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  • Author: T. Ericsson x
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Summary

Wood fibre length of Scots pine (Pinus sylvestris L.) was measured in wood sticks and 5-mm increment cores. The aim was to evaluate whether fibre length estimates from such small-diameter cores could be used to calculate genetic parameters, in spite of the increased amount of cut fibres produced at boring. The correlation between mean fibre lengths obtained from cores and sticks, with substantially fewer cut fibres, was high (r = 0.87, n = 53) and of the same magnitude as the correlation between samples from varied positions in the same tree (r = 0.87, n = 46). As regards evaluation of genetic tests and ranking for selection purposes, values from non-destructively sampled 5-mm cores from 0.5 m tree height appear to serve well. Fibre length development along annual ring classes started to differentiate between trees at annual rings 13–15, and after ring 16 there was a slight tendency towards stabilisation which may be interpreted as a reasonably advanced transition from juvenile wood to mature wood.

Abstract

X-ray diffraction (XRD), Mössbauer spectroscopy (MS), and magnetization (SQUID) data are reported for a “pyrrhotite-like” compound (δ-FeSe), belonging to the central portion of the Fe-Se system.

The δ-phase(s) extends compositionally over a range of around Fe0.94Se-Fe0.86Se at 870 K, but narrows around Fe7Se8 at room temperature. Lattice parameters for the primitive hexagonal cell decrease regularly with increasing vacancy concentration x in Fe1 − xSe; c = 5.97 – 5.87 Å, a = 3.65 – 3.62 Å. An observed regular decrease in cell axes ratio, c/a = 1.644 – 0.145 x, is described as due to increased ordering with increased vacancy concentration. The disordered high-temperature 1c structure is maintained at room temperature for vacancy-poor compositions, while superstructures, 3c and 4c, form for vacancy-rich compositions. Using a bond model for the magnetic coupling, MS spectra for ordered 3c and 4c superstructures can be well fitted assuming three well-defined surroundings, while those for disordered 1c show a distribution in surroundings. A spin direction change, from the c-plane towards the c-axis with decrease in temperature, is sharp at 130 K for 3c, extended and incomplete for 4c (∼220 – 120 K), and again rather sharp for 1c at ∼ 220 K. It is suggested that the spin flip at 130 K for 3c, which is also visible (but weak) in SQUID measurements of 1c samples, is indicative of an element of short range order in the disordered structure.

Summary

We propose a method to estimate fibre length distribution in conifers based on wood samples from increment cores processed by automatic optical fibre-analysers. Automatic fibre-analysers are unable to distinguish: a) fibres from other tissues, “fines”, and b) cut from uncut fibres. However, our proposed method can handle these problems if the type of distributions that fibre lengths and fines follow is known. In our study the length distributions of fines and fibres were assumed to follow truncated normal distributions, characterised by means and standard deviations of the two distributions. Parameter estimates were obtained by the maximum likelihood method. Wood samples from two 22-year-old Scots pine trees at breast height were used to evaluate the performance of the method. From stem discs at 1.5 m, adjacent samples of 5 mm increment cores and wood pieces were taken. The cores were trimmed 1 mm at each side and samples were, after maceration, analysed in a Kajaani FiberLab 3.0. The results showed that the method works well and gives a possibility to distinguish fine and fibre length distribution.