Ectomycorrhizal fungal succession in jack pine stands following wildfire

Abstract

SUMMARYA study was conducted to determine if ectomycorrhizal fungi in an age sequence of jack pine (Pinus banksiana Lamb.) stands which had regenerated following wildfire disturbance followed a successional pattern. Ectomycorrhizal development and number of symbionts were assessed in the forest floor and 0‐20 cm deep mineral soil in 6, 41, 65 and 122‐yr‐old stands by conducting a macrofungal fruit body survey and examining pine root tips microscopically for mycorrhizal status and types of fungi forming the symbiosis. The majority of roots were located in the mineral soil with no substantial invasion of the forest floor except in the 122‐yr‐old stand. Over 90 % of the jack pine root tips were mycorrhizal and the majority of fruit bodies were produced by ectomycorrhizal species, regardless of stand age. There was no decrease in ectomycorrhizal colonization of roots with stand age. Both fruit body and root assessments revealed a distinct sequence of mycorrhizal fungi with stand age consisting of early‐stage fungi [Coltricia perennis (L:Fr.) Murr., Thelephora spp., E‐strain]; multi‐stage fungi [Suillus brevipes (Pk.) Kuntze, Inocybe spp., Cenococcum geophilum Fr., Mycelium radicis atrovirens Melin] and late‐stage fungi [Cortinarius spp., Lactarius spp., Russula spp., Tricholoma spp., Hygrophorus spp., Hydnellum peckii Banker, Suillus tomentosus (Kauff.) Sing., Snell & Dick, Piloderma byssinum (Karst.) Jül. and Sarcodon scabrosus (Fr.) Karst.]. Many of the basidiomycete species fruiting above ground were detected also on the roots below ground. Fruit bodies of SO species of ectomycorrhizal fungi were recorded while 39 distinct mycorrhizal types were identified on the roots. There was a significant increase in mycorrhizal species richness between the 6 and 41‐yr‐old stands and this was primarily the result of partial replacement of Suillus brevipes on the 6‐yr‐old trees by late‐stage fungi in the older stands. Very few species present in the 6‐yr‐old stand were completely replaced in the older stands; rather, the multi‐stage species present in the young stand were joined by late‐stage species in the mature stands. The species abundance distribution of fungi on the roots in the 6‐yr‐old stand was best described by a geometric series which is typical of an early successional community while the distributions in the three oldest stands conformed to a lognormal series which is indicative of a stable, species rich community. Both the composition and structure of the ectomycorrhizal community had stabilized 41 yr after wildfire.