Biodiversity, decomposition, and CO2 emissions effects after the implementation of regenerative ditch borders in a Dutch peat agroecosystem

The majority of NW European peatlands are degraded due to management associated with conventional livestock farming (i.e. increased drainage, high nutrient inputs and frequent mowing). This leads to increased CO₂ emissions, eutrophication, land subsidence, and biodiversity loss. Creating regenerative ditch borders along the drainage ditches that surround agricultural fields could locally ameliorate some of these negative effects. We investigated the impacts of implementing regenerative ditch borders on carabid beetle and plant diversity, soil characteristics, litter decomposition (Tea Bag Index (TBI) and leaf and root litter bags), and CO₂ emissions in a Dutch fen agroecosystem throughout one year. On average we found lower numbers of carabid beetles in regenerative ditch borders, but a higher presence of specialist species. Species diversity remained unaffected by ditch border type. Plant diversity was higher in regenerative ditch borders. We also measured a clear shift in the dominant plant species between ditch border types, shifting from Lolium perenne in conventional borders to Phragmites australis in regenerative borders. Regenerative ditch borders were associated with higher values of soil moisture, soil organic matter content and carbon-to-nitrogen ratio and lower bulk density and soil compaction in comparison to conventional borders. The decomposition rate of standardized litter (TBI) was unaffected by ditch border type, but local leaf litter collected from regenerative borders (P. australis leaves) decomposed 75% slower than leaf litter from conventional borders (L. perenne leaves). Thus, litter decomposition between ditch border management types was driven by lower litter quality of aboveground litter produced at regenerative borders, and not by changes in soil characteristics (e.g. higher moisture levels). Nevertheless, projections from a locally-calibrated soil respiration model estimates that soil moisture effects significantly reduced CO₂ emissions from regenerative borders compared to conventionally managed sites. Changes in vegetation composition and microenvironmental conditions resulting from regenerative management can therefore be expected to increase carbon storage and reduced peat respiration rates in ditch borders. This study highlights the importance of combining vegetation shifts with emission mitigation measures from peat agroecosystems and identifies possible trade-offs between biodiversity conservation and ecosystem services.