A Study on the C, N, and P Contents and Stoichiometric Characteristics of Forage Leaves Based on Fertilizer-Reconstructed Soil in an Alpine Mining Area

In this study, we analyzed the C, N, and P contents and stoichiometric characteristics of forage leaves of five species (Elymus breviaristatus cv. Tongde, Poa crymophila cv. Qinghai, Puccinellia tenuiflora cv. Qinghai, Festuca sinensis cv. Qinghai, and Poa pratensis cv. Qinghai) in “fertilizer-reconstructed soil” through integrative soil amendment with parched sheep manure and granular organic fertilizer in an alpine mining area. A model is fitted in order to screen out the best forage species suitable for vegetation restoration in the alpine mining area and the most favorable fertilizer dosage to improve the nutrient content of forage leaves. The results showed that (1) increasing the dosages of granular organic fertilizer and sheep manure had little effect on the C content of the five types of forage grasses, but they could significantly increase the N and P contents and N/P of the manually restored grassland in the alpine mining area (p < 0.05). (2) The productivity and stability of the five species were ranked as follows: Elymus breviaristatus cv. Tongde > Puccinellia tenuiflora cv. Qinghai > Festuca sinensis cv. Qinghai > Poa pratensis cv. Qinghai > Poa crymophila cv. Qinghai. (3) According to the fitted least squares model and the willingness to maximize the C, N, and P contents of the leaves, the ranking of the five forage grasses was described by the Prediction Profiler as follows: Elymus breviaristatus cv. Tongde > Puccinellia tenuiflora cv. Qinghai > Festuca sinensis cv. Qinghai > Poa crymophila cv. Qinghai > Poa pratensis cv. Qinghai. (4) The predictive model suggested that the optimal contents of C, N, and P in Elymus breviaristatus cv. Tongde, Festuca sinensis cv. Qinghai, and Poa pratensis cv. Qinghai leaves could be achieved with the application of 3.6 kg/m(2) of granular organic fertilizer and 45.0 kg/m(2) of sheep manure. For Poa crymophila cv. Qinghai leaves, the ideal content was attained by applying 0 kg/m(2) of granular organic fertilizer and 45.0 kg/m(2) of sheep manure. Lastly, the optimal C, N, and P contents in Puccinellia tenuiflora cv. Qinghai leaves could be obtained through the application of 3.6 kg/m(2) of granular organic fertilizer combined with 0 kg/m(2) of sheep manure. In conclusion, the study’s results highlight the significant practical value of the fertilizer-reconstructed soil for vegetation restoration in alpine mining regions.