Speuld is the site of a 30-year-old Douglas fir plantation, at which large scale manipulations have been carried out as part of the NITREX project. The site is located in central Netherlands on well drained, acidic sandy soil which receives extremely high deposition of acidic compounds, in particular nitrogen pollution. The response of the ecosystem to reduced deposition of pollutants has been studied by a large scale experimental programme in which a roof beneath the tree canopy act to exclude acid throughfall. Clean rain is added beneath the roof. At Speuld, several models will be applied (MERLIN, SMART2, and NUCSAM) and their compatibility and applicability assessed.