Soil amendment with biochar and manure alters wood stake decomposition and fungal community composition

Biochar and manure can be used for sustainable land management. However, little is known about how soil amendments might affect surface- and below-ground microbial processes and subsequent wood decomposition. In a split-split-split plot design, we amended soil with two rates of manure (whole plot; 0 and 9 Mg ha-1) and biochar (split-plot; 0 and 10 Mg ha-1). Wood stakes of three species (hybrid poplar, triploid Populus tomentosa Carr.; aspen, Populus tremuloides Michx.; and pine, Pinus taeda L.) were placed in two positions (horizontally on the soil surface, and inserted vertically in the mineral soil), which served as a substrate for fungal growth. In 3 years, the decomposition rate (mass loss), moisture content, and fungal community (via high-throughput sequencing methods) of stakes were evaluated. Results indicated that biochar and/or manure increased the wood stake decomposition rates, moisture content, and operational taxonomic unit (OTU) abundance. However, the richness and diversity of fungi were dependent on wood stake position (surface > mineral), species (pine > the two Populus), and sample dates. This study highlights that soil amendment with biochar and/or manure can alter the fungal community, which in turn can enhance an important soil process (i.e., decomposition).