Collaborative Research: An Isotopic Record of Response to Climate Change in Spines of Saguaro Cactus

合作研究：仙人掌刺对气候变化响应的同位素记录

• 批准号: 0717403
• 负责人: David Dettman
• 金额: $ 15.2万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-15 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0717403&HistoricalAwards=false
• 关键词: Collaborative; Research; Isotopic; Record; Response

Wildlife species in the Sonoran Desert depend on resources supplied by large, water-storing cactuses and other succulents during periods of annual drought. The flowers and fruits of the giant saguaro cactus, for instance, provide water, nutrients and energy to numerous insects, birds and mammals during the driest periods of the year. Growth and reproduction of saguaro are extremely sensitive to climate variability and change, with potentially important impacts on dependent communities. This project develops a novel approach for assessing climate fluctuations, growth, stress responses, and reproduction of saguaro using information recorded in the isotope composition of saguaro spines. Variation in the oxygen and carbon stable isotope ratios in saguaro spines records patterns of water uptake and evaporation and changes in photosynthetic processes associated with water stress. Because spines are produced at the growing tip of the cactus and retained on the plant for up to 100 or more years, a long-term, high-resolution record of water balance and photosynthetic stress is potentially available for any saguaro plant. The age of spines is verified using radiocarbon (14C) dating techniques. This new project will construct precisely dated, high resolution isotope records from spines grown and retained throughout the life of saguaro plants across climate gradients in Arizona. The project hypothesizes that that 1) oxygen isotope ratios of spines record the source and amount of water to saguaro plants and variation in evaporative conditions; and 2) carbon isotope ratios reflect water stress effects on photosynthesis. Comparison of annually-resolved isotope records from spines with growth rates, flower/fruit production, and climate records covering the last 50 to 80 years will reveal saguaro''s response to local and regional environmental variation. In addition to two post-doctoral students, the proposal will fund original undergraduate research. The project will develop a curriculum unit on cactus-water relations for an existing K-12 outreach program.

索诺兰沙漠中的野生动物物种在每年干旱期间依赖大型储水仙人掌和其他多肉植物提供的资源。例如，巨型仙人掌的花朵和果实在一年中最干旱的时期为众多昆虫、鸟类和哺乳动物提供水、营养和能量。仙人掌的生长和繁殖对气候变率和变化极为敏感，对依赖的社区具有潜在的重要影响。该项目开发了一种新方法，利用仙人掌脊柱同位素组成中记录的信息来评估仙人掌的气候波动、生长、应激反应和繁殖。仙人掌刺中氧和碳稳定同位素比率的变化记录了水分吸收和蒸发的模式以及与水分胁迫相关的光合作用过程的变化。由于刺是在仙人掌的生长尖端产生的，并在植物上保留长达 100 年或更长时间，因此任何仙人掌植物都可能获得水平衡和光合胁迫的长期、高分辨率记录。使用放射性碳 (14C) 测年技术来验证脊柱的年龄。这个新项目将从亚利桑那州不同气候梯度的仙人掌植物的整个生命周期中生长和保留的刺中构建精确年代的高分辨率同位素记录。该项目假设：1）刺的氧同位素比记录了仙人掌植物的水源和水量以及蒸发条件的变化； 2）碳同位素比反映了水分胁迫对光合作用的影响。将过去 50 至 80 年的每年解析的脊柱同位素记录与生长率、花/果实产量以及气候记录进行比较，将揭示仙人掌对当地和区域环境变化的反应。除了两名博士后外，该提案还将资助原创本科生研究。该项目将为现有的 K-12 外展计划开发一个关于仙人掌与水关系的课程单元。