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Volume 9 Journal of Earth Science & Climatic Change Climate Change Congress 2018
November 22-23, 2018
November 22-23, 2018 Bucharest, Romania
8th International Conference on
Environment and Climate Change
Carmen Postolache, J Earth Sci Clim Change 2018, Volume 9
DOI: 10.4172/2157-7617-C6-054
Soil responses to nitrogen addition: Evidence from a natural grassland
Carmen Postolache
University of Bucharest, Romania
Over the last century, anthropogenic reactive nitrogen flows surpassed natural turnover rates, significantly altering its
biogeochemical cycle. Our study focuses on soil responses to nitrogen additions in a natural grassland from Neajlov
catchment (Romanian LTSER site). We used plots of 2 m2 for fertilization with NH4NO 3 to simulate increased bioavailable
nitrogen inputs of 0, 5 and 10 kg/ha/year which were fertilized during summer period. Topsoil samples were monthly collected
and analyses were performed in triplicates. For each replicate, we measured pH, soil water and organic matter contents, along
with enzymatic rates of nitrate reductase and urease. Inorganic nitrogen species were determined using spectrophotometric
methods after extraction with KCl. We assessed the mineralization potential of soil microbial community via ammonium
formation under hypoxic conditions. Study showed a slight acidification, more discernable for the highest nitrogen addition.
We noted a temporal accumulation of both nitrate and ammonium, especially during fertilization period. As expected,
enzymatic rates showed seasonal variation, but we documented lower rates as bioavailable nitrogen increased. We observed
strong correlations between soil extracellular enzymes and substrates, which were clearer when warm and cold season were
analyzed separately. Urease activity positively correlates with organic matter, R2 values of 0.31 (warm season) and 0.41 (cold
season), whereas R2 for nitrate reductase and N-NO3- were 0.49 and 0.47 respectively. Our findings suggest that more subtle
responses of nitrogen surplus are found at soil microbial community level and that a natural ecosystem is more able to absorb
this type of pressure.
Biography
Carmen Postolache is currently Dean of Faculty of Biology, Member of the University of Bucharest, Head of Research Platform in Biology and Systems Ecology,
Member of the Institute of Ecology and Environmental Management. She has obtained PhD degree (1999) in Chemistry at the University of Bucharest. Since 1991,
her research was focused on biogeochemical cycles of nutrients and heavy metals, ecotoxicology and water quality issues. In the last 20 years, she was a Member
of 19 national projects and Principle Investigator for Romanian team in 8 international projects. She published more than 50 papers in international journals.