[Root respiration and its temperature sensitivity at various growth stages of winter wheat in the Loess Plateau, Northwest China]

Understanding the effects of crop growth stage on root respiration (R_A) and its temperature sensitivity (Q₁₀) has important theoretical and practical significance for enriching the carbon cycle theory of cropland. In a rain-fed agricultural ecosystem on the Loess Plateau, soil respiration rates were in situ measured in adjacent bare soil (soil microbial respiration, R_H) and non-fertilized winter wheat (soil respiration, R_S=R_A+R_H) with an automated CO₂ flux system from 2009 to 2014 to investigate the effect of growth stage on R_A and Q₁₀. The results showed that net photosynthetic rate in the seedling, elongating, filling, and the ripening stage was 5.9, 14.4, 12.0, and 4.4 μmol·m^-2·s^-1, and the corresponding root activity was 51.0, 100.8, 84.4, and 31.8 μg·g^-1·h^-1, respectively. R_A differed significantly among different growth stages, which was 0.26, 0.67, 0.91, and 0.56 μmol·m^-2·s^-1. The variation of R_A was closely related with soil moisture, soil temperature, net photosynthetic rate, and root activity, which presented parabolic, exponential, linear, and linear models respectively. Furthermore, Q₁₀ in each stage was 2.61, 4.88, 2.26, and 6.93, respectively, the variation of which was closely related with net photosynthetic rate, root activity, and soil moisture, with the contribution rate of root respiration being 29%, 53%, 46% and 31%, respectively. In conclusion, in addition to environmental factors, growth period of winter wheat was an important factor affecting R_A and Q₁₀.