【Objective】 This study was conducted under the controlled experimental conditions in the phytotron. The effect of different tree species collocations on negative air ion (NAI) and the relationship between leaf nutrient elements and the NAI were investigated, in order to explore the mechanism of NAI production in the forest and provide a theoretical reference for the selection of tree species and their collocation in the future healthy forest. 【 Method 】 The NAI concentrations of six typical subtropical tree species and their collocations were continuously monitored in a phytotron at the Hushan Experimental Base, Qianjiang Source Forest Ecology Station, Hangzhou, Zhejiang, China from June to September 2018. At the same time, the leaf element content was measured. One-way ANOVA and LSD multiple comparisons (α = 0. 05) were used to test the collected data, and the correlation between NAI concentration and leaf nutrient content was analyzed using Person’ s analysis. 【 Result】 The contents of manganese and potassium ions in plant leaves were significantly positively correlated with the NAI concentration (P<0. 05), the content of iron ion in broadleaf leaves was significantly positively correlated with the NAI concentration (P < 0. 01), and the contents of nitrogen and copper ions in coniferous species were significantly positively correlated with the NAI concentration (P<0. 01). Different collocations of tree species led to significant differences in NAI concentration, and there was a tree species mixing interaction. The interaction showed a positive effect when the mixed species were two and four species, and the interaction effect on NAI increased with increasing leaf area and average NAI concentration of single species. The interaction showed a negative effect when the mixed tree species were five and six species. At mixed species of 2-6 species, the interaction effect showed a tight non-linear increasing relationship with the leaf biomass of each species mixed treatment, with the regression equation y = -0. 063 1x2+ 78. 322x – 23 783. 【Conclusion】 For raising the NAI concentration around plants, the contents of manganese and potassium ions in leaves have a positive effect, and the content of iron ion in broad-leaved leaves and the contents of nitrogen and copper ions in coniferous leaves have a more significant effect. The quantitative composition of different tree species leads to differences in NAI concentration, and interaction effects are influenced by leaf biomass, leaf area, tree height collocation, and individual tree species NAI effects. Overall, the NAI concentration effect of the tree species collocation depends on their interaction, with coniferous species being more conducive to elevate NAI concentration and species with high NAI effects being more conducive to elevate NAI concentration when they are in the uppermost space of the collocation. The research on NAI concentration effect of tree species collocation and leaf element content would provide a scientific basis for tree species selection and structural collocation of efficient recreational forests. © 2022 Chinese Society of Forestry. All rights reserved.
