Distribution and Stoichiometric Characteristics of Soil Carbon and Nitrogen Stocks in Forest Soils at Different Elevations in Liziping, Sichuan, China

The forest soils at altitudes of 1800, 2100, 2400, and 2700 m was taken as the research object to study the vertical distribution characteristics of physical and chemical properties, carbon and nitrogen storage and stoichiometry in forest soils, and Mantel analysis and Pearson correlation coefficient method were used to analyze the relationship between the carbon and nitrogen storage of forest soil, carbon and nitrogen stoichiometry of soil, and the soil physical and chemical properties. The results showed that the soil microbial carbon and nitrogen content, organic carbon content, and water content at 2400 altitude were significantly larger than those at other altitudes, and total phosphorus content was significantly larger at 1800 m altitude (P < 0.05), while the soil total nitrogen content at 2700 m altitude was significantly larger than those at other altitudes. The soil organic carbon stock first increased and then decreased with the rise of altitude, while the soil total nitrogen stock first decreased and then increased, and the soil carbon to nitrogen ratio was consistent with the trend of soil carbon to nitrogen stoichiometric imbalance, and the maximum values of microbial entropy carbon, microbial entropy nitrogen, carbon to nitrogen ratio, and carbon to nitrogen stoichiometric imbalance at the altitude of 2400 m were 3.58, 12.64, 34.79, and 2.74%, respectively; the soil water content and total potassium were significantly correlated with soil carbon stock, and the total phosphorus of the soil was not only significantly correlated with the soil N, but also significantly affects soil microbial amount of carbon and nitrogen ratio, microbial entropy nitrogen and carbon and nitrogen stoichiometric imbalance; Mantel analysis shows that soil carbon and nitrogen ratio, carbon and nitrogen stoichiometric imbalance and microbial entropy nitrogen are the important influence factors of soil nitrogen storage, and soil carbon and nitrogen ratio is an important influence factor of soil carbon storage. This study provides scientific basis for understanding the accumulation of soil carbon and nitrogen and the mechanism of carbon and nitrogen cycling in the altitude gradient forests of nature reserves.