Vegetation and soils already subjected to long-term acid rain could face even more stress in the form of nitrogen-laden precipitation, according to William D. Bowman, professor of ecology and evolutionary biology at the University of Colorado at Boulder.
In a paper released this week in the journal Nature Geoscience, Bowman detailed his study of acid precipitation on grassland soils of the Western Tatra Mountains of Slovakia. The study site received high levels of acid precipitation during the Soviet era of industrialization in Eastern Europe. Soils at their research site are at an unprecedented level of acidification, similar to those found near acid-mine drainage sites.
"Soluble iron is increasing in the soils, while aluminum, the usual toxic culprit damaging plants and soil organisms, is decreasing," said Bowman.
In addition to extreme soil acidification, plants at the research site decreased growth when subjected to simulated levels of nitrogen pollution expected to occur in the next several decades. Plants typically increase growth when given additional nitrogen, but the loss of important plant nutrients, such as calcium, which are already extremely low in soils impacted by acid precipitation, coupled with the toxic aluminum and iron, inhibit plant growth.
"Some plants may be more susceptible than others," said Bowman, "but the combined levels of iron and aluminum that we've observed will negatively impact most vegetation. This study is a good example of the juncture between soil chemistry and ecosystem function. It also reminds us that chemical pollution is still a problem in many regions of the world."