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The alpine meadow ecosystem on the Qinghai–Tibetan Plateau (QTP) is very sensitive to warming and plays a key role in regulating global carbon (C) cycling. However, how warming affects the soil organic carbon (SOC) pool and related C inputs and outputs in alpine meadow ecosystems on the QTP remains unclear. Here, we combined two field experiments and a meta‐analysis on field experiments to synthesize the responses of the SOC pool and related C cycling processes to warming in alpine meadow ecosystems on the QTP. We found that the SOC content of surface soil (0–10 cm) showed a minor response to warming, but plant respiration was accelerated by warming. In addition, the warming effect on SOC was not correlated with experimental and environmental variables, such as the method, magnitude and duration of warming, initial SOC content, mean annual temperature, and mean annual precipitation. We conclude that the surface SOC content is resistant to climate warming in alpine meadow ecosystems on the QTP. [ABSTRACT FROM AUTHOR]

Background and aims: Long-term nitrogen (N) addition can affect soil organic carbon (SOC) pool within different soil fractions with different turnover rates. However, the mechanisms of these effects, particularly in alpine grassland ecosystems, are not clear. Methods: We studied the responses of SOC content in different soil fractions to N addition based on a six-year N addition field experiment in an alpine meadow ecosystem on the Tibetan Plateau. We measured soil chemical and microbial properties, and SOC content in bulk soil, particular organic matter (POM) and mineral-associated organic matter (MAOM) fractions in response to N addition. Results: N addition increased soil N availability, decreased soil pH and microbial biomass, but had minimal effect on plant biomass, soil enzyme activity, and SOC content in bulk soil. With increasing levels of N addition, SOC in the POM fraction (POC) showed a significant negative trend, while SOC in the MAOM fraction (MAOC) did not change significantly. Conclusions: As plant biomass input and soil enzyme activity were not significantly altered with N addition, the decline in POC was likely caused by changes in microbial physiology (carbon use efficiency), while the insignificant change in MAOC may be determined by the balance between input (from microbial necromass) and output (from microbial decomposition). Taken together, our study showed that the less-protected POC fraction is more vulnerable to N addition than the more-protected MAOC fraction in the alpine grassland. This finding may improve the prediction of soil C dynamics in response to N deposition in alpine grassland ecosystems on the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Cover cropping is widely used for soil management in vineyards. But few studies have compared the effect of different cover cropping management methods on soil properties and fungal communities in vineyards. Therefore, we examined the effects of traditional management (shallow tillage to remove weeds), cover with single species (two treatments covered with different herbages), cover with mixed species (two combination treatments named M1 and M2 respectively), and cover with a crop on soil physicochemical properties and fungal community structure in a vineyard in northern China in 2020 and 2021. Soil total carbon and mineral nitrogen increased under Carex lanceolata Boott, Medicago sativa L., M1, and M2 covers but decreased under Glycine max (L.) Merr. Compare to traditional management. Soil organic carbon content increased under Carex lanceolata Boott, Medicago sativa L., M1, and M2, with increasing planting time. Cover cropping management had a minor effect on fungal diversity in the short term. Effects on beneficial and pathogenic fungi varied with cover type. With a cover of Glycine max (L.) Merr, the abundance of Fusarium brachygibbosum , a pathogen that affects grape production, increased, but that of Chaetomium , a genus that inhibits pathogens, also increased. With a cover of Carex lanceolata Boott, the abundance of Didymella glomerata , another pathogen that affects grape production, increased, but that of Metarhizium , an entomopathogenic fungus, also increased. Compared with Carex lanceolata Boott, covers with mixed species (M1 and M2) showed minor effects on soil pathogens, so covers with mixed species could benefit the vineyards more than other cover cropping management in North China. • Cover cropping management can improve soil carbon and nitrogen in vineyard. • Cover cropping management has impacts on grape productivity-related fungi. • SOC is the major drivers of fungal diversity and Didymella glomerata. [ABSTRACT FROM AUTHOR]

The response of soil carbon storage to warming is critical for the climate due to the large flux of carbon between soil and atmosphere. Despite evidence that warming enhances carbon fluxes to and from the soil, how soil carbon stock respond to warming remains uncertain. Here we combine three complementary methods to explore the responses of soil carbon stock to warming in the alpine grassland on the Tibetan Plateau. These methods include sampling sites along temperature (elevation) gradients, measuring soils from two OTC warming experiments, and conducting a meta-analysis of field warming experiments across the plateau. Firstly, we sampled soils along two elevational gradients with similar vegetation (Kobresia meadow): 3200-4200 m on Mt. Qilian and 4400-5200 m on Mt. Nianqingtanggula. In the first gradient, with decreasing elevation (or warming), belowground biomass (BGB) did not change, while aboveground biomass (AGB), microbial biomass carbon (MBC) and soil organic carbon (SOC) all increased. In the second gradient, with decreasing elevation (or warming), AGB did not change, while BGB, MBC and SOC all declined. Moreover, the turnover rate of bulk SOC estimated by its 14C content, did not show clear trend with elevation in both gradients. These results suggest the responses of SOC dynamics to warming were inconsistent along the two elevation gradients. Secondly, in a seven-year OTC warming experiment in an alpine meadow (Kobresia humilis), four different levels of warming (0.4~2.0 C) with or without clipping, did not have significant effect on AGB, BGB, MBC, SOC and its two fractions (particulate organic matter (POM) and mineral-associated organic matter (MAOM)). Moreover, in a 20-year OTC warming experiment in two alpine meadows (dominated by Kobresia humilis and Potentilla fruticosa respectively), warming by 1-2 C did not change AGB, BGB, MBC, SOC and its two fractions (POM and MAOM), except that it reduced microbial biomass (MBC) and necromass (amino sugar) and MAOM-C in the surface soil of Potentilla fruticosa meadow. Finally, the meta-analysis of all existing warming experiments in alpine grassland on the plateau showed that warming overall had a minor effect on soil carbon stock. Such minor effect was independent of ecosystem (meadow or steppe), and the method, magnitude and duration of warming. Although evidence from more long-term, coordinated and distributed experiments and data from subsoils and permafrost are needed, our integrative analysis suggests that warming may not lead to soil carbon loss in alpine grasslands on the Tibetan Plateau. [ABSTRACT FROM AUTHOR]