Study of the Carbon Budget of a Temperate-Climate Vineyard: Inter-Annual Variability of CO₂ Flux

Abstract

Agriculture can improve the global carbon budget by reducing emissions and increasing soil carbon sequestration. Woody crops like vineyards present biological, structural, and management peculiarities, such as perennial structure, abundant pruning debris, and interrow cover cropping, which could potentially sequester a significant amount of CO₂. However, such ecosystems are still poorly understood. Here, we present results from a long-term study from northeastern Italy on the carbon budget of a vineyard (cv. Sauvignon blanc, Guyot pruned, vertical shoot-positioned trellised, with grass-covered alleys). We used the eddy covariance technique to continuously monitor the net ecosystem CO₂ exchange (NEE), and here we present the first three years of data (May 2014 to April 2017). The vineyard acted as a moderate carbon sink, with an average annual net carbon uptake of 134 g C/ m². However, the inter-annual variability of NEE was high, and environmental conditions during the growing season had a strong impact. The annual carbon uptake was greatest in 2014 (207 g C/m²), when there was abundant rain in summer. In contrast, in 2015, several heat waves decreased the annual carbon uptake to 69 g C/m². Elevated air temperature and low soil moisture in summer significantly reduced net carbon flux during times when the vineyard activity was at maximum. Nevertheless, we show that a vineyard can behave as a carbon sink in the medium-to-long term, which should be factored into agricultural and environmental policies, complementing the standard life cycle assessment of the wine production chain.