论文总字数：18654字

摘 要

土壤pH是影响土壤微生物群落结构和营养物质循环的重要因素之一。为了解土壤pH对亚热带湿润地区森林土壤氮循环过程的影响，本实验采集江西鹰潭双圳花岗岩母质针叶林土壤，用石灰调节pH值为5.78，6.91，8.03，与未调节的土壤构成四个不同的pH处理：（1）pH=4.36，对照；（2）pH=5.78；（3）pH=6.91；（4）pH=8.03。在25ºC、60%WHC、20和50mg N kg^-1(NH₄ 或NO₃^－)施肥水平下培养21天，分别测定培养前后无机态氮、N₂O、CO₂的变化。

结果显示，无论是施入50 mg N kg^-1还是20 mg N kg^-1(NH₄ 或NO₃^－)的土壤，均表现为培养末期NH₄ 含量增加，且施入石灰比例越高，pH越高的土样，增加越明显，但施入石灰比例越高的土样NO₃^－含量的增加越不明显。pH升高的土样，N₂O的排放峰值较对照的第7天提前至第3天，但CO₂的排放峰值较对照的第1天推迟至第3天。低氮水平下，pH调节对N₂O最大排放速率无明显影响；高氮水平下，pH升高一定程度会增大N₂O最大排放速率，但pH=8.03的土样N₂O最大排放速率则降低。低氮水平下，对照处理N₂O累积排放最大，但高氮水平下pH调节至6.91的土样N₂O累积排放最大。高氮和低氮水平下，pH升高的土样，CO₂的排放峰值较对照的第1天推迟至第3天，但最大排放速率无差异，pH升高的土样CO₂累积排放量高于对照。结果说明，调节pH立即施肥培养，矿化速率受pH变化的影响明显，但硝化作用所受影响不明显。N₂O、CO₂排放速率、峰值时间的影响受pH升高程度和施氮水平的协同影响，pH升高的土样高氮水平下N₂O、 CO₂排放增加，但pH高于8.0后N₂O排放减少。

关键词：土壤pH 土壤硝化 NH₄ -N NO₃^－-N N₂O

Abstract

Soil pH is one of the key factors influencing microbial community structure and nutrient cycling.To know the impact of soil pH on the soil nitrogen cycling in forests in subtropical humid areas，in this study，the soil from granite parent material coniferous forest in ShuangZhen，YingTan，JiangXi was subjected to different pH treatments by CaO addition：(1)pH=4.36，the control；(2)pH=5.78；(3)pH=6.91；(4)pH=8.03.Incubation of 21 days with conditions of 25℃，60%WHC，20mg N kg^-1 and 50mg N kg^-1(NH₄ or NO₃^－)，inorganic nitrogen(IN)，N₂O and CO₂ were determined respectively before and after the incubation.

The results showed that the NH₄ content increased after the incubation in both of soils by 20mg N kg^-1 (NH₄ or NO₃^－) and 50mg N kg^-1 addition，and the higher percentage of CaO addition was，soil pH of which was higher，the more obvious increment of NH₄ was，yet the more unconspicuous increment of NO₃^－ was.Compared with the control，the peak time of N₂O emissions was advanced from the seventh day to the third day in soil whose pH increased，but the peak time of CO₂ emissions was delayed from the first day to the third day.At low nitrogen(N) condition，pH treatments had unapparent influence on the maximum rate of N₂O emissions.At high N condition，increasingly soil pH enlarged the maximum rate of N₂O emissions in some degree，but the maximum rate of N₂O emissions was lowest in the soil whose pH is 8.03.At low N condition，the cumulative emissions of N₂O was maximum in the controlled experiment.However，at high N condition，the cumulative emissions of N₂O was maximum in the soil whose pH was adjusted to 6.91.At high and low N condition，the peak time of CO₂ emissions was delayed from the first day to the third day compared with the control，but the maximum rates of emissions were indifferent in soil whose pH increased.The accumulated emissions of CO₂ in soil whose pH increased was higher than that in the controlled experiment.The results showed that the change of pH had obvious impact on mineralization rate but unconspicuous influence on nitrification by pH treatments and incubation of

fertilization.Synergistic effect of N application levels and degree of pH increasing had influence on the emissions rates of N₂O and CO₂ and the peak time of them.At high N condition，the emissions of N₂O and CO₂ enlarged in soil whose pH increased，but the emissions of N₂O decreased when pH was above 8.0.

Keywords:soil pH；soil nitrification；NH₄ -N；NO₃^－-N；N₂O

目 录

摘 要 I

Abstract II

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 2

1.1.4 土壤反硝化作用 2

1.2 土壤硝化作用与N₂O排放 3

1.3 土壤硝化作用影响因素 4

1.3.1 温度 4

1.3.2 水分 4

1.3.3 pH 5

1.4 pH对N₂O排放的影响 6

1.5 本实验的研究目的与主要内容 6

1.6 研究展望 6

第二章 材料与方法 7

2.1 土样采集及制备 7

2.2 实验试剂 7

2.3 实验仪器 7

2.3.1 气象色谱法测定氧化亚氮 7

2.3.1.1 原理 7

2.3.1.2 气相色谱条件 8

2.3.2 半自动定氮仪 8

2.4 实验方法 8

2.4.1 土壤理化性质的测定 8

2.4.2 不同pH土壤硝化活性测定 9

2.4.3 不同pH土壤N₂O与CO₂排放速率及通量测定 9

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 12

3.1土壤理化性质 12

3.2 铵态氮、硝态氮含量及变化 12

3.2 N₂O排放速率 16

3.3 N₂O累积排放通量 18

3.4 CO₂排放速率 19

3.5 CO₂累积排放通量 22

3.6 讨论 22

请支付后下载全文，论文总字数：18654字