Extra helpings of key nutrients given to tropical rain forest soils caused them to release substantially more carbon dioxide into the atmosphere, a concern to scientists monitoring global change, says a new University of Colorado at Boulder study.
The study showed when either phosphorus or nitrogen -- both of which occur naturally in the rain forest soils -- were added to forest plots in Costa Rica, they caused soil microbes to increase their CO2 emissions to the atmosphere by about 20 percent annually, said Cory Cleveland of CU's Institute of Arctic and Alpine Research.
The study is important because human activities are changing the amount of phosphorus and nitrogen in ecosystems all over the globe, including the tropics, Cleveland said. Tropical rain forests play a dominant role on Earth in regulating atmospheric CO2, the primary greenhouse gas that has increased by roughly 33 percent since the Industrial Revolution began about 1760.
A paper on the subject by Cleveland and CU-Boulder Associate Professor Alan Townsend of INSTAAR is being published the week of June 19 in the Proceedings of the National Academy of Sciences. The National Science Foundation funded the study.
"One big question is how tropical rain forests are responding to climate change," said Cleveland, an INSTAAR research associate who led the study. "What we have demonstrated is that even small changes in nutrients could have a similarly profound impact on the release of CO2 from tropical forest soils."
Tropical forests contain up to 40 percent of the carbon stored on Earth's continents and account for at least one-third of the annual exchange of CO2 between the biosphere and the atmosphere, said Cleveland. Earth's soils are believed to store several times more carbon than all of the planet's vegetation.
"This is the first time anyone has taken a close look at how changes in key nutrients may alter soil CO2 emissions in tropical forests," said Cleveland. "Processes in the tropics affect what is happening around the globe, so this study has some big implications."
Phosphorus is known as a "limiting nutrient" because its availability can govern the growth rate of many organisms, said Cleveland. While slash-and-burn agriculture in the tropics often reduces soil phosphorus in the long run, the practice can initially make more phosphorus available to tropical soil microbes, increasing their metabolism and the amounts of CO2 they emit, he said.
Phosphorus and many other nutrients are regularly transported around the Earth by global wind patterns, sometimes riding on huge transcontinental dust clouds, said Townsend, who also is associated with CU-Boulder's ecology and evolutionary biology department. "There is strong evidence that humans are increasing the size of these dust clouds as both land-use patterns and climate change, which in turn can change the availability of nutrients to forests," he said.
Nitrogen pollution also is increasing around the world, including in tropical forests, a result of fossil-fuel combustion and crop fertilization activities, said Townsend. "Human activity has changed the availability of nitrogen all over the world, especially in the last 50 years," he said. "This study was surprising because of the large effect both of these nutrients had on the release of CO2 to the atmosphere."
About three-quarters of anthropogenic emissions of CO2 to the atmosphere during the past 20 years are thought to be due to fossil-fuel burning, the researchers said. The rest is predominantly due to land-use changes like deforestation.
The new study, which took place in 2004 and 2005 in Costa Rica's Golfo Dulce Forest Reserve, included a series of 25 meter-square plots that were fertilized with phosphorus, nitrogen, or a combination of the two, said Cleveland. Soil respiration was measured using plastic tubes in the ground running into vented, closed chambers.
According to the National Academy of Sciences, temperatures on Earth have risen by more than 1 degree F in the past century due to build-up of greenhouse gases in the atmosphere, primarily CO2. According to the academy, the warming process has intensified in the past 20 years has been accompanied by retreating glaciers, thinning arctic ice, rising sea levels and longer growing seasons in many regions.
Cory Cleveland | EurekAlert!
Dispersal of Fish Eggs by Water Birds – Just a Myth?
19.02.2018 | Universität Basel
Removing fossil fuel subsidies will not reduce CO2 emissions as much as hoped
08.02.2018 | International Institute for Applied Systems Analysis (IIASA)
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
19.02.2018 | Materials Sciences
19.02.2018 | Materials Sciences
19.02.2018 | Life Sciences