Spatial and temporal variation of soil respiration in relation to environmental conditions in a vineyard of northern Italy

In recent years, vineyard soil respiration has been a subject of great interest, but unfortunately there is a lack of information about the true amount of CO2 flux, and the effects of cultivation practices on this important process. The purpose of this investigation was to study the partitioning of vineyard soil respiration (RS) between its main components – autotrophic (RA) and heterotrophic (RH) respiration – and assess the effect of grass cover on the CO2 budget. The effect of soil temperature and soil water content (SWC) on temporal variability of soil respiration was monitored in a commercial vineyard (Vitis vinifera L. cv. Sauvignon blanc) in Northern Italy. An automated soil CO2 flux system was deployed with 6 long-term chambers installed on two adjacent alleys on grass covered soil (between the vine rows) and bare soil (alongside chemically treated rows), to measure RS components. Two additional chambers were installed on two trenched plots (60×60×60 cm) intended to eliminate the root contribution on total RS and quantify actual microbial RH. During the experimental period RS fluxes measured in the vine rows were about 57% of the inter-row in average. The contribution of the autotrophic component (RA) was responsible for about 67% of the total CO2 flux on average, reaching a minimum of about 30%. A robust exponential relationship (R2 = 0.70) was found between RS and upper soil temperature with an optimal volumetric SWC ranking between 0.25 and 0.35. With values of SWC higher than 0.34, the heterotrophic component of soil respiration approached zero (<0.004 mg CO2 m2 s-1), suggesting transient anoxic conditions due to rainfall, leading to a break in basal microbial metabolism. Photosynthesis of grass cover played an important role in vine alley CO2 fluxes with maximum NPP values of about -0.5 mg CO2 m2 s-1 under clear weather conditions. A better understanding of carbon balance in vineyards is of great importance to promote sustainability and improve cultivation techniques.