The role of soil nutrient limitations on terrestrial carbon cycle in the Swiss Alps under climate change

Mountain regions, and the European Alps in particular, are warming faster than other land areas or the global average. The Alps are among the most sensitive terrestrial systems and have rapid and substantial responses to climate change. Consequently, the carbon cycle in high Alpine regions is expected to be significantly impacted by changes in vegetation cover and dynamics. Only a few studies offer insights into how vegetation types and carbon dynamics evolve at high elevation, considering changes in climate and soil conditions. We investigated changes in climate and soil nutrient development due to changes in vegetation type and cover amount using an ecohydrological model (T&C) and focused on the impacts of the changes on the carbon cycle in the Swiss Alps, where extensive glacier retreat is expected. Specifically, we used the Advanced Weather GENerator (AWE-GEN) model to simulate future realizations of climate at the hourly scale with ten RCM realizations under both low (RCP 4.5) and high (RCP 8.5) greenhouse gas emission scenarios. These future realizations drove the T&C model which reproduces all essential components of the hydrological cycle, vegetation dynamics, and soil biogeochemistry to simulate the carbon cycle dynamics over the 21st century. Our study will examine whether the increase in vegetation in glacier forefields is shifting the carbon cycle (e.g., from the carbon sources to carbon sinks). We will present the results of numerical modeling and discuss whether vegetation growth might be restricted despite increased warming by soil nutrient limitations, thereby reducing the rate of CO₂ uptake. This study highlights the impact of soil nutrients on vegetation pattern changes and terrestrial carbon cycle dynamics in high-elevation environments.