Spatial Distribution of Sclerotia Grains in Low-pH Forest Soils, Central Germany

Abstract

The relationship between the distribution of fungal sclerotia grains and soil chemical properties was studied in forest soils in the Harz Mountains, Germany. In addition, the micro-topographical distribution of sclerotia grains was examined in a single forest stand. Sclerotia grains were predominantly found in surface horizons (Ah, E horizons) within 10 cm of the soil surface, and the density of grains ranged from 0.01 to 4.99 g kg−1 soil. The content of ergosterol, a biomarker of viable fungal biomass, was correlated with sclerotia grain density in soils. Sclerotia grain density was higher in soils with high ratios (>0.6) of organic bonding aluminum to amorphous aluminum, and with high contents of exchangeable aluminum (Al3+) (>0.54 g kg−1). The content and state of active aluminum appeared to be the factor responsible for the development of sclerotia, because sclerotia grains were not detected in acid soils with a low content of free colloidal aluminum. The intensive clay destruction associated with past lessivage, or clay particle leaching, may have depleted the free colloid aluminum in these forest soils. Although there was no clear relationship between sclerotia distribution and microtopography, field examination of sclerotia grains in soil showed that the presence of sclerotia grains is an indicator of soil chemical properties such as acidity and the degree of soil humification.