**4. Brazilian environmental characteristics**

Brazil extends from the equatorial to the subtropical belt. Environmental characteristics are highly changeable along Brazilian territory due to large territorial size. The country is characterized by a large diversity of soil types, resulting from the interaction of the different

Natural Potential for Erosion for Brazilian Territory 7

The largest part of its eastern front is characterized by a morphoclimatic domain called "sea of hills", with convex upslope and rectilinear lower slopes, sometimes with benches or shoulders, sometimes concave by the colluvial accumulation. In southeastern and partly in the south, hills are preceded by the scarps of the *Serra do Mar*, which limits the Atlantic

Figure 3 depicts the relief compartments, showing predominance of plain regions along Amazon region and predominance of plateaus mainly along southeastern and southern

Three main groups of natural processes take place on the slopes of these humid tropical areas: (i) weathering-pedogenesis, forming thick weathered mantles reworked by; (ii) overland and sub-surface flow, and river flow; and (iii) mass movements, especially on scarped slopes, such as those of *Serra do Mar* and *Serra da Mantiqueira*, in the southeast, and the *Serra Geral*, in the south. Such natural processes vary according to geographic position, declivity, range and length of the scarps, as well as their geological nature, the thickness of

Fig. 3. Relief compartments map for Brazilian territory. Source: IBGE (n.d.) with legend

Climatologically, the minimal temperature (annual average values) ranges from 4 to 24oC. Average temperature (annual average values) ranges from 8 to 30oC. Maximum temperature (annual average values) ranges from 15 to 35oC. In all cases, northern / northeastern regions present highest values, while southern region presents the lowest ones (INMET, n.d.).

translated according to map shown in Sayre et al (n.d.).

plateau (Cruz, 2000).

regions (IBGE, n.d.).

alteration beds and climatic conditions (Cruz, 2000).

relieves, climates, parent material, vegetation and associated organisms. This diversity and the consequent potential uses are reflected in the regional differences. There are nineteen major soil orders occurring along territory (Figure 2). The complex formed by the FAO System Xanthic, Rhodic and Haplic Ferralsols (named, according to Brazilian classification system (EMBRAPA, 2006), as Latossolos, and as Oxisols, according to Soil Survey Staff, 1999) is the predominant category and takes place in 38.7% of the Brazilian territory. The complex formed by the FAO System Rhodic and Haplic Acrisols and some Lixisols (named, according to Brazilian classification system (EMBRAPA, 2006), as Argissolos, and as Ultisols, according to Soil Survey Staff, 1999), is the second predominant category, taking place in 20.0% of the Brazilian territory. So, such two soil major classes represents more than a half of the Brazilian soils (FAO, 2004).

Fig. 2. Soil Classes occurring along Brazilian territory. Source: FAO (2004).

relieves, climates, parent material, vegetation and associated organisms. This diversity and the consequent potential uses are reflected in the regional differences. There are nineteen major soil orders occurring along territory (Figure 2). The complex formed by the FAO System Xanthic, Rhodic and Haplic Ferralsols (named, according to Brazilian classification system (EMBRAPA, 2006), as Latossolos, and as Oxisols, according to Soil Survey Staff, 1999) is the predominant category and takes place in 38.7% of the Brazilian territory. The complex formed by the FAO System Rhodic and Haplic Acrisols and some Lixisols (named, according to Brazilian classification system (EMBRAPA, 2006), as Argissolos, and as Ultisols, according to Soil Survey Staff, 1999), is the second predominant category, taking place in 20.0% of the Brazilian territory. So, such two soil major classes represents more than

Fig. 2. Soil Classes occurring along Brazilian territory. Source: FAO (2004).

a half of the Brazilian soils (FAO, 2004).

The largest part of its eastern front is characterized by a morphoclimatic domain called "sea of hills", with convex upslope and rectilinear lower slopes, sometimes with benches or shoulders, sometimes concave by the colluvial accumulation. In southeastern and partly in the south, hills are preceded by the scarps of the *Serra do Mar*, which limits the Atlantic plateau (Cruz, 2000).

Figure 3 depicts the relief compartments, showing predominance of plain regions along Amazon region and predominance of plateaus mainly along southeastern and southern regions (IBGE, n.d.).

Three main groups of natural processes take place on the slopes of these humid tropical areas: (i) weathering-pedogenesis, forming thick weathered mantles reworked by; (ii) overland and sub-surface flow, and river flow; and (iii) mass movements, especially on scarped slopes, such as those of *Serra do Mar* and *Serra da Mantiqueira*, in the southeast, and the *Serra Geral*, in the south. Such natural processes vary according to geographic position, declivity, range and length of the scarps, as well as their geological nature, the thickness of alteration beds and climatic conditions (Cruz, 2000).

Fig. 3. Relief compartments map for Brazilian territory. Source: IBGE (n.d.) with legend translated according to map shown in Sayre et al (n.d.).

Climatologically, the minimal temperature (annual average values) ranges from 4 to 24oC. Average temperature (annual average values) ranges from 8 to 30oC. Maximum temperature (annual average values) ranges from 15 to 35oC. In all cases, northern / northeastern regions present highest values, while southern region presents the lowest ones (INMET, n.d.).

Natural Potential for Erosion for Brazilian Territory 9

Fig. 5. Soil loss prediction through USLE approach and using GIS, modified from

This equation is based only in textural characteristics of the soil. Due this simplicity and feasibility of obtaining, it is still largely used (Waswa et al, 2002, Lopes-Assad et al., 2009). We also used a complementary database regarding soil erodibility that occurs specifically along São Paulo State (Silva & Alvares, 2005). Soil erodibility values were classified into five

Degrees of limitation K Factor (t.h.MJ-1.mm-1) null K ≤ 0.010 weak 0.010 ≤ K < 0.020 moderate 0.020 ≤ K < 0.030 strong 0.030 ≤ K < 0.040 very strong K ≥ 0.040

Official Brazilian soil map (IBGE, 2001) was crossed with the soil erodibility map, and thus we obtained average values of the K factor as large groups of Brazilian soils. For this, we

Mongkolsawat et al. (1994).

Source: Giboshi (1999).

classes, as shown in Table 1 (Giboshi, 1999).

Table 1. Values and interpretation classes for soil erodibility.

used the tool "Zonal statistics as table" in GIS ArcMAP 10 (Theobald, 2007).

Driest areas occur in northeastern region, where annual rainfall amount is approximately 600 mm. Northern region encompasses areas whose annual rainfall amount and erosivity are expressive (annual rainfall amount is usually over 2,500 mm), for example Amazon region (Silva, 2004). In most of Brazilian territory, annual rainfall depth ranges from 1,000 to 2,000 mm (Figure 4).

Fig. 4. Annual rainfall amount map of Brazilian territory (in mm.y-1). Source: Silva (2004).
