WASHINGTON - A research at the University of Nebraska-Lincoln (UNL), US, 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 the research, UNL biologist Johannes Knops has demonstrated how one invasive plant species replaces native species 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, 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,” he added.

In other words, pines mine the soil for organic nitrogen, decrease soil fertility and use this nitrogen to outcompete other species.

According to Knops, the higher nitrogen residence time creates a positive feedback that redistributes nitrogen from the soil into the plant’s nitrogen cycling, and this strengthened the species to support its invasion.

“What this higher nitrogen residence time means is that the plant is taking nitrogen from the soil and using it to make the plant grow more efficiently, and it also gives them an upper hand in being able to invade other species,” he said.

This study is the first to study all together and pinpoint the mechanism that explains why this pine is a successful invader. (ANI)