Effects of climate, fire and vegetation development on Holocene changes in total organic carbon concentration in three boreal forest lakes in northern Sweden

Abstract

Abstract. Near infrared spectroscopy (NIRS), diatoms, pollen, charcoal, loss-on-ignition (LOI), and nutrient elements in lake sediments were used to assess important factors controlling Holocene changes in the total organic carbon (TOC) concentration, pCO 2 , color and pH of lake water in three boreal forest lakes in northern Sweden. The results suggest that mire formation, fire frequency and humidity are the most important forcing factors on millennial timescales. Mires produce humic acids that become available to the lakes, whereas fires may reduce the pool of carbon in the catchments, and humidity controls the transportation of allochthonous carbon into the lakes. Vegetation development and temperature as sole factors are of minor importance for the TOC concentrations in these lakes on a millennial timescale. Two of the sites indicate that liming and possibly fish introduction and rotenone treatment in recent time has led to increased TOC, color and pH in the lake water, and changed the diatom community composition to an assemblage that has never been present before. Given the predicted climate change scenario that suggests a more humid climate, expanding mires and less frequent fires, our paleolimnological data suggest that TOC concentrations can be expected to increase in boreal forest lakes in the future. Since supersaturation and emission of CO 2 from lakes is correlated to the TOC concentration of lake water, higher TOC concentrations may lead to increased emission of CO 2 from lakes to the atmosphere.

Siberian larch forests and the ion content of thaw lakes form a geochemically functional entity

“…2) contradicts earlier assumptions that with forest expansion during the Holocene, soil acidity and, thus, humic-acid export to lakes increases 27 . Our results support inferences from other studies 28 that processes other than tree immigration into catchments, such as mire expansion or fire, were the drivers of observed lake acidification.…”

Climate Change Impacts on Sediment Quality of Subalpine Reservoirs: Implications on Management

“…Therefore, it is hardly predictable how these contrasting mechanisms will affect contaminant concentrations: anthropogenic pollutants may potentially be diluted by increased coarse material fractions [3], but concentrations of trace elements deriving from natural erosion may increase [105]. On the other hand, the increased forest and plant coverage [106] will result in higher capacity of soils to storage organic material and the degradation of litter and vegetation will potentially increase the flow of TOC to reservoirs [77,107,108]. This will potentially reduce bioavailability of pollutants due to the enhanced presence of ligands, with resulting reduced toxicity risk for aquatic organisms.…”

The fate of buried organic carbon in colluvial soils: a long-term perspective

“…Raymond and Bauer, 2001;Mayorga et al, 2005), while SOC reaching lakes and oceans has been shown to be well preserved over longer timescales (e.g. Rosen and Hammarlund, 2007;Galy et al, 2007).…”