Cyclic Freezing Effects on Tracheid Bordered Pits
Keywords:<i>Tsuga heterophylla</i>, sapwood, heartwood, freezing, thawing, bordered pits, pit damage, pit aspiration, microtome-cryostat
Repeated freezing and thawing of wet wood of western hemlock (Tsuga heterophylla (Raf) Sarg.) caused changes in some tracheid bordered pits ranging from partial pit aspiration to tori loose and moved out of the pit cavities. Influencing factors were: lower temperatures, position in the specimen, number of freeze cycles, water content of the wood, and manner of preparation. The most damaging effects by cyclic freezing occurred near the end-grain surface of the blocks. At 1 cm from the end, very little change occurred.
Lowering the freezing temperature and increasing the number of freeze cycles increased the number of pits affected but not in direct ratio. Pit damage near the block ends was slightly greater in green wood that was water-saturated before cyclic freezing. Storing sapwood blocks for 8 months before cycling tended to decrease the number of unaspirated pits. In fresh sapwood, 96% of the bordered pits were unaspirated; in heartwood only 7%. In green heartwood, cyclic freezing deaspirated some of the pits near the block ends. Relationships of the results to natural phenomena are discussed.
Choong, E. T., B. H. Box, and P. J. Fogg. 1970. Effects of intensive cultural management on growth and certain wood properties of young loblolly pine. Wood Fiber 2(2):105-112.nCooper, G. A., R. W. Erickson, and J. G. Haygreen. 1970. The drying behavior of prefrozen black walnut. For. Prod. J. 20(1): 30-35.nCooper, G. A., and S. H. Barham. 1972. Prefreezing effects on three hardwoods. For. Prod. J. 22(2):24-25.nErickson, H. D., and Y. H. Chen. 1973. The microtome-cryostat for cutting woody tissues. Wood Fiber 5(1):59-68.nErickson, R. W., M. M. Chen, and T. Lehtinen. 1972. The effect of unidirectional diffusion and prefreezing upon flexural creep in redwood. For. Prod. J. 22(10):56-60.nGraf, O., and K. Egner. 1940. Versuche über die Festigkeitseigenschaften verschiedener Hölzer in gefrorenem Zustand und besonders nach wiedhalten Gefrieren und Auftauen. Mitteilungen des Fachausschusses für Holzfragen beim Verein Deutscher Ingenieure und Deutschen Forstverein No. 25:18-30.nKubler, H. 1962. Schwinden und Quellen des Holzes durch Kalte. Holz Roh- Werkst. 20(9): 364-368.nLin, R. T., E. P. Lancaster, and R. L. Krahmer. 1973. Longitudinal water permeability of western hemlock. I. Steady state permeability. Wood Fiber 4(4):278-289.nThunell, B. 1940. Inverkan av upprepad frysning och upptining i vattenmättat tillstånd på furuvirkes hallfasthetsegenskaper. Medd. ProvningSanst., Stockh. No. 82:8.n
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