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Effects Of Simulated Nitrogen Deposition On The Chemical Properties Of Soil Solution In Moist Evergreen Broad-leaved Forest

Posted on:2020-02-21Degree:MasterType:Thesis
Country:ChinaCandidate:H Y MaFull Text:PDF
GTID:2370330590498024Subject:Forest cultivation
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Since human beings entered the industrialized society,there are more and more human activities such as the burning of fossil fuels,the massive use of agricultural fertilizers and the development of animal husbandry.They have caused more and more nitrogen?N?compounds to be discharged into the atmosphere,resulting in an increasing global atmospheric N deposition.Over the past half century,a large number of studies have been conducted worldwide to reveal the effects of N deposition on ecosystems.Soil solution is the medium for chemical reactions to the soil solid phase,and as the same time it is the carrier for the exchange of environmental substances such as soil,plants and aquatic ecosystems.Therefore,soil solution can quickly reflect the environmental changes.It provides a reference for further exploring the influence of N deposition on the forest ecosystem and the mechanism of action.There is a moist evergreen broad-leaved forest in Bifeng Gorge,Ya'an.Thus,in this study,we selected the forest as the research object.We set up three N treatments levels including the control?CK?,low nitrogen?LN?,high nitrogen?HN?,through applying N fertilizer artificially.We used negative pressure soil solution sampler to collect soil solution from different soil layers?layer A:37-45 cm,layer B:52-60 cm?once a month for a year.And we analyzed the chemical changes to reveal the response of soil solution in different forest layers of N deposition.The results showed that:?1?The DOC annual concentration in the soil solution of layer A and B were 12.68mgL1 and 10.94 mgL1 in the natural state.LN and HN treatments significantly reduced the annual concentration of DOC in soil solution of layer A by 20%.The simulated N deposition had no significant effect on the DOC concentration in soil solution of layer B.The aromatic index of two depths did not change significantly under simulated N deposition.?2?In the natural state,the annual concentration of NH4+in the soil solution were 0.10mgL1?layer A?and 0.05 mgL1?layer B?,and the annual concentration of NO3were3.94 mgL1?layer A?and 4.27 mgL1?layer B?.Simulated N deposition significantly increased the content of NO3in soil solution of each layer,with an increase of 250%?layer A?and 170%?layer B?under LN treatment and 690%?layer A?and 630%?layer B?under HN treatment.And the NH4+content increased significantly only under HN treatment,with an increase of 1050%?layer A?and 460%?layer B?.?3?The annual average pH of soil solution in the natural state were 6.39?layer A?and6.18?layer B?.The simulated N deposition reduced the pH significantly.The simulated N deposition had no significant influence on the concentration of Ca2+and Mg2+in soil solution.Under HN treatment,the concentration of Al3+increased significantly by 310%?layer A?and 230%?layer B?.?4?In the natural state,the annual concentration of Zn2+in the soil solution were 0.14mgL1?layer A?and 0.10 mgL1?layer B?,and the annual concentration of total iron ions were 0.60 mgL1?layer A?and 0.50 mgL1?layer B?.The influence mechanism of simulated N deposition on total iron ions and Zn2+was different.Addition of N significantly promoted the concentration of soil solution Zn2+and significantly reduced the concentration of total iron ions.?5?In the natural state,the annual concentration of SO42in the soil solution were164.97 mgL1?layer A?and 92.85 mgL1?layer B?,and the annual concentration of SiO42were 11.94 mgL1?layer A?and 11.450.86 mgL1?layer B?.The simulated N deposition significantly inhibited the SO42concentration of soil solution in layer A.The SO42concentration of soil solution layer B and the SiO42concentration of two layer depths did not change with the increase of N deposition.?6?In the natural state,the annual average conductivity of soil solution were 197.65?scm1?layer A?and 125.53?scm1?layer B?,and the annual average redox potential of soil solution were 249 mV?layer A?and 276 mV?layer B?.The conductivity and redox potential of the two soil layers showed obvious seasonal dynamics,which were higher from march to July.The simulated N deposition significantly increased the conductivity and redox potential of the soil solution.
Keywords/Search Tags:nitrogen deposition, evergreen broad-leaved forest, soil solution, chemical property
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