Rewilding blanket bog from former conifer plantations: hydrological processes, aquatic biogeochemistry and carbon fluxes.

Ombrotrophic blanket mires are significant components of the upland hydrological and biogeochemical cycles, but are scarce in the North York Moors, one of the driest uplands in the British Isles. Our research focuses on a rewilding project centred on May Moss (SSSI), which includes the largest (71 ha) intact, ombrotrophic blanket mire in the North York Moors National Park. The peatland is located on the watershed between the flood-prone River Derwent and Eller Beck (River Esk) catchments. East of the intact mire is a 70.6 ha area managed by the Forestry Commission and planted with Pinus contorta and Picea sitchensis forestry 1975-1983. In 2009, funds received from the SITA Trust (Enriching Nature Programme), facilitated the large-scale removal of forestry and a programme of peatland rewetting.

Since August 2010, adjacent intact and restoring sites on May Moss have been monitored, to assess the hydroclimate controls over intact blanket bog hydrology and the extent of hydrological recovery of a deforested blanket bog. Hourly hydroclimate monitoring includes assessment of the evaporative fluxes and recorded changes in the bog water table. Monitored differences between the sites since 2017 have highlighted their responses to drought, summer water table drawdown and winter recharge, and suggest an incomplete recovery of the deforested site a decade later.

Water samples collected from the intact (Eller Beck) and restoring (Long Grain) catchments every two days since summer 2017, parallel to hourly discharge data, have been analysed for water biochemistry. Parameters include colour (UV-vis spectroscopy), dissolved and particulate organic carbon, dry mass chemistry and organic components (e.g. quantifying fulvic and humic acid proportions by near-infrared spectroscopy). The data show differences in water quality between the intact and recovering catchments, but similarities in temporal patterns and seasonal behaviour. For example, both catchments experienced a significant shift from humic to fulvic acid-dominated that accompanied the water table rise ending the 2018 drought. Sudden changes in the water table appear to produce flushing or changes in water sources within the peatland.

Monthly and replicated campaign-based measurements of net CO₂ exchange rates (NCER) on the intact and restoring sites accompany the biogeochemical time series developed for waters draining May Moss. In addition, we have built and are evaluating prototype low-cost replicated automated Arduino gas flux chambers for measuring CO₂ and CH₄ fluxes as a viable alternative to expensive conventional chamber-based flux systems. Together, the coupled monitoring of aqueous and gaseous C fluxes from both intact and recovering sectors of May Moss parallels hydroclimate analyses that quantify and close the net hydrological budget, and provide a robust basis for assessing the controls over the carbon budget of intact and recovering peatlands.