Knowledge Resource Center for Ecological Environment in Arid Area
| 模拟增温及氮水添加对科尔沁沙质草地土壤氮矿化作用的影响 | |
| 其他题名 | Effect of Simulated Warming, Water and Nitrogen Addition on Soil Nitrogen Mineralization in Kerqin Sandy Grassland |
| 陈静 | |
| 出版年 | 2014 |
| 学位类型 | 硕士 |
| 导师 | 李世杰 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 土壤氮矿化作用是陆地生态系统氮素生物地球化学循环的关键过程，通过土壤氮素的矿化作用，植物可以获取其生长所必须的营养元素，这在很大程度上决定了陆地生态系统初级生产力。科尔沁沙质草地是我国北方沙质草地的典型代表区域之一，但是，由于人为活动加剧，如放牧、开垦和樵柴等，导致该地区植被遭到破坏，进而产生了较为严重的土地沙漠化，致使土壤贫瘠化和质地粗化，保水能力下降，而这些因素都直接或间接的影响土壤氮矿化/硝化作用。并且，科尔沁沙地地处干旱半干旱区，对全球变化尤其敏感，使该地区土壤氮矿化特征不同于其他生态系统。因此，在全球变化愈趋严重的大背景下，研究沙质草地土壤氮矿化作用对增温、水分和氮素添加的响应机理是刻不容缓的，这有助于全面预测未来气候对沙质草地生态系统结构和功能的影响。本研究通过野外控制试验，针对科尔沁沙质草地土壤氮素的矿化过程对环境变化的响应过程，应用土壤学、生物地球化学和生态学等学科的方法及原理，以期回答以下问题：(1) 氮素添加影响沙质草地土壤有效氮和净氮矿化的机理过程是怎样的？(2) 氮水添加后沙质草地土壤有效氮和净氮矿化是怎样变化的？(3) 不同湿度条件模拟增温是否影响沙质草地土壤净氮矿化?得出主要结论如下： 1. 科尔沁沙地土壤无机氮以硝态氮为主，由于沙质草地土壤结构疏松、透气性好，致使该地区土壤的硝化作用很强， NH+ 4-N几乎全部被硝化为NO- 3-N，因此NO- 3-N是该地区土壤中有效氮的主要形态，大约占了无机氮的70%。该地区土壤净硝化速率、净氮矿化速率和净氮矿化无机氮量呈现季节性变化规律，一般在5月最低，7月最高，之后下降，这主要是由于科尔沁沙地水热同季引起的。 2. 不同施氮量显著提高了科尔沁沙质草地土壤硝态氮、铵态氮和无机氮含量。土壤硝态氮含量分别较对照提高了47.67%（5 g/m2）、171.28%（10 g/m2）和284.01%（20 g/m2）；铵态氮含量分别较对照提高了96.53%（5 g/m2）、186.60%（10g/m2）和296.42%（20 g/m2）；总无机氮的含量分别较对照提高了63.21%（5 g/m2）、176.15%（10 g/m2）和287.96%（20 g/m2）。科尔沁沙质草地土壤矿化/硝化速率在不同施氮量处理下显著增加，平均净矿化速率随施氮量呈上升趋势，分别较对照提高了174.14%（5 g/m2）、295.03%（10 g/m2）和340.13%（20 g/m2）。但是，氮素对土壤氮矿化作用的影响存在一个阈值，在科尔沁沙地沙质土壤，氮素添加量少于10 g/m2，对土壤氮矿化作用的影响随着氮素添加量的增加而增加，可是当氮素添加量超过10 g/m2，对土壤氮矿化作用的影响与10 g/m2的氮素添加量无显著差异。 3. 添加水分对科尔沁沙地土壤硝态氮含量、铵态氮含量、总无机氮含量没有显著影响，但是添加氮素对土壤无机氮含量有显著影响，并且氮素×夏季增雨和氮素×冬季增雪处理对沙质草地土壤无机氮含量的效应比单独添加氮素或水分更明显，说明水分和氮素对科尔沁沙地土壤的氮矿化存在交互作用。冬季增雪对科尔沁沙地土壤氮矿化作用无显著影响，而添加氮素或者夏季增雨可以显著提高土壤氮矿化/硝化速率，且同时添加氮素和水分对土壤氮矿化速率的影响较添加氮素或水分更大。 4. 无论是否增温，科尔沁沙质草地土壤氮矿化作用随着土壤湿度增加明显提高。净硝化速率和净矿化速率在土壤湿度9.5%时最大，土壤湿度达到12.5%时明显下降。增温使沙质草地土壤氮矿化作用发生显著变化，但增温的效应与土壤湿度存在一定的关联。在相对适宜的土壤湿度条件下（土壤湿度为6.5%～12.5%），该地区土壤的净矿化速率和净硝化速率在增温条件下可以显著增加；但是在土壤含水量过低或者过高的条件下，增温对土壤的净矿化速率和净硝化速率影响不显著。 |
| 英文摘要 | Soil nitrogen mineralization is the key process of nitrogen biogeochemical cycling in terrestrial ecosystems, as it can provide essential nutrients for plant growth and largely determines the primary productivity of terrestrial ecosystems. Kerqin sandy grassland is one of the typical areas of sandy grassland in northern China, but sufferedseveredesertification due to improper human activities such as over-grazing, cultivating grassland and collecting firewoods. Land desertification led to serious loss of soil nutrients and organic matter, the decrease of water holding capacityand so on, which have a direct or indirect impact on soil nitrogen mineralization/ nitrification. Moreover, Kerqin sandy land is located in the arid and semi- arid areas and is particularly sensitive to global change, where soil nitrogen mineralization characteristics of the region may be different from other ecosystems. Therefore, it is necessary to carry out a study on the response of sandy grassland soil nitrogen mineralization to temperature increase, water and nitrogen addition to fully predict the impacts of the future climate on structure and function of sandy grassland ecosystem.In this study, we mainly examined responses of soil nitrogen