Soil organic carbon composition and its influencing factors in rubber plantation of different ages

【Objective】The carbon content and influencing factors of soil components in different age classes of rubber forest were compared and analyzed, so as to provide a theoretical basis for the soil quality in Yunnan and even China's rubber planting areas and the efficient development of natural rubber industry.【Method】Taking the ninth branch of Jinghong farm in Xishuangbanna as the sampling site, the soil samples of different soil layers of rubber forest of five age classes(2, 10, 16, 27 and 34 a) were selected as the test samples. Main physical and chemical properties and each component content of soil organic carbonwere measured, single factor analysis of variance and correlation analysis were used to analyze the differences and influencing factors of soil organic carbon components in different age classes and different soil layers(0-10 cm, 10-20 cm, 20-40 cm).【Result】The soil physical and chemical properties of five different age classes of rubber forest were different. The soil pH was 2.59-4.47, the water content was 17.48%-40.38%, the soil bulk density was 0.99-1.40 g/cm, the total nitrogen was 0.75-1.37 g/kg, the total phosphorus was 0.45-1.68 g/kg, and the total potassium content was 1.70-22.71 g/kg. The content of soil organic carbon components in 5 rubber forests of different ages varied, among which the total soil organic carbon content ranged from 7.51-20.13 g/kg. The content of readily oxidized carbon ranged from 2.81-7.20 g/kg, accounting for 13.96%-95.87% of the total organic carbon content in soil. The content of stable organic carbon ranged from 1.82-4.69 g/kg, accounting for 9.04%-62.45% of the total soil organic carbon content.The content of water-soluble organic carbon ranged from 0.23-0.52 g/kg, accounting for 1.14% to 6.92% of the total soil organic carbon content. The variation law of soil organic carbon components in different soil layers was similar, that was, with the increase of soil depth, the carbon content of each component decreased, which was 0-10 cm>10-20 cm>20-40 cm.The results of correlation analysis showed that the components of soil organic carbon were closely related. Total organic carbon had extremely significant positive correlation with easily oxidized organic carbon and stable organic carbon(P<0.01, the same below), but had no significant correlation with water-soluble organic carbon(P>0.05, the same below).Soil physical and chemical characteristics had different effects on soil organic carbon components. Soil total organic carbon had extremely significant positive correlation with soil water content, total phosphorus content and total potassium content, and significant positive correlation with total nitrogen content(P<0.05, the same below), and significant negative correlation with soil pH and soil bulk density. Easily oxidized organic carbon was extremely positively correlated with soil water content, total phosphorus content and total potassium content, and extremely negatively correlated with soil bulk density and pH. Stable organic carbon was significantly positively correlated with total phosphorus content and total potassium content, and negatively correlated with soil bulk density and soil water content. Water soluble organic carbon was significantly positively correlated with total potassium content and soil pH, but not with other indicators.【Conclusion】There is strong correlation between the components of soil organic carbon in rubber forest of different age classes, and soil pH, soil bulk density, soil water content and the contents of total nitrogen, total phosphorus and total potassium are important factors affecting the contents of soil organic carbon components. There is a close mutual restriction and promotion relationship among the physical and chemical indexes.