Knowledge Resource Center for Ecological Environment in Arid Area
| 内蒙古草原温室气体（CH4，CO2，N2O）的时空格局及其对全球变化的响应 | |
| 其他题名 | Temporal and spatial patterns of greenhouse gases (CH4, CO2, N2O) and their responses to climate change in Inner Mongolia grasslands, China |
| 刘伟 | |
| 出版年 | 2013 |
| 学位类型 | 博士 |
| 导师 | 李凌浩 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 在全球变化和人类活动的共同影响下，大气中的温室气体浓度不断升高。作为地球表面最重要的陆地生态系统之一，草原约占全球陆地植被面积的40%，是温室气体重要的源和汇。因此，准确评估草原对于温室气体交换的影响具有重要意义。内蒙古草原作为欧亚大草原的重要组成部分，对于研究温室气体交换具有广泛的代表性。以往的研究大都在典型草原的群落或流域水平开展，而对于区域水平的大尺度时空格局研究甚少。全球变化涉及多个气候因子的综合影响，而有关多因子交互作用的研究还比较少。本研究主要开展了两方面的工作。首先在具有明显降水梯度变化的内蒙古草原，大致沿中国东北样带（NECT），在1200km的范围内自东向西设置了12个观测站点，利用静态箱-气象色谱法，探讨了不同草原类型（草甸草原、典型草原和荒漠草原）温室气体交换的时空格局及其影响因素。第二，通过原状土柱培养法，在人工气候室内模拟短期多种气候因子变化（增温、增雨和氮沉降）对三种草原类型温室气体交换的影响。探讨了多种气候因子之间的交互作用，并进一步分析了气候变化背景下影响温室气体交换的生物、土壤和气候因子。通过对野外和室内3种温室气体交换的测定，分析了CO2、CH4和N2O之间可能存在的生态计量关系。主要研究结果与结论如下：（1）在内蒙古草原，3种温室气体都具有一定的季节变化。CO2排放在所有的站点都具有明显的单峰曲线形式；CH4吸收在东部（降雨量较多）站点季节变化比较明显，存在单峰曲线的形式，而在西部站点季节变化的波动比较大；在整个生长季，N2O排放都比较低，只在生长旺季偶尔出现较高的N2O排放。在空间尺度上，土壤温度、土壤水分和3种温室气体都具有较大的变异性。6到10月份，CO2排放总量平均值为1.56 ± 0.17 kg CO2 m-2（变化范围0.3~2.5 kg CO2 m-2），自东向西逐渐减少。CH4吸收量平均值为1.34 ± 0.16 kg C ha-1（变化范围0.20 ~ 2.15kg C ha-1），在中部典型草原具有最大的CH4吸收量。N2O排放具有很大的变异性，排放总量平均值为0.11 ± 0.02 kg N2O ha-1（变化范围0.02~0.25kg N2O ha-1）。（2）在季节动态上，CO2排放与土壤温度之间存在显著的正指数相关性，与土壤水分的相关性不是很好。在荒漠草原，随土壤水分升高，CO2排放有增加的趋势。CH4吸收随土壤温度的升高而增加，土壤水分过高或过低都不利于CH4吸收，最适含水量在不同草原类型差别比较大。N2O排放与土壤温度和土壤水分之间没有显著相关性。（3）在空间尺度上，CO2排放与土壤水分、地上生物量、全氮、有机碳和机械组成存在显著相关性。土壤水分、全氮和有机碳通过对植物生长和微生物活性的影响造成CO2排放的空间差异，而土壤机械组成在一定程度上调控了土壤的水分和养分状况。随降雨量的增加，CO2排放的温度敏感性显著增加，这说明气候变暖对于湿润地区的CO2排放影响更大。CH4吸收与土壤温度、土壤水分、地上生物量和pH存在显著相关性。内蒙古草原CH4吸收的最适pH值为7.71，降雨量过高或过低都不利于CH4吸收。降雨量通过对土壤水分和植物生长的影响，与pH值和土壤温度，共同决定CH4吸收的空间格局。由于N2O排放存在较大的空间异质性，没有发现显著影响N2O排放空间格局的因素。（4）多种气候因子对于3种温室气体交换具有不同的影响。增温显著促进了CH4吸收，促进了CO2和N2O的排放。增雨显著抑制了CH4吸收，促进了CO2和N2O的排放。施氮在短期内对于CH4吸收和CO2排放没有显著影响，只是在典型草原显著降低了CH4吸收；而施氮对于N2O排放具有显著的促进作用。对于CH4吸收和CO2排放来说，多因子之间的交互作用不是很显著，只在增温和增雨之间存在一定的交互作用；而对于N2O来说，多因子之间2因子和3因子都存在显著的交互作用。（5）对于CH4吸收而言，在草甸草原和荒漠草原，根据多个单因子计算的期望值会高估多因子交互作用对CH4吸收的影响；在典型草原结果相反。对于CO2排放，在草甸草原和典型草原，多因子交互作用满足乘积效应；只是在荒漠草原，根据多个单因子计算的期望值会低估多因子交互对CO2排放的影响。多因子交互作用对N2O排放的影响与对CH4吸收的影响作用相反。不同草地类型对于多因子交互作用响应的差异主要与土壤状况和初始水分条件有关。（6）气候变化通过改变土壤微环境、养分状况和生物的生长和活性，间接影响温室气体的交换过程。在一定的温度条件下，土壤水分、微生物生物量和土壤无机氮含量都会显著影响草原生态系统3种温室气体的交换。此外，CH4吸收还与土壤可溶性碳含量存在显著正相关关系；随地上生物量增加，CO2排放显著增加。（7）结合自然草原样带与室内控制实验，进一步分析了3种温室气体间可能存在的生态计量关系。本研究发现CO2排放与N2O排放之间存在显著正相关关系，N2O排放与CH4吸收之间存在负相关关系。在自然状态下，CO2排放与CH4吸收为正相关，而在控制实验中为负相关，这可能主要与控制实验排除了温度的影响有关。综上所述，在内蒙古草原，3种温室气体均具有较大的空间异质性。为了更精确地评估半干旱草原的温室气体交换，应该在有条件的情况下进行多点的、长期监测。鉴于气候变化多因子效应的复杂性，不能简单地根据多个单因子效应来预测多因子效应对于温室气体交换的影响。3种温室气体均受到微环境、土壤养分状况和生物的影响，因此对于3种温室气体之间生态计量关系的探讨有助于我们在生态系统水平上对于温室气体交换的认识。 |
| 英文摘要 | Due to global change and anthropogenic activities, the concentration of greenhouse gases, such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), in the atmosphere has been rising continuously. As one of most important terrestrial ecosystems on the earth surface, grasslands account for about 40% of the total terrestrial vegetation area, functioning as an important source as well as sink for greenhouse gases. Therefore, it is urgent to precisely evaluate the impact of grasslands on the greenhouse gas exchange. As an important component of the Eurasian