Carbon forms and fluxes in different land use systems

增加土壤中的碳(C)储量对于缓解快速变化的全球气候具有重要意义。边际农地造林被认为是增加土壤碳储量的可行选择。然而，土地利用变化，特别是植树造林对土壤碳动态的影响是复杂的，人们对此知之甚少。在这项研究中，我们将研究加拿大西部草原-森林过渡带的四种不同的土地利用系统，即农业、草地、人工林和原生林。我将1)调查土地利用变化对每个土地利用系统中二氧化碳(包括土壤微生物和根部微生物)、甲烷和一氧化二氮排放的影响及其导致全球变暖的潜力；2)评估冬季土壤温室气体(GHG)排放对年排放量的相对贡献及其受土地利用变化的影响，以帮助了解不同土地利用系统的温室气体年总通量；3)评价土地利用变化对土壤有机碳形态(包括低分子有机酸)及其在底土中的分布的影响；以及4)土壤有机碳形态与土壤碳稳定性的关系。这项研究将全面核算所有三种痕量温室气体以及不同土地利用系统中温室气体排放的全年比率，从而为计算国家温室气体排放清单提供急需的数据，因为需要针对具体国家的方法来考虑区域气候和土地利用对温室气体排放的影响。这些数据将有助于确定每个土地使用系统的排放系数，使各国政府能够调整政策，促进那些提供更大环境服务的土地使用系统。将研究植树造林通过增加整个区域的碳固存和碳稳定来缓解气候变化的潜在好处。因此，这项研究将为土壤有机碳稳定机制和土地利用变化对温室气体排放影响的机制提供新的信息。这项研究最终将对气候变化的国际条约谈判产生影响。

To increase carbon (C) storage in the soil is important for mitigating the rapidly changing global climate. Afforestation of marginal agricultural land is considered a viable option for increasing soil C storage. However, the effects of land use change, afforestation in particular, on soil C dynamics are complex and poorly understood. In this research we will study four different land use systems, agricultural, grassland, forest plantation and native forests in the grassland-forest transition zone across western Canada. I will 1) investigate the effect of land use change on the emission of carbon dioxide (both by soil microbial organisms and by roots), methane and nitrous oxide, and their resulting global warming potential in each land use system; 2) evaluate the relative contribution of winter soil greenhouse gas (GHG) emissions to annual emissions and how that is affected by land use change, to help understand the total annual GHG fluxes of the different land use systems; 3) evaluate the effects of land use change on soil organic C forms, including low molecular weight organic acids, and C distribution in the subsoil; and 4) relate soil organic C form to soil C stability. This study will provide a full accounting of all three trace GHGs and on year-round rates of GHG emissions in different land use systems and will thus provide the much needed data for the calculation of national inventories of GHG emissions, as country-specific methodologies are needed to account for the impact of regional climate and land use on GHG emissions. Such data will help determine the emission factor for each land use system, allowing governments to adjust policies that will promote those land use systems that provide greater environmental services. The potential benefit of afforestation for climate change mitigation through increased C sequestration and C stability across the region will be studied. This study will thus provide novel information on the mechanisms of soil organic C stabilization and the mechanisms underlying the effects of land use change on GHG emissions. This research will eventually have implications for international treaty negotiations on climate change.