How Secondary Forests Heal: Biomass Recovery and Restoration Pathways in the Colombian Amazon

Redacción HC
16/01/2025

In the Colombian Amazon, decades of deforestation have left a legacy of fragmented landscapes — but also a growing opportunity: secondary forests (SF). These regenerating woodlands, left to recover after disturbance, hold enormous potential for carbon storage, biodiversity revival, and ecosystem resilience. However, understanding how quickly and effectively they regain ecological function is key to designing science-based restoration strategies.

A new study published in Diversity (2025) by Carlos H. Rodríguez-León and colleagues explores how biomass, diversity, and forest structure evolve over time in different topographic settings — specifically comparing hills (<300 m) and mountains (>300 m) in Caquetá, Colombia. The findings shed light on the temporal and spatial dynamics of forest recovery, offering practical guidance for policymakers and land managers seeking to scale up restoration in the Amazon basin.

Why Study Secondary Forests?

Secondary forests (SFs) are essential for Latin America’s ecological restoration efforts. They naturally reoccupy abandoned pastures, agricultural plots, and degraded lands, representing a low-cost and scalable option for climate mitigation. Yet, not all SFs recover equally — and little is known about how local factors like terrain and soil conditions influence that recovery.

The study’s central question: How do key forest attributes like biomass, species diversity, and soil properties recover over time in different Amazonian landscapes?

Understanding these dynamics is crucial for setting realistic carbon goals, selecting priority areas, and designing effective territorial policies for long-term sustainability.

Tracking Forest Recovery Over Time and Terrain

The researchers conducted a chronosequence analysis — a common ecological method that infers recovery patterns by comparing forests of different ages — across 54 secondary forest plots (0.25 ha each), ranging from 5 to 40 years old. These were compared with 25 mature forests as benchmarks.

Measured Variables

• Aboveground biomass (AGB): estimated using the Chave equation
• Species diversity: richness and diversity indices (Shannon, Simpson)
• Forest structure: tree height, diameter, stem density
• Soil quality: pH, organic matter, magnesium saturation, etc.

Analytical Techniques

• Generalized Linear Models (GLMs)
• Non-Metric Multidimensional Scaling (nMDS)
• Structural Equation Modeling (SEM) to test causal links

What the Forests Revealed: Biomass and Beyond

1. Biomass Accumulation Is Steady — and Uneven

Secondary forests increased biomass and diversity with age, confirming the principle of ecological succession. However, mountains recovered faster: after 40 years, they had regained ~63% of mature forest biomass, compared to just ~42% in hills. In hill regions, the annual carbon gain was estimated at 0.708 Mg C ha⁻¹ year⁻¹ — a relatively modest pace.

“Biomass accumulation was driven primarily by forest age, with topography modulating the speed of recovery.”

2. Forest Age Is the Primary Driver

Using SEM, the team found that forest age had the strongest direct effect on biomass (effect size E = 0.74, p<0.001). Soil properties played a minor but significant role (E = −0.23, p=0.024), while diversity and structure contributed indirectly — closely correlated with the forest’s age.

3. Soil Matters, But Not Equally Everywhere

While soils influenced regeneration, their effects were more evident in hills, where lower quality and higher degradation may delay succession. This underscores the need for targeted soil management in flatter terrains.

4. Species Composition Evolves Gradually

The nMDS analysis showed progressive shifts in species composition over time, regardless of topographic differences. This suggests that succession follows similar species turnover patterns whether on hills or mountains — albeit at different speeds.

Restoration and Policy Takeaways

1. Not All Secondary Forests Are Equal

Mature secondary forests (>40 years), especially in mountainous areas, should be prioritized for carbon financing, biodiversity corridors, and legal protection. Meanwhile, hill forests require assisted regeneration techniques — such as agroforestry, soil amendments, or enrichment planting.

2. One Landscape, Two Strategies

• Mountains: favor natural regeneration, minimal intervention needed.
• Hills: require soil conservation practices to accelerate ecological recovery.

3. Indicators for Monitoring

Restoration efforts must use measurable indicators like AGB, diversity, and structural attributes to track progress and allocate resources effectively.

4. Territorial Governance

Sustainable land-use planning in post-deforestation zones must recognize geomorphological heterogeneity. The study supports territorial zoning that integrates biophysical conditions into forest policy.

The Next Frontier: Long-Term Monitoring and Modeling

Despite its insights, the study has limitations. As a chronosequence analysis, it infers trends without tracking the same plots over time. Future research should:

• Conduct longitudinal monitoring to validate these findings
• Include climatic and connectivity variables
• Expand to other Amazonian regions for broader applicability
• Define AGB and diversity thresholds to prioritize intervention zones

Conclusion: A Time-Lapse of Forest Healing

This research provides an invaluable time-lapse of ecological restoration in one of the planet’s most vital ecosystems. It shows that age remains the best predictor of ecological recovery, but landscape characteristics influence how fast forests bounce back.

“Forest restoration is not just about planting trees — it’s about letting forests grow, adapt, and mature within the right ecological and social context.”

For land managers, donors, and policymakers, these findings underscore the value of differentiated, evidence-based restoration strategies that reflect the true complexity of Amazonian landscapes.

Topics of interest

Biodiversity