Rangelands in Arid Ecosystem

The world’s rangelands constitute an important global resource. Range has been defined by the society for range management as land which supports vegetation useful for grazing on which routine management of that vegetation is through manipulation of grazing rather than cultural practices. Grazing systems are biological systems controlled by: athe biotic factors of climate and site, bthe management inputs and decisions of man, and 3internal regulatory mechanisms involving feedback.

the north western desert falls in the arid region except for the coastal strip.Water resources are scarce and variable.As a result the local community has developed a wide range of strategies for managing water resources in this region.Traditionally, they move around for water, pasture and croplands, based on the rainfall pattern.But recently and after being sedentary, together with population growth, overuse of water resources, over grazing and uprooting of indigenous vegetation.Climate changes, and other political and social forces, there has been an increased pressure on land resources that affected its performance and provision of goods and services.
One of the most common forms of land use in the Western Mediterranean coastal region of Egypt is animal husbandry.Its contribution to the livelihood of Bedouin increases from Alexandria to the westward direction.Grazing material and fire-wood as energy sources are two major basic needs of the inhabitants of the western desert of Egypt.The western Mediterranean desert land is one of the richest phytogeographical region in Egypt for natural vegetation because of its high rainfall.The natural vegetation includes many species of annuals, mostly herbs and a few grasses, perennial herbs, shrubs, sub-shrubs, and a few trees.These species represent 50% of the total flora of Egypt.The botanical composition is spatially heterogeneous depending on soil fertility, topography, and climatological conditions but with sub-shrubs dominating the vegetation (Ayyad and Ghabbour, 1977).
The Mediterranean desert west of Alexandria is referred to as Mareotis (or Mariut) and It is one of the arid regions which has a long history of intensive grazing and rain-fed farming.It is seldom found that any one family is engaged either in cultivation or in herding usually there is a mixture of these activities.In such region the yield and nutritive value of consumable range plants are highly dependent upon rainfall (Le Houérou and Hostte 1977;Heneidy 1992).However, the conditions of the pasture and vegetation performance also depend upon rainfall.
The total area of the rangeland is about 1.5 million hectare.The number of animals per folks varies among the Bedouin, and between regions.A herd size of about 200 head of sheep and 60 head of goats, may be reaches to 300 heads.The total number of animals which graze the rangelands is about 1.5 million head, therefore the average stocking rate is one head /ha.(Heneidy, 1992).
There is no consistent range management strategy in control of the season long grazing in the area, which varies mainly with climatic condition, availability of watering points and availability of supplementary feed.Absolutely the stocking rate leads to the problem of overgrazing.Overgrazing has been one of the main factors causing the deterioration of ecosystem productivity in the Mediterranean coastal region.It has resulted in severe reduction of perennial cover, soil erosion and formation of mobile dunes.
Grazing and rain fed farming provide a clear example of the impact of man's disruptive action on arid and semiarid regions.Continued uncontrolled grazing, wood cutting and farming have, however, induced a process of degradation.This is coupled with severe environment, uncertainty of rainfall and a change in socio-economic circumstances, has resulted in an advanced stage of desertification.As a result, the region now is producing at a rate less than its potential, and is continuing to lose the productivity it had.The degradation of renewable natural resources in arid and semi-arid areas has become a matter of great concern.This region includes several types of habitats (e.g.sand dunes, saline depressions, coastal ridges, non-saline depressions, wadies, inland plateau, inland ridges, etc….).The causes of degradation of rangeland in the Mediterranean coastal region of Egypt, are mixes of environmental, socio-political and socioeconomic conditions (Ayyad, 1993;Heneidy and Bidak, 1998).In recent years reclamation and cultivation of desert areas in Egypt became a necessity.The coastal Mediterranean semi-arid stripe and the inland new valley areas are possible promising fields for such a purpose.

Selection of stands for vegetation analysis
Several stands were distributed within the study area extending from the non saline depression to the inland plateau.These stands were selected to represent major apparent variations in the physiogonomy of vegetation and in topographic and edaphic features.For sampling of the vegetation, about fifty 1 X 2 m 2 quadrates were located randomly in each stand.The presences of each species in each quadrate were recorded, and the number of its individuals counted.The number of individuals and occurrences of each species in the quadrates was then used to calculate its density and frequency respectively.The lineintercept method was used for estimation of cover.The lengths of intercept of each species in a stand was measured to the nearest centimeter along five, 50 m long transects.This length was then be summed and expressed as a relative value of the total length of the five transects.Relative density, frequency and cover for each perennial species were summed up to give an estimate of its importance.

