Tree species composition influences nitrogen loss fr...( MADISON WI MARCH 16 2009--Throughout...)

MADISON, WI, MARCH 16, 2009--Throughout the world, nitrogen compounds are released to the atmosphere from agricultural activities and combustion of fossil fuels. These pollutants are deposited to ecosystems as precipitation, gases, and particles, sometimes many hundreds of miles downwind of their release point. The Catskill Mountains of southeastern New York are a case in pointthough they contain little in the way of industrial or agricultural pollution sources, they receive some of the highest nitrogen deposition rates in North America due to pollutants drifting in from midwestern power plants and east-coast cities.

Anyone who grows plants for food, fiber, or flowers, knows that nitrogen is crucial for healthy plant growth. But excess nitrogen that leaches from a forest can acidify the soils and streams and decrease water quality. Prior research has shown that in addition to plant uptake, microbial processes are very important in retaining nitrogen in forest soils, and that forested watersheds in the Catskills vary markedly in the amount of nitrogen they can absorb and prevent from leaching away. So why would atmospheric nitrogen deposition lead to increased losses of nitrogen from some forests and not from others? A study funded by the National Science Foundation and the U.S. Department of Agriculture provides some answers. The research, which is focused on the tree species control on nitrogen cycling dynamics in the Catskill Mountains, is published in the March-April 2009 issue of the Soil Science Society of America Journal.

Part of a long-term research project on nitrogen cycling in Catskill forests, this study utilized a stable isotope technique to determine how the microbes consume and transform nitrogen in the soil under stands of five different tree species that are common in the Catskills. Half of the forest plots also had experimental nitrogen fertilizer treatments. The study showed that forests dominated by sugar maple are
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