Effects of atmospheric Nitrogen pollution on Soil Carbon Sto rage and Greenhouse Gas Emission from Forests Soils

森林生态系统的保护支持一系列重要功能，包括为野生动物提供栖息地、调节水资源和捕获大气中的二氧化碳（CO2），以便长期储存在土壤和生物质中。森林捕获了全球人类活动排放到空气中的二氧化碳的三分之一，植树造林越来越被认为是减缓气候变化的一个重要自然选择。森林在土壤中长期储存碳（C）的能力取决于森林产生的C的质量/数量，而这又受到森林主要环境的影响。农业产生的大气氮污染物，包括活性氮（氨和氮氧化物）的沉积也会影响附近的森林碎片。由于森林是大气污染物的有效清除者，活性氮的这种沉积在碎片的边缘比在内部更高。在活性氮沉降促进森林生长的同时，它也会增加一种强有力的温室气体--一氧化二氮的排放，对全球变暖产生负面影响。最近的研究表明，活性氮沉降通过促进土壤微生物的分解，增加了土壤碳的流失。在森林边缘，碳的损失和土壤中一氧化二氮排放量的增加都可能是最高的。然而，这些过程在氮饱和度较高的森林中鲜为人知。因此，本研究旨在探讨活性氮沉降对森林土壤碳质量、分解速率、微生物群落功能和温室气体排放的影响。这将在氮沉积强度梯度上进行探索，从边缘进入森林内部，位于农业景观中。这项工作将在英国进行，包括在英国森林研究所实习和在CEH进行同位素培训，以及在加拿大劳伦特大学进行微生物实验，以实现目标。主要预期成果将是对改变重要森林功能的沉积水平/阈值有新的认识。我们将对农业景观中森林的大小和形状提出建议，以提高森林的环境质量功能。

Conservation of forest ecosystems support a range of vital functions including providing habitat to wildlife, regulation of water resources and capturing atmospheric carbon dioxide (CO2) for long-term storage in soils and in biomass. Forests capture about 1/3rd of the CO2 emitted into air due to human activities globally and afforestation is increasingly being recognised as a crucial natural option for mitigating against climate change. The ability of forests to store carbon (C) in soil on a long-term basis depends on the quality/quantify of C produced by forests, which in turn is influenced by the prevailing environments of the forests.Deposition of agriculturally-derived atmospheric nitrogen pollutants, including reactive nitrogen (ammonia and nitrogen oxides), can also impact nearby forest fragments. As forests are effective scavengers of atmospheric pollutants, this deposition of reactive nitrogen ishigher at the edges of fragments than in the interior. Whilst reactive nitrogen deposition enhances forest growth, it also causes an increase in the emission of a potent greenhouse gas-nitrous oxide, with negative implications for global warming.Recent research has shown that reactive N deposition increases the loss of soil C through enhanced decomposition by soil microbes. Both losses of carbon and enhanced soil nitrous oxide emissions can be highest at the edges of forests. However, these processes are less known in more nitrogen saturated forests. Therefore, the aim of this research is to investigate the impacts of reactive nitrogen deposition on forest soil carbon quality, decomposition rates, microbial community functions and greenhouse gas emission. This will be explored across a gradient of nitrogen deposition intensity, moving from the edges into the interior of forests, located in agricultural landscapes. The work will be undertaken in Britain including an internship at Forest Research and isotopic training at CEH in UK and microbiology experimentation at Laurentian University, Canada to achieve the objectives.The key expected outcome will be to develop a new understanding of the levels/thresholds of deposition that alters important forest functions. The new knowledge we will make recommendations as to the size and shape of forests in agricultural landscapes for enhancing environmental quality functions of forests