The word savannah has experienced many definitions offered by experts who have studied the subject.
Two are given, the first mentioned by a European specialist school, the second by a specialist on the North American continent. *the savannah as a tropical training with dominance of herbaceous plants (grasses ...) and containing a greater or lesser proportion of woody vegetation and associated trees. *the second taking the first definition but additionally expand the concept outside of tropical formations.
Definitions that can be encountered: *vegetation type including a continuous extension (area) of grasses, herbaceous plants dotted with trees and/or shrubs, shrubs showing characteristics similar adaptations.
The transition between savanna and tropical forest is well defined, sharp. *open training with predominance of grasses, usually interspersed with trees and / or shrubs, this in a tropical climate. *expanse of herbaceous plants, tropical grasses, with or dsans trees and scattered shrubs. *ecological systems formed from tropical grasslands, where some woody species live isolated in competition with grasses and other herbaceous plants. *areas with trees and shrubs scattered on a grass mat, without any protection training.
Human influenceativités agricultural and livestock, cultivation of sugar cane for bio-fuel, ...) were forgotten in the calculation of impacts, however we will include aspects physiognomy, climate (seasonal), latitudes, geographical, ecological aspects that impact on vegetation or like events like fire.
Only a few farmers or big landowners chose to apply special methods of protecting their environment, but in rare cases more (in part due to lack of awareness), management methods for limiting external inputs in production and crop production (eg in the case of farm Vagafogo in Pirenópolis in the Goiás State).
Savannah Types
As we have seen before, types of savannas known through documents, books show some divergence in the perception or conceptualization of that plant formation.
Besides climatic factors (rain, duration of droughts), appear in these times of particular phenomena of climate change (el niño and a niña).
These are terminology proposals, based on the composition of flora and different according to the authors.
According to the specialist Cole (1986) *Savanna planted width trees - set of deciduous and semi deciduous, of tall trees (over 8 m high) and tall grasses (over 80 cm) and many spaces between the trees. *Savannah park - fields of tall grass like plant (40 to 80 cm high), with deciduous trees (less than 8 m high) scattered. *Savannah field - Tropical type fields (grass) without trees or shrubs. *Savannah with low trees and shrubs - perennial grasses groups with low growth (less than 80 cm high), widely spread, with an abundance of annual plants, and sprinkled with trees and low-growing shrubs, such as less frequently less than 2 m high, widely scattered. *Grove of trees and shrubs - group of trees and shrubs without partitioning.
Geographic distribuition savannah
Savannas may be similar from one continent to another (eg between those of Africa and those of Australia). Biomasses caatinga and cerrado show a wealth of plants in the same climate. Whatever the specialist, the main factors that were detailed ambientaux can be summarized as follows: -the climate, -the floor, -the hydrology, -the geomorphology, -the fire, -the grazing.
In tropical savannas, as they extend in different latitudes and altitudes, there are different climate changes that result from the diversity physiognomy of this biomass.
About the ground, the nature of the origin material, relief, climate, organisms and time interact to its constitution, and thus also indirectly affect the formation or distribution of savannas. In many places in the world appear great sensitivities of plant communities and species to changes in environmental conditions (status of soil nutrients or wet condition).
The climate
Through rainfall and temperature, it is involved in the formation and spread of savannahs mainly conditioned by the relative wet factors.
The grounds Texture
The low availability of nutrients and the shallowness of some soils are important elements in the distribution of different landscapes in the savannas.
The texture is fundamental to the retention of humidity (and also in the drainage and the availability of nutrients in the ground). This last point can be used to identify differences between areas of savannah.
The geomorphology and the hydrology
In every continent, savannas are characterized by sequences similar type of land, representing the geomorphological evolution of the landscape influenced by the interactions of changes in climatic conditions and geological events
Fire The potential impact of fire on vegetation depends on the following factors: -The time of event, -the time at which the fire spreads, -the strength and direction of the wind.
Cerrado vegetation has adapted to fire (the first back to the late Pleistocene of the Quaternary area).
Fires and notes their subjects are common in most savannas of the world. Biomass (cycle and productivity)
The primary productivity of savannahs presents a wide variety through the more or less important contribution of factors affecting these various faces (physionomies).
Across the planet, the expanses of savannah have been widely used for grazing activities and other forms of human occupation (in Africa, for example).Savannas are directly associated with the evolution of the human species.
Until the second half of the previous century, there was no particular concern about the degradation of the environment by humans.
The problem was and continues to be the irrational mode of the occupation of environmental space, whether in the aquatic environment, in tropical forests, or even to the different layers of our atmosphere.
Much of the area of the cerrado is located on the Planalto Central of Brazil (2 million quilomètres / sq), covering the states of Mato Grosso, Mato Grosso do Sul, Rondônia, Distrito Federal, Goiás, Tocantins, Maranhão, Piauí, Bahia, Minas Gerais and São Paulo.
This is the second large plant formation after the Amazon.
The limits, they are north, east, ... are defined by transition zones where species of two or more morphoclimatic areas intermingle, giving creation to landscapes include embedded subregions.
The climate has an influence on the organization and production of geographical areas (very related to hydrological availability) and not only the composition of landscaped mosaics determine the typologies of environmental units of the cerrado.
Rainfall and air mass characteristics can have a positive impact as the original maritime air masses (anticiclone Atlantic). They are breaking on the continent, advancing or retreating under the influence of negative action centers of continental origin (eg, mainland Equatorial mass and continental tropical mass in the Centro West region during the summer). Another example is the tropical continental mass that is a system that has a great importance in the programming of rain in various parts of the cerrado biomass.
This joint action of the various climatic phenomena appear two different seasons of Cerrado: *a rainy season from Septembro until March and April with the months of November, December and wettest January, *an April dry season, May to August and September, this depending on the geographical location of the region concerned.
The climate classification can be made from different criteria (natural landscape and climate indices). The most commonly used method is to Köppen and Thornthwaite that defines 5 major climates groups: *letter A-->mégathermie climate (tropical), with average temperature of the coldest month above 18°C, *letter B-->dry climate, arid expanses and semiarid with xerophytic vegetation (plants adapted to dry well to midfields type rocky deserts, but also to the canopy of forests tropicales. Thecacti and other succulent plants grow in deserts, while some bromeliads inhabit the treetops of the shadeforest), *letter C-->mesothermal climate (warm temperate), with average temperature of the coldest month between 3°C and 18°C, *letter D-->microthermique climate (temperate or boreal fees), with average temperature of the coldest month below -3°C and the hottest month above 10°C, *letter E-->polar climate, with average temperatures of all lower month at 10°C, *letter H-->altitude climate and mountains.
To refine this classification, -a second letter used to complete depending on the intensity of rainfall, -and a third according to the temperature variations, this for the letters B, C and D. (See Climate Classification).
In the case of the Cerrado, we see two types of climate: megathermal or wet tropical (A) with a subtype savannah climate with dry winters and summers rains (w), this in much of the cerrado. hot temperate or mesothermal (C), with dry winters (tropical altitude) and average temperature of the upper month at 22°C (wa) (South of Minas Gerais and Mato Grosso do Sul). However, climate change due to irresponsibility of human beings, the industrial world and the political world, all linked to poor waste management mean that this classification is to be taken today as a possible indication.
