It's because of biological interactions that occur naturally in the forests, Brookshire and four colleagues said in a paper they published Jan. 15 in the online version of the journal Nature Geoscience.
Disputing some long-held beliefs about high nitrogen levels in tropical forests, Brookshire said pollution isn't always the reason behind it. It can also be caused by natural interactions between the forest and nutrient cycles. Brookshire and his team suggested that in mountainous tropical forests, nitrogen availability may not limit plant growth or its response to higher carbon dioxide levels in the atmosphere.
Brookshire began his study in 2006 when he was a postdoctoral researcher at Princeton University. He continued it after moving to MSU in 2009. He is now an assistant professor in the Department of Land Resources and Environmental Sciences.
To conduct their study, Brookshire, two scientists from Princeton University and two researchers from the Stroud Water Research Center in Avondale, Pa., used data collected between 1990 and 2008 to examine the concentration of dissolved nitrogen compounds and the isotopic composition of nitrate in streams in six mountain forests in Costa Rica and 55 mountain forests across Central American and the Caribbean.
All of the forests were old-growth tropical forests with no signs of large-scale disturbance. They were classified as mountain evergreen, mountain rainforest or cloud forest. Evergreen forests in Costa Rica are at lower altitudes. Rainforests are at higher elevations. Cloud forests are at the highest elevation. They are bathed in clouds or moisture for much of the year.
The researchers also examined new samples that Brookshire collected in Costa Rica and Trinidad. Sampling was an exciting process that involved hiking through thick forests and swimming through narrow rock gorges, Brookshire said. He was able to avoid snake bites, but not the stinging insects or oppressive humidity.
"You don't dry out," Brookshire said.
The research team found high levels of nitrate in the streams of the tropical forests, indicating large losses of bioavailable nitrogen, Brookshire said. They also found evidence that the loss wasn't recent or a one-time thing. They discovered that the nitrate resulted from plant-soil interactions and not directly from atmospheric deposition.
Tropical forests are significant reservoirs for carbon, and their future relies on forest interactions with nutrient cycles, he said.
Scientists in the past have compared the effect of industry and agriculture on the temperate forests of the northern hemisphere, but relatively little research has been conducted on forests near the equator, Brookshire said. He decided to look at forests in Costa Rica and Trinidad because he already had colleagues there and they, like him, were intrigued by the fact that some tropical forests have dramatic nitrogen exports without apparent human causes.
"These systems have a natural capacity to build up levels of nitrates in soil that we only see in the most polluted temperate forests," Brookshire said.
The research published in Nature Geoscience will continue, Brookshire said.
"This is an on-going research project to figure out how forests work in the larger earth climate system and how they might respond to global change," Brookshire said. "The deep mysteries about how these ecosystems work, we are just beginning to understand. Things are much more complex than previously thought."
Co-authors on the Nature Geoscience paper were Lars Hedin and Daniel Sigman at Princeton University, and Denis Newbold and John Jackson from the Stroud Water Research Center. Their research was supported by grants from the A.W. Mellon Foundation, the National Science Foundation, the National Oceanic and Atmospheric Administration and research endowments at Stroud.
Evelyn Boswell | EurekAlert!
Gas hydrate research: Advanced knowledge and new technologies
23.03.2018 | Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ
New technologies and computing power to help strengthen population data
22.03.2018 | University of Southampton
Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
23.03.2018 | Event News
19.03.2018 | Event News
16.03.2018 | Event News
23.03.2018 | Materials Sciences
23.03.2018 | Agricultural and Forestry Science
23.03.2018 | Physics and Astronomy