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Title: Soil carbon stocks across tropical forests of Panama regulated by base cation effects on fine roots

We report that tropical forests are the most carbon (C)- rich ecosystems on Earth, containing 25–40% of global terrestrial C stocks. While large-scale quantifi- cation of aboveground biomass in tropical forests has improved recently, soil C dynamics remain one of the largest sources of uncertainty in Earth system models, which inhibits our ability to predict future climate. Globally, soil texture and climate predict B 30% of the variation in soil C stocks, so ecosystem models often predict soil C using measures of aboveground plant growth. However, this approach can underestimate tropical soil C stocks, and has proven inaccurate when compared with data for soil C in data-rich northern ecosystems. By quantifying soil organic C stocks to 1 m depth for 48 humid tropical forest plots across gradients of rainfall and soil fertility in Panama, we show that soil C does not correlate with common predictors used in models, such as plant biomass or litter production. Instead, a structural equation model including base cations, soil clay content, and rainfall as exogenous factors and root biomass as an endogenous factor predicted nearly 50% of the variation in tropical soil C stocks, indicating a strong indirect effect of base cation availability on tropicalmore » soil C storage. Including soil base cations in C cycle models, and thus emphasizing mechanistic links among nutrients, root biomass, and soil C stocks, will improve prediction of climate-soil feedbacks in tropical forests.« less
ORCiD logo [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. University of California, Los Angeles, CA (United States). Department of Geography
  2. Bangor University (United Kingdom). School of Environment, Natural Resources and Geography; University of Oxford (United Kingdom). Department of Zoology; Smithsonian Tropical Research Institute, Ancon (Republic of Panama)
  3. Smithsonian Tropical Research Institute, Ancon (Republic of Panama); Morton Arboretum, Lisle, IL (United States); Field Museum of Natural History, Chicago, IL (United States)
  4. University of Oxford (United Kingdom). Department of Zoology
  5. Smithsonian Tropical Research Institute, Ancon (Republic of Panama)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Additional Journal Information:
Journal Volume: 137; Journal Issue: 1-2; Journal ID: ISSN 0168-2563
Research Org:
Univ. of California, Los Angeles, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
54 ENVIRONMENTAL SCIENCES; Aboveground biomass; Clay; Litterfall; Phosphorus; Precipitation; Rainforest
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