Modelling impacts of lateral N flows and seasonal warming on an arctic footslope ecosystem N budget and N₂O emissions based on species-level responses

Summary, in English

Future Arctic tundra primary productivity and vegetation community composition will partly be determined by nitrogen (N) availability in a warmer climate. N mineralization rates are predicted to increase in both winter and summer, but because N demand and –mobility varies across seasons, the fate of mineralized N remains uncertain. N mineralized in winter is released in a “pulse” upon snowmelt and soil thaw, with the potential for lateral redistribution in the landscape. In summer, the release is into an active rhizosphere with high local biological N demand. In this study, we investigated the ecosystem sensitivity to increased lateral N input and near-surface warming, respectively and in combination, with a numerical ecosystem model (CoupModel) parameterized to simulate ecosystem biogeochemistry for a tundra heath ecosystem in West Greenland. Both measurements and model results indicated that plants were poor utilizers of increased early-season lateral N input, indicating that higher winter N mineralization rates may have limited impact on plant growth and carbon (C) sequestration for a hillslope ecosystem. The model further suggested that, although deciduous shrubs were the plant type with overall most lateral N gain, evergreen shrubs appear to have a comparative advantage utilizing early-season N. In contrast, near-surface summer warming increased plant biomass and N uptake, moving N from soil to plant N pools, and offered an advantage to deciduous plants. Neither simulated high lateral N fluxes nor near-surface soil warming suggests that mesic tundra heaths will be important sources of N₂O under warmer conditions. Our work highlights how winter and summer warming may play different roles in tundra ecosystem N and C budgets depending on plant community composition.

• Author: Laura H. Rasmussen; Wenxin Zhang; Per Ambus; Per Erik Jansson; Barbara Kitzler; Bo Elberling
• Department/s: Dept of Physical Geography and Ecosystem Science; BECC: Biodiversity and Ecosystem services in a Changing Climate; MERGE: ModElling the Regional and Global Earth system
• Publishing year: 2022-03
• Language: English
• Pages: 195-213
• Publication/Series: Biogeochemistry
• Volume: 158
• Issue: 2
• Links: http://dx.doi.org/10.1007/s10533-022-00894-z
• Document type: Journal article
• Publisher: Springer
• Topic: Climate Research
• Keywords: Arctic tundra; Climate change; CoupModel; Solute transport; Winter N mineralization
• Status: Published
• ISBN/ISSN/Other: ISSN: 0168-2563