Effects of lengthening growing season and increasing temperature on soil carbon fluxes and stocks in Arctic tundra

生长季延长和温度升高对北极苔原土壤碳通量和碳储量的影响

• 批准号: 0902109
• 负责人: Jianwu Tang
• 金额: $ 9.99万
• 依托单位: Marine Biological Laboratory
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2010-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0902109&HistoricalAwards=false
• 关键词: Effects; lengthening; growing; season; increasing

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Abstract Global warming is lengthening the growing season and increasing temperature in the arctic ecosystem. The lengthened growing season is featured by earlier snow melt and later fall freeze-up. Photosynthesis and respiration may respond differently to these changes, resulting in changes in the seasonal pattern, the annual carbon budget, whole-system carbon stocks, and the nutrient supply in the Arctic. Given the large amount of carbon stored in the arctic system and high sensitivity of carbon to temperature, the changing seasonality will influence the global carbon cycle and the climate system.The objectives of this project are to examine if and how microbial respiration, root respiration, and photosynthesis respond differently to earlier snow melt in spring and later soil freeze-up in fall, if and how these processes respond differently to enhanced temperature in the growing season, how the annual carbon budget changes, and what the implication is for the future arctic tundra ecosystem and the global carbon cycle.The study site will be in a tussock tundra ecosystem at the Toolik Field Station on the North Slope of Alaska. Open-top chambers will be used to manipulate temperature and the growing season. A mini-trenching approach will be used to partition soil respiration and separate the different response between root respiration and microbial respiration to the manipulated growing season and soil temperature. Combining two treatments (warming and trenching), 9 warming, 9 warming + trenching, 9 trenching, and 9 control plots will be established.Microbial and root respiration will be continuously, automatically measured with a belowground CO2 profile system, which is a better approach than the chamber measurement method in the tundra ecosystem. This continuous system allows examination of the mismatch of photosynthesis and respiration in response to the change in temperature and the timing of snowmelt and refreezing, while causing negligible disturbance to soils and aboveground plants in the tundra. Corresponding measurement of soil temperature, water content, canopy air pressure, air temperature and water vapor pressure will also be conducted. A portable photosynthesis measurement system with imbedded light sources will be used to measure leaf photosynthesis and its response to light. Periodic measurement of photosynthesis and leaf respiration will be extrapolated with a photosynthesis model. Continuous time-series data of photosynthesis, leaf respiration, root respiration, and microbial respiration with its correlation with temperature will be analyzed to examine the response to changing seasonality. Net ecosystem production will be calculated to examine changes in the annual carbon budget, its coupling with nitrogen availability, and implication for the carbon stock in the arctic and global system.

该奖项根据 2009 年美国复苏和再投资法案（公法 111-5）提供资金。 摘要 全球变暖正在延长北极生态系统的生长季节并增加温度。生长季节延长的特点是融雪较早，秋季结冰较晚。光合作用和呼吸作用可能对这些变化做出不同的反应，导致北极的季节模式、年度碳预算、全系统碳储量和养分供应发生变化。鉴于北极系统中储存的大量碳以及碳对温度的高度敏感性，季节性变化将影响全球碳循环和气候系统。该项目的目标是研究微生物呼吸、根系呼吸和光合作用对春季雪融化较早和秋季土壤结冰较晚的反应是否以及如何不同，这些过程对生长季节气温升高是否以及如何反应不同，年度碳预算如何变化， 以及这对未来的北极苔原生态系统和全球碳循环有何影响。研究地点将位于阿拉斯加北坡 Toolik 野外站的草丛苔原生态系统中。敞顶室将用于控制温度和生长季节。将采用小型挖沟方法来划分土壤呼吸，并区分根系呼吸和微生物呼吸对所控制的生长季节和土壤温度的不同响应。结合两种处理（加温和开沟），将建立9个加温、9个加温+开沟、9个开沟和9个控制样地。微生物和根系呼吸将通过地下CO2剖面系统连续、自动测量，这是比苔原生态系统中的室测量方法更好的方法。这种连续系统可以检查光合作用和呼吸作用随温度变化以及融雪和再结冰时间的不匹配，同时对苔原中的土壤和地上植物造成的干扰可以忽略不计。还将对土壤温度、含水量、冠层气压、气温和水蒸气压进行相应的测量。带有嵌入式光源的便携式光合作用测量系统将用于测量叶片光合作用及其对光的响应。光合作用和叶片呼吸的定期测量将通过光合作用模型进行推断。将分析光合作用、叶片呼吸、根呼吸和微生物呼吸的连续时间序列数据及其与温度的相关性，以检查对季节性变化的响应。将计算净生态系统产量，以检查年度碳预算的变化、其与氮可用性的耦合以及对北极和全球系统碳储量的影响。