Iron and calcium translocation from pure gypsum and iron-amended gypsum by two brown rot fungi and a white rot fungus

Abstract

Abstract Wood-degrading fungi commonly grow in contact with calcium (Ca)-containing building materials and may import Ca and iron (Fe) from soil into forest woody debris. For brown rot fungi, imported Ca2+ may neutralize oxalate, while Fe3+ may facilitate Fenton-based degradation mechanisms. We previously demonstrated, in two independent trials, that degradation of spruce by wood-degrading fungi was not promoted when Ca or Fe were imported from gypsum or metallic Fe, respectively. Here, we tested pine wood with lower endogenous Ca than the spruce blocks used in prior experiments, and included a pure gypsum treatment and one amended with 1% with FeSO4. Electron microscopy with microanalysis verified that brown rot fungi Serpula himantioides and Gloeophyllum trabeum and the white rot fungus Irpex lacteus grew on gypsum and produced iron-free Ca-oxalate crystals away from the gypsum surface. Wood cation analysis verified significant Fe import by both brown rot isolates in Fe-containing treatments. Wood degradation was highest in Fe-gypsum-containing treatments for all three fungi, although only wood degraded by I. lacteus had significant Ca import. We suggest that Fe impurities may not exacerbate brown rot, and that both brown and white rot fungi may utilize Ca-containing materials.