Recipient Organization
MICHIGAN TECHNOLOGICAL UNIV
1400 Townsend Drive
HOUGHTON,MI 49931
Performing Department
School of Forest Resources and Environmental Science
Non Technical Summary
Fungi, especially the basidiomycetes, cause wood decay. Fungal decay only occurs when the wood is relatively wet and warm, and does not have protective chemicals (naturally occurring extractives or wood preservatives) present. The exposure climate has a large effect on how rapidly wood decays, because climate controls wood's moisture content and temperature. In the United States, decay in wood-in-use is controlled by keeping the wood moisture content below the minimum level required for fungal growth and/or treating with a wood preservative. Accurate prediction of wood decay rate in a given climate has a large number of potential benefits, especially: 1) providing the ability to tailor wood preservative loading to a particular climate (e.g. reducing the loading for low decay rate regions), thereby reducing the total pesticide load on our environment, 2) adjusting preservative loading for regions as climate change occurs, 3) providing a quantitative basis for correlating accelerating product testing in tropical climates to typical North American temperate conditions. This project will evaluate six different test methods (weight loss, compression strength parallel to grain, dynamic MOE, static MOE, static MOR, visual rating) to determine the optimum procedure for measuring decay rate. Small pine and aspen stakes will be exposed above-ground at seven field sites with distinctly different climates (Alberta, MI; Gainesville, FL; Eatonville, WA; Hilo, HI; Silsbee, TX; Moutain View, HI; and Belle Glade, FL.). At intervals, specimens will be removed from the field sites and evaluated for decay using the methods described above.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
Overall Objective:Determine climate variables that affect the rate at which wood decays. Sub-Objectives: 1.Evaluate the 6 different methods of measuring the extent of wood decay - weight loss, compression strength parallel to grain, dynamic Modulus of Elasticity (MOE), static MOE and Modulus of Rupture (MOR), and visual ratings. 2.Using the optimized method from Sub-Objective 1, determine the deterioration rate of wood exposed above-ground in seven distinctly different climates - Alberta, MI; Gainesville, FL; Eatonville, WA; Hilo, HI; Silsbee, TX; Moutain View, HI; and Belle Glade, FL. 3.Develop a model that predicts above-ground wood decay rate based on climate variables, e.g.: annual rainfall, monthly rainfall events, annual temperature, monthly mean temperature, total monthly rainfall, and mean monthly relative humidity. Expected Outputs: 1.Scientific Publications - We expect 2-3 publications in relevant journals such as Forest Products Journal, Journal of Wood Science and Technology, or Holzforschung. 2.Technical Presentations - At least 3 presentations at technical conferences organized by associations such as the American Wood Protection Association (AWPA), International Research Group on Wood Preservations (IRG), and the Forest Products Society (FPS). Timeline: Experimentation, data collection, and analysis will continue for the entire duration of the project. Manuscript submission will begin in the fall of 2013 and continue through 2014.
Project Methods
1. Test Specimens Southern pine sapwood (Pinus spp.) was hand selected to meet the requirements of American Wood Protection Association (AWPA) standard E7-01. Aspen (Populus tremuloides) was purchased locally. Specimens were machined from the radial face of the selected wood to generate stakes (6.5 x 38 x 254 mm) for field exposure and randomly allocated into groups designated for each field exposure site. 2. Field Exposure The field stakes were exposed horizontally above-ground at the seven field sites. The exposure rack was constructed of PVC tubing. The side rails of the racks had a full-length slot that faced inward, with drainage holes drilled to face the ground. The stakes were inserted horizontally into a pair of slots and slightly separated, such that the fully assembled rack with specimens installed had the appearance of twin xylophones. The installed stakes were about 0.6 m above the ground, and exposed to direct sunlight for at least part of the day. The stakes were inspected in the field after 3, 6, 9, 12, and 18 months of exposure. During each inspection, a visual decay rating was assigned, and nine stakes of each specimen type were removed and returned to Michigan Tech for laboratory evaluation using non-destructive static bend MOE, ultimate compression strength parallel-to-grain, and weight loss. 3. Measures of Decay 1.Field visual evaluation used the AWPA E7-01 scale. 2.Bending MOE determined using a non-destructive four-point static bend procedure on the specimens after conditioning to constant weight in an environmental chamber set to 20 degree C and 65 percent RH. Test specimens will be flexed to a constant load of 10 kg at a deflection rate of 1.25 mm/min. 3.Compression parallel to grain will be measured according to ASTM D143 (ASTM 2002). The specimens will be rigidly supported in a jig to ensure compression failure. 4.Weight losses due to decay will be determined from the pre- and post-field exposure oven-dry weights of the stakes. The specimens will be dried at 105 degree C for 24 hours immediately before final weights were obtained.