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

以前的研究已经证明了菌根在从“稳定的”无机磷库中利用磷的重要性，并暗示了二氧化碳和草酸在邻位磷库的不同利用中的作用。此外，一些早期定居的物种(如盐碱蓬、沙拉卡利)产生草酸的能力导致了这样的假设，即植物或相关真菌分泌物与土壤基质的相互作用在干旱生态系统中的磷动态中起着关键作用。拟议的研究重点放在两种风化剂，二氧化碳和草酸盐，这两种物质可以促进无机磷的释放。反过来，磷在池之间分配的诱导转移影响演替。这些假说将通过一系列理论和生态系统层面的实验来验证。这些实验是评估假说的一个合乎逻辑的过程。具体地说，该项目将确定：1.过去演替研究中存档土壤、蒸渗仪和田间土壤中草酸盐的存在：2.草酸盐驱动的钙磷矿物风化对演替的影响；3.不同磷有效性系统中草酸的产生速率：4.CO2或草酸与土壤中参与磷释放的矿物质的反应速率；5.草酸盐潜在降解速率；6.CO_2和草酸盐与钙磷矿物反应的动力学和平衡条件模型；7.磷化学模型的实验室、蒸渗仪和田间试验。这些实验结果将为半干旱生态系统中影响磷循环和早期演替的某些过程提供一个机制模型。调查人员完全有资格进行这种类型的研究，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.