Knowledge Resource Center for Ecological Environment in Arid Area
| 中亚温带典型荒漠碳循环对水、氮增加的响应 | |
| 其他题名 | Responses of the Carbon Cycle to Water and Nitrogen Addition in a Temperate Desert of Central Asia |
| 谢继萍 | |
| 出版年 | 2013 |
| 学位类型 | 硕士 |
| 导师 | 李彥 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 生态系统碳通量变化是碳循环研究的重要组成部分，也是生态系统对气候变暖响应的重要研究内容。气候变化模型预测，未来中亚干旱区的降水和氮沉降量呈现逐渐增加的趋势，已有研究表明降水和氮沉降增加会对植物群落组成和碳循环产生重要影响，但其对温带荒漠生态系统群落生长和C收支平衡的研究还较少。本研究利用箱式法，对中亚典型荒漠草本植物群落碳通量在2011~2012年两个生长季的变化进行了连续观测，分析了荒漠草本植物群落碳通量对模拟降水和氮增加的响应；同时，跟踪调查了荒漠草本植物群落的生长和相关群落环境因素的变化，分析了影响碳通量变化过程的环境因素和碳通量变化的内在机理。该研究对于预测荒漠生态系统对未来气候变化的响应与适应具有重要的意义。主要结果包括以下几个方面： 1). 小量水、氮增加对植物群落有显著影响，草本群落生物量在2011年达到82.32 g?m-2，而2012年降水稀少，总生物量只有2011年的23.96%(19.72 g?m-2)，但在增水和增氮处理下均有明显的增加趋势。其中增水处理下的植物株高、植被覆盖度、植物密度和丰富度出现显著性差异，这也说明了水分是荒漠植物最重要的限制因子。 2). 温带荒漠草本群落的碳通量在日尺度上呈现单峰的变化趋势，NEE平均值为0.51μmol?m-2?s-1，最大值出现在中午14:00时左右，日变化过程主要受温度驱动；在季节变化上，碳通量对降水的季节变化敏感：在降水充足条件下，总生态系统生产力(GEP)表现出更大的截获，而在干旱胁迫下，呼吸作用(ER)明显大于光合作用，净生态系统碳交换NEE在2011年为61.16 g?C?m-2?a-1，2012年为111.45 g?C?m-2?a-1。这一结果说明，净生态系统碳交换在整个生长季呈净释放，水分增加会在一定程度上减缓碳释放，而N沉降增加对净生态系统碳交换没有显著影响。 3). 碳通量与环境因子(温度、PAR、降水、土壤含水量)的相关分析表明：降水和土壤含水量与碳交换NEE呈现正相关，暗示温带荒漠草本群落碳通量主要由降雨控制；光合作用GEP在湿润条件下首先受到土壤温度的影响，在干旱胁迫是受PAR的影响。除降水外，土壤含水量和温度是影响生态系统碳通量的另外两个关键因子。 4). 温带荒漠草本植物群落碳通量在小量水、氮增加处理下没有显著的响应，但在降水稀少的干旱年，碳通量对小量水、氮增加有显著响应。本文通过模拟降水和大气氮沉降的增加，初步分析得出温带荒漠草本群落碳通量主要受控于降水的年际和季节波动，降水增加有助于降低碳释放。 |
| 英文摘要 | Ecosystem carbon flux is an important part of the carbon cycle research, and it has become one of the core contents of climate warming research. Climate changing models has predicted that future precipitation and nitrogen deposition will gradually increase in temperate desert of the central Asia. The existing studies show that precipitation and nitrogen deposition can exert important impacts on plant community composition and diversity, but researches about the growth of temperate desert herb community and C balance is less. This study used the carbon flux chamber to observe the dynamics of carbon flux in the desert herbal communities in 2011 and 2012. We analyzed the responses of carbon flux in herb community to simulated precipitation and nitrogen increasing; meanwhile, monitored the plant growth and changes of environmental cues. Finally, we analyzed the relationship between environmental factors and carbon flux components, and then confirmed which factors did dominate carbon flux change process. This study has the potential values in predicting the responding and adaptation of desert ecosystem to climate changing. The main results are follows: 1) The small amount of water and nitrogen addition had a significant effect on plant community. The plant biomass was 82.32 g?m-2 in 2011. Under drought stress, the total biomass was only 19.72 g?m-2 in 2012. But increased nitrogen plus water obviously had increased with the trend. Showing increases in the watered treatment, plant biomass, plant height, plant coverage, plant density and plant richness had shown significant differences. It also suggested that the water is the most important limiting factor to desert plants. 2) The carbon flux in the desert plant communities showed a unimodal change trend at a day scale: the mean net ecosystem exchange (NEE) was 0.51μmol?m-2?s-1, and the maximum appeared at about 14:00. The daily variation process was driven mainly by temperature. At the seasonal scale, carbon flux was sensitive to seasonal change of precipitation: the gross ecosystem productivity (GEP) showed greater carbon interception after abundant rainfall, and under drought stress, the respiration (ER) was significantly greater than photosynthesis. The NEE was 61.16 g?C?m-2?a-1in 2011, and 111.45 g?C?m-2?a-1 in 2012. This result showed that net ecosystem carbon exchange was negative in the whole growing season, and carbon released slower when moisture was increased. But N deposition did not significantly influence net ecosystem exchange. 3) The correlation analysis of carbon flux with environmental factors (temperature, PAR, precipitation, soil moisture content) showed that a positive correlation between precipitation, soil moisture content and NEE. It is suggested that the carbon flux was mainly controlled by rainfall in the temperate desert plant communities. The soil temperature was the first key factor to the photosynthesis under humid conditions. It is affected by PAR under the drought stress. Besides precipitation, soil moisture content and temperature become other two key factors in the desert system. 4) Based on simulated precipitation increase and atmospheric nitrogen deposition, the carbon flux in desert plant communities had no significant response to small amount of water and nitrogen addition. In drought stress, the carbon flux responded to small amounts of moisture addition increased significantly. And nitrogen alone and their interaction had no significant influences. The herbaceous community in temperate desert derived carbon flux was mainly controlled by precipitation interannual and seasonal fluctuations, precipitation increases to help reduce carbon emissions. |
| 中文关键词 | 温带荒漠 ; 箱式法 ; 净生态系统交换 ; 降水 ; 草本群落特征 |
| 英文关键词 | temperate desert box method net ecosystem exchange |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院新疆生态与地理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287277 |
| 推荐引用方式 GB/T 7714 | 谢继萍. 中亚温带典型荒漠碳循环对水、氮增加的响应[D]. 中国科学院大学,2013. |
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