| Summary: | IntroductionClimate warming in the Arctic is much faster than the global average (IPCC, 2013). This rapid climate warming increases aboveground productivity of tundra vegetation (Epstein et al., 2012, Hudson & Henry, 2009, Verbyla, 2008), and also shifts vegetation composition in tundra ecosystems, as deciduous shrub expansion has been observed in many tundra areas (Callaghan et al., 2011, Frost & Epstein, 2014, Myers-Smith et al., 2011). However, the effects of climate warming on belowground parts of tundra vegetation are still largely unknown. Since belowground parts account for the major part of plant biomass in tundra ecosystems (Poorter et al., 2012), it is important for us to understand the potential warming effects on plant belowground parts, particularly fine roots, which is the active part for nutrient and water uptake. Moreover, roots of different plant functional types (PFTs) can significantly differ in morphology, physiology, phenology, rooting depth, and root life span (Bardgett et al., 2014, Iversen et al., 2015). Therefore, warming effects on plant roots may be different among functional types, and the potentially different responses of PFTs’ roots may play an important role in vegetation shifts in tundra. Here, we aimed to study seasonal changes and vertical distribution of root biomass across a vegetation gradient at a Siberian tundra site, focusing on the differences between graminoids and dwarf shrubs, also we aimed to elucidate the relationships of aboveground and belowground biomass with ambient temperature over a broad climate gradient, using data from 36 field studies across the tundra biome.
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