Modelling of rare plant species richness by landscape variables in an agriculture area in Finland

A multivariate linear regression model is proposed for predicting and mappi ng rare vascular plant species richness in Finnish agricultural landscapes according to landscape variables. The data used in developing the model wer e derived from a floristic inventory from 105 0.5 km x 0.5 km grid squares. Using a stepwise multiple regression technique, four landscape variables w ere found to explain 71.8% of the variability in the number of rare plant s pecies. The results suggest that the local 'hotspots' of rare plants (squar es with greater than or equal to5 rare taxa) are mainly found in heterogene ous river valleys, where extensive semi-natural grasslands and herb-rich fo rests occur on the steep slopes. According to other similar studies, interm ediate human disturbance increases the number of rare species in agricultur al landscapes. It appears that empirical models based on landscape variable s derived from digital maps can provide relatively accurate surrogates for extensive field surveys and fine-scale observations on the distributions of rare taxa in agricultural landscapes. Potential reasons for the performanc e of the model and the ecology and habitats of the species concerned are di scussed.