| Taking Spartina alterniflora area（S area）and Beach area（M area）in Jiaozhou Bay wetland as the research objects,the soil P forms and P in vegetation organs in the study area were studied in May,July,September and November 2017.The temporal and spatial characteristics of total phosphorus（TP）,inorganic phosphorus（IP）and IP(Ca2-P,Ca8-P,Ca10-P,Al-P,Fe-P and O-P)contents in soils of S and M regions and their correlations with soil physical and chemical properties were compared and analyzed.At the same time,the proportion of IP to TP was dynamically analyzed,and the correlations among various IP forms were obtained.This study can provide data for further understanding the nutrient cycling mechanism of P in Spartina alterniflora wetland ecosystem in Jiaozhou Bay,and make up for the lack of soil IP classification in this area.The main results are as follows:（1）The soil TP content ranged from 335.36 mg/kg to 549.96 mg/kg,with an average of 429.45 mg/kg.The content of TP in S area is much higher than that in M area.The distribution of TP content in soil in S area and M area decreases with the deepening of soil layer.The change of soil TP content in the two regions with the month showed a"Z"type.Among them,the highest value of TP content in all soil layers in S region appeared in July,and the lowest value appeared in May.The change trend of TP content in different soil layers in M region is more consistent.The highest value of TP content in each soil layer appears in July,and the lowest value appears in September.（2）Total TP of Spartina alterniflora showed a trend of increasing,decreasing and slightly increasing with the passage of months,with the highest value in July and the lowest value in September.The content of TP in different organs was the highest in leaves.The TP content in roots peaked in November and the minimum appeared in May;the maximum of TP content in stems appeared in July and the minimum appeared in September;and the maximum of TP content in leaves appeared in July and the minimum appeared in September.（3）The average soil IP content in S and M regions was 227.8 mg/kg,accounting for53.11%of TP content,and the overall change was relatively stable.The average IP content of soil in S and M regions were 249.74 mg/kg and 205.86 mg/kg,respectively.The IP content in S region was significantly higher than that in M region.The highest annual average IP content of soils in S and M regions appeared in the surface layer of0-10 cm,and the lowest IP content appeared in the soil layer of 50-60 cm.In terms of time distribution,the change trend of soil IP content in S region was opposite to that in M region.In S region,soil IP content decreased first and then increased,while in M region,soil IP content increased first and then decreased.（4）The average soil Ca-P content of Spartina alterniflora wetland in Jiaozhou Bay is120.15 mg/kg,mainly Ca10-P.The average contents of Ca2-P,Ca8-P and Ca10-P were 19.2mg/kg,11.51 mg/kg and 89.44 mg/kg,respectively.（5）The soil Al-P content of Spartina alterniflora wetland in Jiaozhou Bay ranged from 7.70 mg/kg to 20.48 mg/kg,with an average content of 11.91 mg/kg.The average Al-P content of S and M soils was 12.25 mg/kg and 11.58 mg/kg,respectively.The content of Fe-P ranged from 59.80 mg/kg to 150.71 mg/kg,and the average content was88.65 mg/kg.The average content of Fe-P in S region and M soil was 106.95 mg/kg and70.36 mg/kg,respectively.The content of O-P ranged from 1.87 mg/kg to 9.4 mg/kg,with an average of 5.25 mg/kg,accounting for the smallest proportion of IP.（6）Soil organic matter,pH and soluble salt are the main factors affecting the changes of phosphorus content in S region of Spartina alterniflora wetland in Jiaozhou Bay.In addition to the three factors mentioned above,the factors affecting the change of phosphorus content in various forms of soil in M region also include water content.In addition,there is a certain coupling relationship between various forms of phosphorus content.（7）After IP classification,the content of Ca10-P>Fe-P>Ca2-P>Al-P>Ca8-P>O-P were ranked as follows:Ca10-P>Fe-P>Ca2-P>Al-P>Ca8-P>O-P,of which Ca-P content accounted for 52.74%of IP content.Because of the growth of invasive species Spartina alterniflora,except Ca10-P,the above contents were in S zone>M zone,and all forms of IP increased in varying degrees.TP,IP,Al-P,Fe-P and O-P increased by 22.4%,21.3%,5.8%,52%and 10%,respectively. |
