**Table 2.**

#### **Figure 4.**

*Study area map. P1 – NEOSSOLO LITÓLICO Distrófico fragmentário (RLd) /Dystric Leptosol (LPdv), P2 – NEOSSOLO REGOLÍTICO Distrófico leptofragmentário (RRd)/Leptic Regosol (RGle), P3 – NEOSSOLO REGOLÍTICO Eutrófico típico (RRe)/Eutric Regosol (RGeu) and P4 – ARGISSOLO AMARELO Distrófico típico (PAd)/Haplic Acrisol (ACha).*

#### **Figure 5.**

*Toposequence of the study area with the respective topographic profiles in the landscape and the respective soils. P1 – NEOSSOLO LITÓLICO Distrófico fragmentário (RLd)/Dystric Leptosol (LPdv), P2 – NEOSSOLO REGOLÍTICO Distrófico leptofragmentário (RRd)/Leptic Regosol (RGle), P3 – NEOSSOLO REGOLÍTICO Eutrófico típico (RRe)/Eutric Regosol (RGeu) and P4 – ARGISSOLO AMARELO Distrófico típico (PAd)/Haplic Acrisol (ACha).*

In downloaded, profile P4 (**Figure 4**), the soil was classified as ARGISSOLO AMARELO Distrófico típico, presenting sequence of horizons A-AB1-AB2-Bt, deep soil (>100 cm), with yellowish color, indicating a sign of good drainage and low base


*Physical Quality of Soils in a Toposequence of a Forest Fragment under Livestock Activity… DOI: http://dx.doi.org/10.5772/intechopen.106560*

*P1 – NEOSSOLO LITÓLICO Distrófico fragmentário (RLd) /Dystric Leptosol (LPdv), P2 – NEOSSOLO REGOLÍTICO Distrófico leptofragmentário (RRd) /Leptic Regosol (RGle), P3 – NEOSSOLO REGOLÍTICO Eutrófico típico (RRe) /Eutric Regosol (RGeu) and P4 – ARGISSOLO AMARELO Distrófico típico (PAd)/Haplic Acrisol (ACha). Hz= Soil profile horizon; CEC= cation exchange capability; BS= base saturation; m= aluminum saturation; OC= organic carbon.*

#### **Table 3.**

*Chemical characteristics of the toposequence profiles in the Arroio Pelotas, RS, Brasil.*

saturation (<50%). These characteristics, together with the chemical attributes described in **Table 2**, corroborate with Streck et al. [24] which gives these soils parameters of low natural fertility, high acidity, and low cation exchange capacity (CEC).

The second soil class identified was that of the Neossolos, present in the sampling points P1, P2 e P3 (**Figure 4**). The Neossolos are characterized by being soils of recent formation, consisting of mineral or organic material that does not present express changes in relation to the source material, due to the low intensity of action of the pedogenetic processes, and that does not present horizon B diagnosis [27]. Despite having good natural fertility, this class has limitations in the production of annual crops, since it has a strong restriction on the entry of mechanization due to stoniness and rockiness, which impairs root development and water storage by low effective profundiade [24].


*P1 – NEOSSOLO LITÓLICO Distrófico fragmentário (RLd) /Dystric Leptosol (LPdv), P2 – NEOSSOLO REGOLÍTICO Distrófico leptofragmentário (RRd) /Leptic Regosol (RGle), P3 – NEOSSOLO REGOLÍTICO Eutrófico típico (RRe) /Eutric Regosol (RGeu) and P4 – ARGISSOLO AMARELO Distrófico típico (PAd) /Haplic Acrisol (ACha).*

#### **Table 4.**

*Granulometric characteristics of the toposequence profiles in the Arroio Pelotas, RS, Brasil.*

At the top, profile P1 (**Figure 4**), the soil was classified as NEOSSOLO LITÓLICO Distrófico fragmentário, presenting a sequence of horizons A-A/CR/R-CR/R, an effective profunity less than 50 cm that configures with shallow soil, high base saturation on horizon A (>50%) and lithic contact between 50 and 100 cm from the surface of the soil.

On the top slope, profile P2 (**Figure 4**). The was classified as NEOSSOLO REGOLÍTICO Distrófico leptofragmentário, presenting a sequence of horizons A-AC-C-C/CR, an effective depth between 50 and 100 cm configuring as shallow soil, low base saturation along the profile (<50%) and fragmentary lytic contact at a depth greater than 50 cm and less than or equal to 100 cm from the soil surface.

