Climate control on terrestrial biospheric carbon turnover.

Area of Science:

• Earth System Science
• Biogeochemistry
• Environmental Science

Background:

• Terrestrial vegetation and soils store substantial carbon, three times more than the atmosphere.
• Anthropogenic activities raise concerns about perturbing these reservoirs and exacerbating climate change.
• Extrapolating point observations to ecosystem-scale budgets requires understanding complex vertical and lateral processes across scales.

Purpose of the Study:

• To investigate the controls on organic carbon (OC) turnover at the river basin scale.
• To utilize radiocarbon (¹⁴C) ages of plant-derived biomarkers (leaf-wax lipids and lignin phenols) from global rivers.
• To establish relationships between biomarker ages and environmental factors like temperature and precipitation.

Main Methods:

• Analysis of radiocarbon (¹⁴C) ages of leaf-wax lipids and lignin phenols in river samples.
• Statistical analysis of biomarker ages against mean annual temperature and precipitation.
• Comparison of riverine biospheric-carbon ages with basin-wide soil carbon turnover times and soil ¹⁴C ages.

Main Results:

• Significant negative relationships were found between biomarker ¹⁴C ages and mean annual temperature and precipitation.
• Riverine biospheric-carbon ages were found to scale proportionally with basin-wide soil carbon turnover times and soil ¹⁴C ages.
• A broad distribution of soil OC reactivities and the presence of a long-lived soil OC pool were identified.

Conclusions:

• Soil organic carbon (OC) cycling is a primary control on exported biomarker ages in rivers.
• Soil OC is globally vulnerable to increased temperature and precipitation.
• Riverine biomarker ages can constrain carbon dynamics' sensitivity to environmental controls and inform past/future soil OC perturbations.