Within-stem water distribution in living trees of some conifers.

摘要

Water distributions within living stems of 11 species from three conifer families were observed with soft X-ray photography. The 11 species grown at Mito, Ibaraki Prefecture, Japan, include: Cupressus lusitanica, Chamaecyparis obtusa 'Naka 11', C. obtusa 'Naka 9', Taxodium distichum var. nutans, Metasequoia glyptostroboides, Cunninghamia lanceolata, Pinus strobus, Pseudotsuga menziesii, Picea abies, P. sitchensis and Abies firma. The moisture contents at breast height of the trees were also measured. The sapwood of all the species, except one, was almost saturated with free water. Intermediate wood, which was a narrow white band between the sapwood and heartwood, was generally common in species with coloured heartwood. In heartwood, water distribution varied not only among species, but also within species, and even within a stem. In seven of the 11 species investigated, well-developed wetwood (the phenomenon of free water accumulated in heartwood) was observed. The frequent presence of wetwood led to the conclusion that it was a common feature in some groups of conifers. It is suggested that the view that wetwood is an abnormal feature may be incorrect because so far wetwood surveys have only focused on a few species that are important for forestry, e.g. hard pines. An extensive survey of many specimens belonging to various species is required to understand the mechanism of wetwood development..