Costing the legacy of forestry on a Northern Irish blanket bog

Glenwherry Hill Farm, Co. Antrim (Glenwherry) is a research facility, owned by the Northern Ireland Department of Agriculture, Environment and Rural Affairs, occupies an area of 2600 hectares in the Antrim Hills between Larne and Ballymena, Co. Antrim. Activities at the farm aim to assess the environmental and economic impact of upland land use with a view to establishing sustainable long term land use programmes for uplands across Northern Ireland, as well as similar areas of the UK and the Republic of Ireland.
Blanket peat and peat soils underlie more elevated areas of the site (provide range), with the substrate below the peat consisting of Tertiary basalt bedrock, locally overlain by glacial tills. Land use across more elevated parts of Glenwherry includes low intensity sheep farming and coniferous forestry (Sitka Spruce and Lodgepole Pine), along with conservation efforts supporting a large population of native red grouse (90 breeding pairs) on open moorland. A number of streams flowing across the farm supply the Killylane Reservoir, run by Northern Ireland Water and supplying, on average, 12 megalitres a day to a population equivalent of 60,000 people.
Since summer of 2019 researchers at Glenwherry, in collaboration with QUBBES personnel, began to monitor hydrogeological conditions in piezometers installed on open blanket bog and in afforested areas on thick peat soil. October 2019 saw hydrometric infrastructure expanded to include two flow gauging points (culverts) at the outlets of two adjacent catchments; one of these drained an area of open blanket bog, while the second contained afforested peatland, felled from October 2019 onwards. Flow gauging at both points from early November, coupled with 24/7 water sampling, permitted contrasts in flow regime and water quality to be compared to investigate the impact of forestry and clear felling with background conditions observed at the Moorland Culvert.
A round of groundwater sampling, completed in January 2020 aimed to examine the contrast in water quality (DOC/colour) from remaining afforested catchment areas, with conditions observed at the outlets of the felled area (Forest Culvert) and the Moorland.
Results
Figure A.1 summarises the results of water quality sampling and reveals a distinct difference in water quality between the forested and formerly afforested areas, and the area of open blanket bog. Non-parametric analysis of variance (ANOVA) of the data reveal the difference to be statistically significant at the 95% level. Similarly, comparison of more easily analysed colour data suggests that samples collected from the Forest Culvert had colour levels approximately 250 Pt/Co (mg/l) units higher than those from the Moorland Culvert. Both DOC and colour correlate strongly, suggest that the Forest Samples had comparable colour levels.