Acorn dispersal effectiveness after 27 years of passive and active restoration in a Neotropical cloud forest

Ecological restoration can mitigate the negative effects of loss and degradation of natural ecosystems. However, the efficacy of restoration strategies (active vs. passive) in recovering crucial ecological interactions such as animal seed dispersal remains largely unknown. We evaluated the seed dispersal effectiveness of Quercus insignis, an endangered large-seeded oak of the cloud forest in a landscape in which passive (natural regeneration) and active (mixed plantations) restoration practices were implemented 27 years earlier. We compared acorn forager identity, acorn removal, seed fate (burial, post-dispersal predation), and dispersal distances of Quercus insignis under four vegetation conditions: cattle-grazed pasture with isolated trees (CP), 27-year-old forest under passive restoration (PR), 27-year-old forest under active restoration (AR), and mature forest (MF). We calculated seed dispersal effectiveness (i.e. the number of dispersed seeds that go on to establish as seedlings) for each vegetation condition and identified the main dispersal agents. We also examined the potential influence of masting and seed size on seed dispersal. We found that both restored forests presented similar acorn removal percentages and foragers, with Sciurus aureogaster as the main effective disperser. PR exhibited greater acorn burial and seedling establishment, and thus higher effective seed dispersal, than AR. Dispersal distance was similar in both restored forests. Masting modulated acorn dispersal patterns; in the non-mast year, PR, AR, and MF reached similar values but in the mast year, both restoration strategies had higher acorn removal and post-dispersal predation than those observed in CP and MF. Acorn removal and dispersal distance increased with acorn size. Our results suggest that passive restoration allows for higher effective acorn dispersal than active restoration, especially in the mast year. Nevertheless, natural acorn availability and seed size should be considered in restoration projects as they modulate the recovery and effectiveness of the seed dispersal process.