Plants and Nitrogen – a love & hate relationship
Author: Melanie Batista of Universidade de Lisboa
I want to tell you about my visit to the LTER site at Whim Bog, Edinburgh, Scotland. The Centre for Ecology & Hydrology, based on the Natural Environment Research Council, manages a LTER site with facilities to study the effects of dry and wet nitrogen deposition. Nitrogen is an essential element for plant growth, however, like everything in life, too much is just too much. Wet deposition occurs when nitrogen enters the system in the form of precipitation, and dry deposition refers to forms of nitrogen dissolved in the atmosphere. Excess of nitrogen can lead to severe changes in ecosystems, especially if they are oligotrophic – meaning that they are adapted to low nutrient conditions. Studying these changes is exactly what this LTER site is about. The site is a peatland ecosystem, dominated by the shrub Calluna vulgaris and the sedge Eriophorum vaginatum.
During my visit I studied the effects of dry deposition of nitrogen in the plant community – I assessed plant diversity and structure, using a set of transects along a gradient of ammonia (NH3). This gradient is imposed to the plant community by an automated free air release facility that releases gaseous ammonia. The system fumigates only when wind speed and direction are within determined values, creating an ammonia gradient covering about 60 m in extend, with ammonia values ranging between ambient (c. 0.5 NH3 µg m-3) and 100 µg NH3 m-3 (annual averages).
One last thing about the Scottish experience. You ever heard about midges? Before my trip to Edinburgh I never heard about them. And, until my last day of my field work, when I was starting to think the midges were little more than a myth, they appeared in full force. It seems that until then there were never the perfect conditions. But, on that last afternoon, the sun shone brightly after a light rain, the wind had stopped blowing, and from one second to another, millions of little flying dots appeared from under the shrubs to land on our hands, faces, ears… everywhere. So I learned what midges are.
About the author
Melanie is a fellowship researcher at the Centre for Ecology, Evolution and Environmental Changes, Universidade de Lisboa. She studies plant functional diversity, mainly of the Mediterranean vegetation in Portugal, in response to different environmental changes, such as desertification and grazing.
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