Zhang Zhe, Huang Yong-Zhen, Zhang Chao, Ye Shao-Ming, Wang Sheng-Qiang
Forestry College of Guangxi University, Nanning 530004, China.
Ying Yong Sheng Tai Xue Bao. 2022 Apr;33(4):939-948. doi: 10.13287/j.1001-9332.202204.001.
Exploring the distribution of phosphorus (P) fractionsin soil aggregates is helpful to improve soil P availa-bility during Chinese fir planting. In this study, soil samples were collected in the 0-20 cm soil layer from Chinese fir plantations with different stand ages (9 a, 17 a, and 26 a) and one nearby abandoned land (CK) in Rongshui County, Guangxi, China. Soil aggregates were classified into >2 mm, 1-2 mm, 0.25-1 mm, and <0.25 mm size classes through dry-sieving process, and then soil P fractions in different sized aggregates were measured. These results showed that: 1) The composition of soil aggregates showed significant difference among different stand ages. As the major aggregate fractions in soil, the contents of >2 mm aggregates increased firstly and then decreased over time, and peaked in the 17 a Chinese fir plantation. The changes of soil mean weight diameter (MWD) and geometric mean diameter (GMD) during Chinese fir planting were the same as the content of >2 mm aggregates. 2) Soil total P, inorganic P, and organic P contents did not differ among different sized aggregates. However, soil available P content was mainly distributed in >2 mm aggregates with a range of 1.23-7.33 mg·kg. Compared with CK, soil total P, available P, and inorganic P contents were significantly higher in Chinese fir plantations, and their contents increased firstly and then decreased over time. Soil total P (322.40 mg·kg) and available P (7.33 mg·kg) contents were the highest in the 9 a plantations, and soil inorganic P content (114.05 mg·kg) was the highest in the 17 a plantation. Moreover, soil organic P content showed an order of 9 a > 26 a >17 a > CK, with the highest content (210.00 mg·kg) in the 9 a plantation. 3) The distribution of P stock in soil aggregates was related to the contents of different sized aggregates, with >2 mm aggregates having the highest P stock. Except for organic P, soil P stock increased firstly and then decreased with the increases of stand age. In conclusion, Chinese fir planting was helpful to improve soil aggregate stability and to promote the increase of soil P level before the stand age of 17 a. However, Chinese fir planting could result in the degradation of soil aggregates and in the decrease of soil P level after 17 a. The formation and stabilization of >2 mm aggregates played an important role in the maintenance of soil quality and soil P supply level after 17 a Chinese fir planting.
探究土壤团聚体中磷（P）组分的分布有助于提高杉木种植期间的土壤磷有效性。本研究在中国广西融水县不同林龄（9年、17年和26年）的杉木人工林以及附近一块撂荒地（CK）的0-20厘米土层采集土壤样本。通过干筛法将土壤团聚体分为>2毫米、1-2毫米、0.25-1毫米和<0.25毫米粒径等级，然后测定不同粒径团聚体中的土壤磷组分。结果表明：1）不同林龄间土壤团聚体组成存在显著差异。作为土壤中的主要团聚体组分，>2毫米团聚体的含量随时间先增加后减少，在17年生杉木人工林中达到峰值。杉木种植期间土壤平均重量直径（MWD）和几何平均直径（GMD）的变化与>2毫米团聚体的含量变化一致。2）不同粒径团聚体中的土壤总磷、无机磷和有机磷含量无差异。然而，土壤有效磷含量主要分布在>2毫米的团聚体中，范围为1.23-7.33毫克·千克。与CK相比，杉木人工林中土壤总磷、有效磷和无机磷含量显著更高，且其含量随时间先增加后减少。9年生人工林中土壤总磷（322.40毫克·千克）和有效磷（7.33毫克·千克）含量最高，17年生人工林中土壤无机磷含量（114.05毫克·千克）最高。此外，土壤有机磷含量顺序为9年>26年>17年>CK，9年生人工林中含量最高（210.00毫克·千克）。3）土壤团聚体中磷储量的分布与不同粒径团聚体的含量有关，>2毫米团聚体的磷储量最高。除有机磷外，土壤磷储量随林龄增加先增加后减少。总之，杉木种植有助于在17年生之前提高土壤团聚体稳定性并促进土壤磷水平增加。然而，杉木种植在17年生之后可能导致土壤团聚体退化和土壤磷水平降低。>2毫米团聚体的形成和稳定在17年生杉木种植后土壤质量和土壤磷供应水平的维持中起重要作用。
