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Effects of big herbivores on the functioning of decomposers and primary producers in High Arctic tundra (GrazeAct)
Call year: 2021
Status: active
IADC_id: 172
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Future changes of the C balance in Arctic remain one of the primary uncertainties in the C-cycle-climate models since the report of IPCC in 2013. This gap should be closed calling for clever experimental approaches in order to improve existing knowledge on the drivers of C balance considering multiple interactions and feedbacks. On the local scale, herbivores impact the structure and functioning of terrestrial ecosystems, affecting cycles of C and N. The sign and magnitude of change in the C cycle depends on how grazing affects its two primary components: primary producers, decomposers and their interaction. While negative effects on the productivity of vegetation could be expected, by modifying the quality of the organic matters inputs to the soil (litter and feaces) and affecting microbial efficiency, grazing can have either positive and negative effects on the ecosystem C balance in terms of C sequestration capacity. rnIn this project, we aim to study the effect of reindeer grazing on the functioning of the main players of the ecosystem C balance, primary producers and soil decomposers. Experiment will be performed in plots excluded from grazing of the Svalbard reindeer and in the surrounded grazed areas of the village of Ny-Ålesund and will involve the competences in the field of plant biology, botany and soil science. We will take an advantage of 13C pulse-labelling experiment conducted by our group in Ny-Ålesund in 2018. The obtained labelled litter of the most representative in the territory plant species (Salix Polaris, Dryas octopetala, Carex rupestris and moss mixture) will be used to study the litter decomposition dynamic and its incorporation to soil organic matter and soil aggregates in plots subjected to grazing and excluded from it. Weekly measurements of CO2 and CH4 from soil will be used to evaluate the effect of grazing and its exclusion on seasonal dynamic and magnitude of C emissions. Isotope analyses of the evolved CO2 and CH4 will serve to determine the efficiency of the decomposition of litter of different quality and its contribution to the soil C efflux alongside decomposition of older SOM. This data will be coupled to botanic survey and characterization of the target plant species in terms of the efficiency of photosynthetic machinery, productivity and the litter quality. Characterization of the microbial pool in terms of size, functional diversity and efficiency in the utilization of the substrate will be assessed in the laboratory analyses.rnBy realization of this project we expect to get a complete view on the interaction of grazing with the C balance of the High Arctic ecosystems. The novelty comes from 1) the multi-disciplinary character of the project ensuring a complex assessment of plant-soil-atmosphere-grazing interactions; 2) the methodology utilized, including in situ labelled litter incubation experiments and coupled flux-isotopic measurements of CO2 and CH4. Both these points to our knowledge have never been applied for such kind of studies in Svalbard.rn
National/International Cooperation:
Norwegian Polar Institute
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