水分胁迫和放牧对荒漠草原生态系统碳交换的影响

论文总字数：23413字

目 录

1 引言 1

1.1 荒漠草原碳循环研究的重要性 1

1.2 影响荒漠草原碳交换的因素 1

1.3 生态系统碳收支的评价指标 1

1.4 研究目的与意义 2

2 材料与方法 2

2.1 研究区概况 2

2.2 样地设置 2

2.3 仪器和观测方法 3

2.4 数据来源和评价方法 3

3 结果与分析 4

3.1 环境因子对荒漠草原生态系统的影响 4

3.2 水分胁迫对荒漠草原生态系统碳交换的影响 5

3.3 放牧对荒漠草原生态系统碳交换的影响 7

3.4 荒漠草原生态系统碳交换对水分胁迫和放牧的综合响应 9

4 讨论 11

4.1 非生物因素对碳交换的影响 11

4.2 土壤水分和温度对生态系统呼吸的影响 12

4.3 放牧对荒漠草原生物量的影响 12

4.4 水分胁迫和放牧的综合影响 13

5 结论 14

参考文献： 14

致谢 18

水分胁迫和放牧对荒漠草原生态系统碳交换的影响

刘 倩

, China

Abstract: The aim of this study was to investigate the integrated responses of ecosystem productivity and respiration to water stress and grazing in temperate desert steppe. Licor-840, closed static chamber technique and scanner were used to measure net ecosystem productivity (NEP), ecosystem respiration (RE), and gross primary productivity (GPP) under different water conditions (irrigated, non-irrigated) and grazing levels (control plots, light grazing, heavy grazing) in a typical temperate desert steppe in Siziwangqi, Inner Mongolia, China, during June and July 2013. Results showed that NEP, RE and GPP were inhibited under water stress. There was a significant positive correlation between soil moisture content (Vwc) and ecosystem productivity, and irrigation could increase ecosystem productivity, thereby increasing carbon sequestration in the desert steppe. Because of the compensatory regenerative growth, light grazing could promote grass growth during the period of vigorous vegetation growth and sufficient soil water supply. However, heavy grazing resulted in lower aboveground biomass and reduced carbon sequestration capacity of the ecosystem. Considering the effects of water stress and grazing, NEP increased by 1.068, 0.912, and 0.397 μmol CO₂ m^-2 s^-1, for each 1% increase in Vwc, respectively, in control plots, light and heavy grazing. It suggests as the degree of grazing increased the response of NEP to changes in soil moisture decreased. Therefore, it was concluded that overgrazing and drought were main limiting factors of the desert grassland ecosystem. Reasonable grazing and irrigation could increase the carbon sink of the temperate desert steppe.

Key words: soil water content; grazing intensity; temperate desert steppe; ecosystem carbon exchange

1 引言

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