Responses of Restored Vegetation Communities, Soil Properties, and Microbial Composition to Different Fertilization...

As a typical ecologically degraded mining area, the Jiangcang Mine in Qinghai is characterized by severely depleted soil nutrients and reduced biodiversity, making scientifically grounded soil-amelioration measures urgently necessary to facilitate vegetation reconstruction and enhance soil ecological functions. To determine the optimal fertilization rate, we conducted a two-factor randomized block experiment over an approximately two-year period after plant sowing, using pelletized organic fertilizer and sheep manure as the primary amendments, with three replicates per treatment, and with application rates selected based on commonly used ranges in alpine grassland restoration and the availability of local organic resources in the mining area. Sheep-manure treatments were set at three levels at 0 (S0), 20 (S1), and 40 (S2) kg·m^-2, while pelletized organic fertilizer was applied at three rates at 0.0 (F0), 1.5 (F1), and 3.0 (F2) kg·m^-2. The combination of the two factors resulted in nine treatments: S0F0, S0F1, S0F2, S1F0, S1F1, S1F2, S2F0, S2F1, and S2F2. The results showed that fertilization significantly improved vegetation height, canopy cover, plant density, and aboveground biomass, with the strongest promotive effects observed under S2F2 and S2F1. Compared with other treatments, S2F2 markedly increased soil moisture content, pH, soil organic matter, available nitrogen, available phosphorus, as well as total nitrogen, 6.96-, 2.91-, 1.70-, 5.04-, 2.51-, and 3.91-fold relative to the control, respectively. The S0F2 treatment significantly enhanced bacterial Observed Richness, Shannon, and Chao1 indices, as well as simultaneously increasing fungal Observed Richness and Chao1 index. Vegetation height and density exhibited the strongest positive correlation under S2F1, whereas vegetation cover and aboveground biomass were most strongly correlated under S2F2. A gray relational analysis performed on 15 indicators ranked S2F0 as having the highest relational degree and comprehensive score, followed by S2F2 and S2F1. In summary, the combined application of approximately 40 kg·m^-2 of sheep manure without pelletized organic fertilizer showed the highest comprehensive restoration performance under the experimental conditions of this alpine mining area.