Factors controlling Pg content in a dark brown forest soil

Abstract

Abstract The green-colored fraction of humic acid observed in Japanese podzols was designated as Pg by Kumada in 1962. Since then, many researchers world wide have investigated the geographical distribution, chemical nature, and origin of Pg. At present, it is considered that Pg contains compounds similar to perylene quinone and that dark-colored hyphae or sclerotia are the main sources of Pg. We attempted to clarify the processes of formation and accumulation of Pg in a Japanese dark brown forest soil. In previous paper, we observed that the Pg content was closely related to the Fe content and more closely related to the length of dark-colored hyphae than to the amount of sclerotia. On the basis of these findings, the following assumptions were made: (i) Pg was mainly derived from dark-colored fungal hyphae. (ii) Pg accumulated in the soil through stabilization by ferric iron. Two laboratory experiments were conducted to verify the above-mentioned assumptions.