BackgroundGrazing is a major modulator of biodiversity and productivity in grasslands. However, our understanding of grazing-induced changes in below-ground communities, processes, and soil productivity is limited. Here, using a long-term enclosed grazing meadow steppe, we investigated the impacts of grazing on the soil organic carbon (SOC) turnover, the microbial community composition, resistance and activity under seasonal changes, and the microbial contributions to soil productivity.ResultsThe results demonstrated that grazing had significant impacts on soil microbial communities and ecosystem functions in meadow steppe. The highest microbial α-diversity was observed under light grazing intensity, while the highest β-diversity was observed under moderate grazing intensity. Grazing shifted the microbial composition from fungi dominated to bacteria dominated and from slow growing to fast growing, thereby resulting in a shift from fungi-dominated food webs primarily utilizing recalcitrant SOC to bacteria-dominated food webs mainly utilizing labile SOC. Moreover, the higher fungal recalcitrant-SOC-decomposing activities and bacterial labile-SOC-decomposing activities were observed in fungi- and bacteria-dominated communities, respectively. Notably, the robustness of bacterial community and the stability of bacterial activity were associated with α-diversity, while this was not the case for the robustness of fungal community and its associated activities. Finally, we observed that microbial α-diversity rather than SOC turnover rate can predict soil productivity.ConclusionsOur findings indicate the strong influence of grazing on soil microbial community, SOC turnover, and soil productivity and the important positive role of soil microbial α-diversity in steering the functions of meadow steppe ecosystems.Electronic supplementary materialThe online version of this article (10.1186/s40168-018-0544-y) contains supplementary material, which is available to authorized users.

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The objective of this research was to investigate the effects of replacing part of corn silage (CS) and alfalfa hay (AH) with Leymus chinensis hay on milk production and composition. Twenty multiparous Holstein dairy cows were used in a randomized block design for a 14-week period and 2 treatments. Treatments were (dry matter basis): (1) Non-Leymus chinensis hay diet (NLC; 35% CS, 15% AH) and (2) added Leymus chinensis hay diet (ALC; 30% CS, 10% AH, 10% Leymus chinensis hay). Adding Leymus chinensis hay increased neutral detergent fiber content and in vitro digestibility of the diet. Cows receiving the ALC diet had higher dry matter intake, milk yield, milk protein yield, lactose yield, solids-not-fat yield, and milk fat content compared with those fed the NLC diet. Somatic cell counts of cows decreased in the ALC compared with the NLC treatment. Cis-11 18:1 and 18:2 contents in milk increased, whereas trans-9 and cis-9 18:1 fatty acid contents decreased. Trans-9, cis-11 conjugated linoleic acid content was not influenced by adding Leymus chinensis hay to the diet. Leymus chinensis hay can be used to replace part of CS and AH in diets of dairy cows to get higher milk yield and good milk quality.

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In this study, the effects of cattle grazing intensity on soil nitrous oxide (N 2 O) fluxes were examined in the Hulunber meadow steppe of north-eastern China. Six stocking-rate treatments (0, 0.23, 0.34, 0.46, 0.69, and 0.92 AU ha −1 ) with three replicates were established, and observations were conducted from 2010 to 2014. Our results showed that substantial temporal fluctuations in N 2 O flux occurred amongst the different grazing intensities, with peak N 2 O fluxes after natural rainfall. Grazing had a long-term effect on the soil N 2 O flux in the grasslands. After 4-5 years of grazing, the N 2 O fluxes under increased levels of grazing intensity began to decrease significantly by 31.4%-60.2% in 2013 and 32.5%-50.5% in 2014 compared to the non-grazing treatment. We observed a significant negative linear relationship between the soil N 2 O fluxes and grazing intensity for the five-year mean. The soil N 2 O flux was significantly affected each year in all of the treatments. Over the five years, the temporal coefficient of variation (CVs) of the soil N 2 O flux generally declined significantly with increasing grazing intensity. The soil N 2 O emission rate was significantly positively correlated with soil moisture (SM), soil available phosphorus (SAP), soil -above-ground biomass (AGB), plant ground cover and height and was negatively correlated with total soil nitrogen (TN). Stepwise regressions showed that the N 2 O flux was primarily explained by SM, plant height, TN, soil pH, and soil -Using structural equation modelling, we show that grazing significantly directly influenced the plant community and the soil environment, which then influenced the soil N 2 O fluxes. Our findings provide an important reference for better understanding of the mechanisms and identifying the pathways of grazing effects on soil N 2 O emission rates, and the key drivers plant community and soil environment within the nitrogen cycle that are mostly likely to affect N 2 O emissions in the Inner Mongolian meadow steppes.

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