15N foliar dilution of lodgepole pine: from where does the atmospheric N originate

土壤微生物是森林生态系统的重要组成部分，在养分循环、维持土壤结构和调节植物生长等方面发挥着重要作用。尽管氮循环在世界各地的森林中起着至关重要的作用，但对森林生长同样重要的一个过程尚未得到充分阐明。例如，黑松是一种分布广泛的物种，可以在各种土壤条件下生长。它在营养贫乏、质地粗糙的土壤上生长的能力，对于一个不知道固定氮的物种来说是独一无二的，这就提出了在这种环境下它的氮源的有趣问题。我建议确定固氮细菌是否能够在生活在松树菌根、根、茎和针组织中固定氮，使用生物标志物来可视化细菌以及原位nif基因表达。

Soil microorganisms are integral components of forest ecosystems, fulfilling critical roles in nutrient cycling, maintenance of soil structure, and regulation of plant growth. A process even as central to forest growth as nitrogen cycling has yet to be fully elucidated, notwithstanding the vital role it plays in forests worldwide. For example, lodgepole pine is a widely distributed species known to grow under a variety of soil conditions. Its ability to grow on nutrient-poor, coarse-textured soils is unique for a species not known to fix nitrogen, and poses interesting questions regarding its nitrogen source in such environments. I propose to determine if nitrogen fixing bacteria are capable of fixing nitrogen while living inside pine mycorrhiza, root, stem and needle tissues using biomarkers to visualize bacteria as well as nif gene expression in situ.