Can the site conditions required for successful natural regeneration of juniper (Juniperus communis L.) be determined from a single species survey

Background: Ecological surveys often aim to inform biodiversity conservation policy and practice. Survey types differ; all require clear aims and good design. A survey in Scotland was carried out to measure the distribution and health of juniper (Juniperus communis) and potential for its natural regeneration. Aims: Explore if one-off national surveys can inform conservation action by examining, as an example, the Scottish juniper data set to: (1) determine site conditions favourable for juniper regeneration, (2) provide recommendations for site management for regeneration. Methods: Associations between site conditions and juniper occurrence were investigated with principal component analysis (PCA) and using species distribution modelling (SDM). To identify changes in site conditions over time, we compared degree of site suitability for natural regeneration (PCA distance) and population age structure. Results: Twenty-one per cent of the sites showed juniper regeneration. Compared to all juniper sites, conditions at regenerating sites were different (e.g. climatically wetter, lower site fertility). Change over time in conditions was suggested by patterns in population age structure. Conclusions: Following the establishment of a juniper population, site conditions may change, becoming unsuitable for natural regeneration. Historical site information to confirm this is lacking. We cannot answer fundamental questions about the causal mechanisms of the natural regeneration of juniper and question whether one-off survey data can inform conservation management.