Nitrogen research shows how some plants invade, take o...( Biologists know that when plants bat...)

Biologists know that when plants battle for space, often the actual battle is for getting the nitrogen.

Now, research at the University of Nebraska-Lincoln gives important new information on how plants can change "nitrogen cycling" to gain nitrogen and how this allows plant species to invade and take over native plants.

In an article published July 6 in the scientific journal Proceedings of the National Academy of Sciences, UNL biologist Johannes "Jean" Knops demonstrates why one invasive plant species is replacing native species -- it's because of its ability to take up and hold on to nitrogen.

Biologists know that nitrogen is crucial to plant growth that invasive species often grow better and acquire more nitrogen, but have been uncertain about which mechanism allows invasive species to gain an advantage.

Over seven years' study at the Cedar Creek Ecosystem Science Reserve in central Minnesota, Knops and PhD candidate Ramesh Laungani studied the nitrogen pool and fluxes in the ecosystem that included seven grassland and forest species, including the Eastern white pine (Pinus strobus), a species that is rapidly invading Minnesota prairies. Over time they discovered that the pine had accrued nearly twice as much biomass as the next most productive species, and more than three times as much biomass relative to the other species.

"The higher productivity of the white pine is caused by an increased biomass nitrogen pool that was not driven by increased ecosystem level nitrogen inputs," Knops said. "But we found the white pine takes up nitrogen and holds on to it much longer, with leads to an accumulation of much more nitrogen in the plant and a depletion of nitrogen in the soil. We concluded high nitrogen residence time was the key mechanism driving the significantly higher plant nitrogen pool and the high productivity of that species."

In other words, pines mine the soil for organic nitrogen, de
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