Study Distribution Characteristics Of Soil Nitrogen Of Seriously Burned Area Under Different Restorations In Greater Xing'an Mountains

In order to reveal the distribution characteristics of soil nitrogen under different restoration methods in the seriously burned areas of the Greater Xing'an Mountains,three different restorations were chosen,including artificial restoration,artificially promoted natural restoration and natural restoration.The characteristics of soil organic nitrogen fractions in three different restorations were analyzed by using the Bremner's method.The soil inorganic nitrogen and microbial biomass were measured and calculated under three restoration methods.The results showed that:(1)The main component of soil organic nitrogen was acidified nitrogen under different restorations in severly seriously burned area of Great Xing' an Mountains,acidified nitrogen accounted for 61.5%?76.3%of total nitrogen,non-acidified nitrogen accounted for 23.7%-38.5%of total nitrogen.The soil acid hydrolysable nitrogen and non-hydrolysable nitrogen decreased with the increase of soil depth.The contents of acid hydrolyzed were higher than non acid hydrolyzed in the same soil layer.The contents of hydrolysable ammino acid nitrogen,amino acid nitrogen and amino sugar nitrogen decreased with the increase of soil depth.Ammonia nitrogen,amino acid nitrogen,amino sugar nitrogen,non-acid hydrolysis nitrogen and acid hydrolysis nitrogen in soil organic nitrogen components under the three restoration methods had significant correlations with soil organic carbon and total nitrogen(P<0.05).Different restorations had significant effects on the characteristics of soil ammonia nitrogen,basic acid nitrogen and acid hydrolysis of unknown nitrogen in severely burned soil of Greater Xing'an Mountains.(2)Under the three different recovery methods,the soil total nitrogen reserves were highest in the natural restoration.The contents of 14-day soil mineralizable nitrogen and ammonium nitrogen were the higest in natural restoration,the lowest in artificial restoration.The contents of nitrate nitrogen was the higest in natural restoration,then artificial restoration and artificially promoted natural restoration.The descend order of ANR was artificially promoted natural recovery,natural recovery and artificial recovery.It showed that the supply of soil nitrogen was better in artificially promote natural restoration.Plants mainly absorbed inorganic nitrogen from soil.The structure of ammonium,nitrate nitrogen and 14-day mineralizable nitrogen indicate that the soil was more conducive to the growth and utilization of vegetation under natural recovery.(3)During the conversion of soil organic nitrogen to inorganic nitrogen,the fixation of microorganisms played a crucial role.Under three different recovery methods,the soil microbial biomass carbon and nitrogen were significantly different.The contents of soil Microbial biomoss carbon and nitrogen were the higest in natural restoration,the lowest in artificial restoration.Under natural recovery method,the soil microbial biomass carbon and nitrogen were higher than other two recovery methods.The microbial biomass content in the upper soil was greater than that in the lower soil.The results of microbial entropy showed that the proportion of soil in naturally restored forests was the highest.In summary,the distribution characteristics of soil nitrogen under three different restoration methods in seriously burned areas of Greater Xing'an Mountains showed that the soil fertility of the surface soil was better than deeper soil.The nitrogen storage of forest soil under natural restoration was the highest.The ability of soil nitrogen cycling in natural restoration was better than other two recovery methods after 30 years.