. Equilibrium moisture contents at lower temperatures and pressures were similar to previous estimates, while at higher temperatures and pressures they were higher than previous results. A diagram of temperature–relative humidity–pressure–equilibrium moisture content in the range of 105–160°C, 75–99% RH and 0.02–0.39 MPa was obtained experimentally.

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