5. Discussion
The world is currently facing serious and very rapid land degradation.
Indeed deforestation and desertification two types of closely related
threats are taking on an unprecedented scale on forests. Land clearing,
fires, overuse of land, overgrazing, deforestation are causing the
destruction of land cover and land. The demand for fuel wood is one of
the main causes of deforestation, especially in dry highlands where
trees grow slowly. Fires are mainly caused by negligence: uncontrolled
discharges, rarely by malicious acts. In addition, it promotes the
leaching of organic matter from soils that were part of the forest
carbon sink. After the fire, the forest canopy and organic matter in the
soil surface horizon (litter and humus) were completely burnt down and
destroyed by fire, reducing the protection of the soil (siband, 1972;
roose 1980). Unfortunately, our study area has undergone an intense
degradation of woodlands, which the maquis is increasing. This
degradation of the natural environment leads to the reduction of
biological potential and by the disruption of the ecological balance and
socio-economic. The forest of Tenira is distinguished by a semi-arid
bioclimatic and is generally this vegetation comes in the form of maquis
indicating the nature of a local bio-climate (Benaouada, 1997). The high
percentages of maquis observed during the study periods is due to the
continuing degradation of this dense forest. This decline of the surface
of dense forest is the result of an anthropogenic exploitation and
frequent fires. This effect adds bioclimatic and soil heterogeneity that
has fostered the development and installation of vulnerable species.
Fires of shrubs in regions of the Mediterranean climate generally burn
with considerable intensity. Average fire return times range from 20 to
30 years to more than a century, and fuel combustion during individual
fire events ranges from 1 to 5 kg/m2 (Olson, 1981).
Spatial variation in fire response is widely a result of differences in
fuel mass before fire, fuel moisture content, fire weather conditions
and site topography. The frequency of fires (both regional frequency and
return time) is regulated by the frequency and timing of ignition
events, fuel accumulation rates and landscape configuration. The
importance of this latter factor has received considerable attention
(Minnich, 1983 and 1988; Turner, 1987; Malanson, 1984). The relative
impact of topography and space variation of fuels depends on weather
conditions and fuel moisture. At moderate to high of this latter,
variations in vegetation structure and localized landscape fragmentation
(due to past fire history) may determine burning patterns. However, when
fuel moisture drops below threshold levels and weather conditions are
extreme (such as hot, dry winds), fire may be regulated primarily by
wide-scale topographic features such as major rivers or divides (Turner
and Romme, 1994). There is general agreement that the above factors
regulate Mediterranean climate fire systems, but quantitative estimates
of their relative importance are difficult, if not impossible. This is
due in part to limited data available, but is also a consequence of the
stochastic nature of several of these factors. Thus, it is incorrect to
view Mediterranean ecosystem fire regimes as being under finely tuned
feedback control. Indeed, the variability in fire regimes resulting from
these largely (Christensen, 1987; Christensen and Muller, 1975 a and b).
The importance of bushy stratum is a remarkable sign of degradation of
vegetation often reaching the irreversible stage. Furthermore, fires are
a major disruption of Mediterranean landscapes. They are linked to
intense human pressures but also to the character of pyrophytique and
xerophytic vegetation (Delabraze and Vallette, 1974; Houérou 1980;
Tatoni and Barbero, 1995). The current situation of this forest stands
as one of the most critical in the Oran region. According to Benabdeli
(1996), urgent, effective and radical solutions must be found
immediately if we do not want to attend a total disappearance of natural
woody vegetation. The main consequences will result in an amplification
of the desertification process, that is gaining more and more space
through the regression of woodlands and rangelands, erosion, disruption
of water systems, the deterioration of the environment and especially by
a decline in economic and social productivity of natural resources
(Benabdeli, 1996). This increase in forest area is mainly due to the
efforts of the forest service in the field of watershed protection by
various techniques including reforestation of Pinus halepensis ,
which constitutes the main essence. Similarly, these improvements are
insufficient to protect the forest; we estimate that after 31 years,
only 9% of reforestation work has been done to protect the forest of
Tenira. In general, and despite the reforestation campaigns conducted
annually since independence, the reforestation rate in Algeria is
between 10% and 12% only. The reforestation rate remains insufficient
to ensure both the physical and biological balance and does not cover
the needs of field of forest products, nor the economic revenues for the
country (Alexandrian and al., 1999). In the province of Sidi
Bel’Abbes, the pastoral activity care is higher and the animals are
forced to graze off, especially in state forests. The size of the herd
necessarily led to the degradation of the forest and damaging the young
plantations (Benabdeli, 1996). Our forests are often solicited by
pastors as an auxiliary source for livestock feed (Benabdeli, 1996). The
cattle farming remains the most practical at the level of forest areas
in high altitudes. More than 1 200 000 head of cattle are found in the
mountainous forest areas (Benabeli, 1998). The permanent increase in
herds imposed a destructive pressure especially on forest areas
(Benabeli, 1998). According Bedrani, 1993, if the number of herds is
high it easily destroys the protective vegetation cover in forestry. The
trampling of the powdery surface of soil causes a reduction in
permeability therefore, its water reserves increase by favoring runoff.
