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!
Sediment from Himalayas may have made 2004 Indian Ocean earthquake more severe
26.05.2017 | Oregon State University
Devils Hole: Ancient Traces of Climate History
24.05.2017 | Universität Innsbruck
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy