川西亚高山三种森林恢复途径对土壤生物有效磷的影响

土壤生物有效磷在提高森林生产力和生物地球化学循环中起着至关重要的作用，研究不同森林恢复途径对土壤生物有效磷的影响对于退化森林的适应性恢复和可持续经营具有重要意义。选取川西亚高山不同恢复途径下形成的3种森林类型，即粗枝云杉人工林（人工种植，PF）、岷江冷杉-红桦天然次生林（自然更新，NF）和粗枝云杉阔叶混交林（人工种植后自然更新，MF），采用基于生物有效性的土壤磷分级方法测定土壤生物有效磷（CaCl₂-P、Citrate-P、Enzyme-P和HCl-P），探究不同森林恢复途径对土壤生物有效磷的影响。结果表明：不同森林恢复途径对土壤生物有效磷影响显著（P<0.05），NF和MF的土壤Citrate-P和Enzyme-P显著高于PF（P<0.05），而PF的土壤HCl-P显著高于NF（P<0.05）。自然更新是3种森林恢复途径中最能提高土壤生物有效磷的方式。3种森林恢复途径下的土壤生物有效磷组分与速效磷均呈现显著的正相关关系，且NF的土壤速效磷与生物有效磷的相关性更强（CaCl₂-P除外）。显著影响NF土壤生物有效磷的土壤理化性质有全钾、铵态氮含量和pH值，且全钾对NF的土壤生物有效磷变异的解释程度最高（r²=0.63，P=0.001）。土壤pH值、钙和可溶性有机碳含量是显著影响MF土壤生物有效磷的主要土壤理化性质（P<0.05）。对PF的土壤生物有效磷具有显著影响的土壤理化性质是土壤有机碳、铁和可溶性有机碳含量。土壤理化性质对3种恢复途径下森林土壤生物有效磷的解释率均超过了80%，森林恢复途径对土壤生物有效磷的影响与土壤理化性质有关。

Effects of three forest restoration pathways on soil biologically based phosphorus in the subalpine of western Sichuan

Soil biologically based phosphorus plays a vital role in improving forest productivity and in biogeochemical cycles. It is very important to study the effects of different forest restoration pathways on soil biologically based phosphorus for the adaptive restoration and sustainable management of the degraded forests. In this study, we determined the soil biologically based phosphorus (CaCl₂-P, Citrate-P, Enzyme-P, and HCl-P) under three restoration pathways of subalpine forests, i.e., Picea asperata plantation forest (artificial planting, PF), Abies faxoniana-Betula albosinensis natural secondary forest (natural without assisted regeneration, NF), and P. asperata/mixed broadleaf forest (natural regeneration after artificial planting, MF), in western Sichuan by using biologically based phosphorus (BBP) method. The results showed that different forest restoration pathways had significant effects on soil biologically based phosphorus (P<0.05). Soil Citrate-P and Enzyme-P of NF and MF were significantly higher than those of PF (P<0.05), while soil HCl-P of PF was significantly higher than that of NF (P<0.05). The natural regeneration is the best way for improving soil biologically based phosphorus among the three forest restoration pathways in subalpine of western Sichuan. The four soil biologically based phosphorus fractions under the three forest restoration pathways showed significantly positive correlation with soil available phosphorus, and the correlations between soil available phosphorus and biologically based phosphorus (except CaCl₂-P) in NF were stronger. The soil physicochemical properties, including total potassium content, ammonium nitrogen, and pH value, significantly affected soil biologically based phosphorus in NF with the highest degree of interpretation by total potassium content (r²=0.63, P=0.001). Soil pH value, calcium content and soluble organic carbon content were the main soil physicochemical properties that significantly affected soil biologically based phosphorus in MF (P<0.05). Soil physicochemical properties that had significant impacts on soil biologically based phosphorus in PF were the content of soil organic carbon, iron, and soluble organic carbon. The interpretation rate of soil physicochemical properties to forest soil biologically based phosphorus under the three restoration pathways exceeded 80%. The effect of forest restoration pathways on soil biologically based phosphorus is related to soil physicochemical properties.