The role of microbes in soil organic carbon accumulation as a natural climate solution

森林对加拿大的经济和环境都很重要。一个好处是森林能够储存碳，这是二氧化碳的一个组成部分，二氧化碳是造成气候变化的重要温室气体。森林中储存的碳比大气中的碳多，其中大部分碳以土壤有机碳（SOC;半分解植物材料和微生物生物量的混合物）的形式储存。这种储存碳的能力导致了世界各地许多在以前的森林土地上植树的项目。加拿大政府已承诺种植20亿棵树，并推广改进的森林管理做法，以便到2050年实现温室气体净零排放。据认为，树木恢复可以作为一种自然气候解决方案（NCS），有助于限制全球变暖。但是，在森林土壤可以计入排放目标之前，还有许多重要的知识空白。 重要的是，过去的土地使用（例如农业）可能会在土壤上留下持久的遗产，影响其储存碳的能力。森林还受到环境变化的越来越大的压力，易受干旱等突发和剧烈的极端气候的影响，预计干旱的频率和强度将增加。目前尚不清楚这将如何影响树木恢复项目和森林管理。土壤微生物在调节土壤有机碳中起着关键作用，但易受环境变化的影响。SOC含量是微生物分解和并入微生物生物质中的碳的稳定化之间的平衡。这种平衡可能会发生变化，环境变化可能导致储存的SOC释放到大气中，进一步加速气候变化。我们对哪些因素知之甚少（例如，过去的土地使用）使土壤微生物容易受到极端气候的影响。这是一个重要的知识差距。 这个发现补助金将资助三个学生主导的研究主题。1)我们将确定微生物对树木恢复的反应及其对SOC储量的贡献。该项目将使用不列颠哥伦比亚省（BC）的树木恢复项目，并探索如何改进实践。2)我们将研究森林管理对SOC的长期影响，使用20世纪90年代初在BC建立的试验。3)我们将研究森林管理和历史土地利用是否允许微生物抵御极端气候，以及这如何影响SOC库存。该项目将在不列颠哥伦比亚省和实验室模拟现场的环境变化。 这三个主题将产生新的见解和减少不确定性的影响，过去的土地利用和环境变化的SOC动态树木恢复和森林管理。这项拟议的研究与不列颠哥伦比亚省政府的森林碳倡议和加拿大到2050年的净零温室气体排放目标保持一致，以实现最大的政策相关性，并将为新的树木恢复/森林管理政策提供基于证据的结果，作为不列颠哥伦比亚省和加拿大全国的NCS。

Forests are important to Canada both economically and environmentally. One benefit is the ability of forests to store carbon, a component of CO2 an important greenhouse gas (GHG) responsible for climate change. More carbon is stored in forests than is found in the atmosphere, with most of the carbon stored as soil organic carbon (SOC; a mixture of semi-decomposed plant material and microbial biomass). This ability to store carbon has led to many tree planting projects on formerly forested land throughout the world. The Canadian Government has pledged to plant 2 billion trees and promote improved forest management practices to achieve net-zero GHG emissions by 2050. It is thought that tree restoration could act as a Natural Climate Solution (NCS) helping to limit global warming. But there are many important knowledge gaps before forest soils can be counted towards emission targets. Critically, past land-use (e.g. agricultural) can leave lasting legacies on soil, that influence its ability to store carbon. Forests are also under increasing pressure from environmental change and are susceptible to abrupt and intense climate extremes, such as drought, that are expected to increase in frequency and intensity. It is not known how this will impact tree restoration projects and managed forests. Soil microbes play a key role in regulating the amount of SOC but are susceptible to environmental change. SOC content is a balance between microbial decomposition and stabilisation of carbon incorporated into microbial biomass. This balance can shift, with environmental change potentially resulting in stored SOC being released to the atmosphere, further accelerating climate change. We know little about what factors (e.g., past land-use) make soil microbes vulnerable to climate extremes. This is an important knowledge gap. This Discovery Grant will fund three student-led research themes. 1) We will determine the microbial response to tree restoration and their contribution to SOC stocks. This project will use tree restoration projects in British Columbia (BC) and explore how practices can be improved. 2) We will examine the long-term impact of forest management on SOC, using trials established in the early 1990s in BC. 3) We will examine whether forest management and historical land-use allow microorganisms to withstand climate extremes, and how this affects SOC stocks. This project will simulate environmental change in the field across sites in BC and in the laboratory. These three themes will generate new insights and reduce uncertainties of the effects of past land-use and environmental change on SOC dynamics following tree restoration and forest management. This proposed research aligns with the BC government's Forest Carbon Initiative and Canada's net-zero GHG emissions target by 2050 to have maximum policy relevance, and will provide evidence-based results for new tree restoration/forest management policies as a NCS in BC and across Canada.