The Vertical Characteristics of Soil Organic Carbon in Different Developing Stages of Rubber Tree(Hevea brasiliensis)Plantations
By means of the direct determination method in soil profiles,the variation characteristics of soil organic carbon(SOC)in different developing stages and its relationship with soil pH,soil C/N ratio and total nitrogen content of rubber(Hevea brasiliensis)plantations in 3 different ages,i.e.,immature period(4 a) and peak yielding period(12 a,19 a)were studied.The results obtained indicated that SOC contents of rubber plantations at 3 different ages increased with soil depth.Generally the order of SOC contents in rubber plantations was: 12 a 4 a 19 a.The content of SOC decreased with depth,whereas the value of soil pH increased with depth.SOC content in different layers had a significant negative relationship(R2≥0.708 8).There was positive linear correlation between SOC and STN of rubber plantations in different ages.Soil C/N ratio along the gradient was with in the range of 8.19~16.49,being favorable to the nutrient release during organic matter decomposition.Soil C/N ratio of rubber plantation decreased with rubber tree age,which showed planting age affected soil C and N content in the vertical distribution.