Estimating meltwater retention and associated nitrate redistribution during snowmelt in an Arctic tundra landscape**The data that support the findings of this study are available from the corresponding author upon reasonable request.

Andreas Westergaard-Nielsen,Signe Normand,Urs A Treier,Bo Elberling,Thomas Balstrøm

doi:10.1088/1748-9326/ab57b1

Andreas Westergaard-Nielsen, Signe Normand + Show 3 more

Open Access

https://doi.org/10.1088/1748-9326/ab57b1

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Abstract

Nitrogen availability in Arctic ecosystems is a key driver for biological activity, including plant, growth and thereby directly linked to the greening of the Arctic. Here, we model the redistribution of meltwater following spring snowmelt as well as the accumulation of meltwater and dissolved nitrate at landscape scale. By combining snow mapping with unmanned aerial systems, snow chemistry, and hydrological modelling, we argue that the majority of nitrate in the snowpack is flushed out of the landscape due to the limited storage capacity of meltwater in the early growing season frozen soil. We illustrate how landscape micro-topography is a crucial parameter to quantify storage capacity of meltwater at landscape scale and thereby the associated pool of soluble compounds such as nitrate. This pool will be available for plants and may be important for plant diversity and growth rates in the wettest part of the landscape. This study illustrates that the evenly distributed nitrate input during the Arctic winter may be redistributed during the initial snowmelt and lead to marked differences in biologically available nitrate at the onset of the growing season, but also that the majority of deposited nitrate in snow is lost from the terrestrial to the aquatic environment during snowmelt.

Highlights

There is a current focus on understanding the varied responses of Arctic terrestrial ecosystems to climatic changes, the net effect of an increasing (Forkel et al 2016) or a decreasing carbon sink strength (Nauta et al 2015, Dahl et al 2017)
This study illustrates that the evenly distributed nitrate input during the Arctic winter may be redistributed during the initial snowmelt and lead to marked differences in biologically available nitrate at the onset of the growing season, and that the majority of deposited nitrate in snow is lost from the terrestrial to the aquatic environment during snowmelt
The statistical distribution is comparable to the manual probe measurements, the probe is limited to 120 cm (figure 3(c))

Summary

Introduction

There is a current focus on understanding the varied responses of Arctic terrestrial ecosystems to climatic changes, the net effect of an increasing (Forkel et al 2016) or a decreasing carbon sink strength (Nauta et al 2015, Dahl et al 2017). Nitrogen (N) in a plant available form is a key component for these responses since N is considered a limiting factor for plant growth in the Arctic (Shaver et al 2006). Future warming and changes in precipitation patterns are likely to catalyze mineralization of stored N, and potentially increase other sources such as atmospheric deposition, which could lead to alterations in Arctic vegetation dynamics (Rousk et al 2017a, Bokhorst et al 2018, D’Imperio et al 2018). Main sources of plantavailable N at catchment scale in most pristine Arctic ecosystems include redistributed internal N from mineralization of soil organic matter and inputs from fauna, and external input from atmospheric deposition and N2 fixation (Skrzypek et al 2015). It means that early season N availability in landscape depressions may rely on external N sources in contrast to aerated soils relying more on internal N (Semenchuk et al 2015)

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