###### Abstract  
The degradation states of archaeological white elm, with an age estimation of \(\sim\)350 years, and poplar, with an age approximation of \(\sim\)1000-1200 years, were studied by means of different chemical and microscopy analyses. Recently cut samples from the respective species were used for comparison reasons. The chemical composition analysis of the archaeological samples showed significantly low holocellulose values, while the lignin, extractive, and ash contents were considerably high, as compared with the recently cut samples. The Fourier-transform infrared (FTIR) spectroscopy also confirmed the changes in the chemical structure of the archaeological elm and poplar samples. The light and scanning electron microscopies illustrated that the erosion bacteria were the main degrading agent in both archaeological elm and poplar, although the hyphae of rot fungi were detected inside the vessel elements of the archaeological poplar sample. archaeological wood; biological degradation; FTIR; light microscopy; SEM +
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application conditions that are mostly degraded by different types of organisms, such as fungi, insects, bacteria, marine organisms, or weathering factors. Among others, the degradation of archaeological wood by fungi and bacteria is the most common [1]. The main wood decomposing fungi are white-rot, brown-rot, and soft-rot. White-rot fungi can simultaneously degrade all polymers in wood, or they can selectively degrade the lignin in wood. Simultaneous degradation of wood is the most common degradation type, and different fungal enzymes are involved to erode the wood cell walls from the lumen to the middle lamella [8], and they often cause bleaching of normal wood coloration [9]. The selective lignin degradation is performed by fungal enzymes to remove lignin and non-cellulosic polysaccharides without extensive degradation of cellulose [10]. This process is particularly useful for bio-pulping, biodegradation of recalcitrant materials, and other applications [11]. Brown-rot fungi degrade wood by the depolymerization of cellulose and hemicelluloses [12] and modification of the lignin structure mainly through demethylation and demethylation [13; 14]. The mechanisms of brown-rot degradation have been extensively studied during the last decades, and it is commonly accepted that in the initial degradation stage enzymes cannot penetrate the micro-pores of the cell wall because of their large hydrodynamic volumes [15; 16]. It is thus assumed that the incipient attack on crystalline cellulose is caused by hydroxyl radicals produced via the Fenton reaction [17; 18; 19]. Considerable losses in wood strength occur very early in the decay process and cubical cracks are the typical macroscopic pattern of brown-rot degraded wood [19]. Although brown-rot fungi commonly decay ancient and historic buildings [20], their activity becomes highly restricted in some terrestrial and aquatic environments, i.e., little oxygen exists in wood that is excessively wet or saturated with water or buried deep in sediments [19]. In contrast, soft-rot fungi are particularly active in soil, moist conditions, and under high preservative loading. Soft-rot degrades the wood structure either by forming diamond-shaped cavities aligned with the cellulose microfibril angle within the S2 cell wall layer or by more generalized degradation of the entire S2 cell wall layer from the lumen outward [21]. The middle lamella is not degraded by soft-rot but may be modified in advanced stages of decay. As decay progresses, extensive carbohydrate loss occurs, which results in large strength loss, and lignin concentrations increase in the residual wood [9]. They can be often found with wood-degrading bacteria. However, they can be differentiated by the remnants of degradation. Soft-rot fungi leave remnants of hyphae in the degradants, while bacteria usually cause granular structure debris [22; 23; 24].