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中起着至关重要的作用。增加农业土壤中的有机质是增加碳（C）储存，限制全球变暖并在2050年达到碳中和的最短期和可行的选择之一。植物根系对土壤有机质的贡献很大;活根释放分泌物，与共生微生物结合，并与土壤颗粒形成团聚体，死根作为进入土壤的主要C和N输入。然而，根也可以通过刺激土壤微生物分解而使SOM不稳定。此外，全球变暖可能会影响植物和地下过程，但对土壤中C和N循环的影响仍不清楚。定量评估根系如何影响土壤中C和N保持和损失之间的平衡，对于发展气候智能型土壤和农业生态系统以及增加SOM和C储存是必要的。然而，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）描述温带农业生态系统中多年生和一年生植物的根系特征，（2）评估根系特征和气候变量如何影响SOM过程，以及（3）确定加拿大东部粘土表层土和底土中增加储存和限制C和N损失的根系特征。该计划包含两个主要主题：（A）不同植物物种的活根和分解根如何影响SOM和（B）气候变量和物种多样性如何影响根系性状和SOM。它包括受控条件下的实验室实验（主题A）和自然条件下的田间实验（主题B）。对特定根系性状的形态、化学、结构和生物特征，以及土壤密度组分中C、N、13 C和15 N浓度的分析，将允许追踪根源C和N，并研究表土中SOM的稳定机制（即，0-20 cm深）和底土（即，>20 cm深度）。几乎没有数据可以评估加拿大东部草原和作物物种、功能群和群落对碳和氮稳定的影响，也没有任何关于根系性状如何影响土壤功能的信息。这个原创的，假设驱动的研究计划将提供有关气候变化缓解和适应的一些最重要的问题的新知识。这项研究计划在功能生态学和土壤科学的前沿将通过在这些领域之间建立桥梁和填补我们对土壤-植物系统的理解的空白产生强大的影响。有了这个研究计划，我将形成1博士，2硕士，3UG学生，这将有助于设计和管理气候智能土壤和农业生态系统。通过发现补助金提供的资金是对加拿大为履行《巴黎协定》承诺和到2050年实现碳中和所必须做出的巨大努力的重大贡献。

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.