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Scientists may have solved an ecological riddle
June 19, 2008A team of scientists may have solved the riddle of why plants that work with bacteria to convert atmospheric nitrogen gas into an essential biological nutrient (ammonia) tend to prevail in the world's tropical regions rather than higher latitudes.
In a paper published this week in Nature, the authors - including Dr Ying Ping Wang from The Centre for Australian Weather and Climate Research - say that nitrogen fixation has long been recognised as an important process in controlling responses of many ecosystems - particularly boreal and temperate forests - to global environmental change.
"However, there have been significant discrepancies between real-world observations and the theories used to predict nitrogen fixation patterns across major sectors of the land biosphere," Dr Wang says.
"We believe our theory provides a unifying framework for nitrogen fixation which can explain the different levels of fixation observed in a wide range of climatically and geographically-defined terrestrial ecosystems right around the world," he says.
The team found that nitrogen-fixing species in phosphorous-limited tropical savannas and lowland tropical forests enjoyed a clear advantage over nitrogen-fixing species found in mature forests at high latitudes, where modern-day temperatures appeared to have constrained their numbers and nitrogen-fixing abilities.
The team developed two new hypotheses for understanding the distribution of nitrogen fixing plants across global ecosystems.
The first is that temperature constrains the distribution of nitrogen fixation, contributing to the lack of nitrogen-fixing trees in mature forests at high latitudes.
The second - that nitrogen-fixing plants hold an advantage in terms of their ability to acquire additional phosphorus - provides an explanation for the persistence of nitrogen-fixing plants in mature lowland tropical forest and savannas.
"Working on the basis of these two hypotheses we have produced a new model, which should help scientists to better predict the effect of climate change on different ecosystems and the interactions between terrestrial biosphere and climate change at decadal-to-century time scales," Dr Wang says.
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"We believe our theory provides a unifying framework for nitrogen fixation which can explain the different levels of fixation observed in a wide range of climatically and geographically-defined terrestrial ecosystems right around the world," he says.
The team found that nitrogen-fixing species in phosphorous-limited tropical savannas and lowland tropical forests enjoyed a clear advantage over nitrogen-fixing species found in mature forests at high latitudes, where modern-day temperatures appeared to have constrained their numbers and nitrogen-fixing abilities.
The team developed two new hypotheses for understanding the distribution of nitrogen fixing plants across global ecosystems.
The first is that temperature constrains the distribution of nitrogen fixation, contributing to the lack of nitrogen-fixing trees in mature forests at high latitudes.
The second - that nitrogen-fixing plants hold an advantage in terms of their ability to acquire additional phosphorus - provides an explanation for the persistence of nitrogen-fixing plants in mature lowland tropical forest and savannas.
"Working on the basis of these two hypotheses we have produced a new model, which should help scientists to better predict the effect of climate change on different ecosystems and the interactions between terrestrial biosphere and climate change at decadal-to-century time scales," Dr Wang says.
CS
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New findings blow a decade of assumptions out of the water
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Nature's process for nitrogen fixation caught in action
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More Nitrogen Fixation Current Events and Nitrogen Fixation News Articles
 | Nitrogen Fixation by John Postgate The fixation of nitrogen--the conversion of atmospheric nitrogen to a form that plants can use--is fundamental to the productivity of the biosphere and therefore to the ability of the expanding human population to feed itself. Although the existence and importance of the process of biological nitrogen fixation has been recognized for more than a century, scientific advances over the past few... |
 | Symbiotic Nitrogen Fixation in Plants (International Biological Programme Synthesis Series) A synthesis of current knowledge on the fixation of nitrogen by systems involving plants, especially legumes, and micro-organisms. Such associations utilise nitrogen from the atmosphere to make amino acids and proteins, and are of primary importance in providing a large part of the nitrogen compounds needed to sustain life. This volume underlines, and in some respects quantifies for the first... |
 | Nitrogen-fixing Leguminous Symbioses (Nitrogen Fixation: Origins, Applications, and Research Progress) (Nitrogen Fixation: Origins, Applications, and Research Progress) This book is the stand-alone final volume of a comprehensive series covering the basic and applied science relating to nitrogen fixation. It addresses the most important nitrogen-fixing symbiosis of all that between legumes and their root-nodule bacteria and therefore deals with the properties and behaviour of both macro- and micro-symbiont. The coverage is comprehensive, beginning with the... |
 | Genetics and Regulation of Nitrogen Fixation in Free-Living Bacteria (Nitrogen Fixation: Origins, Applications, and Research Progress) This book provides a comprehensive and detailed source of information on the genetic and regulatory aspects of biological nitrogen fixation in free-living (non-symbiotic) prokaryotes. Biological nitrogen fixation is represented in a diverse range of microorganisms, among which Klebsiella pneumoniae serves as a paradigm for the genetic analysis of diazotrophy, which is the ability to grow with N2... |
 | Genomes and Genomics of Nitrogen-fixing Organisms (Nitrogen Fixation: Origins, Applications, and Research Progress) This book is the self-contained third volume of a comprehensive series on nitrogen fixation. It presents the state-of-the-art in regards to genomic sciences applied to nitrogen-fixation research. The advent of genomic sciences represents a new era for biology. The classic paradigm based on the gene has now changed to a paradigm that is based on the genome. The knowledge of the complete nucleotide... |
| Nitrogen Fixation by Free-living Micro-Organisms (International Biological Programme Synthesis Series) | |
| The biology of nitrogen fixation (Frontiers of biology) by A Quispel | |
| Nitrogen Fixation by Free-Living Micro-Organisms by W. D. P. , Ed. Stewart | |
| Biological Nitrogen Fixation | |
 | Nitrogen-fixing Actinorhizal Symbioses (Nitrogen Fixation: Origins, Applications, and Research Progress) This book is the self-contained sixth volume of a comprehensive series on nitrogen fixation. It presents the state-of-the-art in regards to actinorhizal symbioses. Like legumes, actinorhizal plants form root nodules that host nitrogen-fixing soil bacteria. However, because the macrosymbionts are, with one exception, woody plants rather than crop plants, actinorhizal symbioses are less well-known... |
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