Consumption
Consumption is the amounts taken by grazing animals-Consumption depends on many factors and it is differ according to types of livestock.Estimation of the consumption rate was carried out using the Bite method as follows.The flock, which normally consists of about 100 heads, was observed for 24 hours twice a week in each habitat.A particular animal in the flock was observed for five inputs, using field glasses and a tape recorder.
During each hour of the daily grazing period, ten animals were observed in a cycle of 50 minutes to represent the hourly consumption behavior to record the observations.Estimation of the consumption of different plant species by the grazing animals is based on three main measures: (a) The number of times each plant species was used in the diet of a single animal (number of bites per unit time).(b) Average size of material removed from each species in one bite.(c) The location on the canopy from which this material was removed.At the end of each month, 20 samples of each species simulating the average bite size were clipped and used to estimate the average of fresh and dry weights of the bite of that species.The weight and the number of bites were used to calculate the fresh and dry weight of consumed material and the amount of water.This technique was applied also by Jamieson & Hodgson, 1979;Chamber et al. 1981;Hodgson & Jamieson 1981;Illius & Gordan 1987;andHeneidy (1992, 1996).The total number of bites per animal per day of each plant species multiplied by the average weight of material removed in each bite will express the amount of material removed per animal per day.This estimate will then be multiplied by the value of the stocking rate of animals in the area to provide an assessment of the amount consumed from different plant species per hectare per day.

Palatability
Palatability of the range plants was determined and classified into four categories according to the palatability index reported by Heneidy (2000) and Heneidy & Bidak, (1999).

Phytomass (standing crop phytomass, accessible parts, and necromass or litter)
Homogeneity of a stand was judged according to edaphic and physiographic features.The direct harvest method was used for phytomass determination according to Moore and Chapman (1986).All above-ground parts of different life-forms of the most common palatable species were excavated in each stand, and directly weighed in the field.Representative individuals of each species were collected in each stand during two seasons, spring and summer (representing the wet and dry season), for standing crop phytomass determination and also to determine the vegetative and accessible parts (available parts) depending upon the morphology and configuration of the plant species (Heneidy, 1992;2003a).Nomenclature and identification were carried out according to Täckholm (1974) and the Latin names of species were updated following Boulos (1995).

Economic value
Economic value of plant species were estimated based on: 1-direct observation in the field; 2-preparing a questionnaire form to the inhabitants.The questionnaire was prepared to obtain information about fuel wood, traditional uses of some plant species; 3-the previous experience in the field of study.

Omayed biosphere reserve as a case study
Omayed Biosphere Reserve (OBR) is located in the western Mediterranean coastal region of Egypt (29° 00 ' -29° 18' E and 30° 52' -20° 38' N).It extends about 30 km along the Mediterranean coast from west El-Hammam to El-Alamin with a width of 23.5 km to the south (Fig. 1).Its N-S landscape is differentiated into a northern coastal plain and a southern inland plateau.The coastal plain is characterized by alternating ridges and depressions running parallel to the coast in E-W direction.This physiographic variation leads to the distinction of 6 main types of ecosystems: 1-Coastal ridge, composed mainly of snow-white oolitic calcareous rocks, and overlain by dunes.2-Saline depressions, with brackish water and saline calcareous deposits (i.e.salt marshes).3-Non-saline depressions, with a mixture of calcareous and siliceous deposits of deep loess.Rainfed farms are a pronounced man made habitat within the non-saline depressions in this region.4-Inland ridges, formed of limestone with a hard crystallized crust, and less calcareous than the coastal ridge.5-Inland plateau, characterized by an extensive flat rocky surface and shallow soil.And, 6-Inland siliceous deposits, sporadically distributed on the inland plateau.The deposits of this ecosystem vary in depth and overly heavier soil with calcareous concretions at some distance from the soil surface.This soil is poor in organic matter and nutrients, particularly in the siliceous sand horizon (Heneidy, 2003b).Major economic activities: Raising herds by grazing, intensive quarrying and rainfed cultivation of grain crops, vegetables and orchards depending on water availability (mainly rain).Irrigated land agriculture is another potential acitivity that is introduced due to the extension of an irrigation canal from the Nile delta to the region.
Major environmental/economic constraints: Land degradation, habitat fragmentation, overgrazing, loss of biodiversity, salinization of soil, over exploitation of mineral and water (ground water) resources are the major environmental constraints The economic constraints stems from the general economic status of the local inhabitants that ranges from low to moderate, due to the following:


Absence of permanent source of income (revenue),  Lack of skills  Major activities are seasonal (agriculture and grazing)  spread of unemployment and thus poverty Integration of environmental conservation and sustainable development can perfectly be implemented in OBR as the area is an ideal site for the sustainable development of 18 natural resources, by rationalizing ecotourism, rangeland management, propagation of multipurpose woody species, and promoting local industries based on native knowledge and experience of inhabitants.Tourism oriented towards natural history and traditional lifestyle is expected, especially with the spreading of nearby tourist villages.Nature watching (vegetation in spring, birds and wild animals, etc.), ancient devices of rain water harvesting and historical buildings (Zaher Bebars citadel from the thirteenth century) are types of tourist attractions in this reserve.

