This study investigated the influence of stand type on soil phosphorus(P)fractions and content with the aim of establishing a scientific basis for enhancing soil P availability and sustaining fertility in forest ecosystems.We examined the P fractions,microbial biomass P,litter and fine root chemical properties,and phosphatase activity in the 0-20 cm and 20-40 cm soil layers of a 77-year-old deciduous broad-leaved mixed forest and a 77-year-old coniferous and broad-leaf mixed forest in Zijinshan Mountain.Redundancy analysis of soil P fractions and environmental factors was conducted.The results indicated that the mixed deciduous broad-leaved forest had higher levels of active and stable P than the mixed coniferous and broad-leaved forest,suggesting greater availability and supply capacity in the former.In both forests,the proportions of soil P fractions to total P(TP)were consistently stable P>medium active P>active P.Significant differences were observed in NaHCO3-Po,NaOH-Pi,NaOH-Po,HCl-Pi,and Residual-P between stand types and soil layers(P<0.05),and NaHCO3-Pi differed significantly between soil layers(P<0.05).Redundancy analysis revealed that the soil P fractions in the deciduous forest was influenced by the litter C/P ratio(C/PL),fine root C/N ratio(C/NF),except for NaHCO3-Po,NaOH-Po,and HCl-Pi,the other P fractions were significantly(P<0.05)or highly significantly positively correlated(P<0.01)with DOC.The seven P fractions were positively correlated with C/PL and negatively correlated with C/NF,but not significantly.In contrast,soil P fractions in the coniferous and broadleaf mixed forest was affected by soil ammonium nitrogen(NH+4-N),litter N/P ratio(N/PL),and fine root P content(PF),with the exception of NaHCO3-Pi,the remaining P fractions showed significant(P<0.05)or highly significant positive correlations(P<0.01)with NH+4-N,were positively associated with PF,and had negative correlations with N/PL,although these were not significant.In conclusion,the deciduous broad-leaved mixed forest significantly enhanced soil available P.Variations in soil P fractions under different stand types were influenced by multiple factors,with changes in soil nitrogen content and microbial biomass P content being common regulatory elements across different stand types.
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