Water-Filled Lumens In Steady-State Flow In Oak and Poplar

C. Arthur Hart


In white oak (Quercus alba, L.) and yellow poplar (Liriodendron tulipifera, L.), steady-state moisture profiles between either 100% or 97% relative humidity and 71% relative humidity were determined by slicing samples perpendicular to the direction of moisture diffusion. Both the shape of the moisture profiles and the magnitude of the moisture contents (exceeding 40% in some oak samples) indicated the presence of water-saturated lumens in both species. Most of these saturated lumens occurred above 20% MC, but in the oak some of them evidently persisted to moisture contents well below 20%. This resulted in a moisture-content gradient that was steeper than the actual hygroscopic gradient for the oak and thus can lead to misinterpretations in comparing oak diffusion coefficients with poplar values. The presence of collapse was indicated by the presence of excessive shrinkage in some specimens of both species, particularly in one group of oak samples. This strongly supports the Tiemann theory of capillary tension collapse.

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