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Abstract Tropical forests account for over 50% of the global terrestrial carbon sink, but climate change threatens to alter the carbon balance of these ecosystems. We show that warming and drying of tropical forest soils may increase soil carbon vulnerability, by increasing degradation of older carbon. In situ whole-profile heating by 4 °C and 50% throughfall exclusion each increased the average radiocarbon age of soil CO2efflux by ~2–3 years, but the mechanisms underlying this shift differed. Warming accelerated decomposition of older carbon as increased CO2emissions depleted newer carbon. Drying suppressed decomposition of newer carbon inputs and decreased soil CO2emissions, thereby increasing contributions of older carbon to CO2efflux. These findings imply that both warming and drying, by accelerating the loss of older soil carbon or reducing the incorporation of fresh carbon inputs, will exacerbate soil carbon losses and negatively impact carbon storage in tropical forests under climate change.
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Radiocarbon of soil CO2 efflux and soils with experimental soil warming and drying in lowland tropical forests in Panama
In 2019, we measured the Δ14C and δ13C of soil respired carbon dioxide (CO2) in Panamanian forests that are subject to either in situ experimental soil warming (4C above ambient temperature to 1.2 m depth) or in situ experimental drying (50% throughfall exclusion). The warming site and one drying site are both within the Barro Colorado Nature Monument in nearby and similar forests on similar soils, enabling direct comparison of warming and drying effects on soil CO2 efflux. A second drying experiment is on the northern side of the Panama Isthmus on infertile soils where mean annual precipitation is greater, representative of a broad geographic area of the tropics. Given the seasonality of these forests, we performed measurements at stages of the seasonal cycle for which we expected the largest variation in CO2 efflux between control and experimental plots based on previous studies – the wet season (October-December) and dry season (March/April) or dry-to-wet season transition (May). This dataset includes Δ14C and δ13C of in situ soil surface CO2 flux as well as CO2 flux rates, volumetric soil moisture, soil temperature, and calculated partitioning of the fraction of total soil respiration from heterotrophs vs roots at the time of isotope sampling in AllSites_SoilResp_14C_data.xlsx. This dataset also includes Δ14C and δ13C of bulk soil, density fractions, and CO2 respired during laboratory incubations in AllSites_bulk_soil14C.xlsx. Datafiles are also available in csv format.
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- Award ID(s):
- 2332006
- PAR ID:
- 10578164
- Publisher / Repository:
- Environmental System Science Data Infrastructure for a Virtual Ecosystem; Tropical Forest Response to a Drier Future: Turnover Times of Soil Organic Matter, Roots, Respired CO2, and CH4 Across Moisture Gradients in Time and Space
- Date Published:
- Subject(s) / Keyword(s):
- 54 ENVIRONMENTAL SCIENCES EARTH SCIENCE > LAND SURFACE > SOILS EARTH SCIENCE > SOLID EARTH > GEOCHEMISTRY > GEOCHEMICAL PROPERTIES > ISOTOPES EARTH SCIENCE > AGRICULTURE > SOILS > SOIL RESPIRATION carbon isotope soil respiration soil carbon
- Format(s):
- Medium: X
- Location:
- SWELTR is on Barro Colorado Island in Panama. P12 is to the west nearby. San Lorenzo is near the canal and Atlantic Ocean in Panama.
- Sponsoring Org:
- National Science Foundation
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