Soil acidification is a significant threat to agricultural sustainability, particularly in paddy fields, where acidic conditions can limit crop productivity and soil health. This study aimed to explore the combined effects of alkaline amendments—lime, magnesia, and silicon fertilizer—on the acid-neutralizing capacity (ANC) of paddy soils and the rice yield, with the objective of identifying effective strategies to mitigate soil acidification and enhance agricultural productivity. From 2018 to 2021, a four-year field trial in Hunan tested lime, magnesia, and silicon fertilizers. Soil samples (0–20 cm depth) were collected once post-harvest in 2021 to evaluate the cumulative treatment effects. After four years, the control soil pH was 6.12. Lime and light magnesia treatment increased it to 6.70 and 6.99, respectively. Silicon fertilizer showed no significant difference (pH 6.05). ANC analysis revealed the following anti-acidification capacity ranking: light magnesia > lime > control > silicon fertilizer. Light magnesia boosted the rice yield by 13.02% over the control. Statistical analyses indicated a significant positive correlation between the soil acid-neutralizing capacity and pH (ANC4.0 = 7.53 × pH − 30.00, R²adj = 0.70; ANC5.0 = 6.96 × pH − 37.49, R²adj = 0.58). The rice yield was correlated with exchangeable magnesium (yield = 0.42 × Ex-Mg + 24.54, R²adj = 0.44). The continuous application of lime and light magnesia enhanced the nutrient availability and soil anti-acidification, with light magnesia also improving the rice yield. These findings provide insights to aid in enhancing soil quality and agricultural productivity in acid-affected regions.

Vegetation degradation in the alpine meadows is becoming increasingly severe under global change, with species loss frequently linked to changes in plant functional groups (PFGs). Changes in PFGs alter plant-derived carbon inputs, which significantly influence soil organic carbon (SOC) sequestration and soil communities. However, the impact of specific PFG removal on soil carbon fractions and nematode trophic groups remains underexplored. In this study, above-ground removal of PFGs was carried out for five consecutive years in the Qinghai–Tibet Plateau alpine meadow, with five treatments: (1) no removal of PFGs (CK); (2) keep non-legume forbs (remove graminoids and legumes, Forbs); (3) keep graminoids (remove legumes and non-legume forbs, Graminoids); (4) keep legumes (remove non-legume forbs and graminoids, Legumes); (5) remove all PFGs (All-plants-removed). Root properties, nematode community, and soil carbon fractions were measured. We found that the Graminoids treatment significantly increased root biomass, whereas the All-plants-removed treatment led to a significant decrease. Nematode abundance was highest under the Legumes treatment, primarily due to increased omnivores-predators. Meanwhile, the soil particulate organic carbon (POC) varied significantly between PFG types, being the highest in the Forbs and CK treatments. Correlation analysis revealed a significant positive relationship between SOC and bacterivore abundance, suggesting that higher SOC enhances bacterivore populations and subsequently influences carbon cycling. We conclude that PFG removal alters soil nematode community structure and POC, underscoring the role of PFGs in below-ground biodiversity and soil carbon sequestration.