| 英文摘要: | TITLE: Does the Arctic plant Eriophorum vaginatum take up organic N?
Chapin et al. (1993) showed that Eriophorum vaginatum, the plant species that dominates arctic tussock tundra, not only can use organic N-sources, but actually grows better with amino acids as a sole N-source than with inorganic N salts. A challenge of this shifting view is that no one has actually quantified, for any plant species growing in the wild, and how much of E. vaginatum?s total N demand is met by organic N-sources! This project would quantify the forms of N it uses, as well as assessing organic nutrient dynamics in several other tundra communities. More broadly, this project would develop approaches for assessing organic nutrition more in other ecosystem types and so test the developing organic nutrition theory of N-limited plants. This project will support undergraduate education by integrating new material into classes at University California Santa Barbara, and by offering research experiences to a University California Santa Barbara undergraduate during year-1 and an Alaskan student to help with the field season in year-2. It will coordinate with the Toolik Long Term Ecosystem Research education program in creating a module on "What Plants Eat." The participants will work with the Santa Barbara Natural History Museum to develop a suite of activities that will engage the public to target three goals: 1. A better appreciation of the role of soil in our lives and ecosystems, 2. To understand the Arctic as a component of the Earth System, and 3. To better appreciate how science and scientists work and think.
The challenge to answering the question "Do plants really use organic N?" has been methodological. This project would use a combination of methods integrated through simulation modeling. The key novel method is microdialysis, in which a probe the size of a root is inserted into the soil, a carrier solution flows through it, and small molecules diffuse into it. Microdialysis will be coupled with intact root uptake kinetic studies, isotope partitioning, and analyzing diffusion and transport of amino acids, NH4+ and NO3- through soil to parameterize a root uptake model that will be used to synthesize and integrate the results. The first phase of the work will be done under controlled conditions in the greenhouse; then having refined the methods and assessed model parameters, the study will be moved into the field to assess seasonal patterns of N uptake and how it is affected by environmental manipulations. |