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Effect Of Short-term Nitrogen Deposition On Soil Respiration And Its Compositions In Quercus Acutissa Forest In Wanfo Mountain

Posted on:2021-03-28Degree:MasterType:Thesis
Country:ChinaCandidate:J S YuFull Text:PDF
GTID:2370330602497567Subject:Forestry
Abstract/Summary:PDF Full Text Request
Nitrogen deposition changes the process of land-atmosphere carbon cycle and damages the functional structure of terrestrial forest ecosystem.To study the response of soil respiration and its components to nitrogen deposition in forest ecosystem under the background of atmospheric nitrogen deposition,and to explore the specific mechanism of its influence,is of guiding significance for the accurate understanding of forest ecological carbon cycle.In this study,typical forests in Anhui province were taken as the research object.From June 2018 to July 2019,simulated nitrogen deposition experiment was conducted in natural Quercus acutissa forest in Wanfo mountain,shucheng county,Anhui province.Three different treatment levels were set:control plots(N0,0 kg N hm-2a-1),low nitrogen(N1,50 kg N hm-2a-1),and high nitrogen(N2,100 kg N hm-2a-1).The effects of nitrogen addition on soil respiration,its compositions and soil physical and chemical properties of natural Quercus acutissa forest were studied.The results are as follows:(1)Soil respiration and its compositions of Quercus acutissa forest showed obvious dynamic changes in months.Nitrogen deposition did not change soil respiration and its compositions in the monthly dynamic changes,but it changed soil respiration.Under the three treatments,soil respiration and soil composition all showed unimodal changes.Treatment with N1 and N2 promoted soil respiration and respiration rates of each component in quercus acutissa forest,but the differences were not significant.Heterotrophic respiration contributed 59.61%and autotrophic respiration contributed 40.39%to the total annual respiration rate in the NO group.The contribution rate of heterotrophic respiration to soil total respiration in N1 group was 56.68%and that of autotrophic respiration was 43.32%.The contribution rate of heterotrophic respiration to soil total respiration in N2 group was 61.03%,and that of autotrophic respiration to soil total respiration was 39.97%.(2)Rs(Soil total respiration),Rh(Heterotrophic respiration)and Ra(Autotrophic respiration)had an extremely significant exponential relationship with soil temperature of 10 cm(p<0.01),and a significant negative correlation with soil moisture content of 10 cm(p<0.05).The two-factor model of soil temperature,soil moisture content and soil respiration explained 80.76%?83.39%of Rs for seasonal variation,82.56%?89.88%of Rh for seasonal variation,and 59.89%?70.96%of Ra for seasonal variation.N1 treatment reduced soil total respiration Q10(Temperature sensitivity)and heterotrophic respiration Q10,while N2 treatment improved soil total respiration Q10 and heterotrophic respiration Q10.Both N1 and N2 treatments improved autotrophic respiration Q10.(3)Nitrogen deposition has a significant effect on soil MBC(Microbial biomass carbon),MBN(Microbial biomass nitrogen),NH4+-N(Ammonium nitrogen),NO3--N(Nitrate nitrogen),C/N,but no significant effect on TN(Total nitrogen),SOC(Soil organic carbon)and pH.The contents of MBC,MBN,NH4+-N,NO3--N,TN and SOC were all increased.The correlation between Rs?Rh,Ra,MBN,TN and SOC was obviously improved by nitrogen treatment.In summary,the physical and chemical properties of the soil had been changed after nitrogen addition,which had corresponding changes on soil respiration and its components.In general,nitrogen deposition slightly increased soil respiration rate.This study explored the mechanism of nitrogen deposition on soil respiration and soil composition,which is of great significance for understanding the carbon cycle of forest ecosystem of deciduous broad-leaved forest in subtropical zone.
Keywords/Search Tags:Nitrogen deposition, Quercus acutissa forest, Soil respiration, Soil temperature, Soil moisture content, Physicochemical properties of soil
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