As Regiões Naturais do Amapá

Observações sôbre Fito e Zoogeografia, Geografia Humana e Geografia Física


  • Alceo Magnanini


Amapá, Geografia Humana, Geografia Física, Zoogeografia, Fitogeografia


The author, Alceo Magnanini, made this paper as a result of his observations during a trip the geographers of the Conselho Nacional de Geografia made to the Territory of Amapá.
A regional analysis, giving more importance to typical phenomena was the main line of work and, as the author himself declares, the formulation of problems is emphasized rather than arriving to conclusions.
The author adopted the following order:
I. Characteristics of the Territory, when a summary of said characteristics is presented. The author emphasizes that Amapá is divisible in two natural and distinct, perfectly characterized regions.
II. The regions of the Territory, when the author denies the concept of natural uniformity for the same, along with the conclusion that there are two natural regions: the coastal and hilean regions.
III. Hilean region: occupies about 80% of the total area of the Territory, covering the arquean peneplain to the contact with the tertiary formation. In this region the Hylea predominates under an equatorial climate. The principal characteristic of the vegetal covering is heterogeneity, being noted the large number of species in detriment of the number of individuals. The author suggests the hypothesis that such a heterogeneity may be due to the extreme variability of the nutritive elements of the soil. Man lives along the margin of the forest, basing his economy in the collecting of animal or vegetal products. In this region, there is also an incipient exploitation of minerals, chiefly iron, gold, manganese and tin.
The author comments, then, the errors that would be caused if common climate classifications were used for the Territory, as long as these classifications make use of interpolations between the few meteorological posts of the Brazilian north. Through deductions the author thinks that there should exist an isohyet of less than 3000 mm, delineated by the area of fields and savanas and by the lack of humidity-collecting mountains. Such an isohyet is not represented in actual maps of climate.
A reconnaissance of the very important role of rivers follows; according to the author, transport is in the dependence of these natural roads, as well as cultural and commercial relations and sometimes even alimentation. This fact determines the establishment of utility stores strategically placed on river mouths or on the first rapids.
The fauna and flora of the region are considered by the author from a utilitarian standpoint.
In the chapter dealing with mineral wealth the author studies the relations of this wealth to the Vila-Nova geological series.
IV. Coastal region - covering about 20% of the total area of the Territory is of heterogeneous nature.
The author points out that due to the kind of field work done in the region, reconnaissance, it was considered as uniform but further studies will probably transform some zone in regions.
This region is divided in several zones, as follows:
1. Terra Firme zone, meaning not flooded or influenced by tides: this zone presents three principal vegetal aspects: forest, savanas and campos.
The relief of the terra firme is composed of deeply eroded plateaus; the soils are covered by a layer of ferruginous concretions - found in non-forested regions. The author considers the two following hypotheses as probably in the formation of these concretions:
a. classic process of lateritic formation - reputed by the author as possible only in areas where humus is not present.
b. a process considered by the author as a tropical podzolization, occurring in regions where a humors cover is present. The reasons for this statement are the importance of humid acids, the nullity of the argument of the influence of high temperatures on the soil found under bushes, considering the protective role of the vegetal cover and the large quantities of Al and Fe found by Katzer in amazonian waters.
Two vegetal formations characterize the zone: grasslands - campos limpos - and savanas - campos cerrador.
a. Campos limpos - generally located over the gently rolling elevations of the alluvial plain; trees are absent, "ciperaceas" predominate.
b. Savanas - they generally appear as if forming a transition between the forest and the campo limpo. It resembles the cerrados in the Brazilian central plateau, but it presents less species and almost none economical use. The author points out the coincidence of the distribution of this formation with the probably tertiary terrains.
2. "Terra alagável"" zone - meaning periodically flooded: in this region there is a continuous action of precipitation of alluvial material either by the action of floods in the interior - as is the case of the varzeas, or by the action of tides, forming marshes, along the littoral.
The economy of this zone is based on cattle - raising during the dry season and on hunting and fishing during the rainy season, much like the economy found on the island of Marajá.
The physical aspects of this zone are:
a. Matas de varzeas: meaning forest living on the varzea, luxuriant vegetation growing along rivers, sometimes interrupted by grasslands in a few places. This forest is installed on the soils periodically fertilized by flood deposits and it is the habitat of the seringueira - Hevea brasiliensis - and of a large number of economically important species. These varzeas win certainly be used for agriculture in the future.
b. Campos de várzea, meaning grasslands in the várzea: 1. grasslands occurring on the lake region, medium Curipi, and along the coastal plain from Oiapoque to Macapá. During the floods - rainy season - this region can only be passed by using small canoes; during the dry season it can be passed on foot. 2. Campos de várzea meândricas, meaning varzeas along meanders, which are special cases of várzea ciliar; 3. várzea ciliar, meaning a broader várzea, where zonal vegetation is found.
3. Coastal zone: where marshes appear, and which has as a characteristic the ciriubal - Avicenia nitida, different from the marshes in the rest of Brasil.
This formation extends from Macapá to the month of the Oiapoque.
This is the zone where fishing nuclei appear.
The coast of the Territory has three different aspects: the coast along the northern margin of the Amazon, characterized by the amazonian forest; low coast in the vicinity of the month of the Araguari to the north of Maracá island: shallow littoral where mud and sand banks are frequent and where the ciriubal dominates; the coast to the north of Maracá island, following an NNW direction, where some points and capes appear, as, for example, capes Cassiporé and Orange, and Mosquito point.