The clearings leave a strong imprint on the physiognomy of this forest,
where large areas have been converted into pasturage and cereal field.
The extension of agriculture on the plains of Tenira led at the
inhibition on the foothills on the edge of forests. Currently, private
populations of farmland on the mountains continue to carry out plowing
in different levels of the forest edges, clearings, mountain tops
(Benabdeli, 1993). According to the results obtained, the installation
of annual crops is very important. Indeed, deforestation and land
clearing for agriculture have accelerated soil erosion. By the
intensification of crops requires an increase in inputs (fertilizers,
mechanization, irrigation, chemical control of parasites and weeds)
which can lead to a certain imbalance in the soil, but that the
resulting degradation depends on clearing, plant cover, and the cropping
system in place. Clearing new lands which are more and more fragile, the
biomass of a dense forest (> 800 t / ha: might believe that
the soils are extremely fertile. The rock is so deeply altered that all
that remains in the soil cover is quartz, kaolinite, a little iron and
aluminum, and some traces of incompletely altered minerals. The roots
are concentrated in the surface horizons where organic matter and
available nutrients are found. Brutal clearing or poorly adapted
cultivation techniques, the humus horizons are stripped there remains
only a crusted, compact, inert, almost sterile mineral mass.
Biogeochemical assessments show that under natural vegetation (forest or
undegraded savannah) the inputs of nutrients by rain, dust and
biological returns (roots and meso-fauna) exceed the losses by erosion
and by deep drainage. The balance being positive, the forest fallow
accumulates on the surface (in the litter and the humus) organic matter
capable of storing water and nutrients, and the nutrients that the roots
have recovered in depth (Roose, 1980; Beirnaert, 1941; Fauck and al.,
1969-77; Godefroy, I974; Roose 1972-82; Lal, 1982). This population
exerts continuous pressure on the forest types by clearing and
overgrazing this disrupts forest protection and development. However,
any clearing interrupts this chain of potential fertilization
accumulation. The contributions decrease (reduction of the meso-fauna
and the efficiency of the root network to capture the nutritive elements
under most cultures) and especially the losses increase. Exporting crops
reduces the stock of easily tradable items; 50% of organic matter is
mineralized after 4 years and part of the nutrients released are leached
(Fauck and al., 1969; Kang and Juo, 1982). Quezel and al.,1992; argue
that in 50 years without a total change of socio-economic and of forest
policy, it should theoretically remain less than half of the current
area covered by forests. The regeneration after 2007 fire was very low
especially for the formation of thuya and lentisc. However, regeneration
between 2007 and 2010 was significant for groupings of aleppo pine. The
progressive destruction of the soil in the root systems of these types
of forests prevents optimal recovery of some species, and the trees are
close to their ecological limits (sauvages, 1961). According Trabaud,
1992 a; five years are sufficient for the burned resumed woody
vegetation. The passage of a fire resulting in the alteration more or
less pushed vital organs of the plant, to the foliage, trunk, and roots,
it follows a loss of tree vigor that could cause its death. In almost
all cases, after the fire, the vegetation quickly returns to its
original state without human interference. Heat can destroy underground
organs or seeds of survival, and thus greatly limits the regeneration of
vegetation, resulting in a floristic impoverishment. The repeated fires
result in a marked floristic impoverishment. Thus, many plants do not
have time to reach sexual maturity before the passage of a new fire. In
these semi-arid areas, in normal circumstances out fires, the vegetation
is in continual struggle against the harsh climate, its poor soil
nutrient, and organic matter. The passage of a fire even in low
intensity translates directly by impairing the vital organs of the
plant; at tree, vigor may cause their death (Benabdeli, 1996).