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The sensitivity of soil organic carbon (SOC) decomposition in seasonally frozen soils, such as alpine ecosystems, to climate warming is a major uncertainty in global carbon cycling. Here we measure soil CO2 emission during four years (2018-2021) from the whole-soil warming experiment (4 °C for the top 1 m) in an alpine grassland ecosystem. We find that whole-soil warming stimulates total and SOC-derived CO2 efflux by 26% and 37%, respectively, but has a minor effect on root-derived CO2 efflux. Moreover, experimental warming only promotes total soil CO2 efflux by 7-8% on average in the meta-analysis across all grasslands or alpine grasslands globally (none of these experiments were whole-soil warming). We show that whole-soil warming has a much stronger effect on soil carbon emission in the alpine grassland ecosystem than what was reported in previous warming experiments, most of which only heat surface soils.

The paucity of investigations of carbon (C) dynamics through the soil profile with warming makes it challenging to evaluate the terrestrial C feedback to climate change. Soil microbes are important engines driving terrestrial biogeochemical cycles; their carbon use efficiency (CUE), defined as the proportion of metabolized organic C allocated to microbial biomass, is a key regulator controlling the fate of soil C. It has been theorized that microbial CUE should decline with warming; however, empirical evidence for this response is scarce, and data from deeper soils are particularly scarce. Here, based on soil samples from a whole-soil-profile warming experiment (0 to 1 m, +4 °C) and 18O tracing approach, we examined the vertical variation of microbial CUE and its response to ~3.3-y experimental warming in an alpine grassland on the Qinghai-Tibetan Plateau. Microbial CUE decreased with soil depth, a trend that was primarily controlled by soil C availability. However, warming had limited effects on microbial CUE regardless of soil depth. Similarly, warming had no significant effect on soil C availability, as characterized by extractable organic C, enzyme-based lignocellulose index, and lignin phenol-based ratios of vanillyls, syringyls, and cinnamyls. Collectively, our work suggests that short-term warming does not alter microbial CUE in either surface or deep soils, and emphasizes the regulatory role of soil C availability on microbial CUE.

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The priming effect (PE) is important for understanding the decomposition of soil organic matter (SOM) and forecasting C-climate feedback. However, there are limited studies on microbial community-level properties and the keystone taxa involved in the process. In this study, we collected soil from a subtropical Phyllostachys edulis forest undergoing long-term N-addition and conducted an incubation experiment to evaluate the effects of single and repeated addition of 13C-labeled glucose. Our results demonstrated that previously N-fertilized soil had a smaller cumulative PE compared with that of the control (11% average decrease). This could be primarily explained (26%) by the lower abundance of bacterial r-strategy group members (B_mod#2, constituting Proteobacteria, Firmicutes, and Actinobacteria phyla) under N-addition treatments. A single C-addition induced a greater PE than that of repeated C-additions (2.66- to 3.11-fold). Single C addition led to greater C to N ratios of microbial biomass and fungi to bacteria, positively impacting cumulative PE, indicating that the shifts in fungal/bacterial dominance play an important role in regulating PE. Moreover, a saprophytic taxa group (F_Mod#3, primarily composed of the phyla Ascomycota) explained 62% of the differences in cumulative PE between single and repeated C-additions. Compared with repeated C-additions, a greater abundance of B_Mod#2 and F_Mod#3, as well as C-related hydrolase activity, was observed under single C-addition, inducing greater cumulative PE. Therefore, sufficient C may facilitate the proliferation of r-strategy bacterial taxa and saprophytic fungal taxa, thereby increasing SOM decomposition. Our findings provide novel insights into the relationship between microbial community-level properties and PE. [ABSTRACT FROM AUTHOR]

Summary: Soil organic carbon (SOC) is a mixture of various carbon (C) compounds with different stability, which can be distinctly affected by the priming effect (PE). However, little is known about how the PE changes with SOC stability.We address this issue by combining results from two experiments and a metaanalysis.We found that the PE increased with the prolongation of soil preincubation, suggesting that higher PE occurred for more stable SOC than for labile SOC. This was further supported by the metaanalysis of 42 observations. There were significant negative relationships between the difference in PE (ΔPE) between labile and more stable SOC and their differences in SOC, microbial biomass C and soil C : N ratio, indicating that soil C availability exerts a vital control on ΔPE.We conclude that, compared with labile SOC, stable SOC can be more vulnerable to priming once microbes are provided with exogenous C substrates. This high vulnerability of stable SOC to priming warrants more attention in future studies on SOC cycling and global change. [ABSTRACT FROM AUTHOR]

Abstract Background High circulating luteinizing hormone (LH) level is a typical biochemical feature of polycystic ovary syndrome (PCOS) whose pathophysiology is still unclear. Certain mutations of LH and LH receptor (LHR) may lead to changes in bioactivity of these hormones. The aim of this study was determine the role of the LH and LHR polymorphisms in the pathogenesis of PCOS using a genetic approach. Methods 315 PCOS women and 212 controls were screened for the gene variants of LH G1052A and LHR rs61996318 polymorphisms by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). Results PCOS patients had significantly more A allele frequency of LH G1052A mutations than controls (p=0.001). Within PCOS group, carriers of LH 1052A allele had lower LH (p=0.05) and higher fasting glucose levels (p=0.04). No subjects were identified with LHR rs61996318 polymorphisms. A new LHR single nucleotide polymorphism (SNP) was found without clear association with PCOS. Conclusions Results suggested LH G1052A mutation might influence PCOS susceptibility and phenotypes.

Abstract Background Tribbles 3 (TRB3) affects insulin signalling by inhibiting insulin-stimulated Akt phosphorylation and subsequent activation. A single nucleotide polymorphism located in the second extron of the human TRB3 gene is thought to be associated with insulin resistance. The latter is a core abnormality in PCOS independent of obesity. The present study was designed to clarify the relationships of TRB3 Q84R polymorphism with PCOS in a Chinese women group. Methods A case-control study with two groups: PCOS group (n = 336) and control group of infertility women for tubal and/or male factor (n = 116) was performed. Genotyping of the TRB3 R84 variant was determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Results The frequency of genotype QQ in PCOS women was significantly lower, while genotype QR and RR were significantly higher than that in control group (p < 0.05). However, the difference disappeared after adjustment for BMI. At glucose1h, glucose2h and insulin2h point, the difference between QQ individuals and R84 allele carriers in PCOS women reached statistical significance during OGTT (p < 0.05). Conclusions TRB3 Q84R polymorphism is associated with obesity and especially glucose metabolism and not associated with polycystic ovary syndrome because of compositional characteristics of phenotype in Chinese PCOS women.