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!
Safeguarding sustainability through forest certification mapping
27.06.2017 | International Institute for Applied Systems Analysis (IIASA)
Dune ecosystem modelling
26.06.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau
Spectrally narrow x-ray pulses may be “sharpened” by purely mechanical means. This sounds surprisingly, but a team of theoretical and experimental physicists developed and realized such a method. It is based on fast motions, precisely synchronized with the pulses, of a target interacting with the x-ray light. Thereby, photons are redistributed within the x-ray pulse to the desired spectral region.
A team of theoretical physicists from the MPI for Nuclear Physics (MPIK) in Heidelberg has developed a novel method to intensify the spectrally broad x-ray...
Physicists working with researcher Oriol Romero-Isart devised a new simple scheme to theoretically generate arbitrarily short and focused electromagnetic fields. This new tool could be used for precise sensing and in microscopy.
Microwaves, heat radiation, light and X-radiation are examples for electromagnetic waves. Many applications require to focus the electromagnetic fields to...
Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers
Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...
Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.
At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...
3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects
A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...
26.07.2017 | Event News
21.07.2017 | Event News
19.07.2017 | Event News
28.07.2017 | Health and Medicine
28.07.2017 | Power and Electrical Engineering
28.07.2017 | Life Sciences