Vegetation -Environment relationships
Five major types of habitat are recognized in the study area: coastal sand dunes, inland ridges, non-saline depressions, wadis and inland plateau.Each of these habitats is characterized by local physiographic variations which effectuate variations in vegetation composition and species abundance.The application of the polar ordination, tabular comparisons and principal component analysis, resulted in the classification of vegetation into groups related to environmental and anthropogenic factors.
Dunes are fashioned by the influence of onshore winds which are predominantly northwestern.Sand moves inland in a series of transverse dunes.Close to the shore, dunes are relatively small and active.Further inland they become larger and, being more heavily covered by vegetation, tend to become more or less stabilized.They exhibit a typical dune from with gentle windward slopes and steep leeward slopes.In the shelter of stabilized dunes, active deposition of sand in front of steep leeward slopes results in the formation of sand shadows Ayyad (1973).Kamal (1988)  All vegetation groups of both eastern and western provinces of the coastal dunes indicates that the vegetation is co-dominated by Ammophila arenaria, Euphorbia paralias, Zygophyllum album and Deverra triradiata, sincethese groups (Kamal, 1988).ii.The salt marsh is characterized by high density of salt tolerant shrubs (e.g.Atriplex halimus, Suaeda spp., and Salsola spp.) .iii.The rocky ridge habitat is dominated by the subshrub (e.g.Gymnocarpos decandrum, Anabasis oropediorum and A. articulata, and Artemisia herba alba).iv.The non-saline depression habitat is dominated by Anabasis articulata Asphodelus ramosus, Plantago albicans, and Thymelaea hirsute.v.The inland plateau habitat is dominated by Thymus capitatus,Globularia arabica, Asphodelus ramosus, Herniaria hemistemon, Scorzonera undulata and Deverra tortuosa Plantago albicans,Thymelaea hirsuta.Noaea mucronata, and Echinops spinosissimus.

Effect of ploughing on species abundance and diversity
This study focuses on the effect of ploughing on plant abundance, vegetation cover, species richness, and taxonomic diversity during the growing seasons (winter and spring) of 1992 and 2000 in the habitat of inland plateau.Ninety-five species belonging to 27 families were recorded High percentages of life-forms and a large number of species were recorded in ploughed and unploughed stripes in the winter and spring of 2000 (Fig. 2).Higher averages of importance values (IVs) and absolute frequencies were recorded for most perennial and annual species in the unploughed stripes compared to the ploughed ones.This may be attributed to crop failure and consequently unfavourable soil conditions.On the other hand, some shrubby species (e.g.Noaea mucronata and Haloxylon coparium) and perennial herbs (e.g.Gynandriris sisyrinchium) attained higher IVs in the ploughed stripes compared to unploughed ones.This may be attributed to the cultivation of Prosopis juliflora trees in the elevated part of the ploughed stripes, which have an ecological role in protecting and enriching the soil with organic matter, thus favouring the growth of these shrubs and perennial herbs.Higher species richness and diversity were associated with low concentration of dominance and low taxonomic diversity in the spring of 2000 in ploughed and unploughed stripes compared to the winter of 1992, for both perennials and annuals.
The lowest taxonomic diversities were exhibited in the spring of 2000 for ploughed and unploughed stripes where the vegetation had the largest number of congeneric species and confamilial genera.Higher species richness and diversity characterized the vegetation of the unploughed stripes, especially in winter and spring 2000, as compared to those of ploughed ones.This study also reveals low species richness and diversity of therophytes in winter for both ploughed and unploughed stripes (Kamal et al., 2003).
Species richness and other diversity measures of ploughed and unploughed stripes showed that species richness (Figure 3) was usually high for perennials in the year 2000 in both ploughed and unploughed stripes.It also indicated that the unploughed stripes are substantially the most diverse, as estimated by Shannon's index (H' = 3).The same trend was also notable for annual species (Figure 4).Accordingly the lowest dominance was attained in spring 2000 for ploughed and unploughed stripes.

