Untangling nutrient co-regulation of ombrotrophic peatland development

Abstract

Ombrotrophic peatlands are the largest terrestrial store of global carbon (C). While hydroclimate controls over peatland development are well known, the importance of nutrient fluxes has been researched less. Atmospheric nutrient fluxes to peatlands have increased with human activity in recent centuries. Here we explore the interplay of nutrient and hydroclimate drivers at Holcroft Moss (northwest England), a lowland ombrotrophic peatland typical of many across northern Europe. Parallel multi-proxy characterization of the organic matter composition and nutrient accumulation rates shows a sequence dominated by switches between fresh less decomposed layers and more decomposed peat containing abundant recalcitrant organic compounds. Hydroclimate variability governs much of the stratigraphy. Shifts to wetter conditions appear to trigger periods of reduced decomposition centred c. 3450, 2600–2500, 2225, 2060, 2000, 1825, 1650–1610, 1540, 1480, 1260, 1125, 1000, 740–720 and 600–550 cal. a BP. In addition, elevated N and P deposition beginning ~1000 cal. a BP, accelerating ~500 years cal. a BP, has led to changes in the co-behaviour between hydroclimate, peat composition and C accumulation rates. Long-term carbon/nutrient accumulation rates at Holcroft Moss are high compared to other UK peatlands measured to date. Higher nutrient fluxes from human activities will persist through the 21st century, with the implications for long-term peatland resilience and this important carbon sink unclear. Restoration and management of peatlands understandably focus on hydrology and vegetation, but we show a parallel need to consider nutrient deposition, which will vary site by site.