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Bundoora, Australia

Hay T.N.,University of British Columbia | Phillips L.A.,University of British Columbia | Phillips L.A.,AgriBio Center for AgriBioscience | Nicholson B.A.,University of British Columbia | Jones M.D.,University of British Columbia
Forest Ecology and Management

Long-term fertilization is being considered as a mechanism to increase growth of pine and spruce trees in British Columbia following a major outbreak of mountain pine beetle. It is important, however, that long-term fertilization not disrupt colonization by ectomycorrhizal fungi or impede their ability to release nutrients from soil organic matter. In order to determine the effect of long-term (up to 14years) fertilization on the structure and function of ectomycorrhizal (ECM) fungal communities on roots of interior spruce, we characterized the ECM fungal community and, on separate samples collected at a different time of year, assayed for extracellular enzymes in the mycorrhizoplane. The study was conducted at three interior spruce (naturally occurring hybrids of Picea glauca [Moench] Voss and Picea engelmannii Parry) plantations in the interior of south-central British Columbia. Three 0.164ha plots per site received no (controls), periodic (200kgha-1N, plus P, K, S, Mg, and B every 6years), or annual (same nutrients adjusted to maintain foliar N concentration at 1.3% and other nutrients in balance; 50 to 75kgha-1 of N, depending on site and year) fertilization. There was no overall effect of fertilization on the composition of the ECM fungal community (OTUs) on spruce roots (permutational MANOVA P=0.4) nor on alpha diversity per plot. At single sites, there was reduced relative abundance of Cortinarius spp. mycorrhizas under periodic fertilization, and increased relative abundance of Lactarius spp. or Tylospora spp. mycorrhizas under annual fertilization. None of the dominant genera increased or decreased significantly across sites. The ratio of carbon-acquiring to mineral nutrient-acquiring enzyme activities in the mycorrhizoplanes increased with frequency of fertilizer application. Increased litterfall may explain the increase in plant cell wall-degrading enzyme activity in fertilized plots. A decrease in activities involved in the release of sulphur was as expected in fertilized plots because the fertilizer contained inorganic nitrogen, phosphorus and sulphur. Although activities of two enzymes involved in nutrient cycling (sulfatase and phosphomonoesterase) tended to decrease, there did not appear to be an overall loss of organic matter-degrading potential from the ECM fungal community on spruce roots under long-term fertilization. © 2015 Elsevier B.V. Source

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