Publication reports on development of methods for monitoring moisture content of wood stored in wet decks

Many forest products companies in the southeastern US store tree-length logs in stacks over which water is continuously sprayed. The continuous application of water keeps the wood saturated, thereby providing the conditions necessary to prevent fungal degradation. These storage facilities are sometimes referred to as “wet decks.”

Although the continuous application of water helps maintain wood quality, forest products companies remain interested in developing and testing methods to improve the efficiency of water use in wet decks. An essential step in these efforts is to develop reliable methods for monitoring moisture content of stored logs above the saturation point.

For several years, NCASI has been cooperating with investigators at the University of Georgia to test the use of time-domain reflectometry (TDR) for measuring the moisture content of wet-stored wood. TDR has traditionally been used to detect faults in cables, and has also been used to measure soil moisture content. Recently, the investigators published a paper titled, “Time-domain reflectometry for the prediction of loblolly pine and sweetgum moisture content.” The paper appeared in the journal BioResources and was authored by Joseph Dahlen, Finto Antony, Anzhi Li, and Kim Love-Myers of the University of Georgia, Laurence Schimleck of Oregon State University, and Erik B. Schilling of NCASI. 

The authors conclude that TDR, in combination with custom-built probes, is effective for measuring log moisture content in wet decks. The authors also provide suggestions for developing accurate calibrations, and present calibration models for loblolly pine and sweet gum, two tree species important in the South.

The abstract for the paper follows.

“Time-domain reflectometry (TDR) can be used to predict the moisture content in porous materials, including soil, and is an exciting tool that could be used to measure the moisture content in wet-stored wood. Three-rod probes with 127 mm- or 152 mm-long rods were inserted into 62 loblolly pine and 34 sweetgum saturated bolts. The bolts were air dried over a span of five weeks. TDR waveforms and moisture content were periodically recorded. In total, 534 and 482 readings were taken for the loblolly pine and sweetgum bolts, respectively. An algorithm in R was written to automatically analyze the apparent length of the TDR rods. Calibration models were developed between moisture content and X (apparent length / actual rod length). A three-parameter logistic model was developed for loblolly pine (R2=0.64) and sweetgum (R2=0.84). The process was repeated using shorter bolts and 152 mm-long rods, resulting in improved models for loblolly pine (R2=0.99) and sweetgum (R2=0.97). Overall, TDR and the algorithm written to analyze the waveforms were accurate in predicting moisture content and could be used to monitor moisture in wet-decks.”

Reference 

Dahlen, J., F. Antony, A. Li, A., K. Love-Myers, L. Schimleck, and E.B. Schilling. 2015. Time-domain reflectometry for the prediction of loblolly pine and sweetgum moisture content. BioResources 10(3):4947-4960. http://ojs.cnr.ncsu.edu/index.php/BioRes/
article/view/BioRes_10_3_4947_Dahlen_Reflectometry_Prediction_Loblolly_Pine_Sweetgum