A 50-year perspective on conservation challenges and legacy effects in temperate Patagonian forests

Accelerated global change, including land use change, is altering plant community composition and challenging conservation in protected areas (PAs) worldwide. Vegetation resurveys of quasi-permanent plots provide insights into these shifts over decades. However, resurvey studies are scarce in the temperate forests of the Andes in northern Patagonia, leaving questions on temporal vegetation dynamics unanswered. We resurveyed vegetation plots of three different forest types (mixed evergreen, coniferous and subalpine) located in Nahuel Huapi National Park >50 years after the original survey, in an area with current minimal but moderate to intense land use in the past. We applied multivariate analyses to assess changes in plant community composition and fitted generalized linear mixed models to compare temporal changes of different life forms and origin groups. Species gains and losses were analyzed by resurvey location and “winner” and “loser” species were identified. Our results indicate biotic homogenization of montane mixed evergreen and coniferous forests, ongoing understory closure and an increasing dominance of non-native species. Conversely, subalpine forests showed a more stable composition over time. These findings underscore the significance of legacy effects, i.e., land-use practices occurring decades ago having residual influences on the current biological composition. We conclude that without conservation management following intensive land use, such as non-native species removal, neither local nor global biodiversity conservation goals are likely to be met. • Resurvey of temperate Patagonian forests shows major shifts in plant communities over 50 years. • Coniferous and mixed evergreen forests exhibit composition change and an increasing resemblance between the types. • In contrast, subalpine forests show a more stable composition and an increase in woody species • Non-native species have increased in frequency, becoming apparent winners under global change. • Legacy effects of past land use still shape forest dynamics and challenge conservation goals.