Temporal And Spatial Variations Of Soil Enzyme Activity In Reed Community In Chongming Dongtan Wetland And The Influencing Factors

Soil enzyme catalyzes reaction of decomposition of organic matter,and has positive effects on soil biochemical reaction,and is closely related to energy flow and material cycling of carbon,nitrogen and phosphorous.To study temporal and spatial variations of soil enzyme activity in reed community in Chongming Dongtan wetland ecosystem,we collected soil samples from six sites(reed distribution area,bare flat without reed distribution × low,middle,high flat position)and of three depths(0-10 cm,10-20 cm,20-30cm)in Chongming Dongtan Nature Reserve.We measured four types of soil enzyme activity(acid phosphatase,alkaline phosphatase,?-glucosidase,Nacetyl-?-glucosidase activity)and four soil physical-chemical characteristics(pH,salinity,organic carbon content,total nitrogen,phosphate content),and used structural equation modeling to analyze the mechanism of temporal and spatial variations of soil enzyme activity.The main results were as follow:(1)Acid phosphatase activity and alkaline phosphatase activity showed significant temporal variation.For acid phosphatase,most of enzyme activity of soils decreased from September to December,while a small number of enzyme activity of soils remained unchanged,and all of the enzyme activity of soils increased from December to March.For alkaline phosphatase,almost half of the enzyme activity of soils decreased from June to September,while nearly half of the enzyme activity of soils remained unchanged,and most of the enzyme activity of soils decreased from December to March,while a small number of enzyme activity of soils remained unchanged.(2)Local climate is one of the main factors mediating the activity of phosphatase.Different times may have some different environment factors(e.g.temperature)to influence the activity of enzyme.So acid phosphatase activity and alkaline phosphatase activity showed significant temporal variation.(3)Alkaline phosphatase activity showed significant spatial variation among different flat positions(low,middle,high).For alkaline phosphatase,most of enzyme activity of soils increased from low positon to middle and high position.(4)Soils from different flat positions(low,middle and high)have different soil salinity influencing the activity of soil enzyme(P<0.05).So alkaline phosphatase activity showed significant spatial variation among different flat positions.According to the results of analysis of structural equation model,the path coefficient of salinity influencing the soil enzyme activity was-0.33,and the salinity simply had low-level effect on the soil enzyme activity.(5)Alkaline phosphatase,?-glucosidase and N-acetyl-?-glucosidase activity showed significant spatial variation between different reed distribution conditions(reed distribution area,bare flat without reed distribution).For alkaline phosphatase and ?-glucosidase,most of enzyme activity of soils decreased from reed distribution area to bare flat without reed distribution.For N-acetyl-?-glucosidase,nearly half of enzyme activity of soils decreased from reed distribution area to bare flat without reed distribution.(6)Soils with different reed distribution conditions have different soil organic carbon content influencing the activity of enzyme(P<0.05).So Alkaline phosphatase,?-glucosidase and N-acetyl-?-glucosidase activity showed significant spatial variation between different reed distribution conditions.According to the results of analysis of structural equation model,the path coefficient of organic carbon influencing enzyme activity was 0.34,and organic carbon simply had low-level effect on soil enzyme activity.(7)Activity of acid phosphatase,alkaline phosphatase,?-glucosidase and N-acetyl-?-glucosidase of soil showed no significant variation among different soil depths.Our research indicated that four types of soil enzyme activity showed some significant temporal and spatial variations,and explained the temporal and spatial variations of the soil enzyme activities.Salinity and organic carbon content were main factors influencing the soil enzyme activity.In addition,factors of temperature and microbe may also affect the soil enzyme activity.Our research would contribute to the better understanding of biochemical reaction process of soil and the biological geochemistry cycling in the Yangtze River Estuary wetland ecosystem,and evaluating the soil fertility status in Chongming Dongtan wetland.