Soil organic carbon (SOC) is known as a vital ecosystem service, resulting from interactions of ecological processes. It is important for its contributions to food production, mitigation, and adaptation to climate change. In this study, we investigated the relationship between tree density and tree trunk circumference with the soil chemical properties in the small tree line area located in Józsefmajor, Hungary. The interrelation between different chemical soil properties also was measured. For this purpose, samples were taken in 24 plots (6 m×13m) from 0–10 soil depths. Tree density and tree trunk circumference in each plot were measured. The Near-Infrared spectroscopy technique (Wavelength Range: 1300–2600nm MEMS (micro-electromechanical systems) technology) was used to estimate the chemical properties of the soil. Pearson and Spearman correlation analysis was applied to study the interrelationships between two multivariate data sets, tree density and trunk circumference were compared with soil properties. The results showed a significant relationship between some soil chemical parameters, especially between soil organic carbon (SOC) and total N and also the cation exchange capacity (CEC) with SOC and total N. Besides, this study shows that the plots containing more trees and with a higher trunk circumference provide higher SOC and total N concentrations. Trunk circumference has a slightly stronger correlation with these two soil properties compared to those of tree density.