Negative relationship between microbial biomass and root amount in topsoil of a renovated grassland

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Abstract
A part of an orchardgrass (Dactylis glomerata L.) meadow was renovated linearly (9 cm in width and 16.5 cm in depth), and reseeded or not with perennial ryegrass (Lolium perenne L.) in autumn. The two boundaries between renovated and unrenovated soils (non-volcanic alluvial soil containing volcanic ash soil) were separated by a nylon mesh screen (ϕ25 μm) or acrylic board to change the amount of grass roots in the renovated soils. In the next spring, the topsoils (0-5 cm) were analyzed to clarify the correlation among the amount of microbial biomass, the amount of roots, and the soil- or root-derived respiration rates during a 10-day period of incubation. The soil respiration rates increased in the presence of the roots. With increasing soil respiration rates, the amount of flush-N determined by the fumigation-incubation method decreased. Under the microscope, it was found that the fungal biomass, the dominant microbial biomass, was negatively correlated (significant at p = 0.05) with the soil respiration rates.