Effect of straw addition on composition and activity of soil microbial biomass

Synopsis The size and activity of the fungal component of the straw-decomposing soil microbial biomass was investigated for three sites in eastern Scotland. The fungi were found (by means of selective substrate-amended respiration, FDA-active hyphal lengths, and cellulolytic plate count) increasingly to dominate the soil microbial biomass with repeated enrichment disturbance from straw incorporation. Development of a biomass with a greater fungal component was also associated with an increased biomass C:N ratio response to straw inputs and more rapid decomposition of 14C-labelled straw, suggesting that continued straw incorporation can cause a “substrate-adapted” microbial biomass to develop which is able to decompose straw increasingly rapidly.