Formerly drained fen peatlands might again act as carbon sinks after rewetting despite high nutrient levels

Hinzke, Tjorven; Li, Guixiang; Tanneberger, Franziska; Seeber, Elke; Aggenbach, Camiel; Lange, Jelena; Kozub, Lukasz; Knorr, Klaus-Holger; Kreyling, Juergen; Kotowski, Wiktor

A harvested Carex plant. We studied biomass production and chemical composition of shoots, roots, and rhizomes. (photo credit: Juergen Kreyling)
A harvested Carex plant. We studied biomass production and chemical composition of shoots, roots, and rhizomes. (photo credit: Juergen Kreyling)

The increasing concentrations of carbon dioxide (CO2) in the atmosphere are responsible for the main part of global climate change. Plants use the carbon (C) contained in atmospheric CO2 to build their tissues. When plants die, CO2 is released again to the atmosphere from decaying plant litter. However, under certain circumstances, this carbon cycle (uptake and release of carbon) is not completely balanced: dead plant tissue remains and accumulates, and a part of the C the plants had taken up does not get back to the atmosphere as CO2. This is what happens in natural, wet peatlands. Here, decay processes are inhibited especially by the high water content in the peat soil. Thereby, peat layers build up from dead plant material and store carbon. This naturally reduces the amount of CO2 in the atmosphere. Therefore, it is important to understand how growth and decomposition of typical peatland plants such as sedges are impacted by environmental conditions.

Peatlands naturally have a high variability of plant nutrients, which nowadays increases due to entry from the atmosphere and agriculture, and during peat degradation caused by drainage. Higher nutrient concentrations can not only cause plants to grow better, but also to decompose and thus release CO2 faster, and can also be toxic for the plants (besides other harmful effects of these higher nutrient concentrations, like water quality deterioration, and extinction of rare species).

In this study, we wanted to understand how these nutrients impact both plant growth and plant decay in fen peatlands. We used five different sedge species, and grew them under different nutrient levels. After the experiment, we weighed the above- and below-ground parts of the plants, and analyzed the chemical composition of the plant tissues. As in fen peatlands peat consists mainly of below-ground plant material, we also performed an experiment to see how fast the roots of the plants grown under different nutrient levels decayed.

Read the article in full here

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