Study on Soil Gross Nitrification and Soil Respiration of Perennial Sowed Grassland in Arid Area of Northwest China
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【Author in Chinese】 陈璐；
【Author's Information】 甘肃农业大学， 草地生物多样性， 2017， 硕士
【Abstract in Chinese】 土壤总硝化过程和土壤呼吸作用与温室气体的排放与消耗密切相关,具有十分重要的意义。目前对于土壤碳氮过程的研究多集中于农田生态系统,对于人工栽培草地的土壤总硝化速率与土壤呼吸的协同研究内容较少。本研究的目的和意义在于通过对人工栽培草地碳氮过程及组分的相关研究,探索和发现土壤温室气体排放及碳氮循环的机制。本研究采用Ba PS(气压过程分离系统),是较新型的研究碳氮转化规律的方法,在一个处于温度恒定且与外界有较低温度交换的密封闭合空间内,通过对压力和气体浓度变化的测定,求得土壤的总硝化过程以及土壤呼速率各项数量值。通过试验西北干旱区种植不同多年生人工牧草(冷地早熟禾、垂穗披碱草、红豆草、紫花苜蓿及无作物种植为对照)的土壤在生长季总硝化速率空间垂直变化的动态,即对不同深度土层的土壤的总硝化作用、土壤呼吸速率的测定,以及不同深度土层的含水量进行测定,研究了土壤季节性变化、土壤含水量与土壤总硝化作用以及土壤呼吸速率的相互关系。并测定了不同深度土壤全氮和土壤有机碳的含量的分布,通过研究不同深度土壤全氮和土壤有机碳分布规律,说明碳氮含量与硝化-反硝化作用与土壤呼吸之间的相关性,并分析土壤总硝化作用与土壤呼吸之间的相关性。本试验取得以下主要研究结果:1不同种人工栽培牧草的土壤总硝化速率随季节的变化,受土壤季节性变化以及土壤含水量的影响较大。生长季的中后期土壤的总硝化速率有明显降低,随着土层深度的逐渐增加,土壤的总硝化速率也随之减弱。土壤呼吸作用也和总硝化速率的变化呈现一直的趋势,随着生长季的来临呈先增加,9月时土壤总硝化速率以及土壤呼吸的速率都达到最大值,并且在11月时二者都逐渐降低。2土壤全氮和土壤有机碳的分布规律也呈现随着土壤深度的变化逐层递减的趋势。土壤全氮含量与土壤总硝化速率呈显著正相关,土壤呼吸作用与土壤有机碳含量呈的正相关性。土壤总硝化速率和土壤呼吸呈显著正相关。不同种人工栽培牧草地的土壤总硝化速率与土壤呼吸随着土壤深度的增加逐渐降低。此外,不同种人工栽培牧草的全氮含量以及土壤有机碳的含量不同时期的分布及变化趋势也一致。3豆科牧草的土壤呼吸速率作用普遍高于禾本科牧草,且均在7月出现最大值,之后随着季节的变化逐渐递减。随着季节的变化,不同土层的土壤有机碳的含量逐渐增加,其中垂穗披碱草土壤有机碳含量最高,红豆草草地土壤有机碳含量高于紫花苜蓿。种植多年生牧草的土壤具有较高的土壤有机碳含量且与土壤呼吸作用具有较显著相关。4土壤总硝化作用和土壤呼吸是土壤碳氮循环及土壤温室气体排放的重要影响因素,与土壤呼吸作用的值密切相关。对不同种供试材料在不同时期的土壤总硝化作用和土壤呼吸速率的比较发现,种植不同种牧草的土壤总硝化作用和土壤呼吸作用均呈现线型相关趋势。
【Abstract】 Soil nitrification denitrification process and soil respiration are of great significance in greenhouse gas emissions and consumption,which is of great significance.At present,the studies of soil carbon and nitrogen is mainly concentrated in the farmland ecosystem,there is less research on the nitrification denitrification rate and soil respiration in the cultivated grassland.The purpose and significance of this study is to study the process and components of carbon and nitrogen in cultivated grassland,to research the mechanism of greenhouse gas emission and carbon and nitrogen cycling in soil.In this study,used Ba PS(Barometric process separation system)method,which is a new way to research carbon and nitrogen transformation.In a closed space in which the temperature is constant and the temperature is lower than that of the outside by measuring the change of pressure and gas concentration to obtain nitrification denitrification process and the number of soil respiration rate.Through the experiment of planting perennial sowed pasture in Northwest Arid Area(Poa crymophila Keng;Elymus nutans Griseb;Onobrychis viciaefolia Scop and Medicago sativa L.)to research dynamic changes of soil nitrification denitrification rate in the growing season,determination of nitrification denitrification and soil respiration rate and soil moisture content,soil temperature,humidity and bulk density in different depths,to study the relationship between seasonal variation of soil,soil water content and nitrification denitrification and soil respiration rate.The contents of total nitrogen and soil organic carbon in different depths were measured,study on the distribution of soil total nitrogen and soil organic carbon in different depths,illustrate the correlation between SOC and nitrogen content of nitrification denitrification and soil respiration.The results showed that:The seasonal variation of nitrification denitrification rate of different kinds of cultivated herbage was affected by the seasonal variation of soil and soil water content.In the middle and late growth season,the nitrification and denitrification rate of the soil decreased significantly,and with the increase of soil depth,the soil nitrificationdenitrification rate also decreased.Soil respiration and change of nitrification denitrification rate has been the trend with the growth season increased in September,when the nitrification rate and soil respiration rate reached the maximum,and in November two have gradually reduced.The distribution of soil total nitrogen and soil organic carbon also showed a decreasing trend with the change of soil depth.There was a significant positive correlation between total nitrogen content and nitrification denitrification rate,and soil respiration was positively correlated with soil organic carbon content.There was a significant positive correlation between soil nitrification denitrification rate and soil respiration.The changes of soil nitrification denitrification rate and soil respiration in different cultivated grassland were the same.In addition,the distribution and change trend of total nitrogen content and soil organic carbon content of different kinds of cultivated forage in different periods.Soil respiration rate of legume forage was higher than that of leguminous forage grass,and the maximum value appeared in July.With the change of seasons,different soil organic carbon content increased gradually,the spike with soil organic carbon content of Elymus nutans grassland highest,sainfoin grassland soil organic carbon content is higher than that of alfalfa.There was a significant correlation between soil organic carbon content and soil respiration.Soil nitrification denitrification and soil respiration are important factors affecting soil carbon and nitrogen cycling and soil greenhouse gas emissions,which are closely related to soil respiration.Different kinds of test materials in soil nitrification and soil respiration in different periods of the different kinds of grass planting,soil nitrification and soil respiration showed a certain trend.With changing seasons,there was a certain correlation between soil nitrification rate and soil respiration rate.