Pcharacteristic Research Of Soil Organic Carbon Composition And Microbial Activity On Forest Swamp Wetland Under The Freeze-Thaw Action

Freeze-thaw cycle was the freezing and thawing process that soil temperature fluctuated up and down at 0? repeatedly in the day and night,due to the season or temperature changed.This phenomenon was one of the important factors that affect the regional soil ecological environment,and appeared generally in high latitudes and high altitude regions.It was the abiotic stress in soil that affect physicochemical and biological properties directly or indirectly,and was a crucial factor that impact carbon and nitrogen biogeochemical process in soil.Xiaoxing' an Mountains region was the main distribution area of permafrost and seasonal frozen soil in China,which happened many times of freezing and thawing process at the beginning of spring and ending of autumn every year.At the same time,part of the wetland was also interfered the different years of drainage afforestation.Soil temperature,hydrological condition and oxidation reduction characteristics changed significantly after drainage afforestation,therefore there were some difference between drainage wetlands and natural wetlands in the freeze-thaw action.Taking the soil in Xiaoxing' an Mountains wetland as the test object,influence and changed trend of soil organic carbon and active carbon component in forest swamp wetland under different freezing and thawing time and temperature was analyzed,and the response of soil microbial biomass and enzyme activity to the freeze-thaw cycle was discussed.It was testified the fact whether the freeze-thaw cycle affect Xiaoxing' an Mountains region of soil nitrogen mineralization,and trended to probe stack effects that dual factors of the freeze-thaw action and drainage afforestation on wetland soil index.In order to predict soil carbon library,microbial activity and human activities in high latitudes and cold regions under the background of global warming,it could provide certain theoretical basis and reference significance.The main conclusions were as follows:(1)With the increase of number of freezing and thawing,four kinds of wetland SOC content in soil remain unchanged basically.On the whole,the content was lower slightly than the contrast of freezing and thawing,but compared to-25 to 5 ?(2.65%~4.72%),there was larger change range in-5 to 5 ?(7.44%~13.24%)freeze-thaw treatment.And the SOC drop rate of drainage wetland after freeze-thaw treatment was also larger than before the contrast of freezing and thawing.(2)With the increase of number of freezing and thawing,DOC content rose up at first and then declined,and peaked after one freeze-thaw cycle.But after freeze-thaw treatment,the growth range of wetland drainage(24.61%~34.94%)lower than natural wetlands(33.49%~51.17%).LFOC declined at first and then rose,reached the minimum after one or two freeze-thaw cycle,but the drop rate of LFOC in drainage wetlands was bigger slightly,PS85 wetland declining range was larger significantly.(3)After freezing and thawing process,MBC and MBN content are lower than before the freezing and thawing,and with the increase of number of freezing and thawing,MBC rose up at first and then declined,and MBN declined at first and then stabilized.There was a larger MBC descend range during shorter drainage time,and the MBN drop rate of drainage wetland in-5 to 5 ? freeze-thaw treatment was also larger than before-25 to 5 ? treatment.(4)The order relationship of invertase and amylase activity in four kinds wetland soil was XATC > PS03 > PS92 > PS85,and with the increase of number of freezing and thawing,soil invertase and amylase activity was gradually reduced.Before and after freezing and thawing,it was a positive correlation during SOC and MBC,invertase,amylase activity that show freezing and thawing alternation is not obvious influence on the change of the correlation.(5)After freezing and thawing process,mineralization nitrogen content rose in generally,which showed freezing and thawing effect could promote mineralization of nitrogen.The growth range of ammonium nitrogen of drainage wetlands lower than natural wetlands,but declining range of the nitrate nitrogen of drainage wetlands was greater than the natural wetland,so increased measure of mineralization nitrogen of drainage wetland was lower than natural wetlands after freezing and thawing cycle.