干湿交替下土壤C、N养分流失机理研究

发布时间：2018-04-18 10:31

本文选题：干湿交替 + 土壤微生物　；参考：《东华大学》2015年硕士论文

【摘要】：全球气候变化背景下，局部地区可能经历频繁剧烈的干湿过程或者是长期干旱后灌溉引起剧烈的干湿交替现象。干湿交替对土壤C、N迁移转化有着重要的影响。因此本实验旨在研究在干湿条件下对土壤C、N养分流失机理。实验通过采集农田土壤在室内进行培育实验，，设置四种不同的水分条件（干湿组、恒湿组、干旱组、淹水组），在人工气候箱中模拟田间气候进行实验，主要进行以下三个方面的研究：多重干湿交替下土壤退水规律及土壤微生物量变化研究；干湿交替下土壤碳素流失机理研究；干湿交替下土壤氮素流失机理研究。通过实验得出了以下一些结论：（1）实验研究过程中，土壤经历的干湿周期越多，土壤的落干期越短，土壤的持水能力也逐渐减弱。多次干湿交替使得土壤水分消退指数变化的规律性增强，通过拟合土壤水分消退指数曲线，能够可靠的预测下个周期水分变化。干旱使得土壤细菌数量剧烈减少，灌水能迅速刺激土壤中细菌的恢复性生长。真菌总数没有出现剧烈的波动，真菌对于干旱的耐受能力比细菌高。土壤MBC含量在灌水后一段时间内能够迅速增加。（2）土壤有机碳的矿化损失是在干旱期减弱，复水后激增。多重干湿交替会破坏土壤的团聚体结构，使原本惰性的有机质暴露出来，被暴露的有机质进一步被微生物分解和矿化，从而有助于灌水后土壤呼吸作用的爆发。干湿交替下在干旱后期土壤DOC呈现了缓慢增加的趋势。干湿交替明显刺激了土壤微生物相关酶的酶活，使得土壤碳素的矿化过程随着土壤相关酶活性的增加而加快。（3）在干湿交替下土壤氮素的矿化-硝化-反硝化作用等一系列过程发生改变。干湿交替能够增强土壤氮素的矿化作用，增加了土壤中可溶性的氮素含量，增加了氮素的淋溶损失。在灌水初期，土壤水分大大超过了土壤的饱和含水量，使得土壤的通气性变差，土壤的反硝化过程加快，能加快土壤氮素流失。土壤的干湿交替处理使得与脲酶与亚硝酸还原酶酶活发生较为剧烈变化。总之，土壤氮素在相关酶活的相互变化、相互影响、相互作用下，流失速度较其他平行组有所加快，但并不显著。（4）干湿交替下土壤团粒结构对C、N的保护减弱。干湿交替下土壤土壤团聚体经历剧烈的缩涨，使得土壤团聚体结构被破坏，这种破坏作用能够随着干湿周期次数的增加逐渐累积，使得土壤越来越多的C、N素从土壤团聚体当中暴露出来，导致其流失加快。
[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.
【学位授予单位】：东华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S158

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