Carbon and Nitrogen Storage in Soil Aggregates from Different Terminalia superba Age Plantations and Natural Forest in Kouilou, Congo*

摘要

A comparative study was carried out in Mayombe, between the soil of natural forest and the soil under three Terminalia superba plantations of 7, 12 and 48 year-old. In each plantation type and natural forest composite soil samples were taken in 0-10 cm layer. The goal was to investigate the dynamic of total carbon and nitrogen in whole and soil aggregate fraction in order to assess the impact of reforestation on the soil fractions. Organic carbon was analyzed by the modified Walkey and Black method.Total nitrogen was determined using the Kjeldhal procedure. Statistically differences between the sites were tested using the Analysis of Variance (ANOVA). The results showed that in the surface soil the carbon content and total nitrogen were respectively 22.2 and 1.56 mug g~(-1)in the forest. The carbon content was between 14.9 and 23.5 mg g~(-1) while total nitrogen was between 1.31 and 2.24 mug g~(-1)in the plantations. The results also revealed that plantation aging had a marked impact on the totalcarbon and nitrogen concentration of soil aggregate fractions. The carbon and the nitrogen associated with the sand and the clay exhibited a significant increase. The carbon concentration was between 1.51 and 2.09 mg g~(-1)in the light aggregate fractions and between 0.95 and 1.04 mg g~(-1)in the organomineral aggregate fraction. The accumulation of total carbon in the whole soil and soil aggregate fractions and their increase during plantation aging suggested that the T. superba plantations could facilitate significant carbon storage.