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题名: 不同土壤有机碳水平桉树林施氮的环境效应研究
作者: 张凯
学位类别: 博士
答辩日期: 2015-05
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 欧阳志云 ; 郑华
关键词: 施氮、土壤有机碳、温室气体、土壤养分淋溶、桉树、环境效应,nitrogen fertilization, soil organic carbon, greenhouse gas flux, soil nutrient leaching, Eucalyptus, environmental effect
其他题名: Environmental effects of nitrogen fertilization in Eucalyptus plantations with different soil organic carbon contents
学位专业: 生态学
中文摘要:       施氮是维持和提高森林生态系统生产力的必要措施,同时也增加了养分流失和环境污染的风险。关于人工林施氮强度对具体某—土壤条件下的养分流失影响已经开展了大量研究,但是不同土壤肥力水平或者土壤有机碳水平人工林对施氮的响应及效应,会由于生态系统碳、氮循环的耦合途径与程度的不同而不同,这种差异鲜有报道。探讨施氮对不同土壤有机碳水平人工林施氮的生态环境效应,对于人工林合理施肥、科学评估与降低施氮的生态环境风险具有重要意义。本研究针对桉树人工林施氮的环境效应,选取土壤有机碳差异显著的两块桉树林样地(高土壤有机碳样地,HSOC;低土壤有机碳样地,LSOC),并设置不同施氮处理(不施氮处理,CK;低施氮量,LN;中等施氮量,MN;高施氮量,HN),通过野外监测和室内分析相结合的方法,研究了施氮对不同土壤有机碳水平桉树林温室气体排放和土壤养分淋溶的影响。主要结果如下:
    (1)广西桉树人工林各施氮处理下土壤CO2、CH4 和N2O 年均通量分别为214~402 mg m-2 h-1、-42~-31 μg m-2 h-1 和12~371 μg m-2 h-1。其中CO2 和N2O排放表现出明显的季节变化,在生长季(4 月~10 月)较高,非生长季(11 月~次年3 月)较低,土壤温度和水分是CO2 和N2O 季节变化的主要驱动因子。
    (2)施氮显著增加了桉树林土壤CO2 和N2O 排放,抑制了CH4 吸收。土壤CO2 年均排放通量表现出随施氮量增加而增加的趋势,在HN 处理下显著高于CK 处理(p<0.05);CH4 年均吸收通量表现出随施氮量增加而降低的趋势,在MN 和HN 处理下显著低于CK 处理(p<0.05);N2O 年均排放通量随施氮量增加而增加,且各处理间差异显著(p<0.05)。
    (3)不同土壤有机碳桉树林土壤CO2 和N2O 排放对施氮的响应存在差异。高土壤有机碳桉树林CO2 排放对施氮的响应更敏感。在LSOC 样地,LN、MN和HN 处理下土壤CO2 年均排放通量与CK 处理无显著差异,而在HSOC 样地,HN 处理下土壤CO2 年均排放通量显著高于CK 处理(p<0.05)。土壤有机碳水平对桉树林N2O 排放的影响在高施氮量处理下更强。在CK 和LN 处理下,HSOC样地土壤N2O 年均排放通量与LSOC 样地无显著差异,而在MN 和HN 处理下,HSOC 样地土壤N2O 年均排放通量显著高于LSOC 样地(p<0.05)。
    (4)广西桉树人工林生长季土壤碳(C)、氮(N)、钾(K)、钙(Ca)、钠(Na)和镁(Mg)淋溶量分别为0.51~1.41 g m-2、0.15~5.13 g m-2、0.15~0.56 g m-2、0.68~2.30 g m-2、0.22~0.49 g m-2 和1.35~4.75 g m-2。
    (5)施氮显著增加了桉树林土壤养分淋溶。土壤N 淋溶量随施氮量增加而增加,且各处理间差异显著(p<0.05);土壤C、K、Ca 和Mg 淋溶量表现出随施氮量增加而增加的趋势,在MN 和HN 处理下显著高于CK 处理(p<0.05); 土壤Na 淋溶量在LN 处理下显著高于CK 处理(p<0.05)。
    (6)不同土壤有机碳桉树林土壤养分淋溶对施氮的响应存在差异。土壤C和N 淋溶量均随施氮量增加而增加,在HSOC 样地的增加幅度高于LSOC 样地,表明高有机碳土壤C 和N 淋溶对施氮的响应更敏感。土壤K、Ca 和Mg 淋溶量也随施氮量增加而增加,但在LSOC 样地的增加幅度高于HSOC 样地,表明低有机碳土壤K、Ca、Mg 等阳离子淋溶对施氮的响应更敏感。
    上述结果表明,桉树人工林施氮对土壤温室气体排放、养分淋溶的影响随土壤有机碳水平的不同而不同,在人工林科学施氮、评估和调控人工林施氮的环境效应过程中,充分考虑人工林土壤有机碳水平将有助于提高人工林温室气体排放通量估算精度、减少人工林土壤养分流失及其环境污染风险。
英文摘要:       Nitrogen fertilization is necessary for agriculture and forest ecosystem to sustain productivity, but it also increased the risk of nutrient loss and environmental pollution. The effects of nitrogen fertilization level on soil nutrient loss have been extensively studied, but the impacts of nitrogen fertilization on nutrient loss in different soils were seldom compared. Organic carbon is the most important soil property. Studying the responses of nutrient loss to nitrogen fertilization from different organic carbon content soils, would not only improve our understanding of the interactions between nitrogen fertilization and soil organic carbon level, but also be helpful for scientific fertilization. Eucalyptus has been wildly introduced to southern China for afforestation. Fertilization is necessary in Eucalyptus plantations to sustain productivity, especially nitrogen. In order to study the environmental effects of
nitrogen fertilization in Eucalyptus plantations, and its interaction with soil organic carbon level, two Eucalyptus plantations with significantly different soil organic carbon level (HSOC, high soil organic carbon level; LSOC, low soil organic carbon level) were selected and four nitrogen fertilization treatments (CK, control; LN, low nitrogen fertilization; MN, middle nitrogen fertilization; HN, high nitrogen fertilization) were settled. The greenhouse gas emission and soil nutrient leaching were measured in Eucalyptus plantations. The main results are as follows:
