Chemical-mechanical damage caused by the brown-rot fungus Gloeophyllum trabeum (Pers.) Murrill on Pinus pseudostrobus Lindl. wood

Introduction: Wood is susceptible to be used as a carbon source by various fungal species damaging the wood, by exposing the wood to different environmental conditions. Its durability has been categorized according to its weight loss, without considering the decrease of the physicochemical and mechanical properties inherent to the weight loss. Objective: To evaluate how the weight loss in Pinus pseudostrobus Lindl. wood exposed to brown-rot fungi Gloeophyllum trabeum (Pers.) Murrill affects the physicochemical and mechanical properties. Materials and methods: Sawn timber pieces of P. pseudostrobus were inoculated with G. trabeum. Periodically (zero, three, six and nine months) and with the help of a universal testing machine, parallel compression (PC), static bending (SB) and perpendicular compression to the grain (CPG) were evaluated, and holocellulose, cellulose and lignin were quantified. Results and discussion: After nine months of interaction with G. trabeum, the pieces of wood were resistant to degradation, considering only weight loss. However, the chemical-mechanical properties evaluated showed that the fungus made a thinning and breakdown of the tissue cells in the wood that induced a significant decrease in the values of SB (100 to 56 N∙mm -2 ) and CPG (42.2 to 20.2 N∙mm -2 ), which reduced its resistance to mechanical stress. Such damage is not reflected in the material’s aesthetic, which is alarming, since the common user of the pinewood could not notice the problem. Conclusions: The wood that has been exposed to fungal degradation is significantly compromised in its mechanical properties, disabling it for construction, because the chemical properties show us that the fungus causes low resistance to mechanical stress by diminishing SB and CPG.