青藏高原高寒草甸碳循环主要过程对氮、磷添加的响应

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	青藏高原高寒草甸碳循环主要过程对氮、磷添加的响应
	杨晓霞
学位类型	博士
导师	贺金生
	2014-05
学位授予单位	中国科学院研究生院
学位授予地点	北京
学位专业	生态学
关键词	青藏高原高寒草甸生产力土壤呼吸氮添加磷添加
摘要	青藏高原正经历着明显的温暖化过程，而由此引起的土壤温度的增加促进了土壤中微生物的活性，同时青藏高原东缘地区大气氮沉降十分明显，并呈逐年增加的趋势，这些均促使土壤中可利用营养元素的增加；高寒草甸是青藏高原地区极为重要的一种生态系统类型，因此深入了解青藏高原高寒草甸生态系统碳循环过程对可利用营养元素增加的响应，是准确预测和有效控制未来全球变化背景下区域及全球尺度陆地生态系统碳储量及碳平衡的重要基础。本研究选取位于中国青海省海北自治州的高寒草甸生态系统，设置四个实验处理：对照，氮添加（10 g N m^-2year^-1，尿素），磷添加（5 g P m^-2year^-1，重过磷酸钙）以及氮磷同时添加（10 g N m^-2year^-1，尿素；5 g P m^-2 year^-1，重过磷酸钙），自2009年开始，历经四个生长季（2009-2012年），测定了不同处理下该生态系统的群落生物量和生产力、土壤呼吸及土壤碳库等，旨在探讨青藏高原高寒草甸生态系统碳循环主要过程及其对氮、磷添加的响应。本研究的主要结果如下： 1. 氮、磷添加均增加了青藏高原高寒草甸生物量和生产力。氮、磷添加均显著促进了青藏高原高寒草甸生态系统的地上生物量，平均而言分别增加了21.6%和46.9%。养分添加后禾草类植物生物量的显著增加是氮、磷提高地上生物量的主要来源。氮添加对青藏高原高寒草甸生态系统地下生物量无显著影响，但磷添加有促进地下生物量的趋势。施肥第四年（2012年）氮、磷添加均显著促进了地上净初级生产力，同时均有降低地下净初级生产力的趋势，综合考虑，氮、磷添加促进了总净初级生产力并且均促使更多的初级生产力分配到地上。 2. 青藏高原高寒草甸生态系统土壤呼吸对氮、磷添加的响应相异。氮添加在第一年促进了青藏高原高寒草甸生态系统的土壤呼吸（18.4%），接下来的两年对土壤呼吸无显著影响，在第四年则显著抑制土壤呼吸（10.2%），土壤呼吸对氮添加响应随时间的变化可能主要源于微生物活动对氮添加的响应随时间的变化；磷添加促进了青藏高原高寒草甸生态系统土壤呼吸（11.9%），这种正响应极有可能源于磷添加对地下生物量的促进，然而由于植物对养分添加的响应具有迟滞效应，磷添加对土壤呼吸的促进作用从第三年开始显著。氮、磷添加对土壤呼吸温度敏感性均无影响，说明在青藏高原高寒草甸生态系统较长期内氮磷添加不会通过影响土壤呼吸温度敏感性而影响土壤呼吸速率。施肥四年后，氮、磷添加均显著降低了异氧呼吸速率，说明在青藏高原高寒草甸生态系统较长期内氮、磷添加会通过抑制异养呼吸而降低向大气的净碳输出。 3. 青藏高原高寒草甸0-10 cm 深度土壤碳含量为74.4 g kg-1，蕴含的碳约为5.58 kg C m-2。氮添加（四年后）促进了青藏高原高寒草甸土壤碳含量的增加（6.3%），而磷添加（四年后）对青藏高原高寒草甸土壤碳含量的影响很小。
其他摘要	Rising soil temperature under the warming process stimulates microbial activity in soil on the Tibetan Plateau; on the other hand, the eastern edge of Tibetan Plateau has been experiencing obvious atmospheric nitrogen deposition with an increasing trend year by year. All of these have led to an increasing in available nutrients in soil. Alpine meadow is one of the most important ecosystems on the Tibetan Plateau as its large area (7.0×105 km², 35% of the Plateau area), and plays a critical ecological function in the region. Therefore, the information about potential responses of carbon dynamics of the alpine meadow ecosystems to increasing available nutrients in soil under climate change on the Tibetan Plateau is essential to explore the regional and global carbon cycling with consequent feedbacks to climate change. This study was conducted on an alpine meadow ecosystem at the Haibei National Field Research Station of Alpine Grassland Ecosystem, Northwest Institute of Plateau Biology, Chinese Academy of Sciences. Four treatments were set: control, nitrogen addition (N; 10 g N m^-2 year^-1, urea), phosphorus addition (P; 5 g P m^-2 year^-1, triple superphosphate), and nitrogen combined phosphorus additions (NP; 10 g N m^-2 year^-1, urea; 5 g P m^-2 year^-1, triple superphosphate). We had measured several important indices of the ecosystem from 2009 to 2012, including net primary productivity, soil respiration, soil carbon content and so on. The effects of nitrogen and phosphorus on carbon influx and efflux, carbon pools were examined, in order to explore the process of carbon cycle and its responses to N and P additions on the Tibetan Plateau. The main results are summarized as follows: 1. N and P additions increased the community biomass and productivity. Across four years, N and P additions averagely increased the community aboveground biomass 21.6% and 46.9% respectively. The increases of aboveground biomass under N and P additions were mainly due to the stimulation on the growth of graminoids. N addition had no effect on the belowground biomass, whereas P addition slightly increased the belowground biomass. Both N and P increase aboveground net primary productivity but had a tendency to decrease belowground net primary productivity in 2012. Totally, both N and P increased net primary productivity and the ratio of ANPP to BNPP.2. N and P additions had contrasting effects of additions on soil respiration in the alpine grasslands of the Tibetan Plateau. The response of soil respiration to N addition varied over the measuring periods: N addition significantly enhanced soil respiration by 18.4% in 2009, then had no effect in 2010 and 2011, but reduced soil respiration by 10.2% in 2012. The temporal variation of response of soil respiration to N addition may largely due to the temporal variation of response of microbial activities to N addition. P addition had positive effect on soil respiration, and the stimulation was probably due to the enhancement of autotrophic respiration through positive effect of P amendment on belowground biomass and root P content. Because of the delayed response of plant to nutrient addition, the stimulation on soil respiration by P addition had not showed significant until in the third year. Both N and P additions significantly reduced seasonal mean heterotrophic respiration in 2012, which meant the net carbon efflux of the alpine ecosystem would be depressed after long-term N and P additions. 3. The total carbon density and content of the top 10 cm soil are 74.4 g kg^-1and 5.58 kg c m^-2. N addition (after four years continuous addition) stimulated the carbon content of the top 10 cm soil (6.3%), whereas P addition had no effect on the carbon content.
文献类型	学位论文
条目标识符	http://210.75.249.4/handle/363003/4025
专题	中国科学院西北高原生物研究所
推荐引用方式 GB/T 7714	杨晓霞. 青藏高原高寒草甸碳循环主要过程对氮、磷添加的响应[D]. 北京. 中国科学院研究生院,2014.

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