In order to investigate the composition and stability of soil aggregates and explore the soil structure of Chinese fir plantation

in this study

0—100 cm soil layers of Chinese fir plantation in different developmental stages were taken as the object

dry sieving was used to determine composition of soil aggregates and wet sieving was used to determine the stability of aggregates. The results showed that under the dry sieve treatment

the soil aggregates of the Chinese fir plantations were dominated by macroaggregates (＞0.25 mm) at each developmental stage

which was above 80%

and the proportion of soil macroaggregates in middle age forest and mature forest was higher than that of young forest in each soil layer

it had significant difference in 0—20 cm soil layers; In each soil layer

for the soil aggregates with clay diameter ＞5 mm

which had a higher proportion and had a significant effect on the composition of soil aggregates with the different developmental stages of Chinese fir. Under the wet sieve treatment

the proportion of water stable macromolecule (＞0.25 mm) was significantly decreased with the increase of soil layer in each developmental stage

for the 0—80 cm soil layers

the proportion of water stable macromolecule of middle age and mature forest was higher than young forest

for the 0—20 cm and 20—40 cm soil layer

the proportion of water stable macromolecule of middle age forest were 41.79% and 39.06% higher than that of the young forest

which had significant difference; The PAD characteristics of soil aggregates displayed an opposite trend as compare to water stable macromolecules in each developmental stage of Chinese fir plantation

MWD and GMD decreased significantly with the increase of soil layer

and the GMD of soil aggregate in middle age forest and mature forest were significantly higher than those of young forest in 0—100 cm soil layers. Therefore

the stability of soil aggregates in Chinese fir plantation decreased with the increase of soil layer

and the soil structure of middle age forest and mature forest was better than that of young forest.