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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 15, issue 9 | Copyright

Special issue: Changing Permafrost in the Arctic and its Global Effects in...

Biogeosciences, 15, 2781-2801, 2018
https://doi.org/10.5194/bg-15-2781-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 09 May 2018

Research article | 09 May 2018

Spatial variation and linkages of soil and vegetation in the Siberian Arctic tundra – coupling field observations with remote sensing data

Juha Mikola1, Tarmo Virtanen2, Maiju Linkosalmi3, Emmi Vähä1, Johanna Nyman4, Olga Postanogova5, Aleksi Räsänen2,6, D. Johan Kotze7, Tuomas Laurila3, Sari Juutinen2, Vladimir Kondratyev5, and Mika Aurela3 Juha Mikola et al.
  • 1Ecosystems and Environment Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, Niemenkatu 73, 15140 Lahti, Finland
  • 2Ecosystems and Environment Research Programme, Faculty of Biological and Environmental Sciences and Helsinki Institute of Sustainability Science (HELSUS), P.O. Box 65, 00014 University of Helsinki, Helsinki, Finland
  • 3Finnish Meteorological Institute, P.O. Box 503, 00101 Helsinki, Finland
  • 4Ecosystems and Environment Research Programme, Faculty of Biological and Environmental Sciences, P.O. Box 65, 00014 University of Helsinki, Helsinki, Finland
  • 5Yakutian Service for Hydrometeorology and Environmental Monitoring, Tiksi, Russia
  • 6Department of Geography, Norwegian University of Science and Technology, 7491 Trondheim, Norway
  • 7Ecosystems and Environment Research Programme, Faculty of Biological and Environmental Sciences and Helsinki Institute of Sustainability Science (HELSUS), University of Helsinki, Niemenkatu 73, 15140 Lahti, Finland

Abstract. Arctic tundra ecosystems will play a key role in future climate change due to intensifying permafrost thawing, plant growth and ecosystem carbon exchange, but monitoring these changes may be challenging due to the heterogeneity of Arctic landscapes. We examined spatial variation and linkages of soil and plant attributes in a site of Siberian Arctic tundra in Tiksi, northeast Russia, and evaluated possibilities to capture this variation by remote sensing for the benefit of carbon exchange measurements and landscape extrapolation. We distinguished nine land cover types (LCTs) and to characterize them, sampled 92 study plots for plant and soil attributes in 2014. Moreover, to test if variation in plant and soil attributes can be detected using remote sensing, we produced a normalized difference vegetation index (NDVI) and topographical parameters for each study plot using three very high spatial resolution multispectral satellite images. We found that soils ranged from mineral soils in bare soil and lichen tundra LCTs to soils of high percentage of organic matter (OM) in graminoid tundra, bog, dry fen and wet fen. OM content of the top soil was on average 14g dm−3 in bare soil and lichen tundra and 89g dm−3 in other LCTs. Total moss biomass varied from 0 to 820g m−2, total vascular shoot mass from 7 to 112g m−2 and vascular leaf area index (LAI) from 0.04 to 0.95 among LCTs. In late summer, soil temperatures at 15cm depth were on average 14°C in bare soil and lichen tundra, and varied from 5 to 9°C in other LCTs. On average, depth of the biologically active, unfrozen soil layer doubled from early July to mid-August. When contrasted across study plots, moss biomass was positively associated with soil OM% and OM content and negatively associated with soil temperature, explaining 14–34% of variation. Vascular shoot mass and LAI were also positively associated with soil OM content, and LAI with active layer depth, but only explained 6–15% of variation. NDVI captured variation in vascular LAI better than in moss biomass, but while this difference was significant with late season NDVI, it was minimal with early season NDVI. For this reason, soil attributes associated with moss mass were better captured by early season NDVI. Topographic attributes were related to LAI and many soil attributes, but not to moss biomass and could not increase the amount of spatial variation explained in plant and soil attributes above that achieved by NDVI. The LCT map we produced had low to moderate uncertainty in predictions for plant and soil properties except for moss biomass and bare soil and lichen tundra LCTs. Our results illustrate a typical tundra ecosystem with great fine-scale spatial variation in both plant and soil attributes. Mosses dominate plant biomass and control many soil attributes, including OM% and temperature, but variation in moss biomass is difficult to capture by remote sensing reflectance, topography or a LCT map. Despite the general accuracy of landscape level predictions in our LCT approach, this indicates challenges in the spatial extrapolation of some of those vegetation and soil attributes that are relevant for the regional ecosystem and global climate models.

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To support C exchange measurements, we examined plant and soil attributes in Siberian Arctic tundra. Our results illustrate a typical tundra ecosystem with great spatial variation. Mosses dominate plant biomass and control many soil attributes such as temperature, but variation in moss biomass is difficult to capture by remote sensing. This indicates challenges in spatial extrapolation of some of those plant and soil attributes that are relevant for regional ecosystem and global climate models.
To support C exchange measurements, we examined plant and soil attributes in Siberian Arctic...
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