Large trees in restored tropical rainforest

Abstract

Restoration interventions aim to accelerate forest recovery by skipping the early stages of succession where short-lived early-successional tree species dominate. Large trees (≥30 cm of Diameter at Breast Height [DBH]) provide ecosystem functions, such as carbon storage and acting as stepping stones for the movement of animals through the landscape. Here, we evaluated two mixtures of planted and, unplanted areas to figure out which restoration treatment was more successful in skipping the early stages of succession. For this, we measured forest structure of large trees in restoration settings after 10 years in Los Tuxtlas, Veracruz, Mexico. In 2006, cattle grazing was excluded from 24 plots (30 × 30 m). Eight of those plots were planted with 12 wind-dispersed species, eight plots were planted with 12 animal-dispersed species (a total of 2,304 planted trees), and eight plots were left to undergo natural succession without plantings. Planted and naturally recruited trees have been assessed periodically since 2007. A total of 835 planted and naturally recruited trees of 45 species reached large size. Including all trees (planted and recruited), the richness and abundance of late-successional trees was higher in plantings than under natural succession while richness of large recruits of late-successional species was as higher in plantings as in natural succession. Also, including all trees, plantings of animal-dispersed species have higher richness and abundance of trees dispersed by bats and both bats and birds; while species and trees dispersed by birds were present equally at all treatments. Richness and abundance of bat-dispersed recruits were similar in plantings and natural succession while plantings of wind-dispersed species had higher bird-dispersed recruits. Composition heterogeneity, driven by natural recruitment, was largest for early-successional trees in natural succession. After 10 years, the first stages of succession (20–30 years) were skipped in plantings: plantings have higher abundance of large seeded late-successional species. For an overall increase in composition heterogeneity in permanent agricultural landscapes, we suggest establishing areas to undergo natural succession along with plantings that include a higher percentage of late-successional species with large seeds.