Existing state
Rangelands constitute about 47% of the total of 332 million hectares.The vegetation resource on these lands is often sparse and droughty.Therefore these lands often require extra measures of management in order to provide forage and wildlife habitat as well as uses on a sustained yield basis (Tueller, 1988).
Generally, one of the most common forms of land use in the western Mediterranean coastal region of Egypt is animal husbandry.Its contribution to the livelihood of Bedouin increases from west of Alexandria to Sallum (border of Egypt).The natural vegetation includes many species of annuals, mostly herbs and a few grasses, perennial herbs, shrubs, sub-shrubs, and a few trees.These species represent 50% of the total flora of Egypt.The botanical composition is spatially heterogeneous depending on soil fertility, topography, and climatologically conditions but with sub-shrubs dominating the vegetation (Ayyad and Ghabbour, 1977).The composition of growth forms in the region expresses a typical desert flora.The majority of species are either annuals (ephemerals) or geophytes (perennial ephermeroid herbs and grasses).Both are "drought evaders" in the sense that the whole plant or the greater part of the photosynthetically active and transpiring (above ground) organs are shed during the rainy season.The majority of other perennials in the study area are evergreen shrubs or sub-shrubs (Chamaephytes).
There are three major land uses in the dry lands: rangelands, rain-fed cropland and irrigated land.The following table shows generally about 88% of the dry lands are used as rangelands, 9% are rain-fed croplands, and 3% are irrigated lands in the arid, semi-arid and dry sub-humid climatic zones.Table 1 shows a list of plant species with different life-forms, in El-Omayed Biosphere Reserve (Heneidy, 1992).

Palatability and preference
Palatability of range land species is a very complex notion, very difficult to generalize as it is linked to many factors that vary in time and place.Some of these variables are linked to the plant, other to the animal, while a third category depends on various environmental factors (Heneidy, 1992, 1996: Le Houéou, 1994).In the north western Mediterranean region, Heneidy (1992) recorded that the temperature is the most effective factors on the animal behaviour.One approach to recording food selectively is based on observation of feeding animals (Bjustad et al., 1970).Grazing animals change their behaviour, and hence their food preferences in relation to differences in temperature and rainfall (Castle and Halley, 1953).Given a free choice, herbivores exhibit marked preferences amongst the available foods but will rarely eat one food to the exclusion of all others.Selectivity of herbage expresses the degree to which animals harvest plants or plant parts differently from random removal.Van Dyne and Heady (1965) use ratios between the proportion of any species, part of plant, or group of plants in the diet, and the proportion of that item in the herbage available to the animal as an expression of relative preference (or selectivity ratio).Using such ratios for the vegetation of the present study has resulted in ranking of perennial species growing in the different habitats during spring as follows (Table 2).
It is interesting to note that species with the highest ranks of relative preference are those with relatively lower availability or abundance.For example, P. albicans is the species with the highest selectivity ratio in the habitats where it grows.It's share in the diet selected by animals in season of maximum consumption is more than fourfold its share in the available forage for the animals.This species represents less than 5% of the grazeable phytomass in the range, but as high as about 22% of the diet consumed.This is also true in the case of H. lippii which provides available forage not more than 7%, while it contributes up to 19% of the animal diet especially in the ridge habitat.On the other hand, the species ranked as of lower selectivity ratio are those which are more available or abundant in the ridge.Fore example, E. fruticosum has a proportion in the animal diet (about 13%) of one third its proportion in the available forage (about 40%).Le Houéou (1980a) discusses such relationship between palatability and abundance, and states that all other attributes being equal, the palatability of a given taxon is inversely related to its abundance in the range, except for a few species which are specially relished in all circumstances.A. microcarpus in the present study represents such species whose selectivity by animals is independent of their abundance on the range.It's selectivity is related more to the phenological development of the plant.Consequently, its highest selectivity ratio is attained during winter at the phase of flower bud development.At this phase, the animals consume much of these flower buds (up to 40% of the diet), while they represent not more than 4% of the available forage.On the other hand, when the above-ground shoot of A. microcarpus dries up during and summer and autumn, it provides about 30% of the material available for grazing and constitutes more than 50% of the animal diet.Many studies (e.g.Cook, 1972;Dicko-Toure, 1980;Le Houéou, 1980b) refer to the relationship between palatability of a given species or taxon, its stage of development (phenology), its relative abundance on the rangeland, and its chemical composition.Cowlishow and Alder (1960) assert that palatability of a given species changes because of changing characteristics that an animal can recognize by its senses of sight, taste and smell.
Table 2 shows a list of plant species and their palatability in Omayed Biosphere Reserve.63% of these species are palatable while, 42% of them are highly palatable.

