In the present study, pot experiments were performed to investigate the soil respiration of seedlings of Populus euphratica in an arid inland river basin. Diurnal variations and the effects of hydrothermal factors were also analyzed. These hydrothermal factors included air temperature, ground temperature (from 0-30 cm underground at 5 cm intervals), soil surface moisture, and air humidity. The results indicated that the total soil respiration of Populus seedlings was slightly higher during the daytime than at night, and the maximum respiration value appeared between 16:00-20:00. During the daytime, heterotrophic respiration was the major mode of soil respiration, accounting for 56.6 of the total, whereas at night, autotrophic respiration was predominant, accounting for 66.5 of the total. Using stepwise multiple regressions, it was determined that changes in the soil respiration of Populus seedlings were closely and differentially related to changes in air temperature and ground temperature. Ground temperature constituted 90 of the decisive influence on soil respiration, while air temperature was 87 of the decisive influence. Regarding autotrophic respiration, air humidity had a much stronger impact on soil respiration compared to temperature. Concerning heterotrophic respiration, the QiO value was 2.15.
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