An automated soil CO2 flux chamber system to study forest soil carbon budget

第68届联合国大会宣布2015年为国际土壤年（IYS 2015; FAO，2015）。2015年国际土壤年的主要目标之一是倡导迅速提高各级（全球、区域和国家）土壤信息收集和监测的能力。土壤是粮食安全和基本生态系统功能的最重要因素之一。土壤储存了地球上最多的有机碳，其中最大的储量发现于北方温带和寒带地区。土壤有机碳的动态仍然知之甚少，是预测人类活动造成的未来气候变化情景的一个主要不确定点。森林在全球碳循环中发挥着不可或缺的作用，它通过光合作用吸收大气中的二氧化碳，并最终通过凋落物和根系分泌物将其沉积到土壤有机碳库中。森林也可以通过树木（主要是根系）的呼吸作用和分解沉积的凋落物的土壤微生物来释放碳。根系呼吸和土壤动物分解有机质引起的呼吸通常被称为总土壤呼吸。如果森林处于平衡状态，光合作用的吸收和呼吸作用的释放是平衡的。然而，这种平衡可能会受到土地使用的干扰，例如收获和气候变化。过去关于树木采伐对森林碳动态影响的许多研究都集中在地上碳过程和储量上。最近的一项综述明确指出，迫切需要研究分析采伐方法对森林土壤碳动态的长期影响，特别是在土壤有机碳储量最高的北方和北方温带森林（Clarke et al 2015）。由于缺乏对采伐和气候变化下土壤有机碳动态的了解而产生的不确定性，限制了我们制定强有力的未来气候预测以及森林管理政策和指导方针的能力。在本提案中，我们要求一个最先进的自动土壤CO2通量室系统，这将使我们能够在最近收获的松树种植园林位于南部安大略土壤二氧化碳（CO2）排放量的长期测量。我们将使用这些数据来量化和评估采伐对林分碳动态的影响。这些数据还将用于验证加拿大地球系统模型中使用的陆地表面模型-加拿大陆地表面碳氮方案。在这个项目中收集的数据将增加我们对土壤碳动态的理解，有助于改善气候预测，并告知当地森林管理者收获对森林土壤碳动态的影响。

The 68th UN General Assembly declared year 2015 the International Year of Soils (IYS2015; FAO, 2015). One of the main objectives of IYS2015 is advocating for rapid capacity enhancement for soil information collection and monitoring at all levels (global, regional and national). Soils are one of the most important factors for food security and essential ecosystem functions. Soils store the largest amount of organic carbon on Earth, with the largest stocks found in northern temperate and boreal regions. The dynamics of soil organic carbon are still poorly understood and are a major point of uncertainty in predicting future climate change scenarios due to anthropogenic actions. Forests play an integral role in the global carbon cycle by absorbing atmospheric carbon dioxide (CO2) through photosynthesis and eventually depositing it into the soil organic carbon pools through litterfall and root exudates. Forests can also loose carbon, through respiration by trees, mainly roots, and by soil microorganisms that decompose the deposited litter. Root respiration and respiration due to decomposition of organic matter by soil fauna is often referred to as total soil respiration. If a forest is in a state of equilibrium, the uptake due to photosynthesis and release due to respiration are balanced. However, this balance can be disturbed by land-use, such as harvesting and climate change. Many past studies on the impacts of tree harvesting on forest carbon dynamics have focused on above-ground carbon processes and stocks. A recent review has clearly identified an urgent need for studies that analyze the long-term impacts of harvesting methods on forest soil carbon dynamics, especially in boreal and northern temperate forests, which have the highest soil organic carbon stocks (Clarke et al 2015). The uncertainty resulting from the lack of knowledge on soil organic carbon dynamics under harvesting and climate change is limiting our ability to develop robust future climate forecasts and also forest management policies and guidelines that account for full carbon dynamics. In this proposal, we are requesting a state-of-the-art AUTOMATED SOIL CO2 FLUX CHAMBER SYSTEM, which will enable us to make long-term measurements of soil carbon dioxide (CO2) emissions in a recently harvested pine plantation forest located in southern Ontario. We will use these data to quantify and assess the harvest impact on the stand's carbon dynamics. These data will also be used to validate the land surface model, the carbon-nitrogen Canadian Land Surface Scheme (CN-CLASS), used in Canadian Earth System Model. Data collected in this project will add to our understanding of soil carbon dynamics, help improve climate predictions, and inform local forest managers on the impacts of harvests on forest soil carbon dynamics.