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| 极端干旱条件下典型草原生态系统土壤胞外酶活性潜势动态分析 | |
| 其他题名 | Dynamics of potential soil extracellular enzyme activities under extreme drought in a typical grassland ecosystem |
| 范文玉 | |
| 出版年 | 2017 |
| 学位类型 | 硕士 |
| 导师 | 郝彦宾 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 摘要由于人类活动对全球变化的影响，全球的降水格局将会发生显著的变化。极端干旱事件发生的频率和强度都将有所增加。随着全球气候变暖，中国北方的年均降水量呈现下降趋势，并且干旱期亦呈现延长趋势。内蒙古典型草原地处半干旱区，干燥少雨，水分是限制生态系统生产力形成的重要因素之一。土壤胞外酶在生态系统物质循环中起着重要作用，并且易受气候变化的影响。大量的研究表明，干旱将导致多种土壤胞外酶活性降低，土壤碳（C）、氮（N）、磷（P）元素循环失衡，同时，土壤胞外酶的来源（植物、微生物）、底物（凋落物）、酶促反应环境（土壤理化性质）均会受到干旱的直接或间接影响。然而对于生长季不同时期发生的极端干旱，土壤胞外酶活性潜势的响应和恢复是否存在差异及其响应机制，尚需要进一步的研究。本研究基于中国科学院内蒙古草原生态系统定位研究站长期围封羊草样地的极端气候控制试验平台，通过室内分析，利用荧光微孔板技术和高通量测序技术等多种研究手段，探究生长初期、盛期和末期极端干旱胁迫以及大降雨脉冲对土壤胞外酶活性的影响。主要实验结果如下：（1）极端干旱显著降低了土壤含水量、微生物氮、硝态氮和速效磷含量，同时土壤总有机碳、微生物碳及铵态氮也表现为下降趋势。该结果表明极端干旱可使土壤碳、氮、磷循环相关的多个指标降低，土壤营养状况趋于贫乏。土壤pH值的升高趋势表明极端干旱加剧了土壤的碱化。极端干旱降低了土壤细菌的丰富度和多样性，但是三个极端干旱时期对细菌群落的结构变化的影响不同，生长初期发生的极端干旱和其它两个时期相比，土壤细菌群落结构变化更大。（2）极端干旱胁迫下土壤胞外酶活性均表现出不同程度的降低趋势。相对于盛期和末期极端干旱，初期极端干旱对酶活性的影响较小。在盛期极端干旱胁迫条件下，β-葡萄糖苷酶、外-β-葡聚糖酶、木聚糖酶、N-乙酰氨基葡糖苷酶的酶活性显著下降；而在末期极端干旱条件下，α-葡糖苷酶、外-β-葡聚糖酶、木聚糖酶、N-乙酰氨基葡糖苷酶的酶活性显著下降，并且在极端干旱处理结束后多数土壤酶类活性得到了不同程度的恢复。总体上，极端干旱时期与土壤N、P循环相关的酶类相对于C循环相关的酶类活性下降更少。（3）在极端干旱胁迫条件下，土壤胞外酶活性的变化主要与土壤含水量、硝态氮和速效磷的变化正相关，这表明典型草原生态系统极端干旱条件下限制土壤胞外酶活性的因素主要为水分和氮磷元素，而非碳元素。 （4）降水脉冲结束24小时后土壤胞外酶活性表现为增加的趋势，尤其是α-葡糖苷酶、β-葡萄糖苷酶、外-β-葡聚糖酶，其活性增加的幅度更大。同时，土壤胞外酶活性也表现出明显的日动态变化特征。对于降水脉冲，土壤胞外酶活性的响应相对于微生物的响应更为迟缓。 |
| 英文摘要 | AbstractGlobal precipitation patterns had undergone drastic changes due to human activities. The frequency and intensity of extreme drought events are predicted to increase. Along with global warming, the trend of annual precipitation declining and drought period extension were observed in in northern China. The typical steppe is located in the semi-arid zone sufferes from dry climate and less precipitation in Inner Mongolia. The availability of water is one of the most important factors limiting the development of ecosystem productivity. Extracellular enzyme plays an important role in material cycle of ecosystem and is vulnerable to the impact of climate change. Large body of studies have shown that dorught leads to decrease some extracellular enzyme activities and overbalances carbon (C), nitrogen (N) and phosphorus (P) cycle in soil. Meanwhile, drought affects extracellular enzyme directly or indirectly in a variety of aspects, such as the source (plants and microorganisms), substrate (litter), enzymatic reaction conditions (soil physical and chemical properties). However, the response and recovery consistency of extracellular enzyme potential activities under different periods of extreme drought and the mechanisms still need further investigation.This study was operated in a Long-term fenced Leymus chinensis field on the Extreme Climate Control Experiment Platform of in the Inner Mongolia Grassland Ecosystem Research Station of Chinese Academy of Sciences (IMGERS). We monitored the effects of extreme drought on soil extracellular enzyme activities using fluorescence microplate technology and high-throughput sequencing technology during the earlier, middle and later of grwoing stage and large rainfall impulse. The results show: (1) Soil water content, microbial nitrogen, nitrate nitrogen, available phosphorus significantly reduced in the treatments of extreme drought, as well as total soil organic carbon, microbial carbon and ammonium nitrogen. The result shows that extreme drought conditions declined the indicators of soil carbon, nitrogen and phosphorus cycle and worsen soil nutritional status. At the same time, the increasing trend of pH suggests drought intensified soil alkalization. Although extreme drought reduced the abundance and diversity of soil bacteria, three periods of extreme drought have different influence on the structural changes of microbial communities, and the extreme drought occuring earlier growing stage has a greater impact on soil microbial community structure.(2) Soil extracellular enzyme activities declined under each extreme drought period. Earlier-growing extreme drought affects enzyme activities less compared with the middee-season and the evening-season extreme drought. Under the stress of middle-grwoing extreme drought, the activities of α-glucosidase, Cellobiosidase, xylanase and N-acetyl-β-glucoasminidase decreased dramatically. Meanwhile, under later-grwoing extreme drought, the activities of β-glucosidase, Cellobiosidase, xylanase and N-acetyl-β-glucoasminidase decreased. However, the majority of soil extracellular enzyme activities can be recovered after extreme drought. In general, the activities of N, P-acquisition enzyme activities decreased less than those of the C-acquisition enzyme activities during the extreme drought period. (3) Under extreme drought conditions, the variation of soil extracellular enzyme activities was mainly related to soil water content, nitrate nitrogen and available phosphorus positively. This result shows that the limiting factors of soil extracellular enzyme activities under extreme drought conditions were water, nitrogen and phosphorus elements, rather than carbon in Inner Mongolia typical steppe.(4) The activities of most soil extracellular enzyme trend to increase withthin 24 hours after large precipitation event, especially for α-glucosidase, β-glucosidase and Cellobiosidase. At the same time, soil extracellular enzyme activities showed a diurnal variation pattern. In addition, the responses of soil extracellular enzyme activities to water impulse were delayed compared with microbes. |
| 中文关键词 | 典型草原 ; 极端干旱 ; 降水脉冲 ; 土壤胞外酶活性 ; 土壤理化性质 ; 土壤细菌群落结构 |
| 英文关键词 | typical grassland extreme drought water impulse soil enzyme activity soil physical and chemical properties soil bacterial community structure |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生物工程 |
| 来源机构 | 中国科学院大学 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287837 |
| 推荐引用方式 GB/T 7714 | 范文玉. 极端干旱条件下典型草原生态系统土壤胞外酶活性潜势动态分析[D]. 中国科学院大学,2017. |
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