期刊
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
卷 120, 期 8, 页码 1605-1618出版社
AMER GEOPHYSICAL UNION
DOI: 10.1002/2015JG003047
关键词
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资金
- United States Department of Energy (DOE) through the Office of Biological and Environmental Research's (BER) Terrestrial Ecosystem Science program [DE-SC0006967]
- United States Department of Energy (DOE) through the Office of Biological and Environmental Research's (BER) Terrestrial Processes program [DE-FG02-95ER6208]
- U.S. Department of Agriculture [2011-67003-30222]
- National Science Foundation [NSF-AGS-1102227, DEB-1145875/1145649]
- National Natural Science Fund of China for Distinguished Young Scholars [51025931]
- China Postdoctoral Science Foundation [2015M570662]
- foundation for young scholars at Wuhan University [206-410500128]
Diurnal hysteresis between soil temperature (T-s) and both CO2 concentration ([CO2]) and soil respiration rate (R-s) were reported across different field experiments. However, the causes of these hysteresis patterns remain a subject of debate, with biotic and abiotic factors both invoked as explanations. To address these issues, a CO2 gas transport model is developed by combining a layer-wise mass conservation equation for subsurface gas phase CO2, Fickian diffusion for gas transfer, and a CO2 source term that depends on soil temperature, moisture, and photosynthetic rate. Using this model, a hierarchy of numerical experiments were employed to disentangle the causes of the hysteretic [CO2]-T-s and CO2 flux T-s (i.e., F-T-s) relations. Model results show that gas transport alone can introduce both [CO2]-T-s and F-T-s hystereses and also confirm prior findings that heat flow in soils lead to [CO2] and F being out of phase with T-s, thereby providing another reason for the occurrence of both hystereses. The area (A(hys)) of the [CO2]-T-s hysteresis near the surface increases, while the A(hys) of the R-s-T-s hysteresis decreases as soils become wetter. Moreover, a time-lagged carbon input from photosynthesis deformed the [CO2]-T-s and R-s-T-s patterns, causing a change in the loop direction from counterclockwise to clockwise with decreasing time lag. An asymmetric 8-shaped pattern emerged as the transition state between the two loop directions. Tracing the pattern and direction of the hysteretic [CO2]-T-s and R-s-T-s relations can provide new ways to fingerprint the effects of photosynthesis stimulation on soil microbial activity and detect time lags between rhizospheric respiration and photosynthesis.
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