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Research article2018Peer reviewed

Effect of thermal modification on the durability and decay patterns of hardwoods and softwoods exposed to soft rot fungi

Gao, Jie; Kim, Jong Sik; Terziev, Nasko; Cuccui, Ignazia; Daniel, Geoffrey

Abstract

The durability and decay patterns of thereto-vacuum (Terrnowoto process for 3-4 h at 160-220 degrees C) treated hardwoods (ash, beech) and softwoods (spruce, fir) TMWs exposed to three soft rot fungi (Chaetorniwn globoswn, Phialophom malorum, P. mutabilis) were investigated using the soil-block test, light- and electron microscopy. Monitoring of mass loss over 1 year indicated that soft rot fungi do not attack softwood TMWs as rapidly or as extensively as hardwood TMWs. Decay resistance progressively increased in hardwood TMWs with increase in temperature but was unclear/or varied in softwood TMWs depending on fungal/wood species, particularly at lower temperatures (160-180 degrees C). Soft- and hardwood TMWs showed a major increase in decay resistance at 200-220 degrees C and 210-220 degrees C, respectively. Light microscopy of decayed hardwood TMWs showed formation of typical soft rot Type-I cavities in fibres at lower temperatures (190-200 degrees C). However, cavities were significantly inhibited or delayed at higher temperatures (210-220 degrees C). Cavity formation in vessels and parenchyma cells were only observed in beech TMW treated at 190 degrees C or references, indicating higher resistance than fibres. Transmission electron microscopy of decayed ash TMW treated at 200 degrees C showed a radial-like distribution of electron dense materials in cavities and lack of fibrillar-like materials within degraded fibre walls, which differed from reference.

Keywords

Fungal resistance; Thermal modification (TM); Thermally modified wood (TMW); Soft rot decay; Soft rot cavities; Soil-block test

Published in

International Biodeterioration and Biodegradation
2018, Volume: 127, pages: 35-45

      SLU Authors

    • Gao, Jie

      • Department of Forest Products, Swedish University of Agricultural Sciences

      • Kim, Jongsik

        • Department of Forest Products, Swedish University of Agricultural Sciences

        • Terziev, Nasko

          • Department of Forest Products, Swedish University of Agricultural Sciences

          • Daniel, Geoffrey

            • Department of Forest Products, Swedish University of Agricultural Sciences

          UKÄ Subject classification

          Wood Science

          Publication identifier

          DOI: https://doi.org/10.1016/j.ibiod.2017.11.009

          Permanent link to this page (URI)

          https://res.slu.se/id/publ/94583