Forest density drives survival and trait variation in south European understorey species: a continental-scale translocation experiment

Despite their importance for forest biodiversity and functioning, little is known about the responses of south European understory herbs to climate change. We used a translocation experiment in southern and central Europe to unravel the short-term effects of macroclimatic (elevation and latitude) and microclimatic conditions (open vs. dense forests, forest edge vs. core position) on plant survival, flowering, and traits in eight understorey specialists. Forest density was the main driver of survival, with positive effects in the warm and water-limited southern region and negative effects in the northern oceanic region. Forest position had weaker effects, influencing survival, growth, and SLA in contrasting ways at the two latitudes. Most species flowered beyond their northern limit, suggesting the ability for reproduction at higher latitudes. Macroclimate effects on forest herbs interact with forest density, influencing their performance and suggesting complex responses to climate change. Increased vulnerability is expected in relatively open and warmer forests.