Population ecology and dynamics of a remnant natural population of European yew Taxus baccata in a lowland temperate forest - implications for use in reforestation

There is increasing focus on reforestation, but the efforts still often include limited subsets of species despite evidence that tree diversity promote biodiversity and ecological resilience. In addition to these benefits, greater inclusion of rare native species in reforestation efforts would also help conserve these species in an uncertain future. Here, we investigate the population ecology and dynamics of the only remaining historical population of the shade-adapted under- and mid-story tree European yew Taxus baccata in Denmark to inform its potential usage in reforestation. The species has been widely extirpated from European landscapes, and while much used in horticulture, is hardly used in reforestation, so there is limited experience with its requirements and performance. We collected data on all individuals in 2015 and compared them with results from a previous census in 1999. Furthermore, we used boosted regression trees (BRT) modelling to investigate the ecological drivers of the distributions of its different life stages. Our results show a stable T. baccata population, with much regeneration in areas of more open-canopy conditions that also support high survival between life-stages. The BRT results show that moss-dominated microhabitats under moderately shaded conditions are important for T. baccata seedling establishment, while higher light availability is important for survival from sapling to adult life-stages. For use in reforestation, we recommend providing moderately shaded microhabitats to allow the seedlings and small saplings to escape competition while also acting as protection from herbivores. Through their long-lived nature, low stature and evergreen foliage, T. baccata would increase the structural complexity of young woodlands, likely enhancing their value for biodiversity, their ecological resilience, as well as their amenity value. Inclusion of T. baccata in reforestation efforts would also aid its spontaneous recolonization of woodland areas, helping it to build larger, more widespread populations with greater resilience to future pressures.