[Effects of economic fruit forest planting on the stability of red soil aggregates in the subtropical hilly area].

The stability of aggregates is of great significance to evaluate water and soil environment in regions plan-ting economic fruit forest. We explored the effects of economic fruit forest types on the structure and stability of soil aggregates in the 0-50 cm soil layer from 5-year-old , , , and forests in the hilly area in northern Hunan. The content, distribution characteristics and stability indices of soil aggregates from each economic fruit forest were quantitatively analyzed by the Shavinov method. The results showed that most soil aggregates were mechanically stable, with a minimum content of 92.3%. After wet sieving, the size of water-stable aggregates in the soil from forest was mainly >2 mm, accounting for 55.9% of the total aggregates. The 0.25-2 mm aggregates were the dominant particles in the , , and forest soils, with contributions higher than 43.6%. The mean weight diameter (MWD) and the geometric mean diameter (GMD) of soil aggregates for the five economic fruit forest types ranged from 1.10 to 3.19 mm and 0.61 to 2.28 mm, respectively. Furthermore, the percentages of soil aggregate destruction (PAD) and fractal dimension () were in the range of 2.9%-37.3% and 2.30-2.68, respectively. With the increases of soil depth, the stability of soil aggregates from , and forest soils became worse; MWD and GMD decreased by 1.7%-57.7% and 4.5%-65.8%, respectively; PAD and increased by 0.4%-17.3% and 1.6%-11.1%, respectively. The effects of economic fruit forest types on the stability of soil aggregates decreased with increasing soil depth. Based on the stability indices, aggregate stability from five economic fruit forests followed the order of > > > > . The type of economic fruit forest improved the stability of soil structure mainly by affecting the content of large-size aggregates. In terms of improving the distribution and stability of soil aggregates, it was suggested that should be given the top priority as the economic fruit forest in the subtropical hilly area, followed by . Whereas planting might reduce the degree of soil agglomeration, thus, the protective measures of soil loss should be considered during planting. Our results could provide theoretical basis and application guidance for the development, utilization, and ecological management of economic fruit forests in subtropical hilly areas.