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Influence of bark beetle outbreaks on nutrient cycling in native pine stands in western Canada

Cigan, Paul W; Karst, Justine; Cahill, Jr., James F; Sywenky, Alexandra N; Pec, Gregory J; Erbilgin, Nadir. 2014. Plant and Soil

Abstract

Aims Using a natural gradient of recent (0%u20134 years) mountain pine beetle (Dendroctonus ponderosae)-caused mortality in lodgepole pine (Pinus contorta) stands in west central Alberta, Canada, we tested the effects of different levels of tree mortality, and time since bark beetle infestation, on initial abiotic environmental changes, and nutrient inputs and cycling. Methods We quantified the impacts of D. ponderosae outbreak on input rates of pine needle litter and nutrients, live root mass (both course and fine), supply rates of plant-available nutrients, and concentrations of total mineral soil phenols. Results Pine needle litter, nutrient concentrations, and needle nutrient inputs are all increased as a function of either tree mortality or time since bark beetle infestation. Supply rates of many mineral nutrients increased in soils across gradients of mortality or time. Shallow fine root mass declined by half in response to beetle disturbance; concentrations of soil phenols also shrank by over half, potentially due to increased root losses. Soil phenolics were negatively associated with the supply rate of soil nitrate. Conclusion We concluded that the effects of tree mortality on stand biogeochemistry in pine stands with no recorded history of mountain pine beetle is similar to earlier studies conducted in the beetle%u2019s historical range.

Key Words

Biogeochemistry Litter chemistry Soil phenolics Mountain pine beetle Insect outbreak