Existing field scale experiments

Existing sites with manipulation experiments are available at Mols (DK), Abisko (S) and Zackenberg (Greenland). These sites have involved manipulations with climatic factors alone or in combination with other factors (e.g. nutrient addition) for 8-20 years and are still in operation. None of these sites are in them selves suitable for the manipulations with multiple stress factors planned in this project (logistics, situation, accessibility etc.). However, they provide an excellent opportunity to supplement the studies at the new site for several reasons:

• Long-term studies – Even though the new site will be manipulated for 4 years, which in terms of research projects is relatively long time, this time span will still be relatively short in relation to the time span for ecosystem processes. This inherently causes a problem when using the results to predict future changes. Using the ongoing long-term studies provides an opportunity to assess the long-term sustainability of the observed changes.
• Generality and representation – results obtained at a single site may inherently cause problems when trying to upscale the results to larger areas, as it often remains uncertain to what extent the results represent general trends or are restricted to the site. The ongoing sites provide an opportunity to assess the generality of the results obtained at the new site by comparing results across sites.