Herbivory and photosynthesis of oaks under elevated atmospheric CO2

大气二氧化碳浓度升高下橡树的食草和光合作用

• 批准号: 0236053
• 负责人: Evan DeLucia
• 金额: --
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-02-01 至 2007-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0236053&HistoricalAwards=false
• 关键词: Herbivory; photosynthesis; oaks; under; elevated

Trees and other plants are under constant assault by insects. It is estimated that on average 18 percent of forest productivity is lost to insect herbivores each year. The investigators hypothesize that this value underestimates the true impact of herbivores, and furthermore, that it will change substantially as the composition of the atmosphere changes. Widespread combustion of fossil fuels is causing a dramatic increase in the concentration of carbon dioxide in the atmosphere. Plants respond to this increase with higher rates of photosynthesis. However, other changes caused by rising carbon dioxide, including the formation of thicker leaves with higher concentrations of sugars and lower concentrations of nitrogen, are very likely to change the nutritional quality of leaves with respect to insect herbivores. In North Carolina the investigators are exposing plots in an intact pine forest to elevated carbon dioxide to simulate predicted atmospheric composition in the year 2050. Preliminary data show that among different kinds of oaks growing in the shade of the pines the amount of leaf tissue removed by insects was different in the high- and low-carbon dioxide plots. However, not all oak species were affected the same way. The investigators hypothesize that herbivory will be greatest for those species with greatest leaf nutritional quality under future atmospheric conditions. To test this hypothesis measures of leaf structure and chemistry for oaks in elevated and ambient carbon dioxide plots will be made. These measurements will be paired with measurements of herbivory and of the numbers and types of insects. Estimates of the amount of productivity lost to herbivores typically are based on measurements of the amount of leaf tissue removed. An assumption inherent in these estimates is that the remaining leaf tissue operates normally. When a caterpillar devours a quarter or half of a leaf, does the remaining tissue have normal rates of photosynthesis? To examine this question, the investigators have designed a unique camera system that measures light fluorescing from leaves. Fluorescence provides a direct measure of the rate of photosynthesis, but unlike other methods the measurement of fluorescence allows determination of how the rate of photosynthesis varies across the surface of the leaf. This instrument can be used to test the hypotheses that insects with different feeding behaviors will have different effects on photosynthetic rates of the remaining leaf tissue. These new measurements of the effect of herbivory on photosynthesis together with the experiments on the effects of elevated carbon dioxide on herbivory will provide new insights into how plant-herbivore interactions will alter ecosystem productivity in a future high-carbon dioxide world. In addition to training doctoral research scientists, this project also will provide the opportunity for undergraduate students, including those of underrepresented groups, to participate in scientific research through a NSF-sponsored Undergraduate Mentoring in Environmental Biology grant administered by the University of Illinois.

树木和其他植物经常受到昆虫的侵害。 据估计，每年平均有18%的森林生产力被食草昆虫夺走。 研究人员假设，这一数值低估了食草动物的真实影响，此外，随着大气成分的变化，这一数值将发生重大变化。 化石燃料的广泛燃烧导致大气中二氧化碳浓度急剧增加。 植物以更高的光合作用速率对这种增加作出反应。 然而，二氧化碳上升引起的其他变化，包括形成更厚的叶片，具有更高浓度的糖和更低浓度的氮，很可能改变叶片对昆虫食草动物的营养质量。 在北卡罗来纳州，研究人员将一片完整的松树林暴露在二氧化碳浓度升高的环境中，以模拟2050年预测的大气成分。 初步数据显示，在松树树荫下生长的不同种类的橡树中，在高二氧化碳和低二氧化碳的地块中，昆虫切除的叶组织数量是不同的。 然而，并不是所有的橡树品种都受到同样的影响。 研究人员假设，在未来的大气条件下，食草动物将是最大的那些物种与最大的叶片营养质量。 为了检验这一假设措施的叶片结构和化学橡树在升高和环境二氧化碳地块将。这些测量将与食草动物和昆虫数量和类型的测量配对。对食草动物损失的生产力的估计通常基于对被移除的叶组织的测量。 这些估计中固有的一个假设是，剩余的叶组织正常运作。 当一只毛虫吃掉四分之一或半片叶子时，剩下的组织还能正常进行光合作用吗？ 为了研究这个问题，研究人员设计了一个独特的摄像系统，可以测量树叶发出的荧光。 荧光提供了光合作用速率的直接测量，但与其他方法不同的是，荧光的测量允许确定光合作用速率如何在叶片表面上变化。 该仪器可用于验证昆虫取食行为对叶片光合速率的影响不同的假说。 这些对食草动物光合作用影响的新测量，以及二氧化碳浓度升高对食草动物影响的实验，将为植物-食草动物相互作用如何改变未来高二氧化碳世界的生态系统生产力提供新的见解。 除了培养博士研究科学家外，该项目还将为本科生提供机会，包括代表性不足的群体，通过由伊利诺伊大学管理的NSF赞助的环境生物学本科生导师资助参与科学研究。