本文選題：干濕交替 + 土壤微生物　； 參考：《東華大學(xué)》2015年碩士論文

【摘要】：全球氣候變化背景下，局部地區(qū)可能經(jīng)歷頻繁劇烈的干濕過程或者是長期干旱后灌溉引起劇烈的干濕交替現(xiàn)象。干濕交替對土壤C、N遷移轉(zhuǎn)化有著重要的影響。因此本實驗旨在研究在干濕條件下對土壤C、N養(yǎng)分流失機理。實驗通過采集農(nóng)田土壤在室內(nèi)進行培育實驗，，設(shè)置四種不同的水分條件（干濕組、恒濕組、干旱組、淹水組），在人工氣候箱中模擬田間氣候進行實驗，主要進行以下三個方面的研究：多重干濕交替下土壤退水規(guī)律及土壤微生物量變化研究；干濕交替下土壤碳素流失機理研究；干濕交替下土壤氮素流失機理研究。通過實驗得出了以下一些結(jié)論： （1）實驗研究過程中，土壤經(jīng)歷的干濕周期越多，土壤的落干期越短，土壤的持水能力也逐漸減弱。多次干濕交替使得土壤水分消退指數(shù)變化的規(guī)律性增強，通過擬合土壤水分消退指數(shù)曲線，能夠可靠的預(yù)測下個周期水分變化。干旱使得土壤細菌數(shù)量劇烈減少，灌水能迅速刺激土壤中細菌的恢復(fù)性生長。真菌總數(shù)沒有出現(xiàn)劇烈的波動，真菌對于干旱的耐受能力比細菌高。土壤MBC含量在灌水后一段時間內(nèi)能夠迅速增加。 （2）土壤有機碳的礦化損失是在干旱期減弱，復(fù)水后激增。多重干濕交替會破壞土壤的團聚體結(jié)構(gòu)，使原本惰性的有機質(zhì)暴露出來，被暴露的有機質(zhì)進一步被微生物分解和礦化，從而有助于灌水后土壤呼吸作用的爆發(fā)。干濕交替下在干旱后期土壤DOC呈現(xiàn)了緩慢增加的趨勢。干濕交替明顯刺激了土壤微生物相關(guān)酶的酶活，使得土壤碳素的礦化過程隨著土壤相關(guān)酶活性的增加而加快。 （3）在干濕交替下土壤氮素的礦化-硝化-反硝化作用等一系列過程發(fā)生改變。干濕交替能夠增強土壤氮素的礦化作用，增加了土壤中可溶性的氮素含量，增加了氮素的淋溶損失。在灌水初期，土壤水分大大超過了土壤的飽和含水量，使得土壤的通氣性變差，土壤的反硝化過程加快，能加快土壤氮素流失。土壤的干濕交替處理使得與脲酶與亞硝酸還原酶酶活發(fā)生較為劇烈變化�？傊�，土壤氮素在相關(guān)酶活的相互變化、相互影響、相互作用下，流失速度較其他平行組有所加快，但并不顯著。 （4）干濕交替下土壤團粒結(jié)構(gòu)對C、N的保護減弱。干濕交替下土壤土壤團聚體經(jīng)歷劇烈的縮漲，使得土壤團聚體結(jié)構(gòu)被破壞，這種破壞作用能夠隨著干濕周期次數(shù)的增加逐漸累積，使得土壤越來越多的C、N素從土壤團聚體當(dāng)中暴露出來，導(dǎo)致其流失加快。
[Abstract]:Under the background of global climate change, local areas may experience frequent and intense dry and wet processes or severe dry and wet alternation caused by irrigation after a long period of drought.The alternation of dry and wet has an important effect on soil C ~ (2 +) N migration and transformation.The purpose of this study was to study the mechanism of nutrient loss of Con N in soil under dry and wet conditions.Four different water conditions (dry and wet group, constant humidity group, drought group, flooding group) were set up to simulate the field climate in the artificial climate box.The following three aspects were mainly studied: soil water degradation and soil microbial biomass change under multiple dry-wet alternation; soil carbon loss mechanism under dry-wet alternation; soil nitrogen loss mechanism under dry-wet alternation.The following conclusions are obtained through experiments:1) in the course of experimental study, the more dry and wet cycles the soil experienced, the shorter the dry period of soil was, and the water holding capacity of soil gradually weakened.The regularity of soil moisture regression index change was enhanced by repeated dry-wet alternation. By fitting the soil moisture regression index curve, the water change of the next cycle could be predicted reliably.Drought reduces the number of bacteria in soil, and irrigation can quickly stimulate the recovery of bacteria in soil.The total number of fungi did not fluctuate sharply, and the resistance of fungi to drought was higher than that of bacteria.The content of MBC in soil increased rapidly after irrigation.(2) the mineralization loss of soil organic carbon decreased during drought and increased rapidly after rehydration.The structure of soil aggregates will be destroyed by multiple dry-wet alternations, and the original inert organic matter will be exposed, and the exposed organic matter will be further decomposed and mineralized by microorganisms, thus contributing to the outbreak of soil respiration after irrigation.The soil DOC increased slowly in the late drought period under the alternating dry and wet conditions.The soil microbial related enzyme activity was obviously stimulated by dry-wet alternation, and the mineralization process of soil carbon was accelerated with the increase of soil related enzyme activity.(3) A series of processes such as mineralization, nitrification and denitrification of soil nitrogen were changed under the alternating dry and wet conditions.The alternation of dry and wet can enhance the mineralization of soil nitrogen, increase the content of soluble nitrogen in soil and increase the leaching loss of nitrogen.At the early stage of irrigation, soil moisture greatly exceeded the saturated water content of soil, which made soil aeration worse, soil denitrification process accelerated, and soil nitrogen loss accelerated.The soil activities of urease and nitrite reductase changed dramatically after soil dry-wet alternate treatment.In a word, the soil nitrogen loss rate was faster than that of other parallel groups, but it was not significant.(4) the soil aggregate structure weakened the protection of Con N under the alternating dry and wet conditions.The soil aggregate structure was destroyed by the soil aggregate structure was destroyed under the condition of dry and wet alternating, which could accumulate gradually with the increase of dry-wet cycle times.More and more soil Con N is exposed from soil aggregates, resulting in accelerated loss.
【學(xué)位授予單位】：東華大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：S158

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