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Effect Of Nitrogen Deposition And Freeze-thaw Cycles On Soil Net Nitrogen Mineralization Under Biological Soil Crust

Posted on:2019-09-23Degree:MasterType:Thesis
Country:ChinaCandidate:J S HuoFull Text:PDF
GTID:2370330566466893Subject:Science
Abstract/Summary:PDF Full Text Request
The ecological environment and human had been affected by global change.Among that the nitrogen deposition had impact on the environmental complex,which composed by soil,plant and microorganism,is one of the focuses for ecologists.Organic nitrogen was converted to inorganic nitrogen in nitrogen mineralization process,which was considered one of the key processes in soil nitrogen cycle.So,the relationship between nitrogen deposition and mineralization rates became one of the important breakthroughs in cross-researching fields.In this paper,variance analysis and linear regression analysis were analyzed to reveal the effects of nitrogen deposition,freeze-thaw cycles and interactions on soil nitrogen mineralization rates under soil biological crusts.The path analysis,multiple regression analysis and redundancy analysis were analyzed to explore the main driving factors and influencing mechanisms of soil nitrogen mineralization.The main conclusions are as follows:?1?The soil contents of total N,nitrate nitrogen and ammonium nitrogen were 40-110mg/kg,0.2-6.5 mg/kg and 1.8-10 mg/kg respectively,and the proportion of soil inorganic nitrogen was 6-20%.The soil nitrification rate,ammoniation rate and net mineralization rate were-1.6-2.6 mg/kg,-2.2-1.8 mg/kg and-3.2-3.3mg/kg respectively.Ranking of soil nitrogen mineralization rates was that:ammoniation>net mineralization>nitrification.?2?At the concentration of addition nitrogen,the soil total N showed a unimodal curve,nitrate nitrogen and ammonium nitrogen content were in a bimodal curve,while the proportion of inorganic nitrogen increased,indicating that soil nitrogen contents and availability increased with exogenous nitrogen addition.The soil mineralization rates were positively correlated with nitrogen addition,and similar to the change trend of soil nitrogen contents.The ammoniation rate were positive value,indicating that exogenous nitrogen increased soil nitrogen content.However,the effects on nitrogen contents were different.?3?At the freeze-thaw times,the total N content in soil was a bimodal curve,nitrate nitrogen and ammonium nitrogen showed a unimodal curve,contrary to the proportion of inorganic nitrogen.The freeze-thaw cycle had negative correlation with nitrification rate,and are positively correlated with ammonification and net mineralization rate,and nitrification rate was mainly negative.This indicated that the meltwater played a limiting role in nitrification rate,but could promote ammonification and net mineralization.?4?The nitrogen addition and freeze-thaw cycle were significantly related to the content of soil total N and NO3-,respectively.But the interaction was significantly correlated with nitrogen contents and inorganic nitrogen proportion,indicating the differences in nitrogen addition and freeze-thaw cycle effecting on soil nitrogen contents.In addition to no significant correlation between nitrogen addition and net mineralization rate,and different factors and soil mineralization rates reach extremely significant level,indicating that nitrogen addition and soil mineralization rate had positive effects,and the freeze-thaw cycle played a promoting role,and the interaction on the soil mineralization rates was more significant.?5?The soil physicochemical properties had direct and indirect effects on mineralization rates.The regression analysis and path analysis were used to establish the standard multivariate regression equation of soil physicochemical properties and nitrogen mineralization rates under nitrogen addition or freeze-thaw cycles.In addition,the standard multiple regression equation under nitrogen addition was that:y1=21.146-2.020x1-0.068x2+0.001x3+0.003x4-0.004x5+0.001x6-0.079x7-4.216x8-0.385x9y2=-42.693+6.092x1-0.062x2+0.0001x3+0.001x4-0.003x5+11.49x6-0.399x7-9.635x8+0.499x9y3=-21.547+4.073x1-0.130x2+0.001x3+0.004x4-0.007x5-9.52x6-0.478x7-13.850x8+0.114x9The standard multiple regression equation under freeze-thaw cycles was that:y1=58.242-6.329x1-3.009x2+0.013x3+0.0001x4+0.008x5-0.001x6+0.001x7-0.139x8-9.119x9y2=7.898+0.23x1-3.224x2+.072x3+0.001x4-0.004x5-0.003x6+12.22x7-0.461x8-7.047x9y3=66.14-6.099x1-6.233x2+0.085x3+0.001x4+0.004x5-0.005x6+0.0001x7-0.6x8-16.166x9Combined the influence of nitrogen addition and snowmelt in spring to soil in desert biological crusts system,to enrich biological crust research theory and methods,and provide reference for the growth of biological soil crust and desert stability.
Keywords/Search Tags:Biological soil crust, Nitrogen mineralization, Physicochemical properties, Microorganism
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