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Soil carbohydrates, such as glucose and fructose, are essential components of soil organic matter (SOM). They serve as the primary carbon and energy sources for soil microorganisms and play a crucial role in regulating SOM stability, both directly and indirectly. Despite their ecological importance, the transformation processes and forms of soil carbohydrates are still not well-understood, despite centuries of extensive study. The use of stable carbon isotopes as natural tracers offers distinct advantages over radioisotope techniques, including safety, cleanliness, and ease of control. As a result, stable carbon isotope analysis has been widely employed in soil carbon cycling research. The examination of carbon isotopic variation in carbohydrates using stable carbon isotope tracers contributes to our understanding of carbohydrate transformation and accumulation processes within the plant-soil-microorganism system. It also enhances our comprehension of soil carbon metabolism. This paper provides an introduction to the types, sources, and pretreatment methods of soil carbohydrates. Furthermore, it reviews the theory and methods of stable carbon isotope analysis as applied to carbohydrates and their relevance to the study of soil carbon cycling. Lastly, it offers a comprehensive summary of current research challenges and prospects for future advancements in soil carbon cycling research.

Rationale: Soil microbial heterotrophic C‐CO2 respiration is important for C cycling. Soil CO2 differentiation and quantification are vital for understanding soil C cycling and CO2 emission mitigation. Presently, soil microbial respiration (SR) quantification models are based on native soil organic matter (SOM) and require consistent monitoring of δ13C and CO2. Methods: We present a new apparatus for achieving in situ soil static chamber incubation and simultaneous CO2 and δ13C monitoring by cavity ring‐down spectroscopy (CRDS) coupled with a soil culture and gas introduction module (SCGIM) with multi‐channel. After a meticulous five‐point inter‐calibration, the repeatability of CO2 and δ13C values by using CRDS‐SCGIM were determined, and compared with those obtained using gas chromatography (GC) and isotope ratio mass spectrometry (IRMS), respectively. We examined the method regarding quantifying SR with various concentrations and enrichment of glucose and then applied it to investigate the responses of SR to the addition of different exogenous organic materials (glucose and rice residues) into paddy soils during a 21‐day incubation. Results: The CRDS‐SCGIM CO2 and δ13C measurements were conducted with high precision (< 1.0 µmol/mol and 1‰, respectively). The optimal sampling interval and the amount added were not exceeded 4 h and 200 mg C/100 g dry soil in a 1 L incubation bottle, respectively; the 13C‐enrichment of 3%–7% was appropriate. The total SR rates observed were 0.6–4.2 µL/h/g and the exogenous organic materials induced ‐49%–28% of priming effects in native SOM mineralisation. Conclusions: Our results show that CRDS‐SCGIM is a method suitable for the quantification of soil microbial CO2 respiration, requiring less extensive lab resources than GC/IRMS. [ABSTRACT FROM AUTHOR]

Similar to higher plants, microbial autotrophs possess photosynthetic systems that enable them to fix CO2. To measure the activity of microbial autotrophs in assimilating atmospheric CO2, five paddy soils were incubated with14C-labeled CO2for 45 days to determine the amount of14C-labeled organic C being synthesized. The results showed that a significant amount of14C-labeled CO2incorporated into microbial biomass was soil specific, accounting for 0.37%–1.18% of soil organic carbon (14C-labeled organic C range: 81.6–156.9 mg C kg−1of the soil after 45 days). Consequently, high amounts of C-labeled organic C were synthesized (the synthesis rates ranged from 86 to 166 mg C m−2d−1). The amount of atmospheric14CO2incorporated into microbial biomass (14C-labeled microbial biomass) was significantly correlated with organic C components (14C-labeled organic C) in the soil (r = 0.80,p < 0.0001). Our results indicate that the microbial assimilation of atmospheric CO2is an important process for the sequestration and cycling of terrestrial C. Our results showed that microbial assimilation of atmospheric CO2has been underestimated by researchers globally, and that it should be accounted for in global terrestrial carbon cycle models. [ABSTRACT FROM AUTHOR]

Background: Gonadotrophin-releasing hormone (GnRH) administration significantly decreases the pregnancy rate of recipient ewes after embryo transfer, possibly because GnRH affects endometrial epithelial cell function. Therefore, this study investigated the effect of GnRH on endometrial epithelial cells., Methods: Transcriptome sequencing was used to determine the regulatory effect of GnRH on the ewe endometrium, and the S100A4 gene, which showed altered transcription, was screened as a candidate regulator of this effect. Endometrial epithelial cells were further isolated, the S100A4 protein was immunoprecipitated, and host proteins that interacted with S100A4 were identified by mass spectrometry. We further verified the effects of S100A4 and GNAI2 on the proliferation of endometrial epithelial cells via overexpression/knockdown experiments and subsequent CCK-8 and EdU assays. The effect of S100A4 deletion in endometrial cells on reproduction was verified in mice with S100A4 knockout., Results: Our results showed that S100A4 gene transcription in endometrial cells was significantly inhibited after GnRH administration. GNAI2 was identified as a downstream interacting protein of S100A4, and S100A4 was confirmed to activate the MAPK signaling pathway to promote cell proliferation by targeting GNAI2., Conclusion: GnRH can suppress the expression of S100A4 in the endometrium, consequently inhibiting the proliferation of endometrial cells through the S100A4/GNAI2/MAPK signaling pathway. These findings suggest a potential explanation for the limited efficacy of GnRH in promoting embryo implantation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Jiao, Chu, Li, Wang, Ren, Wang, Lu, Li, Ren and Wu.)

The study of four years straw mulching and white clover intercropping in a tea plantation in subtropical hilly region showed that the soil temperature in the plantation presented a distinct dynamic temporal-spatial variation and hysteresis, which was greatly accorded with the fittest temperature of tea growth. Straw mulching and white clover intercropping altered the nature of soil thermal exchanging layer (soil surface), decreased daily temperature difference, enhanced the temperature stability in the same soil layer, and had duplex effects of lowering temperature when it went up and increasing and keeping temperature when it went down. The effectiveness was in the order of white clover intercropping > straw mulching > control, 13:00 > 19:00 >7:00,and lowering temperature > increasing and keeping temperature, and decreased with soil depth. Straw mulching and white clover intercropping adjusted the switching point of the temporal-spatial variation of soil temperature, and evidently decreased the emergence of harmful high temperature. During the period of continual high temperature, these measures markedly lowered soil temperature, and effectively shortened the duration of this period.