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Macronutrient cycling in surface waters

large-scale patterns and assessment of global change

Khalili, Maria (2012). Macronutrient cycling in surface waters. Diss. (sammanfattning/summary) Uppsala : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2012:10
ISBN 978-91-576-7694-8
[Doctoral thesis]

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The levels and relative proportions of macronutrients set the conditions for life in surface waters. Man-made disturbances to macronutrient cycling have caused environmental problems such as eutrophication, acidification and global change. In this thesis, macronutrient cycling was studied by performing spatial and temporal large-scale studies of aquatic, terrestrial and atmospheric national monitoring data. Trophic status was found to have a profound impact on nitrate-nitrogen (NO₃-N) concentrations in surface waters. Lakes and streams of the same trophic status displayed opposite NO₃-N patterns. These findings are of great importance when dealing with environmental assessment on the landscape scale, and an awareness of these patterns may also facilitate the design of sampling programs. Trophic status also seems important for trends in total phosphorus (TP) and total organic carbon (TOC) concentrations in boreal and alpine catchments. A temporal study of TP and TOC concentrations showed decreases in nutrient-poor catchments and increases in more nutrient-rich surface waters. Different responses of terrestrial organic matter production and decomposition to temperature increases may be responsible for the observed patterns. Consequently, continued global warming may lead to a stronger polarization between the nutrient-poor northern and the more nutrient-rich southern catchments.

Further studies showed that nutrient conditions in soils and surface waters were strongly affected by atmospheric deposition. By using large data-sets on nutrient content in soils and nutrient concentrations in lakes, it was found that carbon to nitrogen ratios (C:N) in the organic soil layer and in lakes increased from the southern to the northern parts of Sweden, resulting in a strong relationship between soil and lake water C:N. The strong relationship was primarily due to the high correlation between nitrogen (N) in organic soil layer and lake N. Large-scale variations in soil C content were not strongly linked to lake C concentrations whereas soil N seemed to leach in the form of NO₃-N to lakes. By calculating catchment soil, lake and river mouth C stocks, it was estimated that about 10 % of Sweden's total terrestrial net ecosystem production is transported through lakes annually. This indicates that the amount of C exported from soils is substantial and that boreal soils maybe less important as a C sink as previously thought. Furthermore, it was found that the colored portion of C was selectively lost and that the decrease in water color was dependent on water retention time. This implies that under conditions predicted in future climate scenarios of increased precipitation, water reaching the seas will be more colored than today.

The results from this thesis highlight the importance of atmospheric N deposition and trophic status to macronutrient cycling in both terrestrial and aquatic ecosystems.

Authors/Creators:Khalili, Maria
Title:Macronutrient cycling in surface waters
Subtitle:large-scale patterns and assessment of global change
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :May 2012
Number of Pages:35
I.Khalili, M. I., Weyhenmeyer, G. A. (2009) Growing season variability of nitrate along a trophic gradient – contrasting patterns between streams and lakes. Aquatic Sciences 71(1), 25-33.
II.Khalili, M. I., Temnerud, J., Fröberg, M., Karltun, E. Weyhenmeyer, G. A. (2010). Nitrogen and carbon interactions between boreal soils and lakes. Global Biogeochemical Cycles 24(4), GB4011.
III.Weyhenmeyer, G. A., Khalili, M., Fröberg, M., Karltun, E., Kothawala, D., Temnerud, J., Tranvik, L. J. (2012). Selective decay of terrestrial organic carbon during transport from land to sea. Global Change Biology 18(1), 349-355.
IV.Khalili, M. I., Futter, M., Fölster, J., Lundin, L., Weyhenmeyer, G. A. Changes of phosphorus and carbon in Swedish boreal and alpine surface waters (manuscript).
Place of Publication:Uppsala
Publisher:Institutionen för vatten och miljö, Sveriges lantbruksuniversitet
ISBN for printed version:978-91-576-7694-8
Publication Type:Doctoral thesis
Full Text Status:Public
Agris subject categories.:P Natural resources > P10 Water resources and management
P Natural resources > P33 Soil chemistry and physics
T Pollution > T01 Pollution
Subjects:Obsolete subject words > NATURAL SCIENCES > Chemistry > Environmental chemistry
Obsolete subject words > NATURAL SCIENCES > Earth sciences
Agrovoc terms:rivers, lakes, nitrogen, carbon, phosphorus, cycling, soil, soil properties, atmospheric deposition, climatic change, water pollution, sweden
Keywords:nitrogen, carbon, phosphorus, lakes, streams, soil, atmospheric deposition, climate
Permanent URL:
ID Code:8798
Department:(NL, NJ) > Dept. of Environmental Assessment (until 080831)
External funders:Knut and Alice Wallenberg Foundation and Royal Swedish Academy of Sciences
Deposited By: phD-studen Maria Khalili
Deposited On:03 May 2012 08:39
Metadata Last Modified:02 Dec 2014 10:50

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