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

Brendan Nicholas Marais,Christian Brischke,Holger Militz,Lena Reinhardt,Johann Hinrich Peters

doi:10.3390/f11121284

Abstract

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 (WHCsoil [%]) and soil moisture content (MCsoil [%WHCsoil]) 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 (Tsoil) constant. Combinations of soil mixtures with WHCsoil of 30%, 60%, and 90%, and MCsoil of 30%, 70%, and 95%WHCsoil were utilized. A general trend showed higher wood decay, measured in oven-dry mass loss (MLwood [%]), for specimens of all species incubated in soils with WHCsoil of 60% and 90% compared to 30%. Furthermore, drier soils (MCsoil of 30 and 70%WHCsoil) showed higher MLwood compared to wetter soils (95%WHCsoil). The second study (B) built on the first’s findings, and sought to isolate the effect of Tsoil and MCsoil on the decay of European beech wood, while keeping WHCsoil constant. The study used constant incubation temperature intervals (Tsoil), 5–40 °C, and alternating intervals of 10/20, 10/30, and 20/30 °C. A general trend showed drier MCsoil (60%WHCsoil), and Tsoil of 20–40 °C, delivered high wood decay (MLwood > 20%). Higher MCsoil (90%WHCsoil) and Tsoil of 5–10 °C, delivered low wood decay (MLwood < 5%). Alternating Tsoil generally delivered less MLwood compared to their mean constant Tsoil counterparts (15, 20, 25 °C). The results suggest that differences in wood species and inoculum potential (WHCsoil) between sites, as well as changes in MCsoil and Tsoil attributed to daily and seasonal weather patterns can influence in-ground wood decay rate.

Highlights

Wood is one of the oldest raw materials used worldwide
Terrestrial microcosms (TMCs) in accordance with CEN/TS 15083-2:2005 [19] were utilized in semifield experiments
When considering mean MLwood across all soil conditions measured at the 16 week incubation interval, wood species with low durability such as beech and Scots pine sapwood [30] showed the highest mean MLwood, i.e., 18% and

Summary

Introduction

It is used in a variety of manners, both indoors and outdoors. Due to its renewable and biodegradable properties, wood is becoming increasingly important when considering more environmentally friendly and sustainable construction materials. Outdoor wooden components are subjected to a variety of biotic and abiotic degradation factors. In-ground contact, is especially prone to factors linked to accelerated degradation, due in-part to the permanent to semipermanent exposure to moisture (abiotic) and its role in the physiological requirements of wood-decaying fungi (biotic) [2]. Due in-part to ubiquity, wood decaying fungi are considered the most important biotic influencer to in-ground wood decay in the absence of termites and a water body which can host marine borers [4]

Methods

Results

Conclusion