ASSESSING VINEYARDS SOIL CARBON STORAGE: δ13C AND Δ14C AS INDICATORS UNDER COVER CROPS AND TILLAGE

Building up Soil organic carbon (SOC) is essential, for ensuring agricultural viability and mitigating global climate change. Increasing SOC stocks is recognized as a key strategy for mitigating climate change and contributing to soil health and overall ecosystem resilience. Perennial cropping systems, such as vineyards, have received increasing attention for their potential to sequester SOC. Compared to annual crops, vines may contribute to SOC accumulation through their permanent root systems, extensive biomass production, and long-term organic matter inputs to the soil. Vineyard soils, however, are subject to diverse management practices that can either promote or deplete SOC stocks. At either end of the spectrum, we have, for example, permanent plant cover between the rows and ploughing to eliminate all grass, considered a competitor for access to water. However, the effect of these practices on SOC turnover and stabilization remains poorly understood.

Here we show how spontaneous vegetation cover and tillage fundamentally alter soil carbon storage, using δ13C and Δ14C isotopic tracers.  Soil samples were collected from a dozen of paired vineyard sites in Spain, differing solely in their soil management practices (very close from each other)  with soil covered with spontaneous vegetation or repeated tillage. The samples were collected to a depth of 90 cm, with 5 cm interval down to 20 cm, and then 10 cm intervals thereafter. The content of C and N content, as well as δ13C, reveal clear contrasts in carbon sources and depth dependent incorporation,   while Δ14C demonstrates distinct differences in carbon turnover rates and stabilization pathways between management systems.

Our results show that vineyards maintening spontenous vegetation accumulate younger, plant-derived carbon in surface horizons while also enhancing of older carbon at depth, whereas tilled soils exhibit depleted SOC stocks and accelerated carbon turnover throughout the profile. . These findings highlight the pivotal role of allowing natural vegetation to persist, combined with reduced soil disturbance, in fostering persistent SOC pools, thereby strengthening soil resilience under climate change.

Keywords: Soil carbon storage, vineyard soil management, δ13C, Δ14C, plant cover, tillage

Acknowledgments This work is supported by SANCHOSTHIRST project (EJP-SOIL grant agreement N°862695/II/4/SANCHOSTHIRST/2024).