Nitrogen uptake patterns by snow addition in a sub-Arctic dry heath tundra ecosystem

English. The Arctic heath tundra ecosystem is undergoing rapid transformations driven by climate change, which particularly affects snow accumulation and the length of the growing season. In this study, I examined the influence of snow depth on parameters such as water content, soil temperature, microbial activity, and nutrient availability and investigated their implications for plant water availability and nitrogen cycling processes. Through snow fence experiments and 15N isotope labelling and simulations of carbon fluxes with the CoupModel, I found that a longer growing season positively impacted plant productivity, carbon accumulation, and nutrient assimilation. Both evergreen and deciduous plants benefited from an extended growing season, but when the growing season was shortened, evergreen species exhibited greater resilience, while deciduous species were more susceptible to detrimental effects on growth and photosynthesis. Non-growing season alterations in snow cover could have intricate consequences on annual photosynthesis and greenhouse gas emissions, as increased snow depth favored microbial activity in winter and resulted in higher carbon dioxide emissions. These emissions counteracted the carbon sequestration advantages of the growing season, underscoring the importance of considering both the duration of the growing season and snow dynamics in conservation and management strategies.

Spanish; Castilian. El ecosistema de tundra ártica experimenta cambios rápidos debido al cambio climático, especialmente en la acumulación de nieve y la duración de la temporada de crecimiento. Este estudio investigó los impactos de la profundidad de nieve en parámetros clave, como el contenido de agua, la temperatura del suelo, la actividad microbiana y la disponibilidad de nutrientes, y sus efectos subsiguientes en la disponibilidad de agua para las plantas y los procesos de ciclado de nitrógeno. A través de experimentos con vallas de nieve y etiquetado con el isotopo 15N y simulaciones de flujos de carbono con el modelo CoupModel, se determinó que una temporada de crecimiento más larga influyó positivamente en la productividad de las plantas, la acumulación de carbono y la asimilación de nutrientes. Una temporada de crecimiento extendida benefició tanto a las plantas perennes como a las caducifolias. Sin embargo, en caso de una temporada de crecimiento más corta, las plantas perennes demostraron una mayor resistencia, mientras que las plantas caducifolias fueron más susceptibles a los efectos adversos en su crecimiento y fotosíntesis. Las alteraciones en la cobertura de nieve durante la temporada no productiva podrían tener efectos complejos en la fotosíntesis anual y las emisiones de gases de efecto invernadero, ya que el aumento de la profundidad de nieve favorecía la actividad microbiana en invierno y resultaba en niveles más altos de dióxido de carbono. Estas emisiones contrarrestaban los beneficios de la captura de carbono de la temporada de crecimiento, lo que resalta la necesidad de considerar tanto la duración de la temporada de crecimiento como la dinámica de la nieve en las estrategias de conservación y manejo.

English. The Arctic heath tundra, a delicate ecosystem, is facing significant changes due to climate change, particularly in snow accumulation and the length of the growing season. In this study, I looked at how the depth of the snow affects on various parameters such as soil temperature, water content, microbial activity, and nutrient availability. By employing snow fence experiments and utilizing a special computer model called CoupModel, I explored the implications for plant water availability and nitrogen cycling processes. The findings revealed that a longer growing season had a positive impact on plant productivity, carbon accumulation, and nutrient assimilation. Both evergreen and deciduous plants benefited from the extended growing season, although the study highlighted the differing responses between these plant types. While evergreen species exhibited greater resilience to a shortened growing season, deciduous species were more susceptible to adverse effects on growth and photosynthesis. Interestingly, alterations in snow cover during the non-growing season had intricate consequences. Increased snow depth enhanced microbial activity during winter, leading to higher carbon dioxide emissions. This counteracted the carbon sequestration advantages observed during the growing season. These results emphasize the significance of considering both growing season duration and snow dynamics when formulating conservation and management strategies for these vulnerable Arctic ecosystems.