Restoring seed dispersal processes in a tropical agricultural landscape

Introduction / Background / Justification - The Los Tuxtlas Biosphere Reserve includes a large area of agricultural landscape that over the years has gained more land and has reduced the extension of the tropical rainforest in the region. High historical deforestation and fragmentation is threatening biodiversity and have caused the loss of many ecosystem services. Today, not only the conservation of biodiversity is at risk, but also the main livelihood of the communities that live within the reserve. With this scenario in mind, in 2006 we established 24 experimental restoration plots immersed in an active pasture.

Objectives- The main objective of the project was to restore biological interactions to favor the conservation of biodiversity and landscape connectivity.

Methods- Each plot had one of three treatments: 1) plots under natural succession, 2) plantations of tree species dispersed by wind, or 3) plantations of tree species dispersed by animals. For 15 years we have evaluated soil attributes (e.g., fertility, litter), performance (e.g., survival and growth) and functional attributes (e.g., leaf traits) of planted species. Additionally, we assessed seed dispersal, seedling recruitment and its limitation (e.g., demographics, phylogenetic and functional diversity, fruiting, establishment limitation) and the presence of animals (e.g., birds, bats, beetles).

Results- Each treatment revealed distinct restoration pathways that favored different biological interactions. For example, in plots with animal-dispersed trees we found a greater diversity of bats and had earlier seedling growth peeks while plots planted with wind-dispersed trees, seedling abundances recruitment was favored. Nevertheless, the abundance and richness of recruits that are bird-dispersed, late successional seedlings, such as Red Listed Ocotea uxpanapana, were favored in both planted treatments. On the other hand, in natural succession we found more recruits with diameters greater than 30 cm, greater fruiting rates compared to planted plots and greater abundance of insectivorous birds, yet, these plots also had the highest areas covered with invasive ferns. Here, we show a synthesis of 30 parameters evaluated over 15 years of ecological restoration. In the current scenario, the design of multifunctional landscapes through different strategies that allow the optimization of resources will be essential for adaptation to climate change.

Implications/Conclusions- The results of this project can inform larger scale strategies for the region and for other areas with similar climatic and biological characteristics, as well as contribute to a National Restoration Plan.