Temporal And Spatial Distribution Characteristics And Influencing Factors Of Inorganic Sulfur Forms In Spartina Alterniflora Tidal Flat Soil In Jiaozhou Bay

The temporal and spatial distribution characteristics of total sulfur（TS）and different inorganic sulfur forms in Spartina alterniflora tidal flat（Zone A）and bare flat（Zone B）in Jiaozhou Bay were studied.The physical and chemical properties of soil,such as organic matter,total iron,pH,EC,water content and bulk density were determined and the characteristics of sulfur accumulations and distribution in S.alterniflora were analyzed.The effects of plant factors and physical and chemical properties on sulfur content in soil were discussed.The main results showed that:（1）The spatial and temporal distribution characteristics of soil TS content in Spartina alterniflora tidal flat and bare flat were studied.The average content of TS in soils of Zone A（0-60 cm）were（1648.11±287.04）mg·kg^-1,which was much higher than this in Zone B with the content of（1273.77±114.85）mg·kg^-1（n=90,p<0.05）,with the increase of 29.38%.There was a significant increase on soil TS in Zone A compared with Zone B in autumn.In March,the content of soil TS in Zone A was slightly lower than that in Zone B.However,the soil TS content in Zone A was higher than that in Zone B in other months（May,July,September and November）,and the amplification of soil TS were 28.48%,17.72%,57.98%and 49.41%,respectively.The content of soil TS increased with the increase of depth in spring and autumn,and the vertical distribution was basically medium variability in both zones.（2）The sulfur accumulations and distribution characteristics of S.alterniflora in Zone A were studied.The average content of TS in invasive species of the whole plants was（2.89±0.62）g·kg^-1.The average content of TS in every organ of S.alterniflora was July>September>May>November>March.In other months,the content of TS in every organ was root>leaf>stem,except for March.During the growing period,the total biomass of S.alterniflora gradually increased with the season.At the same time,the stem was the highest biomass organ.The sulfur accumulation in S.alterniflora was July>November>September>May>March,and sulfur accumulation was different in different periods.As a whole,the highest value of accumulation factor of sulfur（AF_S）,appeared in July,followed by the lowest in March,September,November and May,respectively.With the exception of March,the root AF_S value was the highest in other months.（3）The physical and chemical properties of soil organic matter,total iron,EC,pH,water content,bulk density were determined.Soil organic matter,total iron and EC were larger in Zone A than in Zone B.The content of organic matter was the biggest difference in autumn.Soil pH in Zone A was smaller than that in Zone B.The water content in Zone A was slightly higher than that in Zone B,and the difference was not significant（n=90,p>0.05）.There was no significant difference in bulk density between the two samples（n=90,p>0.05）.（4）The relationship between soil TS content,physical and chemical properties and plant factors was analyzed.Stepwise regression equations showed that temperature was critical factors on content of soil TS in Zone A,and the key factors affecting the distribution of soil TS content in Zone B were soil EC and temperature.The results showed that the soil sulfur reserves increased due to the growth of S.alterniflora.However,it varied greatly in different seasons.（5）The temporal and spatial distribution characteristics of inorganic sulfur in different forms of soil in Zone A and Zone B were studied.The results showed that the contents of H₂O-S and Adsorbed-S in soil of Zone A were significantly higher than those in bare flat Zone B in different months.HCl-Soluble-S in Zone A was significantly higher than bare flat in March,and the other months were not significant.The content of HCl-Volatile-S in Zone A was significantly lower than that in Zone B only in November.The inorganic sulfur content of different forms in Zone A and Zone B was H₂O-S>HCl-Soluble-S>Adsorbed-S>HCl-Volatile-S,of which H₂O-S accounts for the highest proportion,accounting for 73.90%,74.30%of total inorganic sulfur,respectively,and HCl-Volatile-S accounted for the lowest proportion,about 0.78%and 1.05%.In the Zone A with vegetation coverage,H₂O-S and Adsorbed-S showed significant differences with seasonal changes.（6）The correlations among soil H₂O-S,Adsorbed-S,HCl-Soluble-S,HCl-Volatile-S,physicochemical properties and plant factors were analyzed.The results of stepwise regression analysis showed that the important factor of H₂O-S was EC.In Zone A,Adsorbed-S was greatly affected by total iron and pH,while HCl-Soluble-S was greatly affected by accumulation factor of sulfur and water content.In Zone B,Adsorbed-S was greatly affected by salinity and pH,and HCl-Soluble-S was greatly affected by salinity,pH and depth.The important influence factor affecting the distribution of HCl-Volatile-S content in two types of wetlands was depth.The results showed that the content of inorganic sulfur in Zone A with vegetation coverage was significantly higher than that in Zone B,especially the contents of H₂O-S and Adsorbed-S.The soil sulfur was more effective,but its spatial variability was higher,and the content varies greatly in different seasons in Zone A.