Land-use change effects on soil organic carbon stocks and potential CO2-equivalent emissions in the Ecuadorian Andes

Abstract

Soil organic carbon (SOC), the second largest carbon reservoir at the Earth’s surface, plays a key role in climate regulation and ecosystem functioning by supporting biodiversity, regulating hydrological processes, and maintaining soil structure and fertility. Land-use change, however, can substantially reduce SOC stocks, contributing to soil degradation and the loss of ecosystem services. In this study, we quantified SOC stocks and estimated associated potential CO 2 -equivalent emissions across contrasting land-use types in the central highlands of the Ecuadorian Andes. A total of 144 soil samples were collected from natural ecosystems (paramo grasslands and native forests) and anthropogenically transformed land uses (croplands, pastures, and exotic forest plantations of pine and eucalyptus). SOC stocks were significantly higher in natural ecosystems than in transformed land uses. These differences were associated with a mean SOC loss of 88.1 Mg C ha −1 following land-use change, equivalent to 323 Mg CO 2 -eq ha −1 . Using the IPCC-recommended stock-difference approach combined with multitemporal land-use data, substantial potential CO 2 -equivalent emissions associated with land-use conversion were estimated at local and regional scales. These estimates represent potential emissions resulting from the loss of SOC reserves, rather than direct measurements of soil CO 2 fluxes, and are subject to uncertainty associated with spatial soil variability, land-use classification, and the conversion of soil organic matter to SOC. However, the magnitude of the estimated losses demonstrates the high sensitivity of high-Andean SOC reservoirs to land-use change and underscores their crucial importance for developing climate change mitigation strategies.