Biomass and productivity
El-Kady (1980) estimated the effect of protection and controlled grazing on the vegetation composition and productivity as well as the rate of consumption of phytomass by domestic animals and their grazing behavior, in the ecosystem of non-saline depression.Plots were fenced and different grazing pressures were applied in the vegetation in these plots.Changes in the density, cover, frequency, phytomass and the phenological sequence of species were recorded and compared to those of the same species outside the fenced plots.
Remarkable increases were recorded in total density and cover of perennials, in frequency and presence of animals, and in phytomass as a result of protection and controlled grazing.
It was concluded that partial protection and controlled grazing could be of better consequence than full protection: light nibbling and removal of standing dead by domestic animals may promote vigor and growth of defoliated plants, and the availability of nutrients may be enhanced by the passage of herbage through their guts and out as feces.
Heneidy (1992) reported that the annual above-ground dry matter production of the rangeland at Omayed area in the different habitats were about 2833 kg/ha in the non-saline depression, 1448 kg/ha in the ridge, and 4416 kg/ha on the inland plateau habitats.In general preliminary field observations on the behaviour of grazing animals indicated that almost all the consumed forage is contributed by sixteen perennial species (most common) and annuals (Table 3) throughout the year.In general the total phytomass of new growth was highest in the habitat of the inland plateau, and lowest in the ridge habitat.In general the total phytomass accessible to grazing animals (kg/ha} varied remarkably with season and habitats, from a minimum of 308 kg/ha in the ridge habitat to maximum of 1543 kg/ha in the habitat of inland plateau.Inland plateau habitat is characterized by (1) Remarkably higher annual production (Accessible); (2) Remarkably higher nutritive value; and

Lycium europaeum
The highest contribution by perennial herbs in all habitats was attained during winter and spring (13%, and 10.9% in the none-saline depression, 12.7% and 13.5% on the ridge, and 9.5% and 8.3% on the inland plateau).On the other hand, the maximum contribution by most subshrubs was attained during spring.The contributions by subshrubs in the habitats of non-saline depression, the ridge and the inland plateau in spring were 15%, 14.5% and 10.1% respectively.

Accessible (consumable) biomass
The accessible dry matter production of the subshrubs and forbs together (maximum values of the different seasons) is estimated by Heneidy (1992) as about 741 kg/ha/yr in the non-saline depression, 371 kg/ha/yr on the ridge and 745 kg/ha/ yr on the inland plateau (average of 677 kg/ha/yr, equivalent to about 4.5 kg/ha/yr/mm rainfall).For sub-shrubs te accessible dry matter production represents about 4,5, and 2% of total above-ground phytomass in the non-saline depression, on the ridge and on the inland plateau respectively, while they contribute about 30,20, and 19% to the amount of consumable forage in the tree habitats respectively.On the other hand, The accessible dry matter production of forbs represents about 4,6 and 3% of total above-ground phytomass in the non-saline depression, on the ridge and on the inland plateau, while they contribute about 31, 34 and 27% to the amount of consumable forage in these habitats respectively.The accessible dry matter production of shrubs is about 491, 253, and 879 kg/ha/yr in the three habitats respectively (average of 554 kg/ha/yr, equivalent to about 3.7 kg/ha/yr/mm rainfall).The accessible dry matter production of the large shrubs represents about 5,7, and 6% of total above-ground phytomass in the non-saline depression, on the ridge and on the inland plateau respectively, although they contribute about 10, 39 and 11% to the amount of consumed forage in the three habitats respectively (the higher percent of contribution of shrubs to the diet on the ridge is due to the presence of the highly palatable species (Anabasis oropediorum).This indicates that the shrubs form the skeletal structure of the community, provide the needs for the long term conservation, and share in the annual cycling of material through the food chain.The above mentioned results indicate that a relatively high annual primary production is provided by the rangeland under study (about 3016 kg/ha, equivalent to 20.0 kg/ha/yr/mm rainfall), most of which is used to build up the ligneous structural component of the plant community.Only about 18.4% of the total above-ground annual production is accessible to the grazing animals.Heneidy (1995) reported that the accessible biomass in the different habitats in the east of Matrouh (rocky plateau as about 436, flat plateau is 292, rocky ridge is 620, non-saline depression is 776, and saline depression is 393 kg/ha.).Table 4 summarizes the biomass and accessible parts in the different habitats during the two seasons.The highest total above-ground phytomass of the vegetation is produced in the rocky ridge during the wet season (1897 ± 843 kg ha -1 ) where, the contribution of perennials is 86% while the lowest is in the saline depression (675 ± 22.9 kg ha -1 ) where the contribution of perennials is 91%.However, the highest accessible parts are produced in the non-saline depression 864 ± 35 and 400 ± 64.3 kg ha -1 during wet and dry seasons respectively.Table 5 showed the RUE for primary production level as an average and accessible production of different habitats.RUE to accessible 3.9 7.5 6.6 6.3 1.4

