**8. Final remarks**

Precipitation is one of the most important climatic variables to characterized arid and semiarid environments, especially in these environments precipitation varied from year to year. In Cadereyta, Querétaro, México it was found that maximum rainfall occurs in July and August months, besides that erosivity was major to in comparison with the rest of the year.

Vegetation cover is a very important factor to diminish runoff quantity, and native vegetation of semiarid areas contributes to protect the soil against rainfall erosivity and surface sealing phenomena.

For some insects and epiphytes, trees are the minimum habitat unit and can be considered islands, because, like islands, there are discrete ecological units with fixed borders surrounded by different environment (Flores-Palacios & García-Franco, 2006). In pastureland trees are often isolated and distant from other trees.

Some phreatophytes, especially in drier regions, have extensive, subsurface lateral roots to take advantage of any light rainfall that might occur. Such subsurface root systems help to stabilize the soil. The aerial system too has a role in reducing wind erosion and ameliorating the microclimate although information on changes in humidity and temperature is generally lacking (Wickens, 1995).

The indirect contribution of native species to soil fertility is two-fold. First, there is a contribution through nitrogen is probably minimal since the foliage on the ground probably undergoes two periods of rapid degeneration (Wickens, 1995). Along with the improvement in soil fertility, soil physical and micro-climate conditions, the trees play an important role in soil binding processes and the reduction in the eroding action of both water and wind (Pimentel et al., 1995).

The amount and seasonality of rainfall is also reflected in the amount of vegetation cover within the increase of vegetation (surface and canopy). The annual distribution of vegetation has a tendency to increase shortly after the first rains, as in all arid and semiarid environments. However, there was a greater contribution of shrubs or beneath the surface patches of vegetation with a greater coverage area of vegetation.

#### **9. References**

36 Soil Erosion Studies

Infiltration rates in arid and semiarid depend on factors like vegetation cover, rainfall amount, intensity, and duration, soil type and moisture, slope degree, and land use (Salas, 2000; Wilcox et al., 2003). Soil water infiltration rates are greater under canopies as a result of the soil protection from raindrop impact and compaction by the addition of organic matter from plants, improving soil crumb structure (Salas, 2000; Rango et al., 2006). Trees are a principal factor to increase organic material levels, to moderate soil temperature and to improve soil moisture, resulting in a higher infiltration rate beneath the canopy cover

The typical soils of arid and semiarid environment are poor in fertility. However, when native vegetation is still present, the properties of soils are positively enhanced. Table 2 shows the behavior of fertility of soils in three different native plant species and at bare surfaces. Organic matter in surface with vegetation cover is improved by 100% beneath

Vegetation 1.38 65.12 12.88 22.00 0.88 4.53 586 2404 308 22.8 6.35

*imbricate* 1.39 76.56 7.44 16.00 0.67 3.78 516 2144 289 1.17 6.53 *Prosopis laevigata* 1.31 75.56 8.44 16.00 1.98 5.29 769 2996 308 1.17 9.66 *Acacia farnesiana* 1.32 80.56 7.44 12.00 1.57 9.06 500 1501 213 1.17 33.3 Table 2. Soil characteristics comparing three different plant species of native vegetation.

Soils under trees canopies in semi-arid environments are often more fertile than soils from the surrounding grasslands. Quantities of mineralizable nitrogen, phosphorous, potassium, calcium, organic matter, and the microbial biomass, are significantly higher in soils beneath

Soil characteristics shows are better beneath species vegetation in comparison with bare surface, found up to twice of organic matter, minor values of bulk density, greater values of hydraulic conductivity that foster the increase in infiltration rates (Vásquez-Méndez et al.,

Precipitation is one of the most important climatic variables to characterized arid and semiarid environments, especially in these environments precipitation varied from year to year. In Cadereyta, Querétaro, México it was found that maximum rainfall occurs in July and August months, besides that erosivity was major to in comparison with the rest of the

Vegetation cover is a very important factor to diminish runoff quantity, and native vegetation of semiarid areas contributes to protect the soil against rainfall erosivity and

Matter N K Ca Mg Na Fe

Density Sand Silt Clay Organic

g cm-3 % ppm

(Gutiérrez, 2001; Zehe, 2008).

**7. Vegetation-soil interaction** 

canopy of Prosopis and Acacia.

Without

2010).

year.

**8. Final remarks** 

surface sealing phenomena.

*Cilindropuntia* 

Bulk

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**3** 

*Greece* 

**Deforestation / Reforestation in Mediterranean** 

Forests perform multiple and interrelated social, economic and environmental functions and can be comprised among the ecosystems with the greatest biodiversity. The contribution of forests is multiple and renewable and, therefore, they constitute a most valuable natural

The benefits / values of forests can be divided into those of direct and indirect use. The first category includes the value of timber, which is used, on one hand, in shipbuilding and, on the other hand, in supporting a great chain of industries such as construction, furniture manufacture, printing and packaging. The forestry sector provides about 8% of the total manufacture added value. Forest feedstock, goods and services can also provide important background for the economic reinforcement and green development in the countryside. The primary wood industry offers sawn wood, fibreboard, particleboard, pulpwood, fuelwood as well as wood chips and bark for bioenergy, in fact it employs more than 2 million people and it often involves small or medium enterprises in rural areas (Confederation of European

Apart from wood, which constitutes the main forest product, forest ecosystems provide a range of products of economic value such as bark, resin, honey, small berries, aromatic leaves (laurel), mushrooms, medicinal herbs, game, forage material etc. The value of forest biodiversity can not be ignored. Forests serve not only as shelter of flora and fauna, but also as a valuable natural gene pool. The value of information deriving from forest biodiversity

Recreational, aesthetic and health effects of forests can also be placed among their economic and socio-cultural values of immediate use. Forests, with their great surface, are the only part of every country that is free from pollution sources, while forest light, with its low intensity and high content in green radiation, has a soothing effect on the nervous system. For these reasons, forest-tourism, a specific form of tourism, is being developed which can be combined with walking tourism and ecotourism, and is a constantly developing category of mild and environmentally friendly tourism. Forests that are being managed for recreational purposes raise the value of neighbouring properties (Pearce 2001) and encourage tourism. Moreover, employment, particularly for populations who live near the forests and the exploitation of forest energy sources to produce soft forms of energy

for pharmaceutical use is subject to ongoing scientific research.

(biomass) can be added to the long list of benefits from forests.

**1. Introduction** 

Forest Owners).

resource.

**Europe: The Case of Greece** 

Olga G. Christopoulou *University of Thessaly* 

