| Summary: | Mineral element cycling through the soil-plant system upon permafrost thaw: case study in Interior Alaska Climate warming affects the Arctic region by exposing previously frozen permafrost to thaw, unlocking mineral nutrients, boosting plant growth, and modifying the carbon balance from permafrost regions. In changing Arctic environments, how will permafrost degradation affect plant mineral nutrient availability and soil-plant nutrient cycling via litter degradation? Studies have highlighted that upon thawing, deep-rooted plants benefit from new pools of essential nutrients such as N or P. Therefore, we hypothesized that other mineral elements such as Ca, K, or Mg may also be bio-lifted and recycled in surface soil horizons through deep plant uptake and litter production, providing a source of nutrients for shallower rooted plants. To test this hypothesis, plant leaves and soil samples were collected across a permafrost thaw gradient at Eight Mile Lake, Alaska in September 2019, corresponding to the season of maximal permafrost thaw depth. The sampling transect (vegetation and soil profiles) encompasses a range of active layer depth (−48 to –96 cm) and water table depth (0 to –40 cm). We investigate the influence of permafrost thaw on mineral element distribution in plants and soils by measuring the total content in Ca, K, Mg, Na, P, Si, and Mn: (i) in plant species from three different plant functional types (sedges, deciduous and evergreen shrubs); and (ii) in the corresponding soil profiles. The plant selection includes species with shallower (Vaccinium spp.) and deeper (Carex spp.) rooting depth. In soils, we also determined the content in exchangeable Ca, Mg, K, and Na. The large contrasts between the element distribution in organic and mineral horizons confirm the central role of the vegetation in the mineral elements cycling in these permafrost-affected ecosystems, and highlight the importance to consider jointly active layer depth, water table depth and plant rooting depth to assess the nutrient ...
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