Potentials of typical plant species from rewetted fenlands for the supply of strategic elements

Introduction

Peatlands are formed by the long-term accumulation of organic matter made of slowly decaying biomass under exclusion of air due to high water levels^{1, 2–3}. Covering about 3% of the global land area⁴, peatlands store an estimated 21 to 44% of the carbon sequestered in soils⁵ and large amounts of nutrients⁶. Peatlands are also known to provide various ecosystem services, playing a crucial role in water regulation, and maintaining biodiversity^2,7,8.

In Germany, organic soils cover an area of 1.82 million ha⁹. Their predominant use is agriculture. Large-scale deep drainage of organic soils in the 1960s to 1980s has caused wide-ranging degradation of peatlands³ and severe detrimental impacts on their ecological functions. Drained organic soils turn from sinks to sources of carbon and nitrogen, thus contributing a considerable share of 6.6% to the national greenhouse gas emissions⁹ and impairing water quality^7,10. Degraded peatlands are less capable of holding water in the landscape^11,12 and harbouring specialized plant and animal species^2,7,10,13.

Rewetting of peatlands is regarded as one of the most effective measures to mitigate greenhouse gas emissions from land use, land use change^{14, 15, 16–17} and to restore the water retention function in the watershed^18,19. In topogenic fenlands, i.e. those that would form due to the topography of the landscape, as they prevail in the northeast federal states of Germany, raising water tables induces the establishment of tall, graminoid wetland plants²⁰ such as reed canary grass (Phalaris arundinacea), broad-leafed cattail (Typha latifolia), common reed (Phragmites australis), tall sedges (Carex spec.) and rushes (Juncus spec.)^{20, 21–22}. Thus, rewetted peatlands are no longer available for use as grasslands or arable land. New management strategies for wet peatlands referred to as paludiculture are needed^10,22, with the derived plant biomass referred to as paludibiomass. While a number of paludibiomass-based products such as paper and packaging²³, insulation and construction materials^7,10 and substrates for horticulture and/or peat substitute^10,24 are currently at the stage of advanced research, prototyping and even implementation, alternative solutions are still being sought. The supply of...