Functional trajectory for the assessment of ecological restoration success

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Ecological restoration aims to recover an ecosystem to a state before degradation. Comparison to reference ecosystems (old‐growth forests) is a key component to define if restoration goals have been achieved (“success”). Nevertheless, it is still unknown how the functional composition of the initial community influences the trajectory of the ecosystem through time. Here, we evaluated restoration success based on the functional trajectory of six 20‐year‐old forest communities planted in the Brazilian Atlantic Forest with distinct combinations of ecological groups (pioneers, secondary, and climax). These six communities ranged their species predominance regarding resource‐use strategies, potential size, and functional diversity. To evaluate restoration success, we compared the functional trajectory between the six planted communities after 20 years of secondary succession and calculated their trajectories toward or away from the reference ecosystem. We found that the initial composition influenced the functional trajectory of the communities undergoing restoration and it was a key element to their success. Only the community planted using the highest functional diversity (i.e. pioneer + early and late secondary + climax species) became functionally similar to the reference ecosystem 20 years after planting. The functional trajectories were mostly driven by the mortality of planted individuals than by the colonization of new species. The regeneration is still functionally similar independently of the treatment evidencing little influence of priority effects in this stage of succession. Our study indicated that the initial functional composition of planted forest communities influences the magnitude and direction of their functional trajectory and may influence restoration success.