# Influence of Soil Characteristics on Wood Biodeterioration by Brown Rot Fungi
## 1 Introduction  
Soil-based ecosystems are composed of a range of solid, liquid and gaseous phases. The balance between these physicochemical properties is one of the most important factors for the structure and distribution of microbial communities in soils. In soil formation, microbial diversity and its interaction are directly related to the recycling of nutrients, organic matter decomposition rates, biological population regulations and the degradation of toxic compounds [1]. Depending on the type of soil its biological diversity maybe composed of up to 8800 different genome species [2]. In comparison to other soil organisms, bacteria and fungi are by far the most important microbiota and their particular interactions form symbiotic networks in form of microhabitats and mycsophenes [3]. Moreover, root traits also influence soil C cycling through influencing the growth of fungi over bacteria, such as high lignin and low root N content, promote soil C sequestration [4; 5]. Human activities such as intensive agriculture and industrial residues/contaminants also have an important influence on soil compositions and thus its ecological biodiversity [6]. Soil characteristics tend to react slowly to drastic changes in land use and management [7]; therefore, the development of microbial-soil ecosystems is directly related to coevolution and its adaptation to the environmental changes and external influences [2; 8; 9; 10]. Traditionally, wood has been one of the most used construction materials due to its abundancy, strength-to-weight ratio, production costs and environmental benefits. However, as wood is biodegradable it has a limited service life and requires additional protection for ground contact applications [11; 12; 13]. It is a mandatory requirement to impregnate wood products in ground contact for protection against microorganisms [12; 13]. In 2013, the European Union put new biocide regulations in place, which significantly increase the safety and simplicity requirements of biocides used and placed on the EU market. In recent years, the wood protection industry has started to use Cr- and boron-free wood products and to develop more environmentally friendly wood modification methods [14; 15; 16; 17]. In this context, the exposure of chemically-treated wood e.g., utility poles to soil microorganisms has resulted in the development of several heavy metal tolerance mechanisms. It is believed that complex interactions between the biotic and abiotic environment occur during the degradation of Cu-impregnated wood. However, to date, the exact mechanisms are not fully understood. A number of different mechanisms for metal detoxification by wood decay fungi during colonisation of preservative treated wood have been postulated; (i) the oxidative attack by hydroxyl radicals produced via the fungal Fenton reaction, which results in the fragmentation of cellulose and hemicellulose as well as the oxidative modification of lignin [18; 19; 20]. (ii) The metabolic system of glucose via glycolysis results in the production of oxalate as an end product which is released into the substrate and subsequently changes the pH and also reacts with metal ions to form oxalate complexes [21; 22; 23]. (iii) Melanisation of the outer cortex layers of fungal structures (hyphae, spores) which results in the immobilisation of metal ions from their surface and plays a key role in the longevity and defence against potential antagonists [24; 25]. The combination of such bioprocesses changes the physical, chemical and structural properties of wood [26] allowing hyphae to colonize and degrade the wood more efficiently [27; 28] subsequently altering wood strength and pH [29]. In natural environments, the complexity of the interactions between soil characteristics and metal ions [30], leaching from wood preservatives [17] and adaptation of fungal communities have to be considered [8; 9]. The objective of this study was to assess the influence of soil pH, humic acid and iron on wood decay.