中亚热带森林更新方式对土壤团聚体磷组分的影响

Effects of forest regeneration types on phosphorus fractions of soil aggregates in subtropical forest

土壤团聚体在土壤磷贮存和调节磷有效性中起重要作用,然而森林更新方式如何影响土壤团聚体磷组分仍不清楚。本研究选取米槠天然林经不同强度干扰形成的米槠次生林(轻度干扰)、米槠人促更新林(人促林,中度干扰)及杉木人工林(重度干扰)为对象,通过分析土壤团聚体粒径组成、全土和团聚体磷组分、磷吸附指数(P_(SOR))、磷遗留指数(P_(LGC))、磷饱和度(DPS_(M3))等指标,探究森林更新方式对全土及团聚体磷有效性及供磷潜力的影响。结果表明:森林更新方式显著影响土壤团聚体组成。米槠次生林和人促林土壤粗大团聚体(>2 mm)占比显著高于杉木人工林,而土壤粉黏粒团聚体(<0.053 mm)则表现为相反趋势。土壤团聚体组成显著影响土壤磷组分含量。土壤活性磷组分(可溶性磷P_(SOL)、速效磷P_(M3))含量随团聚体粒径减小而降低;总磷(TP)、有机磷(Po)、中等活性磷组分(无机磷Pi_(OH)、有机磷Po_(OH))、闭蓄态磷(P_(OCL))含量、PSOR、PLGC随团聚体粒径减小呈先降低后升高的趋势,具体表现为粗大团聚体和粉黏粒团聚体中的TP、Po和Pi_(OH)含量显著高于细大团聚体(0.25~2 mm)和微团聚体(0.053~0.25 mm)。森林更新方式显著影响全土和团聚体磷组分含量。米槠次生林全土TP、Po、PSOL和PM3含量显著高于米槠人促林和杉木人工林,米槠次生林不同粒径团聚体P_(SOL)和P_(M3)含量均显著高于杉木人工林。森林更新方式显著影响土壤团聚体磷组分组成及供磷潜力。米槠人促林土壤不同粒径团聚体P_(SOL)和P_(M3)占TP的比例显著低于米槠次生林,米槠次生林土壤不同粒径团聚体P_(SOR)和DPS_(M3)显著高于杉木人工林。综上,自然更新更有利于维持土壤磷有效性,森林更新会通过改变土壤团聚体组成进而影响土壤磷有效性及供磷潜力。

Soil aggregates are important for the storage and availability of phosphorus in the soil.However,how forest regeneration types affect phosphorus fractions of soil aggregates remains unclear.In this study,we examined the composition of aggregate particle size,phosphorus fractions,phosphorus sorption capacity index(P_(SOR)),legacy phosphorus index(P_(LGC))and degree of phosphorus saturation by Mehlich 3(DPS_(M3))in bulk soils and soil aggre⁃gates of Castanopsis carlesii secondary forest(slight disturbance),C.carlesii human⁃assisted regeneration forest(moderate disturbance),and Cunninghamia lanceolata plantation(severe disturbance),aiming to explore the impact of forest regeneration types on phosphorus availability and supply potential of bulk soils and soil aggregates.The results showed that forest regeneration types significantly influenced the composition of soil aggregates.The pro⁃portion of coarse macroaggregates(>2 mm)in the soil of C.carlesii secondary forest and human⁃assisted regenera⁃tion forest was significantly higher than that in the C.lanceolata plantation,while the proportion of silt and clay fraction(<0.053 mm)showed an opposite trend.The composition of soil aggregates significantly affected the con⁃tents of different phosphorus fractions.The contents of soil labile phosphorus fractions(P_(SOL) and P_(M3))decreased as aggregate particle size decreased.The contents of soil total phosphorus(TP),total organic phosphorus(Po),mode⁃rately labile phosphorus fractions(Pi_(OH) and Po_(OH)),and occluded phosphorus(POCL),as well as P_(SOR) and P_(LGC),exhibited a trend of decreasing at the beginning and then increasing as particle size decreased.The contents of TP,Po,and Pi_(OH) in coarse and silt macroaggregates was significantly higher than that in fine macroaggregates(0.25-2 mm)and microaggregates(0.053-0.25 mm).Forest regeneration types significantly influenced the contents of phosphorus fractions of bulk soils and soil aggregates.The contents of TP,Po,P_(SOL),and P_(M3) in the soil of C.car⁃lesii secondary forests was significantly higher than that in C.carlesii human⁃assisted regeneration forest and C.lan⁃ceolata plantation.The contents of P_(SOL) and P_(M3) in different⁃sized aggregates of C.carlesii secondary forests were sig⁃nificantly higher than that in the C.lanceolata plantation.Forest regeneration types significantly influenced the com⁃position and supply potential of phosphorus fractions in soil aggregates.The proportions of P_(SOL),and P_(M3) to TP in different⁃sized soil aggregates were significantly lower in C.carlesii human⁃assisted regeneration forest compared with C.carlesii secondary forest.P_(SOR) and DPS_(M3) in different⁃sized soil aggregates were significantly lower in C.lan⁃ceolata plantation than that in C.carlesii secondary forest.Overall,our results indicated that natural regeneration is more favorable for maintaining soil phosphorus availability,and that forest regeneration affects soil phosphorus availa⁃bility and its supply potential by altering the composition of soil aggregates.