Habitat
Table 5.The net primary production (NPP), accessible production (mean ± SE as kg ha -1 yr -1 mm -1 ) and rain use efficiency (RUE) of different habitats.
The primary productivity of the pasture in different habitats ranges from 169 ± 5.3 to 1083 ± 674 kg ha -1 yr -1 in habitats of the saline depression and rocky ridges respectively.The accessible production level reached its maximum in the habitats of rocky ridge (449 ± 165 kg ha -1 yr -1 ) while the minimum is attained in the saline depression (149.5 ± 1.8 kg ha -1 yr -1 ).
Measurement of plant biomass or productivity has been of interest to range workers and ecologists for some times because herbivores depend directory upon plant biomass for their food (Milner and Hughes, 1970).On the other hand, any ecological argument in land use planning in arid rangelands should be based on a through knowledge of the harvestable primary productivity.Study of the vegetation by Heneidy, (2002a) indicated that it consists of 39 perennial species and 43 annuals.The grazeable (mostly new-growth) phytomass is either accessible or non-accessible to the grazing animals due to morphological configuration of the plant.A portion of the accessible phytomass is actually grazed and another portion is left over (Heneidy, 1992).The study also reveals that the study area is vegetitionaly rich and the woody species are the most abundant life-forms.The woody species are considered the skeletal part of the grazing system in arid ecosystem (Abdel -Razik et al., 1988a).The grazing system represents 60 to 80% of the utilization land of North Africa area in terms of economic output (Le Houèrou, 1993).In the study area most of the land is used as grazing land.
Most perennial species exhibit their greatest vegetative activity during winter and spring, and they are less active or dormant during summer.This observation agrees with that noticed by Abdel-Razik et al. (1988a) at Omayed in the northwestern region.However, some shrubs and sub-shrubs are active throughout the whole year.These species are more conservative in the use of their own resources, especially soil moisture and have developed a root system that is capable of exploiting soil moisture and minerals from a large volume of soil and at depth that is permanently wet, which in-turn enables them to extend their activities under conditions of moisture stress Ayyad et al. (1983).This behavior of plant species occurs in some species in the study area.This type of species plays an important role in the sustainable production of the natural forage of the pasture.
(Noy-Meir, 1973) suggested that the bulk of primary standing biomass of the community in semi-arid regions is made up of woody life-forms.This means that accessible parts do not depend upon the primary above-ground phytomass, but depend upon the configuration and morphological shape of the species and their life-forms (Heneidy, 1992).Fritzi and Bradley, (1992) recorded that the production level of herbivores may depend more upon plant architecture than on the particular species of natural enemies present.
The annual average of the primary production in the western desert was 590 ± 117 kg ha -1 yr -1 , while the accessible production was 410 ± 39 kg ha -1 yr -1 , compared with that of the woody steeps in arid zones which ranges from 300 to 600 kg ha -1 yr -1 (Le Houérou, 1972).This value is less than that obtained by Abdel-Razik et al. (1988a) and Heneidy (1992) at Omayed in the coastal region (668 and 720 kg ha -1 respectively).However, the average of annual forage yield in the saline depression habitat in coastal region was 1560 kg/ha (Heneidy and Bidak 1996) which is three times higher .
The RUE factor is the quotient of annual primary production by annual rainfall.RUE tends to decrease when aridity increases together with the rate of useful rains, and as potential evapotranspiration increases.But it also strongly depends on soil condition and, more than anything, on vegetation condition particularly on its dynamic status.It thus greatly relies on human and animal impact on the ecosystems.The RUE is a good indicator of ecosystem productivity (Le Houérou, 1984).
The average of accessible dry matter production per mm rainfall ranges from 7.5 to 1.4 kg ha -1 yr -1 in the habitats of flat plateau and the saline depression respectively.The average Rain Use Efficiency (RUE) was 5.1 kg ha -1 yr -1 mm -1 for accessible production while for primary production was 10 kg ha -1 yr -1 mm -1 .In Comparison, the average of the grazeable dry matter production per mm rainfall at Omayed area is 4.8 kg ha -1 yr -1 (Abdel-Razik et al., 1988a) while that average of RUE was 10.4 kg ha -1 yr -1 mm -1 at salt marshes in the coastal region (Heneidy and Bidak 1996).Actual RUE figures throughout the arid zones of the world may vary from less than 0.5 in depleted subdeseric ecosystems to over 10 in highly productive and well managed stepped (Le Houérou, 1984).
Generally, the great variations in the productivity levels in different sites are due to variations in soil, climate, vegetation types, and grazing pressure.Consequently Coefficient of Variation (CV) was taken as a measure of this relative variation in production responsiveness at different sites.Calculated CV of the primary production (1.2) indicates that there is a great variation between sites.This variation does not depend upon rainfall and only may hide other factors as mention above (e.g.life-forms, soil condition, topography and human impact ..etc).This result agrees with results obtained by Le Houérou (1988) where he assessed that variability in primary production does not depend only on rainfall, but also on ecosystem dynamic, soil surface condition and texture.The following The rainfall (mm) ± S.E 75.4 ± 6.7 ----0.5 Carrying capacity ranged from 0.5 to 4.4 ha head -1 .The variability of annual production was 1.2 times that of the variability of annual precipitation.Production to Rain Variability Ratio (P/RVR) averages 2.4 world-wide in primary production than in accessible.Conversely, P/RVR increases when rainfall decreases and with ecosystem degradation.Finally natural vegetation is affected by rainfall variability in its composition, structures, morphology, ecophysiological adaptation and physiological processes.RUE decreases with rainfall and with the depletion status of the ecosystem (biomass, permanent ground cover, organic matter, microbial activity), (Le Houérou, 1988).
The relative highly annual production of the range land under study as compared to the average production of North Africa which varies between 200 ton ha -1 yr -1 (Le Houérou, 1975 andSarson &Salmon, 1977) may be attributed to the fact that its vegetation is composed mainly of perennials that can exploit moisture substantial at deep layers of the soil.It is also represents a good production level if compared with the production level at Omayed area 80 km west of Alexandria (Heneidy, 1992).However, this area needs more studies and a good plan for improvement as rangeland within the carrying capacity of the ecosystem, for a sustainable development.

