亚热带丘岗区经果林种植对红壤团聚体稳定性的影响

团聚体稳定性特征对评价经果林种植区内水土环境状况具有重要意义。为探究经果林类型对林下土壤团聚体结构及稳定性的影响,选取湖南北部丘岗区5年生黄桃、梨树、桔树、油茶和猕猴桃5种经果林下0～50 cm土层土壤为研究对象,采用沙维诺夫法量化分析各经果林下土壤团聚体含量、分布特征和稳定性指标的差异。结果表明: 土壤团聚体中大部分为机械稳定性团聚体,含量均在92.3%以上;经湿筛法处理后,油茶水稳性团聚体以>2 mm粒径为主,占总量的55.9%,0.25～2 mm粒径团聚体是黄桃、梨树、桔树和猕猴桃土壤的优势粒级,含量均在43.6%以上;5种经果林平均重量直径(MWD)和几何平均直径(GMD)分布范围分别为1.10～3.19 mm和0.61～2.28 mm,团聚体结构破坏率(PAD)和分形维数(D)分布范围分别为2.9%～37.3%和2.30～2.68;随土层深度增加,黄桃、油茶、猕猴桃下土壤团聚体稳定性变差,MWD和GMD分别降低了1.7%～57.7%和4.5%～65.8%,PAD和D分别增加了0.4%～17.3%和1.6%～11.1%;经果林类型对土壤团聚体稳定性的影响随着土层深度的增加而减小。综合各稳定性指标,5种经果林下团聚体稳定性顺序为油茶>猕猴桃>梨树>桔树>黄桃;经果林类型主要通过影响大粒径团聚体含量来提高土壤结构稳定性。从改良土壤团聚体分布及稳定性方面考虑,建议在亚热带丘岗区经果林种植过程中优先考虑油茶,其次为猕猴桃;黄桃种植可能造成土壤团聚度降低,在种植中需考虑土壤流失的防护措施。本研究结果可为亚热带丘岗区经果林的开发利用及生态治理提供一定的理论依据和应用指导。

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 Amygdalus persica, Pyrus sorotina, Citrus reticulata, Camellia oleifera and Actinidia chinensis 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 Camellia oleifera 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 A. persica, P. sorotina, C. reticulata and A. chinensis 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 (D) 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 A. persica, C. oleifera and A. chinensis forest soils became worse; MWD and GMD decreased by 1.7%-57.7% and 4.5%-65.8%, respectively; PAD and D 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 C. oleifera > A. chinensis > P. sorotina > C. reticulata > A. persica. 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 C. oleifera should be given the top priority as the economic fruit forest in the subtropical hilly area, followed by A. chinensis. Whereas A. persica 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.