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Data from: Removing climbers more than doubles tree growth and biomass in degraded tropical forests

Citation

Finlayson, Catherine et al. (2023), Data from: Removing climbers more than doubles tree growth and biomass in degraded tropical forests, Dryad, Dataset, https://doi.org/10.5061/dryad.zs7h44jb2

Abstract

Huge areas of tropical forests are degraded, reducing their biodiversity, carbon, and timber value. The recovery of these degraded forests can be significantly inhibited by climbing plants such as lianas. Removal of super-abundant climbers thus represents a restoration action with huge potential for application across the tropics. While experimental studies largely report positive impacts of climber removal on tree growth and biomass accumulation, the efficacy of climber removal varies widely, with high uncertainty as to where and how to apply the technique. Using meta-analytic techniques, we synthesise results from 26 studies to quantify the efficacy of climber removal for promoting tree growth and biomass accumulation, and assess when, where, and how removal can be applied most effectively. We find that climber removal increases tree growth by 156% and biomass accumulation by 209% compared to untreated forest, and that efficacy remains for at least 19 years. There was no evidence that enhancement of tree growth varies across region, climate, disturbance context, or removal method, though there are limited studies in Africa and Asia. We also find that biomass benefits are enhanced in older degraded forests and with repeated removal. Extrapolations from our results suggest that climber removal could sequester an additional 6.6 Gigatons of CO2 over 10 years, at low cost, across regrowth and production forests. Climber removal, therefore, could contribute significantly to reducing global carbon emissions and enhancing the timber and biomass stocks of degraded forests, ultimately protecting them from conversion. However, we urgently need to assess the efficacy of removal outside the Neotropics, and consider the potential negative consequences of climber removal under drought conditions and for biodiversity.

Methods

Dataset collected from published articles and associated data. Response data (treatment and control) and variance has then been converted into effect size (standardised mean difference) using metafor and compute.es R packages (Viechtbauer, 2010; Del Re, 2013). Missing variances were imputed using linear relationships between variance, mean growth and sample size. Imputation was run 10 times, generating 10 sets of imputed SD and SS for the tree growth and biomass datasets. Climate variables were calculated from the Climate Research Unit (CRU) (Harris et al., 2020), and elevation was calculated from the International Centre for Tropical Agriculture (CIAT), using the site coordinates with a 1 km buffer (Jarvis et al., 2008).

Usage Notes

finlayson_climber_removal_tree_growth_effect_size: This includes the data required for running the tree growth models: mean tree growth, variance (SD), effect sizes (g and variance), and all variables included in the models in the manuscript. 10 sets of imputed SD and sample sizes are also included, with the corresponding effect sizes.

finlayson_climber_removal_biomass_effect_size: This includes the data required for running the biomass models: mean tree growth, variance (SD), effect sizes (g and variance), and all variables included in the models in the manuscript. 10 sets of imputed SD and sample sizes are also included, with the corresponding effect sizes.

finlayson_climber_removal_study_metadata: Summary of data relating to each study in the analyses. This includes Study ID, study design, removal method, disturbance context, environment and climate variables. Maximum or ranges are given when a single study contributed more than one growth rate to the analysis if growth was measured at several timepoints or for several size classes. 

finlayson_climber_removal_global_extrapolation: Spreadsheet showing all steps in the calculation used to estimate global carbon sequestration potential of climber removal. Details are given of assumptions made and references used.