Tropical forest restoration enriches vascular epiphyte recovery

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Abstract

Questions:

Vascular epiphytes constitute a large proportion of tropical forest plant biodiversity, but are among the slowest plants to recolonize secondary forests. We asked whether tree planting for ecological restoration accelerates epiphyte community recovery. Does the spatial configuration of tree planting matter? What landscape contexts are most suitable for epiphyte restoration?

Location:

Restored pastures in premontane Coto Brus County, Puntarenas, Costa Rica.

Methods:

We surveyed vascular epiphyte species growing on the lower trunks of 1083 trees in 13 experimental restoration sites. Each site contained three 0.25-ha treatment plots: natural regeneration, trees planted in patches or ‘islands’ and tree plantations. Sites spanned elevational (1100–1430 m) and deforestation (4–94% forest cover within a 100-m radius around each site) gradients.

Results:

Vascular epiphytes were twice as diverse in planted restoration plots (islands and plantations) as in natural regeneration; we observed this at the scale of individual host trees and within 0.25-ha treatment plots. Contributing factors included that trees in planted restoration plots were larger, older, more abundant and composed of different species than trees in naturally regenerating plots. Epiphyte species richness increased with surrounding forest cover within 100–150 m of restoration plots. Epiphyte communities were also twice as diverse at higher (1330–1430 m) vs lower (1100–1290 m) elevation sites. Epiphyte groups responded differently to restoration treatments and landscape factors; ferns were responsible for higher species richness in planted restoration plots, whereas angiosperms drove elevation and forest cover effects.

Conclusions:

Tree planting for ecological restoration enriched epiphyte communities compared to natural regeneration, likely because planted forests contained more, bigger and older trees. Tree island plantings were equally effective compared to larger and more expensive plantations. Restoration sites nearer to existing forests had richer epiphyte recolonization, likely because nearby forests provisioned restoration sites with angiosperm seeds. Collectively, results suggest that restoration practitioners can enrich epiphyte community development by planting trees in areas with higher surrounding forest cover, particularly at higher elevations.

Epiphytes make up 10% of the world's vascular plants, but they are rarely considered in ecological restoration. We show that 10-yr old tree plantations hosted twice as many epiphyte species as naturally regenerating forests. Restoration sites near existing forests had richer epiphyte recolonization than isolated sites, suggesting that restoration ecologists can accelerate epiphyte succession by planting trees in appropriate landscapes.

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