Rainforest’s Next Tree Generation at Risk 30 Years Post-Logging

Recent research indicates that seedlings in natural rainforests have higher survival rates compared to areas previously subjected to logging, despite efforts of tree restoration projects. This study is featured in Global Change Biology.

Researchers monitored over 5,000 seedlings for eighteen months in North Borneo. They explored a landscape that included natural forests and areas logged three decades ago, with some undergoing natural recovery while others underwent restoration through methods such as tree planting. A drought induced “mast fruiting” across the region, leading to simultaneous fruit shedding by trees and emergence of new seedlings.

Transient Benefits and Lingering Challenges

Initially, both natural and restored forests showed similar high seedling numbers compared to naturally recovering areas, indicating that restoration efforts enhanced fruit production. However, this advantage proved short-lived: poor seedling survival in restored forests led to equally low seedling numbers in both restored and naturally recovering areas by the study’s end. Seedling populations remained higher in natural forests.

These findings highlight challenges to regeneration influenced by restoration methods—seed availability in naturally recovering sites and seedling survival in areas with mature planted trees. Such variations could have long-term implications for forests’ ability to provide essential ecosystem services like carbon sequestration.

Dr. Robin Hayward, who conducted this research as part of their doctoral studies at the University of Stirling, expressed surprise at the lower seedling survival observed in restoration sites. Reflecting on the aftermath of a fruitful event in the restored forest, Dr. Hayward noted the disappointment in the limited survival of seedlings and raised concerns about the implications for the long-term recovery of various tree species.

Restoration efforts have shown benefits in biomass accumulation in these forests, but achieving full establishment of the next generation of seedlings remains challenging.

Challenges in Forest Regeneration

Dr. David Bartholomew, formerly of the University of Exeter and now with Botanic Gardens Conservation International, highlighted that seedlings in logged forests are stressed due to changes in canopy structure, microclimate, and soil. Current restoration methods seem inadequate in mitigating this stress, especially for specialized species, leading to reduced species diversity compared to intact forests.

Daisy Dent, affiliated with ETH Zürich, Switzerland, and the Smithsonian Tropical Research Institute, Panama, emphasized the complexity of rainforest ecosystems. She noted that factors like seed predation by animals such as bearded pigs may affect seedling survival differently in restored and natural forests.

Selective logging is widespread in tropical regions, highlighting the importance of long-term recovery for preserving carbon stocks and biodiversity. The low survival rates of seedlings three decades after logging raise concerns about future tree regeneration.

Insights into Plant Community Recovery and Future Research Directions

Dr. Lindsay F. Banin from the UK Centre for Ecology & Hydrology explained that the study reveals potential hindrances in the recovery of certain plant community elements. Further research will investigate regeneration process stages to better comprehend observed patterns and promote forest regeneration.

The study underscores the significance of meticulously designing, monitoring, and adjusting restoration projects to revive biodiversity and biomass carbon in the long run, aligning with global objectives outlined in the UN Kunming-Montreal Global Biodiversity Framework and the UN Decade on Ecosystem Restoration.

Variations in local environmental conditions between restored and degraded areas may result from greater biomass and canopy cover in the former. Understanding the low survival rates of seedlings may hinge on analyzing plant traits, indicating the resources plants struggle to access.

Implications for Biodiversity and Ecological Functioning in Disturbed Areas

The study observed disparities in plant traits between logged areas and intact forests, suggesting that some species may struggle to flourish in disturbed areas, while others may adapt their growth patterns. These differences could affect long-term biodiversity and ecological functioning.

While this study examines data 18 months after a single fruiting event, further research is needed to fully grasp the effects of historical disturbance and strategies to enhance seedling survival.

Conducted in the Danum Valley Conservation Area and surrounding Ulu Segama landscape of North Borneo, the study focuses on intact forests dominated by the Dipterocarpaceae tree family. These forests experience large inter-annual fruiting episodes known as masting events, significantly impacting food availability for animal species.

Read the original article on: Phys org

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