Tropical forests cover more than half of the world's tropical land area, but they have suffered severe degradation due to human activities. Meanwhile, traditional large-scale reforestation is costly and prone to causing ecological homogenization.
In a study published in Restoration Ecology, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences showed that the "applied nucleation" method (i.e., planting small tree patches to start recovery) has significantly restored a degraded tropical riparian corridor in southwest China. The study also warned that without active intervention, recovering areas may remain stuck in an early-successional stage dominated by sun-loving pioneer trees.
In 2003, the researchers planted small clusters (or "nuclei") of native trees along a 12-km degraded riparian corridor. Each nucleus included three fig species (Ficus racemosa, Ficus benjamina, and Ficus hispida) and nine other native trees. After only two years of weeding and watering, the sites were left to regenerate naturally.
Over a 20-year monitoring and evaluation period (2003–2023), the researchers quantitatively assessed the effectiveness of the applied nucleation method at both community and landscape scales, while analyzing the impact of planting strategies that centered on fig species as core species for ecological restoration.
The researchers compared three types of sites: planted nucleation areas (NAs), natural expansion areas (EAs) that developed from those nuclei, and reference plots in a nearby seasonal rainforest.
They found that after two decades, tree diversity and biomass in the restored forest (NAs and EAs) reached only 19–30% of the levels in the reference forest. The functional composition revealed a "pioneer bottleneck": light demanding pioneer species accounted for over 75% of the community, whereas shade tolerant species dominated 80% of the reference forest. This indicates that the restored forest remains in an early successional stage.
Notably, fig trees contributed 76.8% of the tree biomass in the NAs, acting as crucial foundation species that rapidly built the structural skeleton of the recovering forest.
"Applied nucleation, which requires less intensive land management and lower input costs than traditional large-scale plantings, offers a feasible path forward. However, recovery is a multi decade process, and restoring biodiversity will require sustained effort and possibly additional active management," said SONG Liang of XTBG.
The researchers recommended using high-biomass foundation species as nucleation cores while implementing proactive management of successional stage differences to optimize restoration outcomes.
First published: 01 June 2026
