Warming effects on metabolomic profiles of plant communities and soils of subarctic grasslands

Abstract

Assessing the impacts of climate change on global ecosystems is a key challenge for the scientific community. Understanding the phenotypic responses of plant and soil ecosystems is crucial for gaining insights into the future climatic landscape of these biological networks. Plants, which dominate the global landscape, are vulnerable to the impacts of climate change. Therefore, characterizing plant community responses is key to understanding their overall ecosystem response. Circumpolar North soils hold the largest reservoir of carbon, form the basis of the regional terrestrial ecosystems, and harbor immense biodiversity. Global warming of the Circumpolar North is reported to be amplified by up to 3.8 times relative to the global average, consequently placing ecosystems, such as sub-arctic grassland soils, at a heightened risk of disturbance. In this dissertation, I investigate: the foliar metabolomic profile of grasses, forbs, and woody plant responses to warming; the interaction of seasonal dynamics on the soil metabolome profile of short-term, 10-year warmed sub-arctic grasslands; and the interaction of root presence on medium-term, 12-year warmed and long-term, >60-year warmed sub-arctic grasslands. I conducted a meta-analysis of published literature focused on assessing plant foliar metabolomic profiles of grasses, forbs, and woody plants to temperature increases of 0–20 °C. Using a combined qualitative and quantitative approach, I found an enrichment in primary metabolite pathways related to sugar metabolism, cell membrane stabilization, and stress response across all plant groups. Secondary metabolite assessment consisted of an upregulation of terpenes and a downregulation of flavonoids in woody plants. These results provide important insights into plant communities and their metabolic mechanisms under future climate implications. To evaluate the combined impacts of seasonal variation and soil warming on sub-arctic grassland soils of southern Iceland, I relied on HPLC-MS untargeted metabolomics to characterize the soil metabolome profile. Both factors altered the soil metabolome, although the season and soil warming interaction were nonsignificant. Seasonal variation was dominated by kaempferol dynamics, highlighting the need for higher-resolution temporal sampling. Soil warming induced shifts in carbohydrates and nucleotides, suggesting changes in microbial activity and nutrient cycling. To explore the plant-soil interactions alongside warming of sub-arctic grasslands soils, I also used HPLC-MS untargeted metabolomics to assess the soil metabolome profile of root inclusion versus root exclusion cores in medium-term and long-term sites in southern Iceland. Although root presence and soil warming indicated no significant interaction, both factors shifted the soil metabolome. The noted shifts in carbohydrates, amino acids, and flavonoid levels in both warming and root presence/absence may have impacts on nutrient cycling and labile carbon availability in sub-arctic grassland soils. In conclusion, this study highlights the potential reconfigurations of foliar metabolite pathways on plant communities and co-occurring factors influencing the soil metabolome profile in warmed sub-arctic grassland soils. The findings detailed in this dissertation provide insight into the future implications of climate change effects on the metabolomic responses in plant communities and seasonal and root presence in soils in a warming climate.

Date of Award	13 Nov 2025
Original language	English
Awarding Institution	Universitat Autònoma de Barcelona (UAB)
Supervisor	Albert Gargallo Garriga (Director), Josep Peñuelas Reixach (Director) & Jordi Sardans (Director)