Trace elements and microbial activity in the rhizosphere

了解微量元素（TE - As、Cd、Ce、Co、Cr、Cu、Ni、Pb、V、Y和Zn）在土壤中的溶解度、植物对它们的吸收和向水体的运输的调节过程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健康的危害至关重要。我们认为，根际由于在土壤植物系统中占有重要地位，是研究土壤中TE物种形成和生物有效性控制过程的理想位点。因此，研究计划的长期目标是确定根际过程对陆地生态系统TE生物地球化学的贡献。基于我们最近的工作，我们提出了三个紧迫的研究问题：问题1：从受控环境中收集的关于根际TE的知识（观察、过程、理论）在多大程度上在田间有效？问题2：基于少数树种研究的发现是否可以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的物种形成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。将研究来自一系列土壤母质的根际物质和北美东北部发现的具有代表性的陆地环境的植被冠层。我们的社会和政策制定者需要在根际研究领域取得进展，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.