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| Titel |
Role of carbon and climate in forming the Páramo, an Andean evolutionary hotspot |
| VerfasserIn |
Daniel Hill |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250110902
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| Publikation (Nr.) |
 EGU/EGU2015-10945.pdf |
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| Zusammenfassung |
| According to a number of genetic diversification measures the Páramo grasslands of the high
equatorial Andes show the greatest rates of speciation on the planet. This is probably driven
by contrasting ranges of the ecosystem between glacial and interglacial periods of the
Pleistocene. During the warm interglacial periods the treeline is high in the Andes restricting
the Páramos to the highest regions of the Andean mountain chain, while in the cool glacial
periods the Páramo areas expand and probably coalesce, bringing isolated populations into
contact with each other. The origin of the Páramo ecosystem is placed close to the end of the
Pliocene and has been related to the finale of regional Andean mountain building.
However, this formation date is also coincident with the global cooling at the end of the
Pliocene, as Northern Hemisphere glaciation and the bipolar Pleistocene ice ages begin.
Furthermore, it is estimated that atmospheric CO2 concentrations dropped from the 400
ppmv typical of the Pliocene to values more typical of the Pleistocene at around this
time.
Global climate model simulations, coupled with a high resolution biome model, give us
the opportunity to test these competing hypotheses for the formation of the Páramo
ecosystem. A series of HadCM3 climate model simulations are presented here varying the
height of the highest altitude Andes and the global climate from its pre-industrial state to
the Pliocene. The climate are topographic changes are varied both independently
and together. These climatologies are then used to drive a high-resolution biome
model, BIOME4, and simulate the impact on Andean vegetation. These models seem
to reproduce the observed changes in high altitude grassland biomes during the
Pliocene.
The climate and biome modelling presented here show that the climate changes
associated with the Plio-Pleistocene boundary are the primary cause of the initial
formation of this unique and important ecosystem. Although the reduction of the
highest altitude Andean regions reduces the available area for grassland biomes, the
effect is significantly smaller than the impact of Plio-Pleistocene climate change. By
individually introducing the Pliocene changes (atmospheric carbon dioxide levels, mean
temperature, minimum temperatures, precipitation and direct sunlight) to the BIOME4
simulations, it is shown that the primary driver of these changes is atmospheric carbon
dioxide levels. The higher Pliocene levels favour the expansion of the forest biomes,
increasing the altitude of the treeline and replacing grassland biomes. This suggests that
in such areas prediction of future changes and plans to preserve these important
ecosystems must consider the impact of both climate change and CO2 fertilization. |
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