Disturbance from restoration reseeding is associated with short‐term topsoil carbon loss and alters soil bacterial communities and functions in degraded alpine meadows of the Qinghai–Xizang Plateau

Background Restoration of degraded ecosystems is widely promoted as a nature‐based solution, yet whether vegetation recovery consistently promotes soil carbon (C) sequestration remains insufficiently understood in climate‐sensitive alpine ecosystems. The Qinghai–Xizang Plateau (QXP) contains vast soil organic carbon (SOC) stocks that may be sensitive to restoration disturbance. Methods We examined the short‐term impacts of tillage (TR) and no‐tillage (NT) reseeding on surface SOC (0–10 cm) dynamics and associated bacterial community responses in a degraded alpine meadow on the QXP. Vegetation characteristics, SOC storage, bacterial community composition, and predicted microbial functions were assessed following restoration treatments. Results Both TR and NT effectively restored aboveground vegetation, increasing biomass and reducing the Grassland Degradation Index. However, both treatments were also associated with lower surface SOC concentrations and carbon storage relative to unrestored degraded meadow, revealing a divergence between aboveground recovery and short‐term topsoil SOC responses. High‐throughput sequencing showed marked shifts in bacterial community composition following reseeding. TR was characterized by enrichment of disturbance‐associated Actinomycetota, whereas NT showed higher relative abundance of copiotrophic Pseudomonadota associated with elevated dissolved organic carbon. PICRUSt2 functional predictions further suggested a shift from anabolic toward catabolic metabolic potential in reseeded soils. Conclusions Restoration reseeding may reduce short‐term topsoil carbon storage while substantially restructuring bacterial communities and their predicted functions during the early stages of restoration.