Biomass and production in the three main habitats
Heneidy (1992) reported that the annual above-ground dry matter production of the rangeland at Omayed area in different habitats was about 3833 kg/ha in the non-saline depression, 1448 kg/ha in the ridge, and 4416 kg/ha on the inland plateau habitats.In general preliminary field observations on the behaviour of grazing animals indicated that almost all the consumed forage is contributed by sixteen perennials (Table 3) throughout the year.In general the total phytomass of new growth is highest in the habitat of the inland plateau, and lowest in the ridge habitat are summarized in the following

Necromass
Generally, pasture production depends, among various factors, on the type and intensity of management, e.g.grazing pattern and stocking rate.Such practices can significantly influence species, life-form and growth-form of plants.Herbivory can also affect the structure and functioning of the community.Therefore, a relatively large proportion of annual productivity is either incorporated in ligneous parts of standing dead material near the end of growth period, since most of species, except the evergreen shrubs, are dormant during the dry summer season.Besides, intense defoliation during the growing season may conserve sufficient soil moisture to allow for adequate growth during the late season even during years with below average precipitation.Therefore, it may be concluded that the accessible forage in the area can support at least three fold the present stocking rate, provided that the supplementary feed be also tripled.In general, the contribution of shrubs to the consumed diet on the ridge habitat is higher than that in the non-saline depression and the inland plateau habitats.Conversely, the contribution of annuals in the non-saline depression is much higher compared to those in the other habitats.In detail the average necromass (Kg/ha) exhibited notable variations with habitat and season (Table 6).For example in the non-saline depression it varied between 46.2 kg/ha in summer and 262.2 kg/ha in autumn, on the ridge it varied between 14.4 kg/ha in spring and 159 kg/ha in autumn, and on the inland plateau it varied between 20.7 kg/ha in soring and 156.6 kg/ha in summer.It may be noted that most of the litter was contributed by shrubs and subshrubs.The annual rate of litter production is about 465, 174 and 177 kg/ha in the non-saline depression on the the ridge and the inland plateau respectively.Thus the average litter loss in the three habitats was about 333 kg/ha/yr, which represents less than 11% of annual production of the area.This may confirm the notion that substantial proportion of production of dry matter is invested in the ligneous structural component of the community.

Ecological stress on the grazing ecosystem
The desert ecosystem is exposed to different types of stress as the following: 1-Overgrazing, 2-Woodcutting, 3-Aridity, 4 -Salinity, and different types of human activities, and 5-Erosion of soil surface (e.g.Plates 2A, B, C and D).Rangelands constitute approximately 90% of the country's land surface area.The products are renewable; thus the ranges are capable of providing continuous goods and services such as forage, fiber, meat, water and areas for recreation.These resources are considered by many people to be an integral part of their traditional Arab heritage, which adds special importance to their value.Concomitantly, rangelands are now in a poor condition due to pressures that have either altered or destroyed them as a result of overgrazing, uprooting of plants and off-route use by vehicles.These factors have resulted in an almost complete removal of vegetation cover, a speeding up of the desertification process and the destruction of wildlife habitats.
Vegetation and land degradation is still widespread in the Mediterranean region.Degradation results from various kinds of mismanagement of the land.This include the introduction or expansion of agro forestry systems with multiple-use of the land to develop tourism, wildlife, hunting and sports, combined with extensive grazing of livestock and game and timber production from elite clones of selected high yielding or highly valued species.

