Ruabon Moor

LINKS

Contacts:

Chris Field

Simon Caporn

Publications

Background

Ruabon Moor is a 35 km² expanse of relatively dry heather-dominated moorland at between 350 m and 600 m above sea level. The land is part of a shooting estate, but is also a Site of Special Scientific Interest (SSSI), a Special Protection Area (SPA) and a Special Area of Conservation (SAC) with Natural Resources Wales and the Royal Society for the Protection of Birds as interested parties. It is classified as H12 Calluna vulgaris-Vaccinium myrtillus heath. The experimental plots are located on a gentle southwest-facing slope at 470 m altitude and represent the longest-running N addition experiment of its type in the world. At the time of establishment of this LTE, there was limited direct experimental evidence of changes in upland heathland in response to nitrogen (N) deposition.

Established in 1989, the experiment has run over two phases, with a new group of 36 larger plots added in 1998. The original plots were subjected to a controlled management burn in March 2000. This removed the heather canopy but left the litter and peat layers intact, and post-fire recovery has been followed ever since. Vegetation structure and heather growth have been surveyed regularly.

Throughout its early years, the experiment was one of several sites operating under the former UKREATE umbrella project funded by the Department for Environment Food and Rural Affairs (Defra) and the Natural Environment Research Council (NERC).

Plot Treatments

The original 1m² plots were established in 1989 with four replicates. Monthly applications of N in the form of ammonium nitrate are added at 0, 40, 80 and 120 kg N per hectare per year. In 1998, a new set of larger 4m² plots were established on the same site, again with four replicates, in a randomised block design of overall size 20 m x 20 m. These plots also then received monthly N treatments added at 0, 10, 20, 40 and 120 kg N per hectare per year but with additional phosphorus treatments of 20 kg per year alongside selected 0, 20 and 120 kg N treatments. These continued until 2003, at which point all plots were split, with treatments continuing on one side whilst the other side became a recovery experiment with no treatments.

Summary of Results to Date

In the early years, the growth of heather responded positively to nitrogen treatment but this led to an acceleration through the heather life cycle stages, so the mature and degenerate phases arrived earlier. In managed heathlands, this could result in the need for more frequent management (cutting, burning) in higher nitrogen-polluted regions. Nitrogen added tended to accumulate in the plant-soil system along with extra assimilated carbon but following burning, increased leaching of inorganic and organic nitrogen was measured. While nitrogen increased growth of the dominant heather, the abundance and diversity of lower plants was reduced, but phosphate treatments increased bryophytes and lichens compensating somewhat for the nitrogen effect. Various results of the experiments have been adopted in field survey of nitrogen impacts on a larger landscape scale.

These earlier results from the experiments provided insight into nitrogen responses in ecosystems and, as with all the UKREATE umbrella sites, contributed to Defra’s guidance on nitrogen and provided the science supporting critical loads and critical levels for nitrogen.

Further Information

Access a full review of the UKREATE project.

For a more detailed review of the history of the Ruabon Moor site and experiment, listen to our on-site podcast with one of the Principal Investigators Simon Caporn.

Treatments and monitoring at Ruabon Moor continue to date. If you are interested in accessing more recent data or in using this site for new collaborative research, please contact either Chris Field or Simon Caporn via the links at the top of this page.