Above- and belowground carbon stocks are decoupled in secondary tropical forests and are positively related to forest age and soil nutrients respectively

Isabel L Jones; Saara J DeWalt; Omar R Lopez; Lynsey Bunnefeld; Zarah Pattison; Daisy H Dent

doi:10.1016/j.scitotenv.2019.133987

Above- and belowground carbon stocks are decoupled in secondary tropical forests and are positively related to forest age and soil nutrients respectively

Sci Total Environ. 2019 Dec 20:697:133987. doi: 10.1016/j.scitotenv.2019.133987. Epub 2019 Aug 19.

Authors

Isabel L Jones¹, Saara J DeWalt², Omar R Lopez³, Lynsey Bunnefeld⁴, Zarah Pattison⁵, Daisy H Dent⁶

Affiliations

¹ Biological and Environmental Sciences, University of Stirling, Stirling FK9 4LA, UK. Electronic address: i.l.jones@stir.ac.uk.
² Department of Biological Sciences, Clemson University, Clemson, SC, USA.
³ Instituto de Investigaciones Científicas y Servicios de Alta Tecnología, Panamá; Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Panamá.
⁴ Biological and Environmental Sciences, University of Stirling, Stirling FK9 4LA, UK.
⁵ School of Natural and Environmental Sciences, Newcastle University, NE1 7RU, UK.
⁶ Biological and Environmental Sciences, University of Stirling, Stirling FK9 4LA, UK; Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Panamá.

PMID: 31484096
DOI: 10.1016/j.scitotenv.2019.133987

Abstract

Reducing atmospheric CO₂ is an international priority. One way to assist stabilising and reducing CO₂ is to promote secondary tropical forest regrowth on abandoned agricultural land. However, relationships between above- and belowground carbon stocks with secondary forest age and specific soil nutrients remain unclear. Current global estimates for CO₂ uptake and sequestration in secondary tropical forests focus on aboveground biomass and are parameterised using relatively coarse metrics of soil fertility. Here, we estimate total carbon stocks across a chronosequence of regenerating secondary forest stands (40-120 years old) in Panama, and assess the relationships between both above- and belowground carbon stocks with stand age and specific soil nutrients. We estimated carbon stocks in aboveground biomass, necromass, root biomass, and soil. We found that the two largest carbon pools - aboveground biomass and soil - have distinct relationships with stand age and soil fertility. Aboveground biomass contained ~61-97 Mg C ha^-1 (24-39% total carbon stocks) and significantly increased with stand age, but showed no relationship with soil nutrients. Soil carbon stocks contained ~128-206 Mg C ha^-1 (52-70% total stocks) and were unrelated to stand age, but were positively related to soil nitrogen. Root biomass carbon stocks tracked patterns exhibited by aboveground biomass. Necromass carbon stocks did not increase with stand age, but stocks were held in larger pieces of deadwood in older stands. Comparing our estimates to published data from younger and older secondary forests in the surrounding landscape, we show that soil carbon recovers within 40 years of forest regeneration, but aboveground biomass carbon stocks continue to increase past 100 years. Above- and belowground carbon stocks appear to be decoupled in secondary tropical forests. Paired measures of above- and belowground carbon stocks are necessary to reduce uncertainty in large-scale models of atmospheric CO₂ uptake and storage by secondary forests.

Keywords: Aboveground biomass; Belowground biomass; Carbon storage; Forest restoration; Land-use change; Necromass; Neotropics; Soil; Succession.

MeSH terms

Carbon Sequestration*
Carbon*
Forests*
Nitrogen / analysis
Phosphorus / analysis
Soil / chemistry

Substances

Soil
Phosphorus
Carbon
Nitrogen