Old growth Afrotropical forests critical for maintaining forest carbon

John R. Poulsen, Vincent P. Medjibe, Lee J. T. White, Zewei Miao, Ludovic Banak‐ngok, Chris Beirne, Connie J. Clark, Aida Cuni‐sanchez, Mathias Disney, Jean‐louis Doucet, Michelle E. Lee, Simon L. Lewis, Edward Mitchard, Chase L. Nuñez, Jan Reitsma, Sassan Saatchi, Charles T. Scott, Benjamin Poulter

Research output: Contribution to journalArticlepeer-review

Abstract

Aim
Large trees [≥ 70 cm diameter at breast height (DBH)] contribute disproportionately to aboveground carbon stock (AGC) across the tropics but may be vulnerable to changing climate and human activities. Here we determine the distribution, drivers and threats to large trees and high carbon forest.

Location
Central Africa.

Time period
Current.

Major taxa studied
Trees.

Methods
Using Gabon's new National Resource Inventory of 104 field sites, AGC was calculated from 67,466 trees from 578 species and 97 genera. Power and Michaelis–Menten models assessed the contribution of large trees to AGC. Environmental and anthropogenic drivers of AGC, large trees, and stand variables were modelled using Akaike’s information criterion (AIC) weights to calculate average regression coefficients for all p

ossible models.

Results
Mean AGC for trees ≥ 10 cm DBH in Gabonese forestlands was 141.7 Mg C/ha, with averages of 166.6, 171.3 and 96.6 Mg C/ha in old growth, concession and secondary forest. High carbon forests occurred where large trees are most abundant: 31% of AGC was stored in large trees (2.3% of all stems). Human activities largely drove variation in AGC and large trees, but climate and edaphic conditions also determined stand variables (basal area, tree height, wood density, stem density). AGC and large trees increased with distance from human settlements; AGC was 40% lower in secondary than primary and concession forests and 33% higher in protected than non‐managed areas.

Main conclusions
AGC and large trees were negatively associated with human activities, highlighting the importance of forest management. Redefining large trees as ≥ 50 cm DBH (4.3% more stems) would account for 20% more AGC. This study demonstrates that protecting relatively undisturbed forests can be disproportionately effective in conserving carbon and suggests that including sustainable forestry in programs like reduced emissions for deforestation and forest degradation could maintain carbon dense forests in logging concessions that are a large proportion of remaining Central African forests.
Original languageEnglish
JournalGlobal Ecology and Biogeography
DOIs
Publication statusPublished - 16 Jul 2020

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