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SOM是增加碳(C)储存、限制全球变暖和到2050年实现碳中和的最短期和最可行的选择之一。植物根系对SOM的贡献很大；活根释放渗出物，与共生微生物结合并缠绕土壤颗粒形成团聚体，而死根则是土壤中主要的碳和氮输入。然而，根系也可以通过刺激土壤微生物对SOM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。对根系如何影响土壤中碳氮保持和损失之间的平衡进行定量评估对于开发气候智能型土壤和农业生态系统以及增加土壤有机质和碳储量是必要的。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)表征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。该计划包括两个主要主题：(A)不同植物物种的活根和分解根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性状和土壤有机质。它包括受控条件下的实验室实验（主题A）和自然条件下的现场实验（主题B）。特定根系特征的形态、化学、建筑和生物特征，以及土壤密度部分中C、N、13C和15N浓度的分析，将允许追踪根系来源的C和N，并研究表层土壤（即0-20厘米深度）和底土（即0-20厘米深度）的SOM稳定机制。在加拿大东部，几乎没有数据来评估草地和作物种类、功能群和群落对C和N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。这一原创的、假设驱动的研究项目将为与减缓和适应气候变化有关的一些最重要问题提供新的知识。这个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。通过这个研究项目，我将培养1名博士，2名硕士，3名本科生，他们将帮助设计和管理气候智能型土壤和农业生态系统。通过“发现基金”提供的资金是加拿大为履行《巴黎协定》承诺、到2050年实现碳中和所必须做出的巨大努力的重要贡献。

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.