Influencing factors and partitioning of respiration in a Leymus chinensis steppe in Xilin River Basin, Inner Mongolia, China

Abstract

Based on the static opaque chamber method, the respiration rates of soil microbial respiration, soil respiration, and ecosystem respiration were measured through continuous in-situ experiments during rapid growth season in semiarid Leymus chinensis steppe in the Xilin River Basin of Inner Mongolia, China. Soil temperature and moisture were the main factor affecting respiration rates. Soil temperature can explain most CO 2 efflux variations (R 2 =0.376-0.655) excluding data of low soil water conditions. Soil moisture can also effectively explain most of the variations of soil and ecosystem respiration (R 2 =0.314-0.583), but it can not explain much of the variation of microbial respiration (R 2 =0.063). Low soil water content (≤5%) inhibited CO 2 efflux though the soil temperature was high. Rewetting the soil after a long drought resulted in substantial increases in CO 2 flux at high temperature. Bivariable models based on soil temperature at 5 cm depth and soil moisture at 0-10 cm depth can explain about 70% of the variations of CO 2 effluxes. The contribution of soil respiration to ecosystem respiration averaged 59.4%, ranging from 47.3% to 72.4%; the contribution of root respiration to soil respiration averaged 20.5%, ranging from 11.7% to 51.7%. The contribution of soil to ecosystem respiration was a little overestimated and root to soil respiration little underestimated because of the increased soil water content that occurred as a result of plant removal.

Ecosystem respiration and its components in a rainfed spring maize cropland in the Loess Plateau, China

“…At our study site, Re averaged 690 g C m −2 during the growing season, which is lower than the values reported previously for spring and summer maize 17 , 20 , 21 , and this result reflects the climate of the plateau, the large diurnal ranges and seasonal variations in temperature, and the low content of soil organic matter. The maximum Re of spring maize at the study site was generally higher than that reported for winter wheat, sugar beet, and potato 2 , 21 , higher than that for grasslands 42 , 43 , and similar to that reported for some forests 31 , 32 , which indicates that physiological activity in spring maize during the vigorous growth stage at our site was stronger than in other crops.…”

Satellite-Based Inversion and Field Validation of Autotrophic and Heterotrophic Respiration in an Alpine Meadow on the Tibetan Plateau

“…However, the Rs/Re was mainly controlled by the availability of stored substrates and the lags between temperature changes of air and soil [78]. The heterotrophic contribution to Rs (β) is relatively robust and showed only a negligible seasonal pattern compared to Ra/Re (1 − β*γ) and Rs/Re (γ) [9,81,84,85], because both autotrophic and heterotrophic respiration increased with seasonal warming [9].…”

“…The contribution of Ra to Re rises with spring warming and generally reaches the maximum value in the vigorous growth period, then declines with autumn cooling [9,49,78,79,83,84]. Although research on Rs/Re (γ) also showed a distinct seasonal pattern similar to Ra/Re before the summer, this ratio increased again in the following autumn [78,85].…”

“…Meanwhile, extremely high SWC inhibited Rm from deep soil layers due to the water block of soil porosity [87], and limited the oxygen supply for decomposition by aerobic microbes [88]. Besides, root exclusion was likely to intensify soil moisture due to a decrease of transpiration under this extremely wet condition [12,84]. Although these pulse effects were not detected by satellite-based Ra/Re (Figure 7b), the daily SWC in this semiarid alpine meadow was generally less than 0.25 ( Figure 3).…”

“…These two days both had extremely high SWC caused by consecutive strong rainfall events (Figure 3), which dramatically stimulated the autotrophic contribution to Re due to the significantly positive relationship between SWC and Ra/Re (p < 0.0001) (Figure 8). Many relevant studies also suggest that high SWC has a more significant effect on plant activity than on soil microorganisms [84]. Meanwhile, extremely high SWC inhibited Rm from deep soil layers due to the water block of soil porosity [87], and limited the oxygen supply for decomposition by aerobic microbes [88].…”