Carbon sequestration in managed forest and grassland ecosystems in Western Canada

科学界普遍认为，气候变化正在发生，而且部分是由人类活动引起的，因为它是由大气中温室气体的增加引起的。最臭名昭著的温室气体二氧化碳的增加主要是由于化石燃料的燃烧和土地利用的变化。陆地生态系统有可能通过将大量碳封存到其生物量或土壤成分中来遏制这些排放。然而，使用陆地生态系统作为一种缓解措施需要进一步的定量证据。我的研究项目考察了气候变化、自然和人为干扰的影响，以及对森林和草原生态系统碳封存的管理实践。我采用自下而上的方法，利用光合作用和呼吸作用的二氧化碳通量室测量，将二氧化碳的组分通量划分和扩大到生态系统水平。通过量化土壤、草地和森林地面植被以及林下和林下灌木和乔木成分的贡献，我量化了这些生态系统的汇或源强度，并评估了它们对不同管理措施（如氮肥和放牧）的反应。通过我的研究项目获得的结果大大增加了我们对森林和草原生态系统在全球碳循环中的作用的理解，以及它们如何应对不同的管理实践和气候变化。它们有助于开发和参数化更好地管理自然资源所需的森林和草地生产力模型，并帮助加拿大在其管理的生态系统中增加碳固存。它们还使加拿大能够制定战略来履行其《京都议定书》的承诺。

There is a general scientific consensus that climate change is occurring and that it is partly induced by human activity as it is caused by an increase in greenhouse gases in the atmosphere. The increase of the most notorious greenhouse gas, carbon dioxide, is mainly due to the burning of fossil fuels and land-use change. Terrestrial ecosystems have the potential to curb these emissions by sequestering large amounts of carbon into their biomass or the soil component. The use of terrestrial ecosystems as a mitigation measure requires, however, further quantitative evidence. My research program examines the influence of climate variability, natural and anthropogenic disturbances, as well as management practices on the carbon sequestration of forest and grassland ecosystems. I use a bottom-up approach, using carbon dioxide flux chamber measurements of photosynthesis and respiration, to partition and scale up component fluxes of carbon dioxide to the ecosystem level. By quantifying the contribution of the soil, grassland and forest-floor vegetation, as well as understory and overstory shrub and tree components, I quantify the sink or source strength of these ecosystems and I assess their responses to different management practices such as nitrogen fertilization and cattle grazing. The results that are obtained through my research program significantly increase our understanding of the role of forest and grassland ecosystems in the global carbon cycle and how they respond to different management practices and climate change. They help in developing and parameterizing forest and grassland productivity models needed to better manage natural resources and help Canada increase carbon sequestration in its managed ecosystems. They also allow Canada to develop strategies to meet its Kyoto commitments.