N trace gas emissions from tropical savanna ecosystems and responses to global changes

热带稀树草原生物群落覆盖了全球陆地表面的11.5%。这些生态系统的稀树草原土壤被认为对全球大气中一氧化二氮（N2 O）和其他重要的大气痕量气体（NO，CH 4，CO2）的浓度有很大贡献。热带稀树草原的特点是由一个强大的季节性的干燥和潮湿的季节，与再湿事件大多伴随着显着的脉冲排放的N和C微量气体。频繁的火灾事件诱发土壤-大气交换的进一步变化，由于N和C输入通过凋落物，存储，损失的影响，因此，在土壤中的养分的可用性。与热带稀树草原系统对全球大气N示踪气体收支的重要性相反，土壤-大气示踪气体交换的原位测量相对较少，并且关于汇/源强度的估计仍然高度不确定。我们将使用国家的最先进的实验和建模方法，以提高在热带稀树草原在当前环境条件下的N和C转化过程的理解和预测未来的土地利用和气候。将在澳大利亚热带稀树草原对氮和碳微量气体交换和基本环境过程控制进行详细的高时间分辨率实地测量（至少涵盖全年），并将与澳大利亚伙伴机构正在进行的项目的补充数据相结合。澳大利亚热带稀树草原覆盖了大约20%的大陆，并且沿着陡峭的降雨和温度梯度，因此，覆盖了广泛的气候和环境条件，这对于世界上其他热带稀树草原地区具有代表性。因此，该项目将产生不仅适用于澳大利亚而且适用于其他大陆的热带草原系统的数据和模型。我们与澳大利亚研究人员的密切合作将提高拟议项目以及澳大利亚合作伙伴项目（澳大利亚研究理事会联系项目LP 0774812-热带稀树草原生态系统总温室气体平衡和养分循环的干扰和土地使用变化综合评估）的研究成果的质量。来自这两个项目的数据将用于开发和完善地球化学模型ForestDNDC-tropica /移动的。模型开发将基于先进的贝叶斯校准技术，并将首次提供模型参数和模型输出的详细不确定性评估。此外，通过在我们的模型框架中实施既定的火灾模块，我们将能够模拟火灾管理，土地利用和气候变化对热带稀树草原生态系统养分周转的综合影响。改进后的模型将被用来调查营养循环和土壤大气交换的N和C微量气体的热带稀树草原生态系统的北方澳大利亚，特别是包括火灾的影响。此外，ForestDNDC-tropica /移动的模型将耦合到一个GIS数据库，用于计算热带澳大利亚稀树草原系统的N示踪气体交换的库存。将进行具体的模型模拟，涵盖预计的气候影响（例如，干旱和火灾强度和频率的变化）和土地利用变化情景，以评估其对生态系统氮营养循环和相关微量气体交换的影响。

The tropical savanna biome covers approximately 11.5% of the global land surface. Savanna soils of these ecosystems are thought to contribute substantially to the global atmospheric concentration of nitrous oxide (N2O) and other important atmospheric trace gases (NO, CH4, CO2). Savannas are characterised by a strong seasonality of dry and wet seasons, with rewetting events mostly accompanied by significant pulse emissions of N and C trace gases. Frequent fire events induce further variability in the soil-atmosphere exchange due to effects on N and C inputs via litter fall, storage, loss and, thus, availability of nutrients in the soil. In contrast to the importance of savanna systems for the global atmospheric N trace gas budgets only relatively few in-situ measurements of the soil-atmosphere trace gas exchange have been performed and estimates about the sink/ source strength are still highly uncertain. We will use state-of-the-art experimental and modelling approaches to improve the understanding of N and C transformation processes in savannas under current environmental conditions and predicted future land-uses and climate. Detailed high time resolution field measurements (covering at least an entire year) on N and C trace gas exchange and underlying environmental process controls will be conducted in Australian savannas and will be combined with supplementary data from ongoing projects of Australian partner institutions. Australian savannas cover approximately 20% of the continent and occur along a steep rainfall and temperature gradient, thus, covering a wide range of climatic and environmental conditions, which are representative for other savanna regions worldwide. Therefore, this project will generate data and models which are applicable not only for Australian but also for savanna systems of other continents. Our close collaboration with Australian researchers will enhance the quality of research outcomes from the proposed project as well as the Australian partner project (Australian Research Council Linkage project LP0774812 - Integrated assessment of disturbance and land-use change on total greenhouse gas balance and nutrient cycling in savanna ecosystems ). Data from both projects will be used to develop and refine the biogeochemical model ForestDNDC-tropica / MOBILE. Model development will be based on advanced Bayesian calibration techniques and will, for the first time, provide a detailed uncertainty assessment of model parameters and model outputs. Furthermore, by implementing an established fire module in our model framework we will be able to simulate the combined effects of fire management, land-use and climate change on nutrient turnover in tropical savanna ecosystems. The improved model will be used to investigate nutrient cycling and the soilatmosphere exchange of N and C trace gases for a range of tropical savanna ecosystems of Northern Australia, specifically including the effect of fire. Further, the ForestDNDC-tropica / MOBILE model will be coupled to a GIS database for calculating inventories of N trace gas exchange for the savanna systems of tropical Australia. Specific model simulations will be conducted covering projected climatic effects (e.g., changes in drought and fire intensity and frequency) and land-use change scenarios for this region in order to assess their impact on ecosystem N nutrient cycling and associated trace gas exchange.