Abstract: Five types of plots, grass (GS), frutex and grass (FG), frutex (FX), arbor and frutex (AF), and arbor (AR) communities, were selected to study the properties of soil aggregates in different revegetation stages and their main influencing factors of purple soils on sloping land in Hengyang, Hunan Province, China by using spatial series instead of time series. The five communities in purple soils on sloping land were similar in site conditions, and denoted as five different successive stages. The relationships between the properties of soil aggregates and the main influencing factors were determined by canonical correlation analysis (CCA) and principal component analysis (PCA). The results showed that the contents of large aggregates increased significantly in the process of revegetation (P<0.05); the aggregates >5 mm diameter were dominant in 0-2 m soil layer, accounting for 50%-80%, followed by the aggregates 5-2 mm diameter with a proportion of 10%-15%. With the deepening of soil layers, the sum of aggregates decreased significantly in GS, FG and AF (P<0.05), increased after a decrease and then decreased in FX (P<0.05), and increased at first and then decreased in AR (P<0.05). In different re-vegetation stages and different soil layers, mean weight diameter (MWD) of aggregates showed different variation patterns: in 0-40 cm soil layer, highest in FW (P<0.05); in 40-80 cm soil layer, decreased after an increase and then increased with re-vegetation (P<0.05); in 80-130 cm and 130-200 cm soil layers, increased significantly with revegetation (P<0.05). With the deepening of soil layers, MWD decreased significantly in GS, FG and FX (P<0.05), and increased at first and then decreased in AF and AR (P<0.05). CCA showed that soil organic matter (SOM) and total nitrogen (TN) had great influence on aggregates >5 mm and 1-0.5 mm, while Al₂O₃, Fe₂O₃ and <0.01 mm physical clay had great influence on aggregates 2-1 mm and 0.5-0.25 mm. PCA showed that SOM, TN, Al₂O₃ and Fe₂O₃ were the main factors influencing soil aggregates, followed by <0.002 mm clay and <0.01 mm physical clay. Our study indicated that re-vegetation could change soil structure, leading to re-distribution of soil aggregates and formation of macro-aggregates, and therefore improving the stability of soil aggregates.

Key words: chemical fertilizer combined with organic fertilizer application, N and P balance, long-term experiment, eco-economic benefit.