Tree invasions have become a major conservation problem after the extensive plantation of non-native trees in natural areas. Many of the species chosen for afforestation programs have escaped from cultivation and are encroaching in treeless and forested ecosystems. Although, tree invasions has been shown to have important ecosystem impacts, efforts to quantify their impacts and legacies in the short and long term have been limited. This information is critical for decision-making and to better manage and restore the invaded communities. Here, we discuss multiple methods to measure and monitor tree invasion impacts, using as a case study the invasion of Pinus contorta in Patagonia, Chile. Pinus contorta, a native species from North America, has been widely introduced for afforestation in cold and mountain environments, and is now considered one of the most invasive trees in temperate ecosystems.
Results/Conclusions
Over the last 10 years we, in collaboration with an international network of scientists, have conducted field observations and field experiments that has shown the profound impacts of Pinus contorta invasion in treeless and forested areas of Patagonia. Our observational studies have shown that pines reduce plant diversity, especially in treeless ecosystems, where pines are a novel life form. Pines also increase the amount of biomass and highly flammable fine fuel in the ecosystems increasing the chances of wildfires. Using permanent plots that benefits from the invasion gradient (i.e. space for time substitution), we have been able to detect the microclimatic effects of pine invasions in the forest and in the steppe, which results in drier and shadier conditions underneath the invasion as pine biomass increases. In these plots, we have also recorded the recovery of the invaded community after the experimental removal of pines, and how invasion legacies remain over time, particularly in areas under more advanced invasions. Our approaches, methods and results can provide critical insights in how tree invasion impacts are quantify and monitor globally, and how ultimately tree invasions are controlled and native ecosystem restored.