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

Agriculture can play a positive role in the global carbon budget through reduction of emissions and increase of soil carbon sequestration. Woody crops, like vineyards, present biological, structural and management peculiarities (e.g. perennial structure, abundant pruning debris, inter-row cover cropping), which allow to potentially sequester a significant amount of CO2. However, only few studies have been conducted over this kind of ecosystems. In this paper, we present results from a long-term study running in North Eastern Italy on the carbon budget of a vineyard (cv Sauvignon Blanc, Guyot pruned, VSP trellised, with grass-covered alleys). We used the eddy covariance technique to continuously monitor the net ecosystem CO2 exchange (NEE), and here we analyze the first three years of measurements (May 2014 to April 2017). The vineyard showed to act as a moderate carbon sink, with an average annual net carbon uptake of 134 gC/m2. However, the inter-annual variability of NEE was considerably high and environmental conditions during vine growing season showed to have a strong impact. The summer of 2014 was characterized by plenty of rainfall and the annual carbon uptake was the highest (207 gC/m2). On the contrary, in 2015, several heat waves reached the area and the annual carbon uptake decreased to 69 gC/m2. Elevated air temperature and low soil moisture in summer significantly reduced net carbon flux in the period of the year when the activity of the vineyard is at its maximum. Nevertheless, we showed that the vineyard can behave as carbon sink on the medium-long term, and we suggest this should be taken into account in agricultural and environmental policies, complementing standard Life Cycle Assessment of the wine production chain.