Co-Authors:
Paudel, I., Institute of Soil, Water and Environmental Sciences, ARO Volcani Center, Bet Dagan, Israel, Department of Soil and Water, The Robert H. Smith Faculty of Food Agriculture and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
Bar-Tal, A., Institute of Soil, Water and Environmental Sciences, ARO Volcani Center, Bet Dagan, Israel
Rotbart, N., Institute of Soil, Water and Environmental Sciences, ARO Volcani Center, Bet Dagan, Israel, Department of Soil and Water, The Robert H. Smith Faculty of Food Agriculture and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
Ephrath, J., Jacob Blaustein Institutes for Desert Research, The Ben Gurion University of the Negev, Sde Boqer, Israel
Cohen, S., Institute of Soil, Water and Environmental Sciences, ARO Volcani Center, Bet Dagan, Israel
Abstract:
Effects of treated wastewater (TWW) and fresh water (FW) on autotrophic belowground respiration and respiratory coefficients (Q10) in summer and winter were determined in a commercial citrus orchard. Efflux of CO2 from soil and the often-ignored CO2 transported in xylem sap were quantified; the latter derived from sap flux, CO2 concentration ([CO2]), pH, and temperature. Xylem [CO2] scaled with xylem sap flux, pH and temperature. TWW and summer increased xylem sap pH (by 12% and 19%), soil CO2 efflux (32% and 65%), and root respired CO2 (10–15% and 55%) in comparison to FW and winter, respectively. About twice as much CO2 from the below ground autotrophic portion of respiration moved in xylem sap as compared to that diffused from the roots into the soil, with seasonal variations of about ±10%. Maximum temperature-dependent respiratory coefficients (Q10) were 4.7 for autotrophic root respiration and 3.8 for bulk soil CO2 efflux, and values varied with water quality and season. Total below ground respiration exceeds that previously reported and is a large part of the tree's carbon balance. Increased respiratory losses caused by poor quality water may explain reduced orchard root growth and overall productivity. © 2017 Elsevier B.V.
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