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Background and aims: Grasslands hold one of the most important soil carbon stocks in the world, which is vulnerable to climate change (i.e. precipitation) and human disturbance (i.e. land-use). This study aimed to investigate responses and mechanisms of soil organic carbon (SOC) decomposition and accumulation to precipitation and land-use in an Inner Mongolian grassland. Methods: Using a randomized complete block design with a split plot, an experiment with land-use regimes (fencing, grazing, and mowing, since 2011) and altered precipitation amount (wet, + 50% precipitation; CT, ambient precipitation; dry, −50% precipitation; since 2016) was conducted to explore their impacts on SOC decomposition (represented by soil heterotrophic respiration and extracellular enzyme activities) and accumulation (represented by SOC and its physical fractions) from samples collected in 2019. Results: SOC decomposition significantly increased under wet treatment, but decreased under dry treatment. Wet treatment increased SOC accumulation via the increment of mineral-associated organic carbon (MAOC), and vice versa for dry treatment. Precipitation amount may affect soil microbial biomass and activities via alterations of water supply, plant-derived carbon input, and other soil properties, leading to changes of SOC dynamics. Nevertheless, land-use regimes had little influences on SOC dynamics. Conclusions: Compared to land-use regimes, precipitation treatments can significantly change SOC dynamics. Overall, SOC increased under higher precipitation amount, but decreased with less precipitation. We emphasize that the SOC stock in Inner Mongolia temperate grassland may have an unexpectable fast response to precipitation alteration, but more investigation is still needed in longer terms. [ABSTRACT FROM AUTHOR]

Purpose: Grasslands are facing the threat of climate change and intensive land use. Soil respiration (Rs) in grassland ecosystems can be potentially altered by changes in precipitation and land use. We aimed to quantify the impact of changes in precipitation and common land use practices in an Inner Mongolia grassland, i.e., mowing and grazing, on soil respiration. Methods: We performed an in situ experiment with altered precipitation (+ 50%, ambient, and -50%) and land use (control or fencing, mowing, and grazing) to explore their impacts on soil respiration and its autotrophic (Ra) and heterotrophic (Rh) components. Results: Altered precipitation had stronger impacts on abiotic and biotic drivers than land use, leading to stronger impacts on Rs and its components. Over the 3-year experiment, Rs, Ra and Rh decreased by 36%, 42% and 33% with reduced precipitation and increased by 29%, 36% and 25% with increased precipitation, respectively. Grazing and mowing caused relatively small decreases in Rs compared to fencing (generally < 10%). However, precipitation and land use interactively impacted abiotic and biotic drivers and thus Rs. The decrease in Rs with reduced precipitation was greater with grazing (38%) and mowing (37%) than with fencing (32%). Conclusions: Rs and its components may decrease under the projected decrease in precipitation and may further decrease with grazing and mowing compared to fencing. Therefore, land use should be considered when predicting grassland carbon cycling in response to future precipitation changes. [ABSTRACT FROM AUTHOR]

Fertilization and mowing are commonly used grassland management measures. However, an understanding of how plant, soil bacterial, and soil fungal diversity responds to these two management measures are limited. We ran a fertilization and mowing experiment using a completely randomized design for 7 years (from 2014 to 2020) to explore the effects of fertilization and mowing on plant, soil bacterial, and soil fungal diversity. We used one-way and two-way Analysis of Variance (ANOVA) to compare how fertilization and fertilization + mowing impacted plant, soil bacterial and fungal diversity. We also used a structural equation model to analyze the maintenance mechanisms about fertilization and mowing affecting plant, soil bacterial, and soil fungal diversity. Our ANOVA results showed that when nitrogen addition level was beyond 8 GNM-2YR-1, fertilization significantly reduced plant taxonomic and functional diversity. However, the fertilization + mowing significantly increased plant diversity compared to fertilization. Fertilization and fertilization + mowing had no significant effect on soil bacterial and fungal diversity, but could change soil bacterial and fungal community structure by altering soil pH. Our structural equation model showed that fertilization reduced plant diversity mainly by increasing light competition in plant community and causing soil acidification. These results confirm light competition and soil acidification as maintenance mechanisms of fertilization and mowing affecting grassland plant diversity. Our findings highlight mowing can mitigate the adverse effects of fertilization on grassland plant diversity. However, the application of fertilization + mowing in grassland management needs to consider fertilization concentration. • Fertilization reduced plant diversity, and mowing can mitigate the adverse effects. • Fertilization and mowing changed soil bacterial and fungal community structure. • Fertilization reduced plant diversity by light competition and soil acidification. • Mowing mainly mitigates effects of fertilization by reduces light competition. [ABSTRACT FROM AUTHOR]