Copper containing wood preservatives shifted bacterial and fungal community compositions in pine sapwood in two field sites

Copper-based preservatives are used for wood protection, which leads to an enrichment of copper tolerant microbial communities in respective soil environments. In this study impregnated pine wood specimens (2 × 2 × 36 cm) were half buried in two field sites with (North Germany, NG) and without (Central Germany, CG) a long preservative history and incubated for 17 and 36 weeks. Pine sapwood specimens were impregnated with either CuTriQAC (containing copper, triazoles and quaternary ammonium compounds), Cu (containing only copper) or water (H2O) as control. The effect of preservative treatment at the wood-soil interface, 1 mm and 7 mm into wood was assessed by quantitative PCR and amplicon sequencing of the fungal ITS region and bacterial 16S rRNA gene of both field sites over time. Fungal and bacterial copy numbers decreased in 1 mm and only fungal in 7 mm into CuTriQAC treated wood in both sites but not in Cu treated wood. Both Cu and CuTriQAC treated wood shifted the richness, evenness of the bacterial and, to a lesser extent, the fungal community composition inside wood. In conclusion, Cu and CuTriQAC treated wood caused a selection towards microfungal ascomycetes and defined bacterial genera, which majority of genera were previously described as diazotrophs. •Quaternary ammonium compounds/triazoles supported Cu to reduce fungal copy numbers.•Bacterial but not fungal community composition shifted in pine wood specimen.•Copper-containing wood preservatives reduced fungal and bacterial richness.•Microfungal ascomycetes were abundant in Cu and CuTriQAC treated wood.•Bacteria in Cu and CuTriQAC treated wood were previously described as diazotrophs.