NitrogenFeedbacks of peatland ecosystems to climate change and nitroAcknowledgementsBledzki, L. A. and J. L. Bubier. 2004 (in press). Bioskop, 2004 (3): 0-0 (org. in Polish) Application of Li-Cor portable CO2 system to evaluate the influence of climate change and nitrogen deposition on peatland ecosystems Approximately 6% of the world’s surface is covered by wetlands, with at least 238 million hectares covering North America. One of the most abundant wetland types in the northern hemisphere is the northern peatland, where deep peat accumulations that have filled in lake basins that formed during the last glacial period can act as controls on global climate1. Functioning of peatland ecosystems are driven by two major cycles, namely N (nitrogen) and C (carbon). Nitrogen The chemical element nitrogen has the greatest total abundance in Earth’s atmosphere, hydrosphere, soils and waters, but more than 99% of this N is in the form not available to more than 99% of living organisms. Breaking the triple bound holding the two N atoms together requires a huge amount of energy, that can be processed in high-temperature (the Haber-Bosh process) or by small number of specialized N-fixing microbes2,3. In nature we divide the N compounds into two groups: nonreactive and reactive. Nonreactive N is N2; reactive nitrogen (Nr) includes all biologically, photochemically and radiatlvely active N compounds. Nr includes inorganic reduced forms of N (ammonia – NH3, ammonium ion – NH4+), inorganic oxidized forms (nitrous oxide N2O, nitrogen oxide – NOx, nitric acid – HNO3, nitrate NO3-, nitrite NO2-), and organic compounds (urea, amines, proteins, nucleic acids)2. In the prehuman world, creation of Nr from N2 occurred in nature through two processes, lightning and biological nitrogen fixation. Nr did not accumulate in the environment because of bacterial denitrification processes balancing N fixation. Human environment alteration changed that and now Nr is accumulating in the environment on all spatial scales (local, regional, global). Since about 1965, production of Nr by human has been greater than production from all natural systems. Now the global increase in Nr production has three major causes: agriculture cultivation of plants that promote N fixation (legumes, rice and other crops), fossil fuel combustion, the Haber-Bosch process to produce fertilizers used in intensive agriculture. Currently humans produce about twice the amount of Nr created naturally, and global nutrient inputs will accelerate over the nest 100 years (30% in nest 30 years) because of increased consumption of fossil fuels and further intensifications of agriculture. In this century the global impact of increased nutrient inputs may exceed the effects of global warming3-6. Nr accumulation contribute many environmental problems: 1) Increases in Nr lead to increased production of tropospheric ozone and aerosols that induce serious respiratory illness, cancer and cardiac disease. 2) Forest and grassland productivity increase and then decrease when Nr deposition increases above the critical thresholds, this also decrease biodiversity in many natural habitats. 3) Nr (together with S) is responsible for acidification of lakes, streams and forests. 4) Nr is responsible for further eutrophication, hypoxia, habitat degradation of lakes and coastal ecosystems. 5) Nr contributes to global climate change and stratospheric ozone depletion, both have impacts on human and ecosystem health2.Bledzki, L. A. and J. L. Bubier. 2004 (in press). Bioskop, 2004 (3): 0-0 (org. in Polish) • Historical context3 • The late 18th century – nitrogen was discovered through the work of several chemists Scheele (1742-1786, Sweden), Rutherford (1749-1819, Scotland), Lavoisier (1743-1794, France), and named “nitrogene” by Chaptal (1756-1832, France). • The mid-19th century nitrogen’s role in crop production by Boussingault (1802-1887) and more deeply by von Liebig (1803-1873), the author of the theory of nutrient limitation. • The end of the 19th century Hellriegel (1803-1873) and Wilfarth (1853-1904) discovered N fixation by microbial communities. • In 1898, Sir William Crookes, president of the British Association for the Advancement of Science, stated that “…all civilized nations stand in deadly peril of not having enough to eat” due to the increasing demands for food and the lack of biologically available nitrogen. This triggered a global search and guano and nitrate deposition in South America were discovered and minded. • In the beginning of 20th century the fossil fuels exceeded biomass fuels in supplying primary energy, that also produces Nr. • In 1913 invention of a chemical process to convert atmospheric N2 to NH3 known as Haber-Bosh process, which allows for unlimited supply of biologically available nitrogen that can be used as fertilizer. • Presently more then half of the food eaten by the world’s human population is produced using N fertilizer from the Haber-Bosh process. Carbon and Peatlands Peatlands serve as large reservoirs of organic C (fixed from atmospheric CO2) that have accumulated since the last glacial period and holds one-third of the world’s soil C pool7. The highest rate of accumulation occurs in colder and more humid climate conditions. This surplus is equal to approximately 100 years worth fossil fuel consumption8 and if decomposed, would increase atmospheric CO2 in an amount equal to the global build up that has taken place over the past 1000 years3. This indicates that this significant sink of CO2 may drive the glacial/interglacial cycle. The present interglacial period is characterized by large amounts of the global C pool being stored in the living biota. Peatlands are able to lower atmospheric C level due to plant growth and slow rate of decomposition. This means that if enough C is removed from the atmosphere, the greenhouse effect will be lowered below its critical level, that can trigger of a glacial period9, but increasing levels of atmospheric C, due to anthropogenic activities can perpetuate an interglacial period. Increasing level of atmospheric CO2 will increase the temperature and in turn release more CO2 (and methane,) from peatlands to the atmosphere. Both, CO2 and methane are greenhouse gases that can contribute to global warming. Feedbacks of peatland ecosystems to climate change and nitrogen depositionBledzki, L. A. and J. L. Bubier. 2004