Effects of climate, disturbance and nitrogen fertilization on the carbon balance of forests in western canada

北方温带和北方森林是生物量和土壤碳(C)的大型储存库，对全球总光合作用做出了重大贡献。重要的是要更好地了解这些碳库对气候变化的反应，研究近年来干扰增加的影响，并制定管理做法，以提高它们的碳汇强度。这项研究将在北方、亚北方和西海岸温带森林中进行。我们的目标是(1)研究气候变化对净生态系统生产力(NEP)、总生态系统光合作用(P)和生态系统呼吸(R)的影响；(2)量化环境因子、物候学和P对R和土壤呼吸(Rs)的影响；(3)将Rs在其异养和根际成分之间进行分配；(4)评估氮肥对不同年龄的西海岸豆杉林碳平衡和N2O排放的影响。以及(5)确定山松甲虫(MPB)的攻击对成熟的亚北方小黑松林分碳平衡和水分平衡的影响。除了使用常规方法将NEP划分为P和R外，我们还将使用EC和室内测量13CO2同位素通量的方法，并使用可调谐二极管激光吸收光谱。异养呼吸将使用改进的沟槽小区根排除技术进行测量，并用于估计净第一性生产力。土壤N2O排放量将使用静态室的注射器采样进行测量。MPB攻击的时间效应将通过两个松林在攻击早期和后期的年度NEP测量来推断。因此，这项研究将提高我们对森林在全球气候系统和碳平衡中的作用的理解。量化施肥和MPB袭击的影响将有助于为加拿大制定一项战略，以增加其森林中的碳固存。这项工作将为C自行车模型的验证和两名M.Sc的合理训练提供有价值的数据。三名博士生，三名博士后研究员和四名技术人员。

Northern temperate and boreal forests are large reservoirs of biomass and soil carbon (C), and make a major contribution to gross global photosynthesis. It is important to better understand the response of these C pools to climate change, to study the impact of increased disturbance in recent years, and to develop management practices that will enhance their C sink strength. This research will be conducted in boreal, sub-boreal and West Coast temperate forest stands. Our objectives are to (1) study the impact of climatic variability on net ecosystem productivity (NEP), gross ecosystem photosynthesis (P) and ecosystem respiration (R), (2) quantify the effects of environmental factors, phenology and P on R and soil respiration (Rs), (3) partition Rs between its heterotrophic and rhizospheric components, (4) assess the effect of nitrogen fertilization on the C balance and N2O emissions in different-aged West Coast Douglas-fir stands, and (5) determine the impact of mountain pine beetle (MPB) attack on the C and water balances of mature sub-boreal lodgepole pine stands.   We will measure above-canopy CO2, water vapour and sensible heat fluxes using the eddy covariance (EC) approach. In addition to using conventional methods to partition NEP between P and R, we will use EC and chamber measurements of 13CO2 isotope fluxes with tunable diode laser absorption spectroscopy. Heterotrophic respiration will be measured using a modified trenched-plot root-exclusion technique and used to estimate net primary productivity. Soil N2O emissions will be measured using syringe sampling of static chambers. Temporal effects of MPB attack will be inferred from annual NEP measurements in two lodgepole pine stands at early and late stages of attack.   This research will improve our understanding of the role of forests in the global climate system and C balance. Quantification of the effects of fertilization and MPB attack will help develop a strategy for Canada to increase C sequestration in its forests. This work will provide valuable data to validate C cycling models and sound training of two M.Sc. and three Ph.D. students, three postdoctoral fellows and four technicians.