Labile organic carbon ( LOC) is an important factor of soil organic carbon
pool，and it can be more sensitive to environment change than any other factor． LOC in aggregate
significantly influences soil quality and protection of carbon pool． In order to achieve the scientific
management of restoration communities after clear-cutting，it is of great significance to investigate the
relationship between soil aggregates and LOC in the area． ［Methods］Concentrations of soil aggregates
and LOC of restoration communities in Chinese pine plantations of the Loess Plateau after clear-cutting
were investigated． There were 3 types of restoration community ( shrub land，abandoned forestland and
young plantation land． ) and no clear-cutting forest as control ( CK) ． Undisturbed soil samples were
collected at 0 － 20 cm soil layer，the volume fraction of aggregate were tested using wet screening，theconcentrations of soil total organic carbon were determined using H2 SO4-K2 Cr2 O7 oxidation，and the
concentrations of soil LOC were measured using KMnO4 oxidation． Analysis of variance and linear
regression analyses were done using SPSS ( 12. 0) ． ［Ｒesults］ 1) Macro-aggregate ( ＞ 250 μm) was
dominant in aggregate composition． Compared with CK，the types of restoration community after clearcutting
presented significant effects on the distribution of aggregates． The percentage of micro-aggregate
significantly decreased ( P ＜ 0. 05) while that of macro-aggregate significantly increased ( P ＜ 0. 05) in
shrub land and abandoned forestland． Aggregate composition in young plantation land showed no
significant changes． 2 ) The concentration of aggregate organic carbon increased with aggregate size
increasing． There was the highest concentration of organic carbon in shrub land． The concentration of
aggregate organic carbon was more sensitive than that of bulk soil organic carbons to different type of
restoration community． 3) The concentration of LOC in soil aggregate decreased with the improvement of
labile state，and LOC concentration of macro aggregate was greater than micro aggregates． Compared with
CK，the organic carbon of soil aggregate became more highly labile under different restoration
communities． The concentration of aggregate LOC significantly increased in shrub land， and the
concentration of LOC in macro-aggregate was more sensitive to different type of restoration community
than that in any other aggregate size． 4) Ｒesults of correlation analysis showed that LOC in aggregates
presented a significant correlation with organic carbon in bulk soil． The correlation of LOC in macroaggregate
with organic carbon in bulk soil was better than micro-aggregate． Highly LOC showed better
correlation with organic carbon in bulk soil than lowly LOC． Therefore，highly LOC in macro-aggregate
correlated best with organic carbon in bulk soil． ［Conclusions］These results proved that different type
of restoration community resulted in soil organic carbon unstable，and aggregate LOC in shrub land
significantly increased． To some degree，our results uncovered the distribution characteristics of soil
aggregate LOC in the Loess Plateau and indicated the effect of clear-cutting on aggregate labile organic
carbon． According to these results， shrub land in restoration community can be a considerable
management measure after clear-cutting Chinese pine forest in the Loess Plateau． Based on previous
researches，our findings indicate that highly LOC in macro-aggregate can be a better index for measuring
the dynamic of soil organic carbon than LOC in bulk soil．
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