mineralization in sandy grassland to environment changes by field experiments. The objective of this study is to reveal: (1) if adding nitrogen to sandy grassland significantly changes the concentrations of soil inorganicnitrogen and net nitrogen mineralization; (2) variations of soil inorganic nitrogen content and net nitrogen mineralization and if there are interactive effects of nitrogen and water on soil mineralization; (3) the response of soil nitrogen mineralization in Kerqin sandy grassland to temperature increase under different soil moisture conditions. The major results in this study are as follows: 1. Nitrate, accounting for nearly 70% of the inorganic nitrogen, gave the primary contribution to soil inorganic nitrogen in soils of Kerqinsandy grassland, which is significantly different from other terrestrial ecosystems. The cause of such pattern is probably due to the loose structure and good air permeability in soils, which facilitate soil nitrogen nitrification. The concentrations of soil inorganic nitrogen and net mineralization/nitrification rate varied significantly with time. Generally, soil nitrogen mineralization increased from May to July, and thereby reached the peak and the decreased gradually from July to September. Higher average temperature and more rainfall occurred in July probably contributed such seasonal pattern of soil nitrogen mineralization. 2. The concentrations of soil nitrate, ammonium, and inorganic nitrogen increased significantly with different level of nitrogen additionsin Horqin sandy grassland. Compared with control treatment, soil nitrate contentswere increased by 47.67%, 171.28% and 284.01 with nitrogen additions of 5g/m2, 10g/m2 and 20 g/m2, respectively; ammonium nitrogen content were increased by 96.53% (5g/m2), 186.60% (10g/m2) and 296.42 (20g/m2); and concentrations of inorganic nitrogen were increased by 63.21% (5g/m2), 176.15% (10g/m2) and 287.96% (20g/m2). Moreover, different nitrogen addition significantly increased soil mineralization/nitrification ratesin Kerqin sandy grassland.Compared to control treatment, the average net mineralization rate were increased by 174.14% (5 g/m2), 295.03% (10 g/m2), and 340.13% (20 g/m2), respectively. The results showed that there is probably a threshold of the effects of nitrogen additionon soil nitrogen mineralization in Horqin sandy soil. Although soil nitrogen mineralization ratesignificantly increased with increasing amount of nitrogen addition, no significant difference were detected in soil nitrogen mineralization rate after the amount of nitrogen addition exceeded 10 g/m2. 3. The results showed that there were no significant effects on concentrations of soil nitrate, ammonium, and total inorganic nitrogen by water addit |
| 中文关键词 | 添加氮素 ; 冬季增雪 ; 夏季增雨 ; 模拟增温 ; 土壤湿度 ; 无机氮含量 ; 矿化速率 |
| 英文关键词 | nitrogen addition，increasing snow in winter increasing rainfall in summer simulated warming soil moisture inorganic nitrogen nitrogen mineralization rate |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287387 |
| 推荐引用方式 GB/T 7714 | 陈静. 模拟增温及氮水添加对科尔沁沙质草地土壤氮矿化作用的影响[D]. 中国科学院大学,2014. |
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