Full-cycle greenhouse gas balance of a Sphagnum paludiculture site on former bog grassland in Germany.

Growing Sphagnum on rewetted bogs (=Sphagnum paludiculture) is an alternative to drainage-based land use because it retains its value as productive land while mitigating greenhouse gas (GHG) emissions. However, studies on GHG exchange covering the full production system and cycle are missing. Here, we combined data of the establishment phase with newly recorded data of a 7-year old Sphagnum paludiculture site in Germany including partial Sphagnum harvest. GHGs were measured with closed chambers at all elements of the system (production fields, ditches, causeways). Over the full production cycle, the production fields were GHG sinks with -3.2 ± 4.2 t ha-1 a-1 (in CO2-eq), while ditches represented sources emitting 13.8 ± 11.5 t ha-1 a-1. New measurements on the causeway indicated that it was a stronger GHG source with 29.3 ± 9.8 t ha-1 a-1 than previously assumed from literature values. Corrected for the area share of its elements and including the partial Sphagnum harvest (in dry mass) of ~13.8 ± 0.6 t ha-1 (=average 7-year CO2 emissions of 3.3 ± 0.1 t ha-1 a-1), the site was a GHG source of 10.7 ± 4.6 t ha-1 a-1, thus reducing emissions by ~20 t ha-1 a-1 compared to the German emission factor for grassland on drained organic soils. Per ton harvested dry biomass, the paludiculture site emitted 9.9 ± 4.6 t of CO2-eq. The causeways were the major contributor to the warming, calling for reducing causeway area in Sphagnum paludicultures. Future 'best-practice' could realistically comprise areal shares of 80 % production fields, 5 % ditches, 15 % causeways and a full Sphagnum harvest with the uppermost 5 cm remaining on site for recovery. In this scenario the site would emit CO2-eq emissions of 4.3 ± 1.9 t ha-1 a-1 or 0.9 ± 2.1 t per ton harvested dry mass.

Axenic in vitro cultivation of 19 peat moss (Sphagnum L.) species as a resource for basic biology, biotechnology, and paludiculture.

Sphagnum farming can substitute peat with renewable biomass and thus help mitigate climate change. Large volumes of the required founder material can only be supplied sustainably by axenic cultivation in bioreactors. We established axenic in vitro cultures from sporophytes of 19 Sphagnum species collected in Austria, Germany, Latvia, the Netherlands, Russia, and Sweden: S. angustifolium, S. balticum, S. capillifolium, S. centrale, S. compactum, S. cuspidatum, S. fallax, S. fimbriatum, S. fuscum, S. lindbergii, S. medium/divinum, S. palustre, S. papillosum, S. rubellum, S. russowii, S. squarrosum, S. subnitens, S. subfulvum and S. warnstorfii. These species cover five of the six European Sphagnum subgenera; namely, Acutifolia, Cuspidata, Rigida, Sphagnum and Squarrosa. Their growth was measured in suspension cultures, whereas their ploidy was determined by flow cytometry and compared with the genome size of Physcomitrella patens. We identified haploid and diploid Sphagnum species, found that their cells are predominantly arrested in the G1 phase of the cell cycle, and did not find a correlation between plant productivity and ploidy. DNA barcoding was achieved by sequencing introns of the BRK1 genes. With this collection, high-quality founder material for diverse large-scale applications, but also for basic Sphagnum research, is available from the International Moss Stock Center.

Temporal dynamics in the taxonomic and functional profile of the Sphagnum-associated fungi (mycobiomes) in a Sphagnum farming field site in Northwestern Germany.

The drainage of peatlands for their agricultural use leads to huge emissions of greenhouse gases. One sustainable alternative is the cultivation of peat mosses after rewetting ('Sphagnum farming'). Environmental parameters of such artificial systems may differ from those of natural Sphagnum ecosystems which host a rich fungal community. We studied the fungal community at a 4 ha Sphagnum farming field site in Northwestern Germany and compared it with that of natural Sphagnum ecosystems. Additionally, we asked if any fungi occur with potentially negative consequences for the commercial production and/or use of Sphagnum biomass. Samples were collected every 3 months within 1 year. High-throughput sequencing of the fungal ITS2 barcode was used to obtain a comprehensive community profile of the fungi. The dominant taxa in the fungal community of the Sphagnum farming field site were all commonly reported from natural Sphagnum ecosystems. While the taxonomic composition showed clear differences between seasons, a stable functional community profile was identified across seasons. Additionally, nutrient supply seems to affect composition of fungal community. Despite a rather high abundance of bryophyte parasites, and the occurrence of both Sphagnum-species-specific and general plant pathogens, their impact on the productivity and usage of Sphagnum biomass as raw material for growing media was considered to be low.

Nutrient dynamics of Sphagnum farming on rewetted bog grassland in NW Germany.

The agricultural use of drained peatlands leads to huge emissions of greenhouse gases and nutrients. A land-use alternative that allows rewetting of drained peatland while maintaining agricultural production is the cultivation of Sphagnum biomass as a renewable substitute for fossil peat in horticultural growing media (Sphagnum farming). We studied Sphagnum productivity and nutrient dynamics during two years in two Sphagnum farming sites in NW Germany, which were established on drained bog grassland by sod removal, rewetting, and the introduction of Sphagnum fragments in 2011 and 2016, respectively. We found a considerable and homogeneous production of Sphagnum biomass (>3.6 ton DW ha--1 yr-1), attributable to the high nutrient levels, low alkalinity, and even distribution of the irrigation water. The ammonium legacy from former drainage-based agriculture rapidly declined after rewetting, while nutrient mobilization was negligible. CH4 concentrations in the rewetted soil quickly decreased to very low levels. The Sphagnum biomass sequestered high loads of nutrients (46.0 and 47.4 kg N, 3.9 and 4.9 kg P, and 9.8 and 16.1 kg K ha-1 yr-1 in the 7.5 y and 2.5 y old sites, respectively), preventing off-site eutrophication. We conclude that Sphagnum farming as an alternative for drainage-based peatland agriculture may contribute effectively to tackling environmental challenges such as local and regional downstream pollution and global climate change.

Clonal in vitro propagation of peat mosses (Sphagnum L.) as novel green resources for basic and applied research.

As builders and major components of peatlands, Sphagnopsida (peat mosses) are very important organisms for ecosystems and world's climate. Nowadays many Sphagnum species as well as their habitats are largely protected, while their scientific and economic relevance remains considerable. Advanced methods of in vitro cultivation provide the potential to work in a sustainable way with peat mosses and address aspects of basic research as well as biotechnological and economical topics like biomonitoring or the production of renewable substrates for horticulture (Sphagnum farming). Here, we describe the establishment of axenic in vitro cultures of the five peat moss species Sphagnum fimbriatum Wils. and Hook., Sphagnum magellanicum Brid., Sphagnum palustre L., Sphagnum rubellum Wils. and Sphagnum subnitens Russ. and Warnst. with specific focus on large-scale cultivation of S. palustre in bioreactors. Axenic, clonal cultures were established to produce high quantities of biomass under standardized laboratory conditions. For advanced production of S.palustre we tested different cultivation techniques, growth media and inocula, and analyzed the effects of tissue disruption. While cultivation on solid medium is suitable for long term storage, submerse cultivation in liquid medium yielded highest amounts of biomass. By addition of sucrose and ammonium nitrate we were able to increase the biomass by around 10- to 30-fold within 4 weeks. The morphology of in vitro-cultivated gametophores showed similar phenotypic characteristics compared to material from the field. Thus the tested culture techniques are suitable to produce S. palustre material for basic and applied research.