Understanding the variations in soil aggregate composition, as well as the contents and stoichiometry of organic carbon (C), total nitrogen (N) and total phosphorus (P), in the surface layer of Cryptomeria japonica plantations with different stand ages can provide a theoretical basis for the optimized management of plantations and the improvement of soil fertility in the Rainy Area of West China. With the dry-sieving method, we measured the contents of soil aggregates with different sizes in the 0-15 and 15-30 cm soil layers across C. japonica plantations with five distinct developmental stages at Hongya Forestry Farm, Sichuan Province, including young stands (7 years old), middle-aged stands (13 years old), nearly mature stands (24 years old), mature stands (33 years old), and over-mature stands (53 years old). We further analyzed the C, N and P contents and ecological stoichiometric characteristics of soil aggregates. The results showed that the particle size composition of soil aggregates in C. japonica plantations varied among stand ages. The nearly mature and mature stands had higher proportion of large aggregates (0.5-1 and 1-2 mm), whereas the nearly mature stand had a lower proportion of micro-aggregates (0.053-0.25 mm) and the silt-plus-clay fraction (<0.053 mm). Moreover, the C, N and P contents and stoichiometric ratios in soil aggregate showed a unimodal pattern, which increased initially and then decreased with stand age, with peak values in the nearly mature and mature plantations. Furthermore, the C, N and P contents in aggregates in 0-15 cm soil layer were higher than that in the 15-30 cm soil layer. The highest C and N contents were found in the aggregates with particle sizes of 0.5-1 and 0.25-0.5 mm. In conclusion, the near-mature and mature stands of C. japonica plantations have higher nutrient content in soil aggregate, underscoring these stages was critical for maintaining soil fertility and advancing sustainable management practices.
探讨不同发育阶段柳杉人工林表层土壤团聚体组成、有机碳(C)、全氮(N)和全磷(P)含量及其化学计量比的变化特征,可为华西雨屏区人工林科学经营管理和土壤肥力提升提供理论依据。本研究以洪雅林场内幼龄林(7年生)、中龄林(13年生)、近熟林(24年生)、成熟林(33年生)和过熟林(53年生)5个关键生长阶段的柳杉人工林为对象,运用干筛法对0～15和15～30 cm两个土层不同粒径土壤团聚体C、N、P含量及生态化学计量特征(C/N、N/P、C/P)进行分析。结果表明: 柳杉人工林土壤团聚体粒径分布随林龄变化存在差异,近熟林和成熟林阶段柳杉人工林具有更高比例的大团聚体(0.5～1和1～2 mm粒径),且近熟林具有更低比例的微团聚体(0.053～0.25 mm)和粉黏粒(<0.053 mm)。土壤团聚体C、N、P含量及其比值均随林龄增加呈先上升后下降的单峰形式,在接近成熟和成熟林分的柳杉人工林中达到最高值。此外,在同一林龄的人工林中,0～15 cm土层团聚体C和N含量高于15～30 cm土层,且在表层土中粒径为0.5～1和0.25～0.5 mm的团聚体C和N含量均最高。综上,近熟林和成熟林阶段柳杉人工林具有更高的团聚体养分含量,是柳杉人工林土壤地力维持和可持续经营管理的关键林龄阶段。.
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