Study on carbon storage and soil nutrient changes at different restoration stages of Potentilla parvifolia shrubs in Eastern Qilian Mountains

This study aimed to scientifically evaluate the change rule of carbon storage and soil nutrients at different habitat restoration stages. This study used a " spatial for temporal gradient” methodology, which compared changes in carbon storage and soil nutrient content at different restoration stages of Potentilla parvifolia shrubs over a period of nearly 20 years (from 1997 to 2018). It provides a theoretical basis for the management of P. parvifolia. The results showed that the carbon storage of shrubs increased by 1.4 to 6.2 times, the carbon storage of the herbaceous understory decreased by 0.9 to 1.7 times, and the carbon storage of the community increased by 1.1 to 2.0 times, with restoration of P. parvifolia. The soil bulk density decreased in the top soil layer (from 0 to 10 cm), and initially decreased and then increased in the 10 to 30 cm soil layer. With the progression succession of P. parvifolia, the total phosphorus, the available phosphorus, and the available potassium content in the soil between shrubs decreased by 0.7% to 6.0%, 6.3% to 28.8%, and 53.9% to 61.0%, respectively; the organic matter and available nitrogen content increased first and then decreased, and the total potassium content first decreased and then increased in the 0 to 30 cm soil layer. The trends observed in the organic matter, total potassium, available nitrogen, available phosphorus, and available potassium content in the soil between the shrubs were same as those observed under the shrubs. To summarize, with restoration of P. parvifolia vegetation, the soil fertility either decreased or first increased and then decreased, and carbon storage increased. Therefore, it is recommended that the large-scale expansion of P. parvifolia shrubs on the grassland for grazing purpose should be controlled, while the progressive succession on the grassland should be promoted to provide environmental benefits.