WHIM

• Ombrotrophic bog
• 20 miles south of Edinburgh
• low background N deposition, approx 8 kg-N and S ha^-1 a^-1
• Experimental facility to separate the effects of oxidised and reduced N on ombrotrophic bog vegetation, Calluna, lichens and mosses in particular.
• Power, no running water, field laboratory, access by car, secure.
• Funded by GANE, Access agreed with William Sinclair Horticulture Ltd. Designed and constructed by Alan Crossley with the help of Frank Harvey, Ian Leith, Alec Horsburgh, Kevin Ingleby, Ken Hargreaves, Mark Theobold and Jennifer Carfrae.

This large field facility is almost completed. The Whim field site has been designed for the application of wet deposited N as NO₃^- or NH₄⁺, at 3 doses up to 64 kg N ha^-1 yr^-1, with and without PK, and NH₃ gas (dry deposition) to replicated plots (4 blocks) at study site 15 km from CEH-Edinburgh. Ion concentrations will be 10 mmol maximum and generally the spray will be applied concomitantly with rain causing further dilution. Importantly this site is in an area of low background N and S deposition. The site is an ombrotrophic bog that has not been managed in recent years and supports a thriving bryophyte and lichen community in 'gaps' where the Calluna has died back. The experiment is the first to compare all 3 N forms at the same site and should yield data on Critical Levels for NH₃.

Measurements of interactions with stress, water relations and frost hardiness are intended. Gutters will be installed to collect throughfall and pre-treatment samples will be collected for chemistry from the vegetation and soil both on the edge and out with the plots. All plots will be surveyed for vegetation cover and composition. One kilometre of boardwalk has been installed to facilitate access to the plots without walking on them and two 6 metre 'Spandecks' have been purchased for sampling purposes. There is mains power in the hut to run the automatic Dosatron irrigation system which will treat 12 m² plots uniformly. The NH₃ will be supplied from a line source carried by the prevailing wind and monitored with alpha badges placed exponentially along a transect. Meteorological equipment has been installed to co-ordinate the spraying and fumigation and rain will be collected for chemistry and spraying purposes at the site.

If you would like to be involved in this experiment please contact Lucy Sheppard at ljs@ceh.ac.uk. At present there is funding for 2 treatment seasons but efforts are being made to secure a more long-term future.