Study On Soil Physical Characteristics And Active Organic Carbon Under Different Waterlogging In Gahai Marsh Wetland

Hydrological conditions are important ecological attributes of wetlands,changes in water conditions such as rainfall,freezing and thawing,wet and dry alternation will affect the direction and intensity of moisture cycling between atmosphere,vegetation and soil.With the change of global climate,the hydrological cycle changed obviously,which led to the shrinking wetland area,the sharp decrease of wetland water resources,the deterioration of water environment,and brought a lot of ecological and environmental problems.The "Pearl of the plateau," said the Gahai wetland is an important part of Tibetan plateau wetland,to maintain wetland biodiversity,plays an important role in regulating wetland climate and water conservation,but in recent years,because of the change of hydrological cycle,the carbon cycle of wetland has changed.Therefore,it is of great significance to study the changes of organic carbon pool in Gahai wetland under the condition of water change to understand the wetland carbon cycle under the background of wetland climate change.Marsh wetland is one of the important types of wetland,which is an important part of water-land natural landscape.The Gahai marsh wetland is 23600hm2,accounting for 54.66% of the wetland area,which is very important for regulating the ecological environment of Gahai wetland.In response to investigate Gahai wetland soil physical properties and active organic carbon fractions of water to,in Gahai wetland as the research object,set up a perennial water,seasonal water and no water three water conditions,study on the effect of water on soil physical properties of activated carbon and wetland components and,to clarify the changes of soil physical properties and active organic carbon fractions in different water conditions and excitation effect.The results was as follows:(1)Gahai marsh wetland changed from perennial flooding area in the process of no flooding area,,soil particle composition and bulk density were significantly different,the perennial water soil dominated by fine sand(<0.2mm).The other two types of coarse sand(2~0.2mm),soil bulk density increased significantly(P < 0.05),soil total porosity,capillary porosity,noncapillary porosity decreased significantly(P < 0.05).(2)swamp meadow soil waterlogged area of perennial average maximum water-holding capacity,capillary water-holding capacity,minimum water-holding capacity,maximum water-holding capacity,non-capillary water retentiony than seasonal flooding and no flooding area higher than 92.95% and 175.03 %,92.68% and 173.19%,145.97% and 328.12%,14.74% and 34.96%,36.15% and 95.95%,and the three water conditions the average soil maximum water-holding capacity,capillary water-holding capacity was significantly different(P<0.05).The soil maximum water-holding capacity,capillary water-holding capacity both have a highly significant negative correlation(P<0.01)with coarse grained soil(2~0.2mm),but a highly significant positive correlation(P<0.05)with fine sand(<0.2mm)and a highly significant positive correlation(P<0.01)with capillary porosity and total porosity.(3)different flooding changes significantly influence on wetland soil active organic carbon components,the maximum value of the whole(0-40cm)appeared in the perennial flooding area,followed by the seasonal flooding area;soil organic carbon (SOC)and microbial biomass carbon(MBC)content in the different soil profiles showed that the seasonal flooding area was the largest in the 20-40 cm area,and the lowest was no flooding area,other layers soil organic carbon,microbial biomass carbon,easily oxidated carbon(EOC)content showed the perennial flooding area was the largest and the lowest was the no flooding area,which indicated that perennial flooding active organic carbon content and component had obvious properties of surface-aggregation.(4)In different season,the SOC,MBC,microbial quotient and EOC under different flooding condition were all changed significantly(p<0.05),no flooding,perennial flooding area SOC and EOC showed a reduction in volatility,seasonal flooding area showed an increase in volatility;MBC and microbial entropy all showed an increase in volatility;active organic carbon ingredient were positively correlated with SOC content(p<0.01),active component increased with the increase of SOC,which showed that organic carbon is an important factor affect the soil MBC,and it is the carbon source of microorganisms.(5)Gahai marsh wetland changed from perennial flooding area in the process of no flooding area,with the decrease of surface water content,the soil quality decreased obviously,which indicated that the soil organic carbon loss was the largest under the condition of no flooding and the soil quality decreased the most.(6)There was a significant correlation between the soil physical properties and the active organic carbon components in the Gahai marsh wetland,and the soils were related to the maximum water-holding capacity,capillary water holding capacity and capillary porosity(P<0.05).soil microbial biomass carbon was significantly correlated with non capillary porosity(P<0.05).