Greenhouse gas emissions and global warming potentials of five paludiculture plants in fen peatlands in southern Germany

The concept of paludicultures is growing in importance as a promising climate mitigation measure and a sustainable alternative to current agricultural use of organic soils. Besides agricultural and economic viability, quantifying the climatic effects of paludicultures is essential to give reliable policy advice and facilitate sustainable management decisions with regard to climate change. Emission factors (EFs) of the relevant greenhouse gases (GHG) carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) for a variety of potential paludiculture plants are still rare, especially from comparable treatments and site conditions.

Five different temperate fen plant species (Carex acutiformis, Phragmites australis, Phalaris arundinacea, Typha latifolia and T. angustifolia) were established as paludicultures with one or two-cut harvest frequencies at three former grassland or arable sites on fen peatland in southern Germany. Ground water levels (gwl) were manipulated to generate a water table gradient spanning annual mean gwl between +4 to −22 cm to derive an optimum gwl for GHG mitigation. One to five years after plant establishment, we measured fluxes of CO₂, CH₄ and N₂O to obtain annual budgets (n=81 / 43 rewetted: gwl +4 to −10 cm, 38 moderately rewetted: gwl −11 to −22 cm) using manual and automatic closed chambers. Besides gas flux measurements, we observed vegetation growth parameters (LAI, NDVI) and biomass yield from harvests. The resulting mean global warming potentials are −13.0 ± 13.9 t CO₂-eq ha⁻¹ yr⁻¹ under rewetted conditions (annual mean gwl ≥ −10 cm) and −1.0 ± 9.8 t CO₂-eq ha⁻¹ yr⁻¹ under moderately rewetted conditions (annual mean gwl < −10 cm). Our dataset revealed that a maximum mitigation potential of paludicultures is achieved at a gwl of −7 cm. These values represent the first EFs of paludicultures for potential integration into the German national GHG inventory.