steppe, Inner Mongolian steppe is a typical area for studying greenhouse gas exchange. Most past studies have focused on typical steppe at community or catchment levels, whereas the study of large-scale spatial-temporal patterns is extremely scarce. In addition, little research has been conducted concerning comprehensive impacts of global change based on multiple climate factor experiments.This work contains two aspects. Firstly, in Inner Mongolia steppe featured with an obvious gradient change in precipitation, we set up 12 research sites along the Northeast China Transect (NECT) from east to west, which ranges for 1200 about kilometers. The spatial-temporal patterns and their influential factors of the greenhouse gas exchange in different grassland types (meadow steppe, typical steppe and desert steppe) were explored. Secondly, using undisturbed-soil-pillar cultivation in phytotron, the impact of short-term change of multiple climate factors (warming, increased precipitation and nitrogen deposition) on the greenhouse gas exchange in the three grassland types were simulated. The interactive effects among multiple climate factors were further analyzed, including biotic, soil and climate factors that may exert impacts on greenhouse gas exchange under climate change. By measuring the field and indoor greenhouse gas exchange, the potential eco-metric relationships among CO2, CH4 and N2O were examined. The main results and conclusions are stated as follows:(1) The three greenhouse gases all exhibited certain seasonal variations in Inner Mongolia steppe. CO2 emissions at all the sites displayed an obvious unimodal curve. CH4 absorption showed obvious seasonal changes and unimodal curves at the eastern sites where the precipitation is high, whereas the seasonal changes at the western sites displayed remarkable fluctuations. During the whole growing season, N2O emissions were relatively low, which occasionally rose to a higher level in the peak season. Considering temporal variations, soil temperature, soil moisture and the three greenhouse gases all showed great variability. From June to October, the total average of CO2 emissions was 1.56 ± 0.17 kg CO2 m-2 (with a range of 0.3~2.5 kg CO2 m-2), which declined gradually from east to west; the average capacity of CH4 uptake was 1.34 ± 0.16 kg C ha-1 (with a range of 0.20 ~ 2.15kg C ha-1), with the typical steppe in the middle displaying the highest capacity; and N2O emissions showed great variability, with the total average emissions being 0.11 ± 0.02 kg N2O ha-1 (with a range of 0.02~0.25kg N2O ha-1) .(2) In the temporal scale, CO2 emissions were significantly positive correlated with soil temperature, but not with soil moisture. In the desert steppe, however, CO2 emissions showed an increasing trend as the soil moisture increased. CH4 uptake increased with the rise of soil temperature. |
| 中文关键词 | CO2 ; CH4 ; N2O ; 中国东北样带（NECT） ; 增温 ; 增雨 ; 氮沉降 ; 生态计量关系 |
| 英文关键词 | CO2 CH4 N2O Northeast China Transect (NECT) |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院植物研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287321 |
| 推荐引用方式 GB/T 7714 | 刘伟. 内蒙古草原温室气体（CH4，CO2，N2O）的时空格局及其对全球变化的响应[D]. 中国科学院大学,2013. |
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