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Seasonal Response Mechanism Of Soil Carbon Pool Of Robinia Pseudoacacia Forest To Nitrogen Addition In Loess Hilly Region

Posted on:2021-05-26Degree:MasterType:Thesis
Country:ChinaCandidate:W C LiuFull Text:PDF
GTID:2370330620472865Subject:Crop Science
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Soil organic carbon pool of plantation is considered as carbon sink which have a huge potential capacity and reducing global atmospheric CO2 greenhouse effect.Thus,the artificial vegetation restoration soil carbon effect and mechanism have become the focus of soil and global change research.As a coupling factor affecting the decomposition and accumulation of soil carbon pool,nitrogen has become an important mechanism to recognize the response of soil carbon pool to the change of ecological measures.In particular,the unprecedented level of nitrogen deposition may have a profound impact on the soil carbon cycle by affecting the process of carbon input into soil,microbial activities and etc.Therefore,this study selected a typical artificial Robinia Pseudoacacia forest ecosystem in Loess Hilly Area to explore the change characteristics of the soil organic carbon component under different nitrogen?N?addition levels(0,1.5,3,6 and 12g N m-2 yr-1).The relationship was analyzed between soil carbon and other factors,which included soil environmental factors,nutrient content and ratio of nitrogen and phosphorus,and soil microbial biomass and enzyme activity.The aim of the study is to provide scientific basis for understanding and predicting the process and mechanism of nitrogen deposition affecting soil carbon pool in plantations.The main results as follow:?1?The effect of seasonal nitrogen deposition on soil organic carbon pool is differentIn all treatments,SOC,LOC and ROC ranged from 4.20 g/kg-8.59 g/kg,0.48 g/kg-2.90g/kg,and 1.94 g/kg-6.77 g/kg,respectively.Under different seasons,N addition significantly changed the content of soil carbon component,but the direction of action was different.In spring and summer,N addition reduced SOC,ranging from 19.86%to 34.10%.In autumn and winter,N addition promoted the SOC,increase the range of 28.06%to 74.16%.But in a whole years,SOC increased significantly in all treatments,and showed a trend of increasing first and then decreasing with the increase of N addition rate.For the soil carbon component,nitrogen application significantly reduced LOC and ROC in summer and significantly increased LOC and ROC in autumn.But overall,LOC consumption and ROC increased significantly over the course of the year.?2?Seasonal N deposition promoted the increase of available N and P content and stimulated the growth of microbial biomass carbonIn all seasons,nitrogen application significantly increased MBC,with an increase range of 20.84%-227.39%.However,the effect on MBN and MBP was inconsistent.MBN decreased significantly in spring?54.98%-52.20%?and increased significantly in summer?62.93%-116.37%?.After N addition,BG,ln?BG?:ln?NAG+LAP?and HY:MBC increased significantly in spring and winter,but decreased significantly in summer and autumn;CAT increased significantly in spring and autumn,but had no significant effect in summer and winter.?3?The interaction between soil microorganisms and environmental nutrients is the dominant factor in the change of soil carbon compositionN addition had no significant effect on soil environmental factors?T and SMC?.DON increased significantly in spring,summer and autumn?18.01%-266.77%?,but did not change significantly in winter after N addition.In all seasons,N addition significantly increased nitrate-N content?44.28%-322.25%?and DON:AP?38.15%-176.42%?.For of soil carbon variance variation,Variance Partitioning showed that the explanation rate of soil environmental factors,soil nutrient content and stoichiometric ratio was less than 1%.And there was no significant interaction between them.However,there was significant interaction between soil nutrient content and stoichiometric ratio and microorganism,which explanation rate of variance variation of carbon components is more than 35%.The above results indicated that the increase of soil available nitrogen content after N addition promoted the growth and reproduction of microorganisms.But the different carbon demand and acquisition methods of soil microorganisms in different seasons resulted in different responses of soil carbon components to N addition.
Keywords/Search Tags:Nitrogen addition, Soil carbon pool, Ecological stoichiometric ratio, Soil extracellular enzyme, Season change
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