Biotic controls on the residence time of soil carbon and nitrogen: new understanding from stable isotope probing and optimization modeling

农业部门的日益全球化和生物能源部门的增长为加拿大农民生产更多的粮食、纤维和原料创造了动力。这必须以可持续的方式进行，使农产品符合加工者和公众的高质量标准，使经济利润和就业机会留在我们的农村社区，使农业活动与农业环境目标保持一致。可持续农业生态系统被设想为保持土壤有机碳(C)，更多地依赖土壤内部氮(N)循环，从而有助于碳固存，避免氮肥的低效使用。在加拿大潮湿的温带地区，养分保持尤为重要，因为在高降水地区，土壤更容易受到养分流失的影响，而加拿大50%的农场位于这些地区。“活土壤”的概念是一种可能的解决方案，因为它依赖于自然存在的土壤微生物和动物同时分解和合成有机碳和氮，但由于这些过程发生得很快，在微观层面上，在土壤孔隙中，我们不知道土壤食物网如何在农场经营层面上促进作物生产。在这里，我们将在三个不同的尺度上解决这个问题：(i)从孔隙尺度上使用稳定同位素探测方法和高分辨率图像分析，（ii）考虑土壤食物网中发生的能量和营养转移，以及（iii）在田间尺度上，使用优化模型确定有机和无机肥料输入通过土壤生物群落的时间转换，与作物养分需求有关。这个研究项目的新颖之处在于它对农业生态系统中控制碳和氮循环的生物过程的基础研究问题的贡献，这些问题被整合到一个应用决策模型中，为加拿大农业社区提供了实际的答案。在过去的6年里，主要研究者培养了许多HQP，其中包括10名硕士研究生和16名博士研究生，期间在国际期刊上发表了90多篇同行评审论文，其中大部分以HQP为第一作者。该提案将通过个性化培训计划支持12名受训者，该计划包括点对点指导，重点是优秀的科学交流、网络和专业技能获取。这为他们未来作为科学领袖的角色提供了出色的准备，学术、政府和工业工作对这些学员的需求证明了这一点，这些工作需要先进的技术技能和管理能力。

Increasing globalization of the agricultural sector and growth of the bioenergy sector creates incentives for Canadian farmers to produce more food, fiber and feedstock. This must be done sustainably, so agricultural products meet the high quality standards of processors and the general public, economic profits and jobs remain in our rural communities and farming activities are aligned with agro-environmental objectives. Sustainable agroecosystems are envisioned to conserve soil organic carbon (C) and rely more on internal soil nitrogen (N) recycling, thus contributing to C sequestration and avoiding inefficient N fertilizer use. Nutrient conservation is especially important in humid temperate regions of Canada because soils are more vulnerable to nutrient loss in areas with high precipitation regimes and 50% of Canadian farms are located in these regions. The living soil' concept is a possible solution since it relies upon the naturally-occurring soil microorganisms and fauna to simultaneous decompose and synthesize organic C and N, but since these processes occur rapidly, at a microscopic level, within soil pores, we do not know how the soil foodweb contributes to crop production at an farm operations level. Here, we will tackle the problem at three different scales: (i) from the pore-scale with stable isotope probing methods and high-resolution image analysis, (ii) considering energetics and trophic transfers that occur within the soil foodweb, and (iii) at the field scale, using an optimization modelling to determine the temporal transformations of organic and inorganic fertilizer inputs through the soil biotic community, in relation to crop nutrient demands. The novelty of this research program is its contribution to fundamental research questions regarding the biological processes that control C and N cycling in agroecosystems, which is integrated into an applied decision-making model that provides practical answers for the Canadian farming community. The principal investigator contributed to the training of many HQP in the past 6 years, including 10 M.Sc. and 16 Ph.D. graduates, More than 90 peer-reviewed papers were published in international journals during this period, most of which had HQP as first author. This proposal will support 12 trainees through an individualized training program that includes peer-to-peer mentoring and focuses on excellent scientific communication, networking and professional skills acquisition. This provides outstanding preparation for their future role as scientific leaders, as evidenced by the demand for these trainees in academic, government and industry jobs that require advanced technical skills and managerial abilities.