Changes of Soil Organic Carbon in Different-aged Eucalyptus Plantations

In this paper,studies were made of soil organic carbon in different-aged Eucalyptus plantations. The results showed that the content of soil organic carbon, readily oxidized organic carbon and chemical recalcitrant organic carbon decreased with the increase of soil depth. And along with the increase of the forest age,they first increased,and then decreased,displaying a broken-line change. The soil organic carbon and readily oxidized organic carbon had the maximum contents at the age of four,and had a very significantly positive correlation. Stable organic carbon reached the maximum at the age of two,and but had a maximum decrease extent at the age of four. This index had a highly significant negative correlation with pH. It meant that the soil quality aged 4 was the best in Eucalyptus plantations,and the maximum was the transformation amount of their stable organic carbon. Root systems of Eucalyptus could absorb chemical stable organic carbon under 1 m thick soil,exhibiting the root's great ability of absorbing nutrients,and also decreasing the stability of soil carbon sequestration at the same time.