Analysis on Formation Factor of Sclerotia of Cenococcum geophilum in Picea abies Forest, Harz Mts., Germany

Abstract

Cenococcum geophilum Fr. is one of the most frequently encountered mycorrhizal fungi in nature. It reveals tolerance to low pH and forms abundant number of sclerotia. In this study, distribution of sclerotia of C. geophilum was investigated in a single stand forest of Picea abies, Harz mountains, Germany to analyze their forming factors. Surface soil samples were collected to examine density of sclerotia based on weight and count of grains, soil pH(H₂O, KCl), content of exchangeable aluminum, total carbon and nitrogen, and humification degree based on melanic index and Pg index. Elemental composition of sclerotia was examined by SEM-EDS analysis. ¹⁴C age of sclerotia was determined by AMS measurement. The averages of sclerotia density by weight and counts throughout all points were 0.54 mg g⁻¹ and 1.3 count g⁻¹, respectively. The distributional correspondence of sclerotia to micro-topography was not clear and demonstrated the formation of sclerotia as a nearly constant phenomenon in the investigated forest soil. However, a large amount of sclerotia tended to distribute in soils with scarce floor vegetation. Content of exchangeable aluminum in soil was an effective factor on accelerating formation of large sclerotia and Al and Fe content in sclerotia were likely to increase in lower pH soils. The existence of sclerotia in forest soil may stand as an indicator of soil chemical properties such as strong acidity and high Al³⁺ content.