Bacteria explain pine barrens ecosystem

The unusual dominance of a single type of underground bacteria in the Long Island pine barrens may explain why so few plants thrive there, according to a report published Thursday.

As early settlers soon discovered, not much grows in the pine barrens beyond the oaks, pines, beeches and berries that can tolerate the acidic, nutrient-poor soil.

To investigate why, scientists from Dowling College, Brookhaven National Laboratory and Southern University at New Orleans conducted the first in-depth analysis of the area's microbial communities.

The researchers sampled soil at 66 sites across the 100,000-acre pine barrens, extracting dirt from Rocky Point to Flanders and as far south as Shirley, said co-author Tim Green, BNL's natural resource manager.

Forest soils typically host a diverse range of bacteria. But in the pine barrens, scientists found that more than 41 percent of the microorganisms were ammonia oxidizers.

Those microbes convert ammonia, produced by decomposing leaves and plants, to other forms of nitrogen called nitrates and nitrites. Normally, they make up less than 1 percent of bacteria in soil.

Lead researcher Vishal Shah, a Dowling College microbiologist, called the discovery "unique," saying it was the first time such high levels of the bacteria have been identified in a terrestrial ecosystem. His team's findings were published in PLoS ONE, an online open-access scientific journal.

Such high concentrations of ammonia oxidizers in the soil would likely leave little nitrogen behind to nourish plants, Shah said. While ammonia tends to stick to soil, nitrates are highly soluble and are easily washed away by rain.

That could explain why plants that thrive in low-nitrogen conditions, such as oaks and huckleberries, predominate in the pine barrens, according to the report.

For now, that's just a theory that Shah and his team are testing in the lab.

"Now that we have isolated the organisms from the pine barrens soil, we are going to investigate the rate at which it uses up ammonia," Shah said.

Green called the research "an important step" to understanding the pine barrens ecosystem.