Four decades of changing dissolved organic matter quality and stoichiometry in a Swedish forest stream

作者：Chris Evans, Sara Jütterström, Johanna Stadmark, Mike Peacock, Martyn N. Futter, Dolly N. Kothawala, Don Monteith, Filip Moldan · 发表于：Biogeochemistry · 年份：2024 · DOI：10.1007/s10533-024-01166-8 · 被引用次数：14 · 研究领域：Marine and coastal ecosystems、Soil and Water Nutrient Dynamics、Hydrology and Watershed Management Studies

Abstract Dissolved organic matter (DOM) concentrations have risen by a factor of two or more across much of Europe and North America during recent decades. These increases have affected the carbon cycle, light regime, drinking water treatability, and the energy and nutrient budgets of lakes and streams. However, while trends in DOM quantity are well characterised, information on how/whether qualitative properties of DOM have changed are scarce. Here, we describe over 40 years of monitoring data from a forested headwater stream in the Gårdsjön experimental catchment, southwest Sweden, which provides a unique record of biogeochemical change, including optical and stoichiometric DOM quality metrics, spanning the entire period of recovery from acidification. For the period 1980–2020 we find a 71% reduction in decadal mean sulphate concentrations, and a similar reduction in inorganic aluminium concentrations, alongside a 64% increase in dissolved organic carbon (DOC) concentrations. Over the same period, colour (absorbance at 420 nm) increased almost twice as much as DOC, whereas dissolved organic nitrogen (DON) increased by only one third as much. These results demonstrate a shift in stream water composition, with DOM becoming dominated by highly coloured, complex, nitrogen-poor compounds. This material is likely more resistant to biological degradation, but more susceptible to photochemical degradation. Changes in DOM stoichiometry could lead to intensified nitrogen and/or phosp...