Studies into Fungal Decay of Wood In Ground Contact—Part 1: The Influence of Water-Holding Capacity, Moisture Content, and Temperature of Soil Substrates on Fungal Decay of Selected Timbers

This article presents the results from two separate studies investigating the decay of wood in ground contact using adapted versions of laboratory-based terrestrial microcosm (TMC) tests according to CEN/TS 15083-2:2005. The first study (A) sought to isolate the effect of soil water-holding capacity (WHC_soil [%]) and soil moisture content (MC_soil [%WHC_soil]) on the decay of five commercially important wood species; European beech (Fagus sylvatica), English oak heartwood (Quercus robur), Norway spruce (Picea abies), Douglas-fir heartwood (Pseudotsuga menziesii), and Scots pine sapwood (Pinus sylvestris), while keeping soil temperature (T_soil) constant. Combinations of soil mixtures with WHC_soil of 30%, 60%, and 90%, and MC_soil of 30%, 70%, and 95%WHC_soil were utilized. A general trend showed higher wood decay, measured in oven-dry mass loss (ML_wood [%]), for specimens of all species incubated in soils with WHC_soil of 60% and 90% compared to 30%. Furthermore, drier soils (MC_soil of 30 and 70%WHC_soil) showed higher ML_wood compared to wetter soils (95%WHC_soil). The second study (B) built on the first’s findings, and sought to isolate the effect of T_soil and MC_soil on the decay of European beech wood, while keeping WHC_soil constant. The study used constant incubation temperature intervals (T_soil), 5–40 °C, and alternating intervals of 10/20, 10/30, and 20/30 °C. A general trend showed drier MC_soil (60%WHC_soil), and T_soil of 20–40 °C, delivered high wood decay (ML_wood > 20%). Higher MC_soil (90%WHC_soil) and T_soil of 5–10 °C, delivered low wood decay (ML_wood < 5%). Alternating T_soil generally delivered less ML_wood compared to their mean constant T_soil counterparts (15, 20, 25 °C). The results suggest that differences in wood species and inoculum potential (WHC_soil) between sites, as well as changes in MC_soil and T_soil attributed to daily and seasonal weather patterns can influence in-ground wood decay rate. View Full-Text