On the middle slope the soil was classified, the P3 (**Figure 4**), in NEOSSOLO REGOLÍTICO Eutrófico típico presenting a sequence of horizons A-AC-C1–C2, an effective depth greater than 100 cm configuring as deep soil, high base saturation (>50%) and lithic contact greater than 50 cm from the soil surface.

The average results for soil density determinations, total porosity, macroporosity, and microporosity are presented in **Table 5**. Forest soil density varied between 1.00

*Physical Quality of Soils in a Toposequence of a Forest Fragment under Livestock Activity… DOI: http://dx.doi.org/10.5772/intechopen.106560*


*SG: no access of cattle in the forest and CG: with access of cattle to the interior of the forest. Means followed by the same letter do not differ statistically from each other by the Kruskal–Wallis nonparametric test (p < 0.05).*

#### **Table 5.**

*Physical parameters of the forest soils in the 0–5 cm and 5–10 cm layers in toposequence in the Arroio Pelotas Hydrographic Basin, Rio Grande do Sul, Brasil.*

Mg m<sup>3</sup> and 1.45 Mg m<sup>3</sup> . Regardless of the position in the relief or access of the animals inside the fragments, the density was lower in the upper layer (0–5 cm) ranging between 1.00 Mg m3 and 1.21 Mg m<sup>3</sup> . While in the lower layer (5–10 cm), the density varied between 1.20 Mg m<sup>3</sup> and 1.45 Mg m<sup>3</sup> . Although forest areas with animal access showed a soil density generally higher than the fragments without access, statistical difference was detected only in the lower layer (5–10 cm) on the middle slope. The critical density values found for sandy soils under agricultural use are cited and range from 1.6 to 1.8 [19], well above that found in this study.

This lower soil density in the upper layer (0–5 cm) was found in studies in natural forests [19, 30, 31]. This general pattern of natural or anthropic soils is caused by the greater intake of organic matter in the most superficial layer of the forest soil. The organic matter from the vegetation has a specific mass of lower density and greater aggregation power among the mineral particles of the soil, resulting in the better structural quality of the soils and, consequently, in the greater amount of pore space and space for root growth.

The lowest soil density in areas occupied by native forests has already been found in different Brazilian Biomes [15, 17, 19, 30–37]. In the same watershed, Flores et al. [32] found in Argissolo Vermelho, that the density of native forest and native field soil was lower than in the cultivation areas, with greater differences in the layer of higher organic matter intake (0 a 0.05 m). In this layer, the native forest had the lowest density (1.06 Mg m<sup>3</sup> ) while no-till was the largest (1.45 Mg m<sup>3</sup> ), and after five years, notillage had half the organic matter of the surface layer of the native forest [32].

In the studies of different Brazilian biomes that used native forests as control of edafica quality in agricultural properties, the density was always lower in native forests compared to more intense land uses, such as annual crops of conventional management, and no-tillage and pastures. It is important to highlight that the density values of the forest soil studied, in all glebes, they had density below the appropriate critical density for plant growth. However, densities close to or above the critical boundary should probably occur on the animal tracks within forest fragments.

The pattern of the lower density of forest soils compared to other forms of landscape use, such as crops, orchards, and pastures, is a consequence of the lower or no soil revolving in these forest environments. Thus, the decompaction of forest soil is largely influenced by the intense and constant activity of edafica fauna and woody plants with a large volume of the root system. Edaphic organisms, mainly microorganisms, have an important role to decompile biomass produced in the different strata of the forest and deposited in the litter, which is incorporated into soil organic matter and promotes better conditions in physical attributes, such as aggregation, porosity, and rate of water infiltration, energy flow, as well as chemical attributes such as nutrient cycling and increased cation exchange capacity [38] in forest soils.

Since then, soil density has been an indirect environmental indicator of the degree of particulate ness. For soils of similar classes, the higher the soil density, the higher its compaction, the lower its total porosity and, consequently, the greater the restrictions on the development of the root system of young plants, water infiltration, and soil aeration [5, 17].

The total porosity of forest soils ranged from 45% to 59%. However, macroporosity and microporosity had different distributions between the relief segments and between the soil layers. The areas without grazing presented nominally higher values in macroporosity and with the statistical difference in the three parts of the relief in the surface layer of the soil (0–5 cm). The forests with cattle access presented macropores in a smaller proportion, ranging from 12–20% in the upper soil layer (0–5 cm) and close values, in the three areas of the relief, to 21.5% in the lower layer (5–10 cm). In the protected areas of grazing, the proportion of macropores was between 19–31% in the 0–5 cm layer and between 18–25% in the 5–10 cm layer. On the other hand, the micropores were more abundant in forest areas with the entry of animals, between 31 and 41% of the porosity of the samples of the 0–5 cm layer and between 22–31% for the 5–10 cm layer. In the areas without the presence of the animals, the microporosity values were lower, between 21 and 32% in the upper layer and 23–32% in the samples of the lower layer. The microporosity was different between the areas with and without the cattle, however, even with higher microporosity values, in the lowered, there was a statistical difference between the middle and upper slope in the surface layer (0–5 cm). There was no statistical difference in the lower layer (5–10 cm) in all parts of the relief. The total porosity of forest soils ranged from 45 to 59% in the upper and lower layer.

