I'm not very sure if a pampa is an example of an ecological succession.
The reason of my doubt is due I've remember hearing that a Pampa is formed when a Valley which has had a river on it, no longer has it due the river changed its course and left the place without water.
But is it okay for this reason to imply that the Pampa (biome) is the result of an ecological succession?. The wikipedia entry doesn't give much details.
But it constrains the term for only the lands located in Brazil and Uruguay. It does not give any indication why some other places such as in Bolivia and Peru also use the term. Given these, could it be confused with a Mediterranean forest or with a Chaparral?.
Are those of the same origin?. Can someone help me here?. I'm confused about these.
This is a difficult question to answer. I would say that is uncommon (though not improper) to think of questions of ecological succession at the biome scale. In this case, the pampa is probably a good example of a climax community (if we exclude human-caused changes). After the rivers changed course there would have been a lot of bare substrate. Over time different plant species would establish and then be replaced by other plant species. After thousands of years you would get to the somewhat stable state of the pampa biome. It is important to note that this biome is maintained by fire and grazing (Vignolio et al 2003). Fire/grazing prevent trees and shrubs from establishing in high densities and maintains the open grasslands of the pampa. In general, every place in the world that has natural life would be the result of ecological succession. Succession is a process that happens as life establishes and ecological communities change.
As for why other places are also called pampas, the word "pampa" apparently comes from a Quechua word for plains, that was then adopted into Spanish. Since Peru and Bolivia both have Quechua speaking populations, it seems reasonable that this work was applied to plains areas in those countries.
Edit in response to comments
Comment about biome scale
The reason behind the scale comment is that typically we observe succession for a given habitat. Part of this stems from the origin of the succession ideas, where Frederic Clements posited that climate was the major driving factor of successional trajectories (Clements 1916). This would actually fit well with the biome view of succession, however in order for this model to explain all the variation we see in the world (eg. why a tree grows in location X but not location Y 4 metres away), you devolve into splitting the world into infinitesimally small micro-climates. Henry Gleason proposed a more individualistic model, which suggested that climate was just one influence, and that each plant species responds to a myriad of different environmental cues (Gleason 1927). The sum of these responses results in the community at a given location. This seems to fit better with our current understanding of succession but is not without problems. In a Gleasonian model, any variation can be expected to result in a different community. Since it would be strange for the pampas region to be homogeneous over 1.2 million km2, there are likely distinct communities within the biome, each developing as a result of factors like soil moisture, soil chemistry, climate, wind exposure, and herbivore use. One can still talk about succession at a biome scale, but at that scale we would be thinking about what factors lead the pampas region to become a grassland, rather than what factors lead grass X, tree Y and forb Z to coexist next to each other.
Factors maintaining grassland type ecosystems are fairly uniform globally. You need some sort of event that will kill woody vegetation but not kill grasses and forbs. Fire and grazing are natural examples (Briggs et al. 2002), but mowing would also maintain grassland (Fidelis et al. 2012). Earthquakes are unlikely to maintain grassland as trees and shrubs are likely to survive earthquakes.
Comment about global pampas
Yes, and no. There are other wet grasslands in the world that would have similar moisture regimes and productivity levels seen in the pampas of South America. However, these are likely not called pampas. Temperate grasslands in Canada and the US are typically called prairies or plains, while the same kind of system is called a steppe in Eurasia. Ecologically they are very similar in function, though they may have very different species present. Perelman, Burkart, and Leon (2003) use prairie and steppe to refer to different sub-communities of the Pampa. Perhaps the closest analogue would be the Great Plains of North America. There is no other area called the Great Plains, but since the great plains are made up of prairie, steppe, and savannah (Oesterheld et al. 1999), there are many other areas globally that exhibit similar ecological function. This can get confusing, as there are cultural usages of these terms to refer to places, and there are ecological uses of these terms to refer to grassland sub-types.
I am not sure I understand how you are relating chaparral/Mediterranean forest to this. Both of those ecosystems will have much higher presence of trees and shrubs than pampas/prairie/steppes (Hanes 1971, Palahi 2008). Chaparrals tend to be dominated by evergreen drought tolerant shrubs, while Mediterranean forests will have more trees present. All of these systems are influenced naturally by fire and drought, so they are similar that way.
Briggs, John M., Alan K. Knapp, and Brent L. Brock. "Expansion of woody plants in tallgrass prairie: a fifteen-year study of fire and fire-grazing interactions." The American Midland Naturalist 147.2 (2002): 287-294.
Clements, Frederic Edward. Plant succession: an analysis of the development of vegetation. No. 242. Carnegie Institution of Washington, 1916.
Fidelis, Alessandra, et al. "Short‐term changes caused by fire and mowing in Brazilian Campos grasslands with different long‐term fire histories." Journal of Vegetation Science 23.3 (2012): 552-562.
Gleason, Henry Allan. "Further views on the succession‐concept." Ecology 8.3 (1927): 299-326.
Hanes, Ted L. "Succession after fire in the chaparral of southern California." Ecological monographs 41.1 (1971): 27-52.
Oesterheld, M., et al. "Grazing, fire, and climate effects on primary productivity of grasslands and savannas." Ecosystems of the world (1999): 287-306.
Palahi, M., et al. "Mediterranean forests under focus." International forestry review 10.4 (2008): 676-688.
Vignolio, Osvaldo R., et al. "Effects of fire frequency on survival, growth and fecundity of Paspalum quadrifarium (Lam.) in a grassland of the Flooding Pampa (Argentina)." Austral Ecology 28.3 (2003): 263-270.