Soil organic matter at the root of solutions for climate change mitigation and adaptation

土壤有机质在减缓和适应气候变化方面起着至关重要的作用。在农业土壤中增加土壤有机质是增加碳(C)储量、限制全球变暖并在2050年前实现碳中性的最短期和最可行的选择之一。植物根对土壤有机质有很大贡献；活根释放分泌物，与共生微生物共生，并包裹土壤颗粒形成团聚体，死根是输入土壤的主要碳和氮(N)。然而，根也可以通过促进土壤微生物对土壤有机质的分解来破坏其稳定性。此外，全球变暖可能会影响植物和地下过程，但对土壤中碳和氮循环的影响尚不清楚。为了开发适应气候变化的土壤和农业生态系统，增加土壤有机质和碳贮量，有必要对根系如何影响土壤中碳和氮的保持和流失的平衡进行定量评估。尽管如此，关于根和微生物如何影响地下过程的数据很少。该计划的长期目标是：(1)表征在温带农业生态系统中使用的多年生和一年生物种的根系特征；(2)评估根系特征和气候变量如何影响SOM过程；(3)确定增加加拿大东部粘性土表层和底层土壤中C和N的储存和限制损失的根系特征。该计划包含两个主要主题：(A)不同植物物种的根的存活和分解如何影响土壤有机质；(B)气候变量和物种多样性如何影响根系特征和土壤有机质。它包括受控条件下的实验室实验(主题A)和自然条件下的实地实验(主题B)。通过对特定根系特征的形态、化学、结构和生物特征的分析，以及对土壤密度组分中C、N、13C和15N浓度的分析，可以追踪来自根的C和N，并研究表土(即0-20厘米深)和底土(即20厘米深)中的土壤有机质稳定机制。几乎没有数据来评估草地和种植物种、功能群体和群落对加拿大东部碳和氮稳定的影响，也没有任何关于根系特征如何影响土壤功能的信息。这一原创的、假设驱动的研究计划将在与气候变化缓解和适应相关的一些最重要的问题上提供新的知识。这项处于功能生态学和土壤科学前沿的研究项目将在这些领域之间建立桥梁，填补我们对土壤-植物系统理解的空白，从而产生强大的影响。有了这个研究计划，我将培养1名博士生、2名硕士、3名UG学生，他们将帮助设计和管理气候智能土壤和农业生态系统。通过探索基金提供的资金对加拿大必须做出的巨大努力做出了重大贡献，以履行《巴黎协定》的承诺，并在2050年前实现碳中和。

Soil organic matter (SOM) plays a crucial role in mitigating and adapting to climate change. Increasing SOM in agricultural soils is one of the most short-term and viable option to augment carbon (C) storage, limit global warming and reach carbon neutrality by 2050. Plant roots contribute substantially to SOM; living roots release exudates, associate with symbiotic microorganisms and enmesh soil particles to form aggregates, and dead roots serve as a major C and nitrogen (N) input into the soil. However, roots could also destabilize SOM by stimulating its decomposition by soil microorganisms. Moreover, global warming will likely affect plants and belowground processes, but effects on C and N cycling in the soil remain unclear. A quantitative assessment of how roots affect the balance between C and N retention and losses in soil is necessary to develop climate-smart soils and agroecosystems and increase SOM and C storage. Still, few data exists on how roots and microorganisms affect belowground processes. The long-term objectives of the proposed program are: (1) characterize root traits of perennial and annual species used in temperate agroecosystems, (2) evaluate how root traits and climate variables affect SOM processes, and (3) identify root traits that increase storage and limit losses of C and N, in topsoil and subsoil of Eastern Canadian clay soils. The proposed program contains two main themes: (A) How living and decomposing roots of different plant species affect SOM and (B) How climate variables and species diversity affect root traits and SOM. It involves laboratory experiments under controlled conditions (Theme A) and field experiments under natural conditions (Theme B). Morphological, chemical, architectural, and biotic characterisation of specific root traits, together with analyses of C, N, 13C and 15N concentrations in density fractions of the soil, will allow tracing root-derived C and N and studying SOM stabilization mechanisms in topsoil (i.e., 0-20 cm depth) and subsoil (i.e., >20 cm depth). Virtually no data exist to asses the influence of grassland and cropping species, functional groups and communities on C and N stabilization in Eastern Canada, nor there is any information on how roots traits impact soil functioning. This original, hypothesis-driven research program will provide new knowledge on some of the most important issues related to climate change mitigation and adaptation. This research program at the cutting edge of functional ecology and soil science will have a strong impact by creating bridges between these areas and filling gaps in our comprehension of the soil-plant system. With this research program, I will form 1 PhD, 2MSc, 3UG students that will help design and manage climate-smart soils and agroecosystems. Funding through a Discovery Grant represents a significant contribution to the huge efforts Canada must make to fulfill the Paris Agreement engagements and achieve carbon neutrality by 2050.