Soil porosity is the intense result of biological activity and the diameter distribution of these pores reflects the condition to determine the physical-water behavior in soils [39]. In the study of the toposequence in Pelotas, the size of the pores indicates alteration due to the presence of animals inside the fragments of protective forests. The macroporosity of the soil surface layer was the parameter that was impaired by the compaction of cattle. The trampling of the animals is indicating a reduction in soil quality, being favorable for greater compaction of the surface layer, due to the increase in soil density and the reduction of macroporosity [40].

In relation to forest species, soil esthesity porosity is fundamental for seed germination and plant growth. A smaller volume of aerating space in the soil restricts the full development of the root system. In this sense, data on critical values for plant growth in different studies showed a minimum limiting value of soil aeration amount (macroposority) of at least 10% [8]. The toposequence soils in Pelotas, despite the loss of aeration space and water infiltration in the unfenced areas, showed macroporosity values above minimum environmental quality values. Even the forest fragments with the presence of the animals maintained adequate soil aeration conditions for plant growth with adaptations to grazing and animal trampling, such as carne-de-vaca (*Styrax leprosus*), embira (*Daphnopsis racemosa*), pitanga (*Eugenia uniflora*), *Cestrum*

*Physical Quality of Soils in a Toposequence of a Forest Fragment under Livestock Activity… DOI: http://dx.doi.org/10.5772/intechopen.106560*

*(Cestrum parquii)* e mamica-de-cadela (*Zanthoxylom fagara*), spiny vines, among other dominant.

Other land uses show less adequate conditions of aerated ground space. In different management systems of agricultural property in Pelotas, CRUZ et al. [41] found in conventional systems, no-tillage and native livestock field, lower aeration values, between 8 and 13% macroporosity for Argissolo Vermelho. Already evaluating soil quality in cultivated areas a few kilometers from the study, FLORES et al. [32] found greater aerate structure in the native forest and in the no-tillage system, 19 and 14%, respectively, already in the conventional planting system and in the native field with high livestock grazing, 8% macroporosity occurred. In Argissolo Vermelho distrófico in the same geological unit of this study, SUZUKI et al. [37] evaluated pasture, production forest, and forest of anthropized native protection in relation to compaction intensity. The authors found in the pasture with more than five years the lowest macroporosity (3.6%), while in the planting of *Eucalyptus saligna* with 20 years, the best macroporosity (19.9%). An intermediate macroporosity and practically below the minimum required plants occurred in the eucalyptus saligna forest in recent formation (four years) and in the anthropized native forest and used as shelter by cattle for five years [37].

## **4. Conclusions**

The higher porosity of esthetic and water infiltration in forest soils, compared to other uses of the landscape, such as crops, orchards, and pastures, is the result of less soil revolving and its permanent vegetation cover. Forest vegetation constantly supplies organic matter to the soil through the litter intake of the treetops, the rhizosphere relationships in the root system, and its mycorrhizae relationships. The long time without soil revolving in production forests or protective forests occurs the action of organisms, plants, and animals in the incorporation of organic matter and the structuring of soil aggregates promoting improvements in forest soil quality by the stability of the environment.

The classification of the soils presented different classes in the toposequence, with Neossolos at the top and on the slopes and Argissolos in the lowlands of the relief, in the riparian forest. The presence of cattle inside the forest fragments, regardless of the position in the relief, indicates a tendency to promote negative effects and the loss of macroporosity in the surface layer of the soil. The soils of the forest fragments with the presence of the animals presented lower significant values of macroporosity in the surface layer, contributing to a certain compaction, compromising the distribution of porosity, and generating negative effects on soil physical quality.

This study evaluated the effects of cattle grazing on the physical quality of forest soils in the extreme south of the Atlantic forest, resulting in technical-scientific subsidies for the implementation of forest fragment isolation in landscapes planned to improve soil quality in the protected forests of watersheds. Thus, conservation by the isolation of protective forests in the planning of rural property benefits the quality of forest soils. Further studies are needed in the Arroio Pelotas watershed to characterize soil physics patterns according to the type of land use, to mitigate environmental impacts of livestock, and encourage a more sustainable activity.
