Forestry law in Switzerland allows cantonal authorities to define forest reserve areas of at least 5 ha. During a university field-training course in botany, postgraduate students carried out vegetation studies to determine the most appropriate size for an area of completely unmanaged forest reserve within a forest division near Bevaix (canton of Neuchâtel). On the 50 plots of an experimental grid a phytosociological survey and forest mensurations were carried out and the amount of dead wood was determined. Plant biodiversity and tree regeneration were studied by means of a plant survey. Each plot was assigned a score depending on its specific value to a forest reserve. Results suggest that a surface area of 7 ha is most likely to achieve the goal. The grid points of the chosen plots are permanently marked in the field, in order to facilitate further inventories and follow-up studies.