Nutrient limitation in tundra

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Effects of a changing climate have already been observed in alpine and arctic tundras. Examples of this are melting permafrost, glacier retreats, an earlier snowmelt and longer growing seasons. Also a vegetation response has been observed in various parts of the arctic, such as an upward movement of the tree line in some areas and a more extensive growth of shrubs at the expense of mosses and lichens.

Tundra [1] vegetation is limited by a short growing season and low temperatures, leading to slow decomposition rates and short supplies of essential elements such as the macronutrients nitrogen and phosphorus. (17 of the natural occurring elements have shown to be essential for plants, meaning that plants require them to grow and complete their life cycle. These elements are divided into macro- and micronutrients, meaning that macronutrients are required in relatively large amounts and micronutrients in smaller amounts.)(1) Nitrogen is available to plants in the mineral forms ammonium (NH4+), nitrite (NO2-) and nitrate (NO3-) converted by microbes from organic nitrogen through the processes of nitrogen mineralization and nitrogen nitrification. In soil, cations as ferric iron (Fe3+), aluminium (Al2+) and calcium (Ca2+) have the capacity to strongly bind in mineral and organic forms of phosphorus to form relatively insoluble substances less available for microbes and plants (2). Understanding how the relative limitation of nitrogen and phosphorus in the subarctic is influenced by temperature is essential to the long-term understanding of how global warming may influence ecosystem processes such as decomposition, nutrient mineralization and vegetation response in this region.

Image:Tabell.jpg Image:Essential elements for plant growth.jpg

References

(1) Brady N C & Weil R R (2008) The Nature and Properties of Soils. Pearson Education, 14th edition, pp. 965

(2) Giesler R et al. (2004) Microbially Available Phosphorus in Boreal Forests: Effects of Aluminium and Iron Accumulation in the Humus Layer, Ecocystems 7: 208-217

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