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Along with global warming and increasing levels of carbon dioxide in the atmosphere, nitrogen intake appears to be deteriorating for nature's terrestrial plants, reveals a recently published international study in Nature Ecology & Evolution.
"Although we have managed to stabilize the carbon dioxide content in the atmosphere at a low enough level to avoid the most severe consequences of climate change, many ecosystems more clearly show the evidence that they are being used. there is too little nitrogen on the ground rather than too much, "says Michael Gundale of SLU.
It is therefore all the more important to succeed in reducing our carbon dioxide emissions.
Too much or too little nitrogen?
The limits of the planet are a term frequently used in the current environmental debate. According to this concept, there are a number of environmental problems each of which has its own limit value, which can not be exceeded without the appearance of threshold effects that can lead to unpredictable environmental effects.
Such a limit concerns the amount of nitrogen that, with the help of humans, is introduced into the life cycle, for example through the production of manure. The role of nitrogen in the eutrophication of lakes and streams is known for a long time and it is often considered that the limits of the planet in terms of nitrogen says reagent have already been exceeded.
38 researchers participate in the international collaboration sought by the American researcher Joseph Craine. Sweden is represented by Michael Gundale of the Department of Ecology and Forest Management of the Swedish University of Agricultural Sciences.
At the same time, there is a fundamental uncertainty as to the true appearance of the trend in nitrogen input into the soil ecosystem. The carbon dioxide content has increased by more than 40% over the last 150 years, which has been positive for photosynthesis of plants and should have increased their nitrogen uptake by the soil. In addition, growing seasons longer than global warming will allow nitrogen plant requirements to be higher than those of some ecosystems.
Historical sheet analyzes show long-term trends
To get an idea of the trend, the researchers analyzed a database of chemical studies on the leaves of hundreds of plant species collected around the world between 1980 and 2017. The study is based on the nitrogen content of more than 43,000 samples. They found a global trend towards reducing nitrogen availability.
Most terrestrial ecosystems, such as forests and unfertilized land, become more oligotrophic, which means that there is not enough nutrients.
"Today, it is often emphasized that the environment is exposed to excessive atmospheric nitrogen deposition and ecological problems, which is certainly true in many areas and environments, but Now it seems that environments that are not strongly affected by nitrogen pollution are beginning to suffer from the opposite problem, namely that climate change is increasingly reducing the availability of nitrogen to nitrogen.
Limit the role of the forest in climate work
According to the article, the new study provides further evidence that forests will not be able to capture as much carbon from the atmosphere as predicted by many current climate models, as forest growth appears to be more limited by nitrogen deficiency than previously thought. This new information indicates that it is extremely urgent to reduce carbon dioxide emissions.
The article also mentions another possible consequence of the fact that ecosystems are becoming increasingly poor in nutritional terms: the decrease in plant protein levels also affects the phytophages that live there. However, this remains to be studied.
The role of Michael Gundale in this study was to provide data on Swedish forest ecosystems and to participate in the interpretation of the analyzes.
– The study shows the overall trend. Until now, however, there is no clear indication that Swedish forests are increasingly limited in nitrogen, but this requires in-depth studies. At the same time, a fairly recent study of Norwegian waters has shown that nitrogen levels have been steadily decreasing over the last 30 years.
L & # 39; section:
Isotopic evidence for the oligotrophication of terrestrial ecosystems. Nature Ecology & Evolution, Vol 2, November 2018, 1735-1744. Joseph M. Craine et al. 2018th
Contact:
Michael Gundale, researcher. Department of Ecology and Forest Care
Sveriges lantbruksuniversitet, Umea, [email protected]
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