Characteristics of soil organic carbon and total nitrogen in rubber plantations soil at different age stages in the western region of Hainan island | 海南岛西部不同林龄橡胶林土壤有机碳和全氮特征研究

[Objective] The aim was to study on the characteristics of soil organic carbon and nitrogen in rubber (Hevea brasiliensis Muell-Arg) plantations at different age stages in the western region of Hainan Island, so as to evaluate the ecological benefits of rubber plantations and provide basic data for studying the effect of tropical land utilization/cover change on the global carbon and nitrogen cycle. [Method] The situs was in Danzhou city, western region of Hainan Island, and the samples were four kinds of rubber plantations soil at different ages and one kind of control check (pepper, Piper nigrum L.) soil. In this research, four quadrats were set up in each sample, and the size of each was 20 cm×20 cm. Four specimens were gathered from four layers of 0-15, 15-30, 30-45, 45-60, and the average of them was the last analysis result of each sample. Soil density was measured by cutting ring method, soil containing and hygroscopic water was detected by oven drying method, soil organic carbon (SOC) was measured by low temperature heated outside potassium dichromate oxidation-colorimetry method, and soil total nitrogen (STN) was detected by semimicro Kjeldahl method. [Result] SOC contents of different layers in rubber plantations soil at different age stages (including the CK pepper soil, the same as below) varied little, and the content of SOC in surface layer (0-15 cm) was higher, while the underlayer (45-60 cm) was lower than the average value; there was significant difference in SOC content among different kinds of soil, and the content was of 6.03-7.78 g/kg, tapping young trees (7 years) CK pepper mature age trees (30 years) prophase of young trees (2 years) tapping trees (16 years); there was no significant difference in SOC storage among different kinds of soil, and the storage was of 61.33-74.29 t/hm2, mature age trees (30 years) tapping young trees (7 years) prophase of young trees (2 years) CK pepper tapping trees (16 years); there was significant difference in STN content among rubber plantations soil at different age stages, the content was of 410.86-664.14 mg/kg2, CK pepper tapping young trees (7 years) prophase of young trees (2 years) mature age trees (30 years) tapping trees (16 years), and STN content of tapping trees (16 years) soil was extremely lowest; there was significant difference in C/N ratio among different kinds of soil, the ratio was of 10.94-14.47, and the ratio of tapping trees (16 years) mature age trees (30 years) tapping young trees (7 years) CK pepper prophase of young trees (2 years). [Conclusion] There wasn’t unhealthy effect of rubber trees planted in tropical area on the content and storage of SOC, the content of STN and the ratio of C/N. there was no significant difference between rubber plantations and CK pepper soil, and the effects of rubber plantation on soil carbon-nitrogen was similar to that of other tropical crops (such as pepper).