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

Abstract

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 (R_S) between its main components – autotrophic (R_A) and heterotrophic (R_H) 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 R_S components. Two additional chambers were installed on two trenched plots (60×60×60 cm) intended to eliminate the root contribution on total R_S and quantify actual microbial R_H. During the experimental period R_S fluxes measured in the vine rows were about 57% of the inter-row in average. The contribution of the autotrophic component (R_A) 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 R_S 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.