Stability and Particle Size Distribution Characteristics of Soil Aggregates in Schima superba Plantations of Different Stand Ages

In order to study the particle size distribution characteristics of soil aggregates in five Schima superba plantations of different age stages, soil samples from the 0—20 cm, 20—40 cm and 40—60 cm layers of 10 a, 15 a, 27 a, 55 a and 64 a were collected for analysis at Shunchang State Owned Forest Farm, Fujian Province.The aim was to investigate the impact of plantation age on the stability and distribution characteristics of soil aggregates in Schima superba plantations.The findings revealed that:（1） large aggregates（＞ 0.25 mm） were predominant in the soil aggregates of various age Schima superba plantations, accounting for over 90% of the total, with the ＞2 mm aggregates being the most abundant, while micro-aggregates（＜ 0.25 mm） made up less than 10%.This suggests that soil aggregates in different age Schima superba plantations exhibited strong agglomeration characteristics.（2） Wet screening resulted in a significant decrease in the proportion of aggregates（＞2 mm） and an increase in the 0.25～2 mm aggregates comPAred to dry screening.In the 0—40 cm soil layer, the water stability weight ratio and characteristic values of 64 a aggregates were notably higher than those of other stand ages, indicating superior soil permeability and water retention in the overmature large-diameter wood forest.（3） Soil aggregates of different sizes exhibited varying trends with changes in stand age and soil layers, with their interactions.In soil mechanical stability aggregates, the influence of stand age was the most significant.In water-stable aggregates, the MWD and GWD of soil aggregates were significantly influenced by stand age, soil layer, and their interaction（P ＜ 0.05）.