Abstract: We explored the effects of Larix gmelinii forest age on distribution, stability and organic carbon content of soil aggregates, based on 28 plots with different forest ages (young, middle-aged, near-mature, mature and over-mature). We measured soil physicochemical indices, soil aggregates and their organic carbon content in different soil layers. The results showed that: (1) The proportion of microaggregates (0.053-0.25 mm) was the lowest in all ages of L. gmelinii forest. Except for the near-mature forest, soil aggregates in all forests were dominated by macroaggregates (0.25-2 mm), accounting for 44.13%-50.34% of the total aggregate content. With increasing stand age, macroaggregate (0.25-2 mm), mean weight diameter (MWD) and geometric mean diameter (GMD) decreased at first and then increased. (2) The organic carbon content of soil aggregates in different aged L. gmeliniiforests was the highest in the 0.25-2 mm and the lowest in the 0.053-0.25 mm aggregates. The organic carbon content of soil aggregates in each particle size decreased with increasing soil depth. (3) Soil macroaggregate content, MWD, GMD and organic carbon content of soil aggregates were significantly positively correlated with total organic carbon, soil water content, available potassium and total phosphorus, and negatively correlated with soil pH and metal oxide content. The relationships between soil microaggregate content and soil physicochemical indices were opposite to that of macroaggregate. Forest age affected distribution, stability and organic carbon content of soil aggregates in L. gmelinii forest. Organic matter and metal oxides contributed to the formation and stability of macroaggregates (0.25-2 mm) and microaggregates (<0.25 mm), respectively.

Key words: cold-temperate zone, forest soil, particle size, stability, soil physicochemical property.