Stoichiometric Characteristics of Carbon, Nitrogen and Phosphorus in Mixed Plantation of Larix olgensis and Fraxinus mandshurica under Different Mixed Proportions

In this study, four types of Larix olgensis and Fraxinus mandshurica mixed plantations were selected as the research object according to rows-mixing ratios(type Ⅰ: 5∶3; type Ⅱ: 6∶4; type Ⅲ: 2∶2, type Ⅳ: 1∶1). We measured the C, N and P in tree leaves, litter and surface soil(0～10 cm) of L. olgensis and F. mandshurica mixed plantations to analyze the difference of nutrient allocation and cycle rule of each component in the plantation ecosystem. The results indicated that the mixed proportion had significant effects on the stoichiometric characteristics of leaves, litter and soil. In the leaf component, N content of type Ⅱ was significantly higher than that of type Ⅲ and Ⅳ, while C∶P and N∶P were significantly higher than that of the other types. P content and C∶N of type Ⅲ were significantly higher than type Ⅱ. In the litter component, C content and C∶N of type Ⅰ and Ⅳ were significantly higher than type Ⅱ, while C content, C∶P and N∶P of type Ⅲ were the lowest among all the types. In the soil component, type Ⅱ had higher C, N, P and higher C∶P, N∶P compared with the other mixed plantations(P < 0.05). The response of soil nutrient contents and stoichiometric ratios to the change of mixed proportion was convergent, N and P were Ⅱ > Ⅰ > Ⅲ > Ⅳ; C∶P and N∶P were Ⅱ > Ⅲ > Ⅳ > Ⅰ. According to the situation of plant nutrient restriction in each mixed proportion, the plantation growth was limited by N element with the exception of type II. There were strong coupling relationships between leaf, litter N and soil nutrient contents. Moreover, C, N and P in soil were significantly positively correlated. Considering the growth rate of plants, decomposition rate of litter as well as soil nutrient supply and retention capacity, our results suggested that L. olgensis and F. mandshurica plantation with row ratio of 6:4 would be preferred in the future construction of plantation.