Ectomycorrhizal weathering of the soil minerals muscovite and hornblende

Abstract

Summary• Ectomycorrhizal fungi are hypothesized to enhance mineral weathering in forest soils. Several studies have shown an increased uptake of mineral-derived nutrients by trees when in symbiosis with ectomycorrhizal fungi. However, it is difficult to determine from these studies if the improved nutrient uptake is the result of increased weathering or better exploitation of the substrate by the ectomycorrhizal fungi.• In a pot experiment, Pinus sylvestris (Scots pine) seedlings were grown with or without ectomycorrhizal fungi, and with or without the mineral muscovite as the only potassium (K) source or the mineral hornblende as the only magnesium (Mg) source. After 27 wk, all pools of non-mineral-bound K or Mg were determined.• The ectomycorrhizal fungus Paxillus involutus increased weathering of muscovite but not hornblende. The other ectomycorrhizal fungi tested, Piloderma croceum and Suillus bovinus , did not increase weathering of either muscovite or hornblende compared with the nonmycorrhizal trees. The P. involutus -mediated mobilization of K from muscovite resulted in increased K content of root plus adhering hyphae, but not of shoots.• In conclusion, ectomycorrhizal fungi may increase weathering of minerals in response to nutrient deficiencies, but this response is species specific.

Rock-eating mycorrhizas: their role in plant nutrition and biogeochemical cycles

“…4). The species enhanced exudation of oxalate compared to nonmycorrhizal seedlings (Van Schöll et al 2006a), released K and Mg (Arocena et al 2004;Glowa et al 2003), but did not show enhanced weathering of muscovite and hornblende in the study by Van Schöll et al (2006b). The species was abundant in various horizons in the Swedish podzol (Rosling et al 2003;Landeweert et al 2003a).…”

“…Both S. variegatus (Ahonen et al 2000;Wallander 2000) and the related S. collinitus produced large amounts of oxalic acid in soils with low pH and Al toxicity, and in soils with high pH and possibly associated P deficiency. However, S. bovinus did not enhance weathering of muscovite and hornblende in the study by Van Schöll et al (2006b). Rhizopogon roseolus also produced large amounts of oxalic acid under a range of pH conditions (Ahonen et al 2000;Arvieu et al 2003;Casarin et al 2003).…”

“…The combined effect of EcM fungi on growth and nutrient uptake by the seedlings and on mineral weathering complicates interpretation of such studies. This problem can be overcome by making a complete mineral budget, with all pools of mobile elements quantified, an approach adopted lately in studies by Van Hees et al (2006a) and by Van Schöll et al (2006b). EcM colonisation by Hebeloma longicaudum increased the mineral weathering of soil from a podzol E horizon compared to non-mycorrhizal seedlings, as measured from the fluxes of Al, Si and K (Van Hees et al 2006a).…”

“…EcM colonisation by Hebeloma longicaudum increased the mineral weathering of soil from a podzol E horizon compared to non-mycorrhizal seedlings, as measured from the fluxes of Al, Si and K (Van Hees et al 2006a). Van Schöll et al (2006b) determined the effect of EcM fungi on K and Mg availability through mineral weathering. Non-mycorrhizal and EcM tree seedlings were grown in pots with muscovite as the only K source or hornblende as the only Mg source.…”

“…Paxillus involutus produced several organic acids (Van Hees et al 2003;Yamaji et al 2005;Van Schöll et al 2006a), enhanced the weathering of muscovite (Van Schöll et al 2006b) and hyphae actively foraged for Mg (Van Schöll 2006). Some strains of this species (complex) showed high tolerance towards Al (Rudawska and Leski 1998) and one of two strains tested by could transport Al (Table 1).…”