Chemical and mineral composition of ectomycorrhizosphere soils of subalpine fir (Abies lasiocarpa (Hook.) Nutt.) in the Ae horizon of a Luvisol

Differences in the properties of bulk forest and rhizosphere soils are ofte n attributed to ectomycorrhizal association, or the symbiosis characterized by a fungal sheath surrounding the root (mantle) and intercellular root co lonization (Hartig net). We compared the soil pH, total C, N, cation exchan ge capacity, and the contents of mica, chlorite, kaolinite, 2:1 expandable clays, feldspars and amorphous materials between two ectomycorrhizosphere s oils (or soil environment in the vicinity of ectomycorrhizae (ECM)) and non -ectomycorrhizosphere soils to study the influence of ectomycorrhizae on ch emical and mineralogical properties of soils. The two ectomycorrhizosphere soils were characterized by ectomycorrhizal colonizition dominated by (1) P iloderma spp., and (2) Mycelium radicis atrovirens and cottony yellow-brown (MRA-CYB) types or where Piloderma spp. colonization was <2%. Our results showed that total C and N were higher in ectomycorrhizosphere than non-ecto mycorrhizosphere soils, and the ectomycorrhizosphere soils dominated by Pil oderma spp. had almost twice the total C and N as ectomycorrhizosphere soil s with MRA-CYB. Soil pH was lower by half a pH unit in ectomycorrhizosphere soils compared to non-ectomycorrhizosphere soils. Cation exchange capacity as well as exchangeable Ca2+, Mg2+ and K+ were lower in non-ectomycorrhizo sphere soil compared to ectomycorrhizosphere soils. We also found that cati on exchange capacity, exchangeable Ca2+, Mg2+ and K+ values in soils domina ted by Piloderma spp. were higher compared to ectomycorrhizosphere soils wi th insignificant Piloderma spp. Our results suggest that transformation rat e of mica and chlorite to 2:1 expandable clays was predominant in ectomycor rhizosphere compared to non-ectomycorrhizosphere soils, likely as a result of high production of organic acids and direct extraction of K+ and Mg2+ by fungal hyphae. In ectomycorrhizoplane samples, it is suggested that K+ and possibly amorphous Al2O3 and Fe2O3 could reconstitute the degraded mica an d chlorite through the formation of hydroxy-interlayered 2:1 clays.