      1. The annual mean fluxes of soil CO2, CH4 and N2O in Eucalyptus plantations under different nitrogen fertilization treatments were 214~402 mg m-2 h-1, -42~-31 μg m-2 h-1 and 12~371 μg m-2 h-1, separately. Soil CO2 and N2O emission showed significant seasonal variations, with higher fluxes in growing season and lower fluxes in non-growing season. Soil temperature and water content might be the impactors of seasonal variations.
      2. Nitrogen fertilization significantly increased soil CO2 and N2O emission, decreased soil CH4 uptake. The annual mean flux of CO2 emission showed an increase trend with increased nitrogen fertilization, with the flux under HN treatment significantly higher than under CK treatment (p<0.05). The annual mean flux of CH4 uptake showed a decrease trend with increased nitrogen fertilization, with the fluxes under MN and HN treatments significantly higher than under CK treatment (p<0.05). The annual mean flux of N2O emission showed an increase trend with increased nitrogen fertilization, with significant differences between different nitrogen fertilization treatments (p<0.05).
      3. The responses of soil CO2 and N2O emissions to nitrogen fertilization were more sensitive in high organic carbon soils. In LSOC site, there was no significant difference of soil CO2 emission between nitrogen treatment and CK treatments, however, in HSOC site, soil CO2 emission was significantly higher under HN treatment than under CK treatment (p<0.05). Under CK and LN treatments, soil N2O emission showed no difference between HSOC and LSOC sites, however, under MN and HN treatments, soil N2O emission was significantly higher under HSOC site than under LSOC site (p<0.05).
      4. The fluxes of soil carbon (C), nitrogen (N), potassium (K), Calcium (Ca), sodium (Na) and magnesium (Mg) leaching in Eucalyptus plantations during growing season (May to November) were 0.51~1.41 g m-2, 0.15~5.13 g m-2, 0.15~0.56 g m-2, 0.68~2.30 g m-2, 0.22~0.49 g m-2 and 1.35~4.75 g m-2, separately.
      5. Nitrogen fertilization significantly increased soil nutrient leaching in Eucalyptus plantations. Soil N leaching increased with increased nitrogen fertilization, with significant differences between different nitrogen fertilization treatments (p<0.05). Soil C, K, Ca and Mg leaching showed an increase trend with increased nitrogen fertilization, with the flux under MN and HN treatments significantly higher than under CK treatment (p<0.05). Soil Na leaching was only significantly higher under LN treatment than under CK treatment (p<0.05).
      6. The responses of soil nutrient leaching to nitrogen fertilization were different in Eucalyptus plantations with different soil organic carbon. The increase of soil C and N leaching caused by nitrogen fertilization were significantly higher in HSOC site than in LSOC site, but the increase of soil K, Ca and Mg leaching caused by nitrogen fertilization were significantly lower in HSOC site compared with in LSOC site. In conclusion, the effects of nitrogen fertilization on soil greenhouse gas fluxes and nutrient leaching were different in Eucalyptus plantations with different soil organic carbon contents. Thus, soil organic carbon content should be considered during nitrogen fertilization, assessing and regulating nitrogen fertilization-induced environmental effects in Eucalyptus plantations. That would helpful for precisely assessing greenhouse gas fluxes, reducing soil nutrient leaching and the risk of
environmental pollution.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/34465
Appears in Collections:城市与区域生态国家重点实验室_学位论文

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Recommended Citation:
张凯. 不同土壤有机碳水平桉树林施氮的环境效应研究[D]. 北京. 中国科学院研究生院. 2015.
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