Analysis Of Dissolved Organic Matter Content And Spectral Characteristics Of Soil Leakage In Temperate Forests

Currently there are still a lot of disagreements in the research on the change of soil organic matter along with nitrogen deposition in the world.Some foreign scientists use three dimensional fluorescence technology to detect soil organic matter and make great progress.In this thesis,soil leachates samples were collected from a mature broadleaf and Korean pine mixed forest and an adjacent white birch forest at the foot of Changbai mountains,By using continuous flow analysis and three-dimensional fluorescence spectroscopy technology,Changes in the biodegradability of soil leachates dissolved organic matter?DOM?as well as the concentrations and relative contributions of DOM components were studied two forest by measuring the biodegradable soil leachates dissolved organic matter concentration and parallel factor analysis of DOM fluorescence excitation-emission matrices.We studied the changes in concentrations and spectral characteristics of DOM in two forest soil leachates during the most productive period of vegetation growth?July?and the end of spring thaw?May?.The soil leachate samples were collected from a long-term temperate forest experiment field which experienced nine-year anthropogenic treatments,including different forms[?NH₄?₂SO₄,NH₄Cl and KNO₃)]and doses(22.5and 45 kg N ha^-11 yr^-1)of simulated nitrogen?N?deposition,carbon?C?addition(glucose,64 kg C ha^-11 yr^-1),litter removal and root.By parallel factor analysis for the three-dimensional fluorescence spectroscopy of all the forest soil leachates,three fluorescence components of DOM were obtained,which included fulvic acid-like component,humic-like component and protein-like component.Without considering the influences of the experimental treatments,the concentrations of dissolved organic carbon?DOC?and biodegradable DOC?BDOC?,humification degree and terrestrial contribution of DOM were significantly higher,but the contribution of protein-like component and biological sources of DOM were significantly lower in forest soil leachates during the most productive period of vegetation growth compared with those during the end of spring thaw.The long-term C and N addition had no significant effect on the concentration and biodegradability of DOC in the soil leachates.The effects of long-term simulated N deposition on the concentrations and contribution of DOM components in forest soil leachates were related to the forms and doses of exogenous N.In this study,the DOM biodegradability in forest soil leachates was highly consistent with its activity under the two different periods upon long-term C and N addition,which was well reflected by the fluorescence components of DOM and the related spectral properties.The experimental results can provide a basis for in-depth studying the influencing factors of concentrations,compositions and stability of DOM in forest soil leachates.