Collaborative Research: Price determination in ectomycorrhizal symbioses

许多对物种都参与了互惠互利的交换。自然界中这些共生关系中最广泛和生态上最重要的类型之一是土壤中的真菌与植物根系之间的联系，称为菌根（真菌根）：真菌向植物输出磷和氮等矿质营养物质，植物向真菌输出基于碳的能量来源。然而，正如在其他类型的交换中一样，这些联系中每个伙伴的实际净收益可能取决于当前出口的成本和进口的价值。这种联系甚至可能演变成一方寄生在另一方身上，当土壤中氮和磷浓度的上升使得真菌对植物的出口变得多余时，这种联系就会破裂。理解和预测生物之间的资源交换何时真正有益的一个困难是比较苹果和橘子的问题：如何比较出口一种元素（如碳）的成本与进口另一种元素（如氮或磷）的收益？这个项目将尝试通过使用经济模型来计算物种之间的“资源交换价格”来解决这个问题。实验室实验将测量蒙特雷松与其8种菌根真菌之间的资源交换价格，并显示这些价格如何随着资源丰度的变化而随时间变化，以及在真菌种类之间变化。这将测试科学家是否可以用经济学来理解和预测像真菌和植物这样不同物种之间的相互作用。该项目还将帮助我们了解松树等经济上重要的树木对土壤肥力变化的反应，并帮助我们更准确地模拟碳和氮等元素的全球循环。此外，该项目将培训来自科学领域代表性不足群体的研究生和本科生，并与当地两所高中的教师合作，通过实地考察和为期一年的课堂实验，向年轻学生传授真菌在土壤中的重要作用。

Many pairs of species are involved in mutually beneficial exchanges. One of the most widespread and ecologically important types of these mutualisms in nature are associations between fungi in the soil and the roots of plants, known as mycorrhizae (fungus-roots): the fungus exports mineral nutrients such as phosphorus and nitrogen to the plant and the plant exports sources of energy based on carbon to the fungus. However, as in other types of exchanges, the actual net benefits to each partner in these associations can depend upon the current costs of exports and value of imports. The associations may even grade into parasitism of one partner on the other and fall apart when, for example, a rise in the concentration of nitrogen and phosphorus in the soil makes export from the fungus superfluous to the plant. One difficulty in understanding and predicting when resource exchanges between organisms will be truly beneficial is the problem of comparing apples to oranges: how does one compare the cost of exporting one element, such as carbon, to the benefit of importing a different one, such as nitrogen or phosphorus? This project will try to solve this problem by using economic models to calculate a "price of resource exchange" between species. Laboratory experiments will measure resource exchange prices between the Monterey pine and eight of its mycorrhizal fungi and show how those prices vary over time, as abundances of the resources change, and between the species of fungi. This will test whether scientists can use economics to understand and predict the interactions between species as different as fungi and plants.The project will also help us understand how economically important trees such as the pine respond to changes in soil fertility, and help us more accurately model global cycles of elements such as carbon and nitrogren. In addition, the project will train graduate and undergraduate students from groups that are under-represented in science, and work with teachers in two local high schools to teach younger students about the vital role of fungi in the soil, through a field trip and a year-long experiment right in the classroom.