In forestry, stand conversion influences soil physicochemical and biological properties, yet the effects of conversion of pure plantation to uneven-aged mixed plantation on soil aggregate distribution and stability, C/N/P stoichiometry and enzyme activity remain unclear. We studied the distribution of water-stable aggregate fractions, mean weight diameter (MWD), stoichiometric ratios (C/N, C/P, and N/P), and urease, invertase, and acid phosphatase activity in the soils of pure and uneven-aged mixed plantations (including artificially and naturally established mixed plantations). The mixed plantations showed improved bulk soil and aggregate physiochemical and biological properties, including higher soil organic C (OC), total N (TN), total P (TP), and enzyme activity in the artificially mixed plantations than in the naturally established mixed plantation. Additionally, in contrast to pure plantation soil, mixed plantation soil showed a significant decrease in the microaggregate (MA) (<0.25 mm) mass fractions, and a marked increase in the proportion of large macroaggregate (LMA) (>2 mm), MWD, and other soil properties (especially OC and TN content, stoichiometric ratios, and enzyme activity in LMA). Principal component analysis indicated that compared to other aggregate sizes, LMA had a significant effect on soil properties, and LMA mass fractions were strongly positively correlated with OC, TN, C/N, and MWD in the bulk soils. Moreover, OC and nutrient content, stoichiometric ratios, and enzyme activity in LMA were significantly positively correlated with the corresponding variables in the bulk soils. These findings indicate that LMA properties can be used as sensitive indicators to changes in soil properties after stand conversion from pure to uneven-aged mixed plantation.

在林业中，林分转化影响土壤的理化和生物学特性，但是，纯人工林向不均匀年龄的混交林的转化对土壤团聚体分布和稳定性，C / N / P化学计量和酶活性的影响尚不清楚。我们研究了纯净和纯净土壤中水稳性聚集物组分，平均重量直径（MWD），化学计量比（C / N，C / P和N / P）以及脲酶，转化酶和酸性磷酸酶活性的分布。年龄不均的人工林（包括人工和自然建立的人工林）。混合人工林表现出改善的散装土壤和骨料的理化和生物学特性，包括较高的土壤有机碳（OC），总氮（TN），总磷（TP），人工混合人工林中的酶和酶活性要比天然混合人工林中的酶活性高。此外，与纯人工林相比，混合人工林的微骨料（MA）（<0.25 mm）质量分数显着降低，大型巨骨料（LMA）（> 2 mm）MWD的比例显着增加，以及其他土壤特性（尤其是LMA中的OC和TN含量，化学计量比和酶活性）。主成分分析表明，与其他集料尺寸相比，LMA对土壤特性具有显着影响，并且LMA质量分数与散装土壤中的OC，TN，C / N和MWD呈极显着正相关。此外，OC和养分含量，化学计量比，LMA中的酶活性与土壤中相应变量呈显着正相关。这些发现表明，LMA的性质可以用作从纯林转变为不平均年龄的人工林后土壤性质变化的敏感指标。