REU: Collaborative Research: Influence of Rhizosphere- Mycosphere Chemistry on Phosphorus Dynamics in an Arid Ecosystem

先前的研究已经证明菌根在利用“稳定”无机池中的磷方面的重要性，并暗示CO2和草酸盐在正磷池的不同利用中起着重要作用。此外，一些早期定殖物种（如Halogeton glomeratus， Salsola kali）产生草酸盐的能力导致了植物或相关真菌渗出物与土壤基质的相互作用在干旱生态系统中P动态中起关键作用的假设。提出的研究重点是两种风化剂，二氧化碳和草酸盐，它们可以促进无机池中磷的释放。反过来，池间磷分配的诱导转移影响演替。这些假设将通过理论和生态系统层面的一系列实验进行检验。实验是对假设进行评估的逻辑过程。具体而言，该项目将确定：1；草酸盐在过去演替研究中存档土壤、溶蚀仪土壤和田间土壤中的存在；2. 草酸盐驱动钙磷矿风化作用对演替的影响3. 不同磷效度系统中草酸盐的生产速率；4. CO2或草酸盐与参与磷释放的土壤矿物质的反应速率；5. 草酸盐的潜在降解速率；6. CO2和草酸盐与Ca-phosphate矿物反应的动态和平衡条件模型7. 实验室，溶渗仪和现场测试P化学模型。这些试验结果将为半干旱生态系统中影响磷循环和早期演替的一些过程提供一个机制模型。调查人员完全有资格进行这类研究，而且设施也很充足。

Previous studies have demonstrated the importance of mycorrhizae in utilizing P from "stable" inorganic pools and implicated CO2 and oxalate in differential use of ortho-P pools. Moreover, the ability of some early colonizing species (e.g. Halogeton glomeratus, Salsola kali) to produce oxalate has led to the hypothesis that interactions of plant or associated fungal exudates with the soil matrix plays a pivotal role in P dynamics in arid ecosystems. The proposed research focuses on two weathering agents, CO2 and oxalate, which act to enhance P release from the inorganic pool. In turn, the induced shift in P partitioning among pools influences succession. The hypotheses will be tested through a series of experiments at theoretical and ecosystem levels. The experiments are a logical progression toward evaluation of the hypotheses. Specifically, the project will determine: 1. The existence of oxalate in archived soils from a past successional study, in lysimeter and in field soils; 2. The effect of oxalate driven Ca-phosphate mineral weathering on succession; 3. The rates of oxalate production in systems of varying P availability; 4. The rate of reaction of CO2 or oxalate with soil minerals involved in P release; 5. The potential rate of oxalate degradation; 6. Models of dynamic and equilibrium conditions for CO2 and oxalate reactions with Ca-phosphate minerals; 7. Laboratory, lysimeter and field tests of P chemistry models. The results of these experiments will provide a mechanistic model of some processes which affect P cycling and early succession in a semiarid ecosystem. The investigators are well qualified to perform this type of research and the facilities are adequate.