The biogeochemical consequences of litter transformation by insect herbivory in the Subarctic: a microcosm simulation experiment

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Bibtex

@article{b0cd4749263d4b29bfdb38358ef2867d,
title = "The biogeochemical consequences of litter transformation by insect herbivory in the Subarctic: a microcosm simulation experiment",
abstract = "Warming may increase the extent and intensity of insect defoliations within Arctic ecosystems. A thorough understanding of the implications of this for litter decomposition is essential to make predictions of soil-atmosphere carbon (C) feedbacks. Soil nitrogen (N) and C cycles naturally are interlinked, but we lack a detailed understanding of how insect herbivores impact these cycles. In a laboratory microcosm study, we investigated the growth responses of heterotrophic soil fungi and bacteria as well as C and N mineralisation to simulated defoliator outbreaks (frass addition), long-term increased insect herbivory (litter addition at higher background N-level) and non-outbreak conditions (litter addition only) in soils from a Subarctic birch forest. Larger amounts of the added organic matter were mineralised in the outbreak simulations compared to a normal year; yet, the fungal and bacterial growth rates and biomass were not significantly different. In the simulation of long-term increased herbivory, less litter C was respired per unit mineralised N (C:N of mineralisation decreased to 20 ± 1 from 38 ± 3 for pure litter), which suggests a directed microbial mining for N-rich substrates. This was accompanied by higher fungal dominance relative to bacteria and lower total microbial biomass. In conclusion, while a higher fraction of foliar C will be respired by insects and microbes during outbreak years, predicted long-term increases in herbivory linked to climate change may facilitate soil C-accumulation, as less foliar C is respired per unit mineralised N. Further work elucidating animal-plant-soil interactions is needed to improve model predictions of C-sink capacity in high latitude forest ecosystems.",
keywords = "Biogeochemistry, Herbivory, Nitrogen mineralisation, Soil microbial ecology, Soil respiration, Subarctic birch forest",
author = "Kristensen, {Jeppe A.} and Metcalfe, {Daniel B.} and Johannes Rousk",
year = "2018",
doi = "10.1007/s10533-018-0448-8",
language = "English",
volume = "138",
pages = "323--336",
journal = "Biogeochemistry",
issn = "1573-515X",
publisher = "Springer",
number = "3",

}