Links Between Stream Water Nitrogen and Terrestrial Vegetation in Northeast Greenland

The Arctic is warming and significant changes to the landscape, including increased vegetative cover ("greening"), are expected in the near future. These landscape changes may alter nitrogen (N) availability in terrestrial, stream, and coastal ecosystems, where production is often N limited, but the exact changes in nutrient cycling are uncertain. Here, we analyzed the relationship between vegetation greenness (i.e., NDVI) and dissolved inorganic (DIN) and organic (DON) concentrations in streams draining 14 headwater catchments (mean 3.6 km2, range 0.4-11 km2) across three samplings in the Zackenberg area, Northeast Greenland. We found large variation in DIN and DON concentrations across the sampled streams. We further show that this variation is correlated to water temperature and catchment NDVI, such that increased vegetation greenness and temperature correlated with lower DIN, and increased greenness also correlated with higher DON concentrations in streams. The results suggest that increased terrestrial vegetation due to rising air temperature could substantially alter dissolved N concentrations and form in streams, with potentially cascading impacts on coastal areas. This study links terrestrial vegetation cover to stream water chemistry in High Arctic headwater catchments. We found significant spatial and seasonal variation in dissolved inorganic nitrogen (DIN) and dissolved organic nitrogen (DON) availability in streams. Nitrate (NO3- ${{\text{NO}}_{3}}<^>{-}$) concentration in stream water decreases and DON increases with increasing spectral median normalized difference vegetation index (NDVI) in the stream catchment (i.e., proxy for terrestrial vegetation). This shift in the form of available nitrogen (N) has significant implications as terrestrial vegetation is changing quickly in High Arctic areas, which may then alter the amount and the dominant form of N exported from catchments to coastal areas. High terrestrial vegetation greenness (NDVI) correlates negatively with dissolved inorganic nitrogen concentrations in High Arctic catchmentsDissolved inorganic nitrogen decreases and organic nitrogen increases with increased terrestrial vegetation greennessFuture climate changes in High Arctic areas may alter the amount and form of nitrogen exported from land to sea