Using Ellenberg indicator values to assess soil quality in British forests from ground vegetation: a pilot study.
As a pilot study, descriptions of the vegetation and soil sampling were carried out on 20 British forest sites to investigate the soil factors likely to be of importance in assessing soil quality for silvicultural/ecological purposes, and to see how useful indicator species were in predicting soil factors. Soil analytical properties, mostly expressed in units of kg/ha, were examined statistically by principal components analysis. The vegetation descriptions were treated numerically by assigning to each plant species Ellenberg indicator values for F (soil moisture), R (soil reaction) and N (soil nitrogen). The indicator values were weighted either using the Domin scores for abundance or the frequency of each species in the vegetation. Measures of nitrogen availability (especially mineralizable NO3 and NH4) and pH were the most important variables loading Principal Component 1 (PC1). The site mean indicator values for R (mR) and N (mN) were combined (mR + mN) to provide a simple proxy for 'soil nutrient regime', and the site mean indicator value for F (mF) was used as a proxy for 'soil moisture regime'. The scores for each site on PC1 were related to the values of mR + mN. A grid formed from mF and (mR + mN) was used to ordinate the sites in terms of 'soil quality' (soil nutrient regime and soil moisture regime). Further work along similar lines is proposed to enable local (British) ecological indicator values for plant species to be developed.