Interactive effects of soil temperature and moisture on Concord grape root respiration

Root respiration has important implications for understanding plant growth as well as terrestrial carbon flux with a changing climate. Although soil temperature and soil moisture often interact, rarely have these interactions on root respiration been studied. This report is on the individual and combined effects of soil moisture and temperature on respiratory responses of single branch roots of 1-year-old Concord grape (Vitis labruscana Bailey) vines grown in a greenhouse. Under moist soil conditions, root respiration increased exponentially to short-term (1 h) increases in temperature between 10°C and 33°C. Negligible increases in root respiration occurred between 33°C and 38°C. By contrast to a slowly decreasing Q₁₀ from short-term temperature increases, when roots were exposed to constant temperatures for 3 d, the respiratory Q₁₀ between 10°C and 30°C diminished steeply with an increase in temperature. Above 30°C, respiration declined with an increase in temperature. Membrane leakage was 89-98% higher and nitrogen concentration was about 18% lower for roots exposed to 35°C for 3 d than for those exposed to 25°C and 15°C. There was a strong interaction of respiration with a combination of elevated temperature and soil drying. At low soil temperatures (10°C), respiration was little influenced by soil drying, while at moderate to high temperatures (20°C and 30°C), respiration exhibited rapid declines with decreases in soil moisture. Roots exposed to drying soil also exhibited increased membrane leakage and reduced N. These findings of acclimation of root respiration are important to modelling respiration under different moisture and temperature regimes.