A FUNCTIONAL TRAJECTORY FRAMEWORK FOR THE ASSESSMENT OF ECOLOGICAL RESTORATION SUCCESS

Ecological restoration aims to recover an ecosystem to a state similar to the condition before degradation. Functional comparison to reference ecosystems (like old-growth forests) is a key component to define if restoration goals have been achieved. Nevertheless, it is still unknown if the trajectory towards the reference depends on the functional structure of the initial community planted, which varies according to its functional diversity and the predominance of a given resources-use strategy (acquisitive vs conservative). We developed a framework to assess the success of ecological restoration, based on the functional trajectory of restored communities. We assessed how the initial composition of planted forest communities changed after 20 years and their functional trajectory changes compared to the reference ecosystem in the Brazilian Atlantic Forest, a biodiversity and restoration hotspot. Our main results indicated that 20 years after planting, restoration treatments exhibited different functional trajectories but none became functionally like the reference ecosystem yet. Nonetheless, our results revealed that the functional trajectory of planted sites is affected by the initial composition. Communities planted with a predominance of more conservative species, functionally moved away from the reference, while communities that started with a higher proportion of acquisitive species had the slightest changes in their functional trajectory. This result suggests a stronger predominance of acquisitive colonizers and survivors when planted communities are on the extreme ends of the functional gradient. Only the planted communities that were in the middle of the functional gradient showed a functional dissimilarity concerning their initial composition. These communities had the most evident functional trajectory towards the reference, indicating the predominance of conservative colonizers and survivors. Our study indicated that the initial functional composition of planted forest communities influences both the magnitude and direction of functional trajectory changes in restored communities. The assessment of the functional trajectory of communities under restoration using our framework showed to be effective to understand how ecological restoration can achieve its goals using reference areas as targets.