Effects of atmospheric Nitrogen pollution on Soil Carbon Storage and greenhouse gas emission from forests soils.

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 is higher 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.