Abstract
Understanding if and to what extent agricultural land types can sequester carbon is important for assessing their greenhouse gas mitigation potential. Grassed vineyards have recently been described as large carbon sinks relative to most cropland types, indicating the importance of understanding their carbon cycle in more detail. To this end, we conducted a detailed study along a growing season in a grassed mountain vineyard with two varieties (Chardonnay and Sauvignon blanc) to quantify the overall carbon stock of the system and to attribute the carbon fluxes to the specific components of the carbon cycle of the agroecosystem, including vines organs (shoots, fruits, roots), grasses (shoots and roots) and soil. We combined eddy covariance, soil respiration, biometric measurements, and soil analysis. Our findings determined the studied vineyard to be a moderate carbon sink. We found a gross primary production (2409 ± 35 g C m−2) much larger than previous data for vineyards, but the net ecosystem production (246 ± 54 g C m−2) of the growing season was on the lower end of previous reports. The grassed alleys comprised roughly 60% of net primary production, confirming that they contribute significantly to the C input of the system. The overall carbon stored in the vineyard (152.1 ± 7.1 t C ha−1) was less than that of forests and some orchards primarily due to the lower amount of plant biomass. The soil represented by far the largest carbon storage in the vineyard, and changes in soil organic carbon and litter accounted for >75% of long-term carbon increase. Further studies are needed to unravel the relative contribution of the grapevines and grasses to overall gross primary productivity and soil carbon storage, especially in the context of different management decisions and the increasing frequency of drought events in similar mountain environments.