Treeline displacement may affect lake dissolved organic matter processing at high latitudes and altitudes

• Published in: Nature Communications
• Main Authors: Núria Catalán, Carina Rofner, Charles Verpoorter, María Teresa Pérez, Thorsten Dittmar, Lars Tranvik, Ruben Sommaruga, Hannes Peter
• Format: Article in Journal/Newspaper
• Language: English
• Published: Nature Portfolio 2024
• Subjects: Science; Q; Subarctic
• Online Access: https://doi.org/10.1038/s41467-024-46789-5; https://doaj.org/article/4ff5af10a2c041afa7d25b412680be6b

Abstract Climate change induced shifts in treeline position, both towards higher altitudes and latitudes induce changes in soil organic matter. Eventually, soil organic matter is transported to alpine and subarctic lakes with yet unknown consequences for dissolved organic matter (DOM) diversity and processing. Here, we experimentally investigate the consequences of treeline shifts by amending subarctic and temperate alpine lake water with soil-derived DOM from above and below the treeline. We use ultra-high resolution mass spectrometry (FT-ICR MS) to track molecular DOM diversity (i.e., chemodiversity), estimate DOM decay and measure bacterial growth efficiency. In both lakes, soil-derived DOM from below the treeline increases lake DOM chemodiversity mainly through the enrichment with polyphenolic and highly unsaturated compounds. These compositional changes are associated with reductions in bulk and compound-level DOM reactivity and reduced bacterial growth efficiency. Our results suggest that treeline advancement has the potential to enrich a large number of lake ecosystems with less biodegradable DOM, affecting bacterial community function and potentially altering the biogeochemical cycling of carbon in lakes at high latitudes and altitudes.