Characteristics of Litter and Soil Nutrient Content and Stoichiometric Ratio in Mixed Forest Cunninghamia lanceolata and Broadleaved Trees

In 1996, pure Cunninghamia lanceolata forest were afforested in Kaihua, Zhejiang province, in March 2015, 1-year container seedlings of Eurya japonica, Distylium racemosum and Phoebe bournei were interplanted in pure C. lanceolata stand. In August 2018, sample plots with 100 m × 100 m were established in different mixed forest with pure forest as the control. Litter and soil samples were collected for determination of organic carbon and total phosphorus content. The results showed that compared with the CK, the organic carbon content of litter in C. lanceolata + E. japonica plantation decreased significantly, and the total phosphorus content of litter in C. lanceolata + P. bournei plantation increased significantly, while the stoichiometric ratios of carbon, nitrogen, and phosphorus in litter had no great difference in different plantations. The stand type and soil layer had significant impact on soil nutrient content, and the mixed plantations showed higher soil nutrient contents than pure C. lanceolata plantation. Compared to that in pure C. lanceolata plantation, the average contents of soil organic carbon, total nitrogen and total phosphorus at 0−20 cm layer in mixed plantations increased by 25.2%, 48.8%, and 50.0%, and that at 20−40 cm layer increased by 26.9%, 45.5% and 47.6%. The stand type significantly affected the ratio of soil carbon and phosphorus, and of nitrogen and phosphorus, which had significant positive relation with litter stoichiometry.