Soil respiration dynamics in a semi-fixed sand dune under the pioneer shrub Artemisia halodendron Turcz. ex Bess. in the Horqin sandy land, northeastern China

Soil respiration is a major pathway by which carbon dioxide (CO₂) fixed by terrestrial plants returns to the atmosphere. Studies of the dynamics of soil respiration in sandy land are rare and the contribution (R_c) of plant root respiration to the total soil respiration (R_t) is not well known. In this study, R_t in a semi-fixed dune planted with Artemisia halodendron was separated into autotrophic (root) respiration (R_a) and heterotrophic respiration (R_h) by the root-exclusion method. R_t and its two components were measured or calculated during 2013 on seven dates during the growing season when variation during the day was measured. Both R_a and R_h showed similar dynamics, with the maximum rates observed in July and with large daily variability observed on the earlier dates. R_c ranged from 39.3% to 53.1% during the growing season and exhibited a single peak in early August. Soil temperature at a depth of 20 cm was significantly correlated with soil respiration. R_a was more sensitive to soil temperature than R_h and the temperature sensitivity coefficients (Q₁₀) were 3.39, 2.52, and 2.79 for R_a, R_h, and R_t, respectively. In summary, A. halodendron roots contributed an average of 46% to the total soil respiration, although this contribution varied during the growing season.