**2.1 Impacts on self-organization**

Soil degradation may be ranked to one of the most dangerous human activities on the Earth's surface because soil is not instantly renewable. Degradation commences with vegetation coverage damage as a result of which evaporation decreases. The evaporation diminution foreshadows regional warming which contradictorily results in an intensification of water cycle into short, intense rainfall more frequently accompanied by soil drift or even flash floods [20]. Soil degradation affects ecosystem selforganization. The disruption of soil self-organization is initiated with the decrease in the diversity of functional connections within microbial communities. Disintegration of soil functional interconnectedness involves biodiversity loss and substitution of symbioses for decomposers (saprophytes) that do not exchange available nutrients among organisms, but cause leakage of substances from the ecosystem [21]. Forest soil degradation destroys irreplaceable natural values that improve adaptability of cultural landscape to climate change [22]. The disruption of soil self-organization damages both the continuity of crop production and success of ecosystem restoration.

Soil degradation is divided into quantitative or qualitative one (**Figure 1**). Quantitative soil degradation represents the physical loss of a soil body. Qualitative soil degradation involves unfavorable alterations in soil physical or chemical properties that limit ecosystem functions [23]. Soil losses occur through claim, erosion or desertification:


#### **Figure 1.**

*Division of soil degradation processes along quantitative and qualitative impacts on physical or chemical properties.*

which stopped formation of organo-mineral particles aggregating the soil into more cohesive peds (**Figure 2**). The vulnerability through erosion (erodibility) depends on weatherability of soil-forming substrate, soil cohesion, climate and land use (**Table 1**).

• Desertification is unnatural spread of wastelands after permanent vegetation removal. Causes of unnatural desertification are mainly disproportionate grazing, fires and erosion followed by loss of soil water retention capacity. Deserts spread the fastest in areas naturally adapted to seasonal drought [25]. Approximately 10–20% of the world's semi-deserts and steppes are threatened by desertification. The accompanying phenomena of desertification are decrease in groundwater levels or salinization which make it impossible to restore vegetation and lead to wasteland homeostasis [9].

Qualitative soil degradation is produced by excessive losses of the organic matter, the reduction of the biological activity, acidification, contamination, technological compaction (pedocompaction), technical or wind salinization and

#### **Figure 2.**

*Coupled occurences of soil erosion and spreading of desert in arid environments seriously threat forest restoration due to water availability decrease.*


#### **Table 1.**

*The vulnerability of forest soils by erosion (erodibility) along various parent rocks and developed soil units.*

technical modifications of soil properties. Although qualitative soil degradation potentially occurs in much smaller areas than quantitative one and its effects are usually reversible, they have a similar overlap on landscape functions in the form of reduced water retention capacity and biodiversity, increased runoff and substance imbalances.

Degradation of forest soils is distinctive mainly to the qualitative damage. Qualitative degradation in forests prevails due to the long-term growth of continuous tree species communities. Tree species instantly impede quantitative damage to soils; on the other hand, periodic windthrows during storms mingle the mass among soil horizons, as well as move the soil down the slope. These post-disturbance movements

#### **Figure 3.**

*A series of differently degraded soil bodies in mountain conditions: introskeletal erosion in Dystric Hyperskeletic Leptosol (A); surface scarification of Entic Podzol (B) and accumulated Spolic Garbic Urbic Technosol (C).*

of earth bodies divide microrelief and homogenize soil properties, but at the same time their arrangement is concentrated along the effects of individual global climate changes [26]. However, predominant qualitative degradation of forest soils is manifested by deterioration of physical or chemical properties of solid soil bodies due to external human activities (**Figure 3**) [27].

Deterioration of forest renewal as a consequence of qualitative soil degradation commences with fertility change. Forest felling is accompanied by accelerated leaching of nitrogen substances which can only be ceased by sufficient available calcium [28]. Leaching is preceded by increase in C/N which indicates decrease in ability of soil organic matter to bind mineral nutrients. Soils damaged by compaction of the profile middle part, texturally significantly differentiated or hydromorphic, are exposed to a slow-motion water flow, which expels air for the root growth and similarly increases C/N [29]. The root systems grow merely shallowly with water stagnation and the nutrient loss, making forest stands more susceptible to soil moisture fluctuations [30]. Thus, felling of forests threatened by qualitative erosion impairs the ecosystem ability to restore as a result of exposure to episodic drought [2].

#### **2.2 Physical degradation**

Degradation of soil physical properties includes structural damage, pore loss and compaction. The processes of physical soil damage result in both loss of water retention capacity and humus loss by introskeletal erosion. The decline in soil water retention capacity is usually caused by repeated heavy machinery moving. Heavy machinery moving worsens soil aeration and water permeability. Reduced aeration is reflected in the decrease of blank spaces for plant roots and the consequent reduction in the biological activity.

Forest soils are less endangered by physical degradation than agricultural ones owing to dampening effect of surface humus. Nevertheless, topsoil compaction can initiate introskeletal erosion. The mechanical degradation threat is descending from Histosols and gleyed soils to granularly light drying soil bodies [31]. The risks by mechanical damage to the forest soils vary along the grain-size composition, relief exposure and groundwater level (**Table 2**) [32].

*Soil Degradation Processes Linked to Long-Term Forest-Type Damage DOI: http://dx.doi.org/10.5772/intechopen.106390*


#### **Table 2.**

*Characteristics of forest soil compaction risk after logging machinery movement.*


Introskeletal erosion represents a predominantly vertical subsidence of finegrained soil particles through blank spaces among skeleton to the base of rock mantle. The introskeletal erosion risk resides in unstable occurrence of surface humus. Introskeletal erosion is triggered after removal of the vegetation cover in the exposed sites. Its result is the loss of whole fine-grained matter, followed by impossibility of restoring plant community and permanent exposure of relief [33]. The

threat to the site by introskeletal erosion is distributed along exposure of relief and soil skeletability [34]:

