Trace elements and microbial activity in the rhizosphere

了解土壤中微量元素（TE-As、Cd、Ce、Co、Cr、Cu、Ni、Pb、V、Y和Zn）的溶解度调节过程、植物对这些元素的吸收以及向沃茨的迁移是一项关键的社会挑战，因为这方面的知识对于维持陆地和水生生态系统的完整性以及防止对人类的健康危害至关重要。我们认为，根际，因为它在土壤中占据的战略地位：植物系统，是一个理想的场所来研究控制过程的形态和TE在土壤中的生物有效性。因此，该研究计划的长期目标是建立根际过程的贡献，在陆地生态系统中的TE的土壤地球化学。根据我们最近的工作，制定了三个紧迫的研究问题：问题1：在何种程度上是知识（观察，过程，理论）TE在根际收集的受控环境中有效的领域？问题2：基于对几个树种的研究结果能否推广到大范围的树木：土壤系统？问题3.土壤养分状况对树木根际TE的形态和生物有效性有何影响？该方法结合了森林生态系统的实地研究和生长室实验。将研究源自一系列土壤母质和代表北美东北部陆地环境的植被冠层的生物圈物质。我们的社会和政策制定者需要根际研究领域的进展，以预测土壤：植物系统对环境变化的反应，并在可持续粮食生产的背景下限制TE沿着食物链的流动。

Understanding the processes that regulate the solubility of trace elements (TE - As, Cd, Ce, Co, Cr, Cu, Ni, Pb, V, Y and Zn) in soils, their uptake by plants and transport towards waters bodies is a key societal challenge because this knowledge is vital to maintain the integrity of terrestrial and aquatic ecosystems, and to prevent health hazards to humans. We submit that the rhizosphere, because of the strategic position it occupies in soil:plant systems, is an ideal loci to study the processes controlling the speciation and bioavailability of TE in soils. The long-term objective of the research program is thus to establish the contribution of rhizospheric processes to the biogeochemistry of TE in terrestrial ecosystems. Based on our recent work, three pressing research questions were formulated: Question 1: To what extent is knowledge (observation, process, theory) on TE in the rhizosphere gathered from controlled environments valid in the field? Question 2: Could findings based on the study of a few tree species be generalized to a large spectrum of tree:soil systems? Question 3. What are the consequences of soil nutrient status on the speciation and bioavailability of TE in the rhizosphere of trees? The approach combines field studies of forested ecosystems and growth chamber experiments. Rhizosphere materials originating from a range soil parent materials and of vegetation canopies representative of the terrestrial environments found in north-eastern North America will be studied. Advances in the area of rhizosphere research are needed by our society and policy makers to anticipate the response of soils:plant systems to environmental changes and to limit the flow of TE along the food-chain in a context of sustainable food production.