Spatio-temporal variability and controls of soil respiration in a furrow-irrigated vineyard

An investigation of soil respiration (R-s) is critical to determining the CO2 emissions and carbon balance in grapevines, but unfortunately, there is a lack of information about the magnitude of vineyard R, and the effects of cultivation practices and environmental factors on this important process. The objective of the present study was to evaluate the spatial and temporal variability and controls of R-s in a furrow-irrigated vineyard. An automatic CO2 exchange system was used to measure R-s for a three-year period. The hourly R-s ranged between 0.45-2.20 mu mol m(-2)s(-1) on the ridge and between 0.23-1.62 mu mol m(-2) s(-1) in the furrow, respectively. The spatio-temporal variability in R-s was mainly affected by soil temperature, and soil moisture played a second role. This study failed to separate R-s into the autotrophic and heterotrophic components by measuring R-s in the plant and bare areas, which could be attributed to the deeper distribution of grape roots as well as the fewer root biomass. Continuous measurement of houly R-s showed statistically non-significant differences before and after irrigation in the furrow and on the ridge, respectively. The diel hysteresis between soil respiration and temperature was found in our study. The shape and direction of the hysteresis loops and the time lag were mainly influenced by soil moisture. Finally, based on an empirical temperature-moisture model, the vineyard seasonal total and daily average R-s were estimated to be 470.6, 461.4 and 495.4 g CO2 m(-2), and 2.83, 2.64, and 2.74 g CO2 m(-2) day(-1) in 2013, 2014 and 2015, respectively.