论文总字数：17313字

摘 要

土壤水分是控制微生物的生存和活动的主要因素，为了解土壤水分对亚热带湿润地区森林土壤氮循环过程的影响，本课题采集江西鹰潭双圳林场花岗岩母质针叶林土壤，设置三个水分含量:（1）30%WHC（2）60%WHC（3）100%WHC。20（低氮）和50mg N kg^-1(NH₄ 或NO₃^－)（高氮）施肥水平下，25ºC培养28天，分别测定培养前后无机态氮、N₂O、CO₂的变化。

实验结果显示，低氮水平下，培养末期NH₄ 含量增加，但不同水分含量处理间无明显差异，60%WHC条件下NO₃^-含量增加，但30%和100%WHC条件下减少；高氮水平下，培养末期NH₄ 含量增加且高于低氮水平，但各水分处理NO₃^-含量无明显增加，100%WHC条件下减少。无论是高氮还是低氮水平，土样N₂O最大排放速率和累积排放量随水分升高而增加，60%WHC含水量时，高氮处理土样N₂O最大排放速率高于低氮处理，但100%WHC含水量时高低氮水平无明显差异。培养期间，CO₂排放速率逐渐减小，30%WHC处理土样的最大排放速率低于60%和100%WHC；水分含量高的土样CO₂累积排放量高，30%和60%WHC水分条件下，低氮处理土样CO₂累积排放量高于高氮，但100% WHC水分条件下氮肥水平对CO₂累积排放量无影响。

上述结果显示，调节水分立即施肥培养，同一施氮水平下NO₃^-含量受水分变化的影响明显，但不同水分处理间NH₄ 含量差异不明显，高氮促进矿化。水分含量增加促进N₂O和CO₂的排放，最大持水量条件下，氮肥使用水平对N₂O和CO₂的排放无明显影响。

关键词：土壤水分 氮改良 硝化作用 NH₄ -N NO₃^－-N N₂O CO₂

ABSTRACT

Soil moisture availability is a major factor controlling the survival and activity of microorganisms.This topic collected the soil of linchang,shuangzhen,yingtan,JiangXi and set three moisture content:(1)30% WHC (2) 60% WHC (3) 100% WHC.20 and 50 mg N kg^-1(NH₄ 或NO₃^－) fertilizer levels to understand the influence of soil moisture on the soil nitrogen cycling process in forests in subtropical humid areas.It was cultured for 28 days in 25ºC and was respectively measured before and after the inorganic nitrogen and N₂O and CO₂ changes.

The experimental results showed that under low nitrogen level,NH₄ content increased at the end of culture.But it had no significant differences between different moisture content treatment.It showed that under low nitrogen level, NO₃^－content increased under the condition of 60% WHC,but under the condition of 30% and 100% WHC NO₃^－ content reduced.Under the high nitrogen level,NH₄ content increased and was higher than the low nitrogen levels at the end of culture,but NO₃^－content was no obvious increase between different moisture content treatment.Under the condition of 100% WHC NO₃^－ content reduced.N₂O maximum emission rate and the cumulative emissions of the soil samples increased with the increase of the moisture content, regardless of high nitrogen or low nitrogen levels.When 60% WHC moisture content, high nitrogen processing soil sample biggest N₂O emission rate was higher than that of low nitrogen treatment, but when 100% WHC water content there was no obvious difference between the high and low nitrogen levels.During cultivation CO₂ emission rate decreased gradually, 30% WHC processing soil samples maximum emission rate was less than 60% and 100% WHC.High moisture content of the soil sample led to high cumulative CO₂ emission.When 30% and 60% WHC moisture content,low nitrogen processing soil sample cumulative CO₂ emissions was higher than that of high nitrogen treatment,level of nitrogen fertilizer had no effect on the cumulative CO₂ emissions under 100% WHC moisture conditions.

The above results show that regulating water immediately fertilization culture,NO₃^－ content significantly affected by moisture change under the same nitrogen level.But NH₄ content had no obvious differences between different moisture content treatment.High nitrogen

promoted mineralization.Moisture content increase promoted N₂O and CO₂ emissions.Under conditions of maximum water holding capacity, fertilizer use levels had no significant effect on N₂O and CO₂ emissions.

Key Words: soil moisture;N amendment;soil nitrification;NH₄ -N;NO₃^－-N;N₂O;CO₂

目 录

摘 要 5

ABSTRACT 3

第一章 前言 1

1.1 土壤氮循环过程 1

1.1.1 生物固氮 1

1.1.2 土壤氮素矿化 1

1.1.3 土壤硝化作用 1

1.1.4 土壤反硝化作用 2

1.2 土壤硝化作用与N₂O排放 2

1.3 土壤硝化作用的影响因素 3

1.3.1 pH 3

1.3.2 温度 4

1.3.3 水分 4

1.4 本实验的研究目的与主要内容 5

1.5 研究展望 5

第二章 材料与方法 6

2.1 土样采集及制备 6

2.2 实验试剂 6

2.3 实验仪器 6

2.3.1 气相色谱法测定氧化亚氮 6

2.3.2 半自动定氮仪 7

2.4 实验方法 7

2.4.1 土壤理化性质的测定 7

2.4.2 不同水分条件下土壤硝化活性测定方法 9

2.4.3 不同水分土壤N₂O与CO₂排放速率及通量测定 10

2.5 数据处理 10

2.5.1 净硝化速率 10

2.5.2 净矿化速率 10

2.5.3 N₂O、CO₂排放速率及通量 10

第三章 结果与讨论 11

3.1 土壤理化性质 11

3.2 铵态氮与硝态氮含量及其变化 11

3.2 N₂O排放速率 14

3.3 N₂O累积排放通量 16

3.4 CO₂排放速率 17

3.5 CO₂累积排放通量 19

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