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China Agricultural University (2018)

Effects of Enhanced Precipitation,Temperature and Nitrogen Addition on Nitrogen Fate and Plant Stoichiometry in Temperate Desert Ecosystem in Xinjiang

崔晓庆;

Titre : Effects of Enhanced Precipitation,Temperature and Nitrogen Addition on Nitrogen Fate and Plant Stoichiometry in Temperate Desert Ecosystem in Xinjiang

Auteur : 崔晓庆;

Grade : Doctoral Dissertation 2018

Université : China Agricultural University

Résumé
With global climate and environment change,temperate desert ecosystems,mainly located in Eurasian inland,could be more and more sensitive,with significant changes in rainfall,temperature,and nitrogen(N)deposition.Climate change(e.g.precipitation and temperature)and elevated N deposition are important driving factors for the change of productivity and biodiversity of desert ecosystems.In addition,climate change and N deposition are also related to the global carbon and N cycle and plants C:N:P stoichiometry.Some studies have been carried out to test the effects of precipitation and N deposition on the structure and function of temperate desert ecosystems in China.However,there were no systematic studies considering the effects of precipitation,temperature and N deposition on temperate desert ecosystems in China simultaneously.It’s important for accurately forecasting the structure and function response of temperate desert ecosystems under global climate change.Therefore,a multi-factorial experiment of water(W),nitrogen(N)and temperature(T)at the southern edge of the Gurbantunggut desert in the field observation station of the Fukang Desert Ecosystem of the Chinese Academy of Sciences was established during 2015 and 2017.The field experiment consisted of ten treatments of various W,N and T combinations(W0N0,W0N1,W0N2,W1N0,W1N1,W1N2,and W0N0T0,W0N0T1,W1N1T0,and W1N1T1).In addition,an investigation of desert sample zone and controlled laboratory experments were conducted to quantify how water and N and other environmental factors affect desert plants.During 2015-2017,desert ecosystem biomass,diversity,N fate in plant-soil system,and stoichiometry characteristics were evaluated systematically via field and laboratory experiments as well as investigation of desert belt zone.The main results were summarized as follows:1.Height of herbaceous layer,aboveground biomass,belowground biomass,species number,density,and coverage of herbaceous communities in temperate desert ecosystem were significantly varied among years.Extra water could significantly increase aboveground biomass,species number,density and coverage of herbaceous plant communities.However,exogenous N addition and warming did not significantly alter herb height,aboveground biomass,belowground productivity,species number,density and coverage of herbaceous community.2.With 15N(15NH415NO3)as a tracer,we quantified the two cumulative years of added 15N flux in a Haloxylon ammodendron dominated ecosystem in the Gurbantunggut Desert of Northwest China from 2015-2016 and its response to water and N addition.Herbaceous plants were a significantly larger sink for added 15N than the H.ammodendron trees,the fate of the applied 15N accumulated between 4.11 to 9.05 kg N ha-1 in the herbaceous species and from 2.6 to 6.13 kg N ha-1 in the H.ammodendron.The retention of added 15N varied within the components of H.ammodendron,with the stems retaining most,followed by the root and assimilating branches.Soil was the dominant sink for added 15N,in which the topsoil and subsoil respond differently to water and N addition over the two-year period.N relative recovery percentage in the whole ecosystem ranged from 43%to 61%,significantly increased with water addition but decreased with enhanced N deposition.3.Malcolmia Africana(ephemeral)and Salsola affinis(annual)were chosen to determine the effect of different 15N addition rates(double-labeled 15NH415NO3 added at 0,15,30,60 and 120 kg N ha-1 yr-1)on their growth and 15N retention in a pot experiment under sufficient water supply(soil moisture content to be controlled at 70%of water-filled pore space).Species-specific and rate-dependent effects of N deposition on plant growth and plant N retention were found.

Mots clés : Temperate desert; Simulated climate change; Nitrogen deposition; Nitrogen retention; C:N:P stoichiometry;

Présentation (CNKI)

Page publiée le 4 avril 2019, mise à jour le 5 avril 2019