Afforestation has been implemented on a large scale in the Loess Plateau of China since 1999. This paper aimed to judge the influence of plantation tree types on soil aggregate stability and carbon stocks. The results showed that : (1)the content of soil organic matter and macro-aggregates, the water stability of aggregates were significantly higher in P. tabuliformis plantation compared with R. pseudoacacia and M. pumila plantations, conversely, the content of soil calcium carbonate in P.

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... iformis plantation was the lowest; (2) the content of soil organic matter and organic carbon density were significantly negatively correlated with soil depth, while soil carbonate calcium and in-organic carbon density fluctuated with the increasing of soil depth; (3) compared with topsoil, subsoil was important carbon sink because there were more in-organic carbon; (4) Aggregate organic carbon increased while inorganic carbon decreased with the increasing of aggregate size respectively. We concluded that: (1) R. pseudoacacia played a more important role in soil carbon sequestration compared with P. tabuliformis; while P. tabuliformis was more beneficial to improve soil organic matter and soil structure; (2) subsoil and in-organic carbon were important carbon sinks compared with topsoil and organic carbon; (3) the bigger water stable aggregates having the higher content of soil organic matter and the lower carbonate calcium.