互花米草入侵对胶州湾湿地土壤磷赋存形态的影响

为探讨互花米草入侵对滨海湿地土壤磷循环的影响，基于时空互易原则，选择胶州湾湿地互花米草区（SA区）和光滩区（MF区）为研究靶区，分析了互花米草入侵后湿地土壤中总磷（TP）、无机磷（IP）及其组分含量的差异性以及影响因素.结果表明，互花米草入侵后湿地土壤中TP （472.70 mg ·kg^-1）和IP （239.00 mg ·kg^-1）平均含量明显高于入侵前光滩区TP （386.19 mg ·kg^-1）和IP （212.68 mg ·kg^-1）含量，增幅分别为22.40%和12.38%.研究区无机磷组分以钙磷（Ca-P）和铁磷（Fe-P）为主，分别占IP的45%~61%和31%~49%.互花米草入侵后，10~30 cm层土壤Ca-P含量显著降低（P<0.05），7月尤为明显；Fe-P含量显著增加（P<0.05），0~40 cm土壤层含量高于40~60 cm层（P<0.05），并且7月在10~40 cm土壤表现出明显富集现象.通过结构方程模型发现互花米草入侵后有机质（OM）对TP和Fe-P有显著正向影响（P<0.01），标准化路径系数分别为0.775和0.724.入侵后Fe-P对Ca-P有显著负效应（P<0.01），标准化路径系数为-0.435.结果发现互花米草入侵总体增加了湿地土壤磷含量，同时促进了Ca-P向Fe-P转化，提高了湿地磷的生物利用性.

Effects of Spartina alterniflora Invasion on Soil Phosphorus Forms in the Jiaozhou Bay Wetland

To investigate the effects of Spartina alterniflora invasion on soil phosphorus(P) cycling in coastal wetlands, we selected a S. alterniflora zone(SA zone) and mudflat zone(MF zone) in the Jiaozhou Bay as the target areas for the study. The variability of total phosphorus(TP), inorganic phosphorus(IP), and their component contents in wetland soils after S. alterniflora invasion and their influencing factors was evaluated. The results showed that the average contents of TP(472.70 mg·kg^-1) and IP(239.00 mg·kg^-1) in the soils were significantly higher than those of TP(386.19 mg·kg^-1) and IP(212.68 mg·kg^-1) in the pre-invasion area, with an increase of 22.40% and 12.38%, respectively. The IP fractions in the study area were dominated by calcium-phosphorus(Ca-P) and iron-phosphorus(Fe-P), accounting for 45%-61% and 31%-49% of IP, respectively. The Ca-P content of the soil in the 10-30 cm layer decreased significantly(P<0.05) after S. alterniflora invasion, which was especially significant in July. The Fe-P content increased significantly(P<0.05); in the 0-40 cm soil layer, Fe-P was higher than that in the 40-60 cm layer(P<0.05), and showed significant enrichment in the 10-40 cm soil in July. The structural equation model showed that organic matter(OM) had a significant positive effect on TP and Fe-P after S. alterniflora invasion(P<0.01), and the normalized path coefficients were 0.775 and 0.724, respectively. Fe-P had a significant negative effect on Ca-P after invasion(P<0.01) with a normalised throughput coefficient of -0.435. The study found that S. alterniflora invasion generally increased wetland soil P content, while promoting the conversion of Ca-P to Fe-P, improving wetland P bioavailability.