Abstract
ABSTRACT The net change in the carbon inventory of arctic tundra remains uncertain as global warming leads to shifts in arctic water and carbon cycles. To better understand the response of arctic tundra carbon to changes in winter precipitation amount, we investigated soil depth profiles of carbon concentration and radionuclide activities (7Be, 137Cs, 210Pb, and 241Am) in the active layer of a twenty-two-year winter snow depth manipulation experiment in moist acidic tussock tundra at Toolik Lake, Alaska. Depth correlations of cumulative carbon dry mass (g cm−2) vs. unsupported 210Pb activity (mBq g−1) were examined using a modified constant rate of supply (CRS) model. Results were best fit by two-slope CRS models indicating an apparent step temporal increase in the accumulation rate of soil organic carbon. Most of the best-fit model chronologies indicated that the increase in carbon accumulation rate apparently began and persisted after snow fence construction in 1994. The inhomogeneous nature of permafrost soils and their relatively low net carbon accumulation rates make it challenging to establish robust chronologic records. Nonetheless, the data obtained in this study support a decadal-scale increase in net soil organic carbon accumulation rate in the active layer of arctic moist acidic tussock tundra under conditions of increased winter precipitation.
Highlights
Understanding the arctic carbon cycle today and its likely behavior in the future is essential to recognizing shortand long-term responses and feedbacks to the climate system
We explored a 210Pb-based chrono metric approach to obtain an integrative measure of the temporal change in net soil carbon accumulation rate in the active layer organic horizon of moist acidic tussock tundra in response to the construction of a snow fence near Toolik Lake, Alaska, at 68°38′ N, 149°38′ W; elevation 760 m (Figure 1)
The principal objective of this study was to evaluate the effect of deeper winter snow accumulation on the net accumulation rate of soil organic carbon in the active layer of moist acidic tussock tundra, following the con struction of a snow fence in 1994 as part of the ITEX (Jones et al 1998; Welker, Fahnestock, and Jones 2000; Welker et al 2005; Jespersen et al 2018)
Summary
Understanding the arctic carbon cycle today and its likely behavior in the future is essential to recognizing shortand long-term responses and feedbacks to the climate system. Increases and decreases in snowfall and winter snow pack can lead to different ecosystem impacts (Bintanja and Selten 2014; Bintanja and Andry 2017). The effects of these changes on soil organic carbon inventories depend on soil carbon cycling processes (Schaeffer et al 2013; Ricketts et al 2016; Vitharana et al 2017) and soil active layer depth (Pattison and Welker 2014; Jespersen et al 2018). Improved understanding of the mechanisms driving the arctic carbon cycle continues to be at the forefront of research on the role of the “New
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