Effects Of Surface Fire On Water-soluble Components And Characteristics Of Ash Of Pinus Koraiensis Litter

Ash is the inevitable residues on the soil surface in burned area.Mineral and organic matter of ash can be released into the soil ecosystem through precipitation and surface runoff,it is an important way for fire to indirectly affect the restoration process of the post-fire ecosystem during a certain period of time.However,the ash from the same fuels but produced by different fire behaviors may have different ecological functions.In order to understand the potential effects of fire behavior and ash on nutrient cycling and energy flow in the process of ecological restoration of burned areas,the influence of fire behavior on the ash water-soluble components,the UV-visible spectra and fluorescence spectra of dissolved organic matter and dissolved organic matter was explored in this research.In this study,the surface fuel of plantation was used as experimental materials,different slopes and water content are set as the driving factors of fire behavior,the indoor simulation combustion experiments of the upslope and downslope forest surface fire were performed on the combustion bed.Characteristics of ash,water soluble components of ash,soluble organic matter of ash and its UV-visible and fluorescence spectra were measured in the laboratory.The variance inflation factor(VIF)analysis was used to screen out the non-collinear fire behavior variables from several fire behavior variables:combustion duration,flame height,flame length,flame width,fire intensity,flame height intensity and combustion efficiency,then the independent-samples t-test was used to compare the differences of combustion experiments between different surface fires spreading directions.One-way ANOVA was carried out to test whether the fire behavior,ash characteristics,stoichiometric characteristics of ash water-soluble carbon and nitrogen,dissolved organic carbon,dissolved inorganic carbon varied significantly between different moisture content and different slopes.The influence of fire environment on ash characteristics,the stoichiometric characteristics of ash water-soluble carbon and nitrogen,dissolved organic carbon,dissolved inorganic carbon and non-collinear fire behavior indicators was explored by Multivariate ANOVA.Spearman correlation coefficient was used to evaluate the correlation between fire behavior and the ash characteristics,the stoichiometric characteristics of ash water-soluble carbon and nitrogen,dissolved organic carbon,dissolved inorganic carbon and the UV-visible and fluorescence spectra of dissolved organic matter in ash,the distance-based Redundancy analysis was used to explore the relationship of fire behavior and the ash characteristics,the stoichiometric characteristics of ash water-soluble carbon and nitrogen,dissolved organic carbon,dissolved inorganic carbon and the UV-visible and fluorescence spectra of dissolved organic matter in ash.The stoichiometric characteristics of ash water-soluble carbon and nitrogen and dissolved organic matter and its spectral characteristics from the Pinus koraiensis plantation are directly affected by fire behavior and indirectly affected by fire environment.Fire disturbance can have a continuous potential impact on the ecological restoration process of burned areas by affecting the characteristics of ash.The water-soluble carbon and nitrogen content of ash in the upslope fire experiment group was significantly higher than that in the downslope fire experiment group(p<0.01);In the 5° experiment group,the water-soluble carbon and nitrogen content of the ash is as follows:fuel moisture 25%experimental group>fuel moisture 15%experimental group>fuel moisture 5%experimental group(p<0.05).Further data analysis found that the fire behavior is closely related to the stoichiometric characteristics of the ash water-soluble carbon and nitrogen.The flame width,flame height,combustion efficiency and the water-soluble carbon and nitrogen content of the ash are negatively correlated(p<0.05),and the fire intensity is negatively correlated with the water-soluble carbon-nitrogen ratio of the ash(p<0.05),and the duration is positively correlated with the ash water-soluble carbon and nitrogen content,the correlation coefficient with the water-soluble carbon content of the ash is 0.321(p<0.01).Fuel combustion efficiency and flame width are the most significant fire behavior factors that affect the dissolved organic matter in ash,the concentration of colored dissolved organic matter,and the concentration of fluorescent dissolved organic matter.The flame width and fuel combustion efficiency are negatively correlated with the DOC content and the concentration of CDOM and FDOM of ash.The flame width and fuel combustion efficiency are the most significant fire behavior factors that affect the UV-visible and fluorescence spectra of dissolved organic matter in ash.The flame width,fuel combustion efficiency and ash FI are positively correlated,and are negative related to ash HIX.The analysis of DOM UV-visible and fluorescence spectra of dissolved organic matter in ash shows that the higher the fire intensity and fire severity are,the more aromatic compounds are generated in the combustion process of fuels,and the aromaticity and hydrophobicity of dissolved organic matter of ash are stronger,the ash DOM is mainly terrestrial input,with low degree of humification and self-source.