Causes of land degradation
These causes are essentially linked, either directly or indirectly, to soil denudation in areas, which, because of their topography, slope, geological substratum and soils are erosionprone.They also may be subjected to sedimentation, flooding, water logging, salinisation and alkalization for reasons of the same nature.
Soil surface denudation, in turn, results from a number of causes that may be natural or man-induced.
a. Natural causes play a minor role in Mediterranean region.b.Man-induced causes play by far a major role.These are the following and may act in isolation or in combination of two or more causes: 1-Deforestation due to over-exploitation either for timber, firewood, charcoal, often combined with over-browsing; 2-Long standing overstocking and overgrazing; 3-Forest and shrub land wildfires, combined or not with over-browsing; 4-Inappropriate grazing systems and patterns: heavy stocking combined with continuous grazing; 5-Clearing for cultivation of land that is inappropriate to cropping without adequate precautions of water and soil conservation; 6-Inadequate tillage practices (down slope, steep ground, utilization of disc plough in sandy soils etc.); 7-Unsound cultivation practices and crop distribution patterns; 8-Chemical exhaustion of soil nutrients involving lack of fertility, inappropriate crop rotation practices favouring the leaching of soil nutrients, or export of nutrients consecutive to wild fires.The coastal belt of the western desert of Egypt has some potential of natural productivity and is the site of a variety of landuse and development programme.
The main activities include grazing, agriculture, and woodcutting and over collection especially Matruh to Salloum.Woody plants are, in many instances, the only source of fuel for the desert inhabitants.Batanouny (1999) reported that along the coastal line from Alexandria to Alamein, the sand dunes represent a landscape with special characteristics and features.For more than two decades, due to the conspicuous socio-economic changes, privation, open-door policy in economy and other political changes in Egypt, a great part of the coastlines, has been destroyed.This is due to the continuous construction of summer resort villages.The consequences of the human activities in the area are numerous.These include impacts on the soil, water resources, the flora and fauna, migration birds, trends of the indigenous people, and the cultural environment.
Human activity over thousands of years on the Mediterranean landscape has resulted in major management problems.This long period of intensive grazing, fire cycles, and cutting caused degraded or drastically changes in the natural vegetation of the area (Cody, 1986) and have created a mosaic ecosystems which represent degradation stage (Di Castri, 1981).
Bedouins in Maruit region depend on fuel wood collection from the natural vegetation as an essential source of energy.The daily fuel wood collected by a household was about 29 kg.
The quantity used was about 24 kg/ha, which equal 8.8 ton/year.The excess represents a waste that should be controlled (Heneidy & El-Darrir 1995).All these activities have their effects on the ecological balance of the ecosystem especially if they are carried out at a rate higher than the rate of regeneration of vegetation cover.Heneidy et al. (2002c) recorded, in Omayed Biosphere Reserve that the human activities have more impact on the vegetation than the over grazing by livestock, where various activities (e.g.wood cutting and collection) have different impacts on the plant diversity.
The causes of degradation of the vegetation in the western desert are mixes of environmental, socio-political and socio-economic conditions.Three main lines may be suggested for the initiation of a long-term strategy for the restoration and conservation of degraded vegetation: a. Establishment of pilot areas for protection and controlled grazing in each of the main habitats and communities.b.Initiation of a cooperative system for grazing management between the main social sectors (tribes).c.Formation of an extensive programme me for propagation of endangered species, it is necessary that the decisionmakers and land-users participate in the planning and execution of the activities along these three lines, and that extension services and incentives be ensured in order to encourage their participation.Ayyad (1993) initiated a test programme me for propagation of multipurpose species in the Mediterranean desert and put the main items for executive (1-seed bank, 2-establishment of seed banks, 3-establishment of nurseries, and 4-demonstration of field experiments).

Plants and their defenses
The role of physical defensive factors by range specie against livestock has been interest to many range management researchers.In natural ecosystem, plants are associated with a great number of potential predators and pathogens.Nearly all ecosystems contain a wide variety of bacteria, fungi, nematodes, mites, insects, mammals and other herbivores.By their nature, plants cannot avoid these enemies simply by moving away, but they protect themselves in other ways.The cuticle, periderm, thorns, stinging hairs, and tough, leathery leaves help deter herbivores feeding (Taiz & Zeiger, 1991).Heneidy and Bidak (1998) studied the type of defenses in the range species in the coastal Mediterranean region of Egypt.The vegetation of the region is composed of rangeland species of different life-forms .However, some of these plants may avoid or resist grazing animals by different mode of defenses (spiny leaves or branches, compact woody structure, taste, and fragrant smell. This study depends upon recorded notes through 12 years including daily field observation of different flocks (e.g.grazing behaviours, walking, grazing time, resting time, drinking, number of bites from each species and preference) (Abdel-Razik, et al. 1988aHeneidy, 1992).Heneidy and Bidak (1999) reported that some of the rangelands species have ability for adaptation that avoid grazing activity and how these defenses affect on the palatability, aversion, and consumption.
Fifty-two plant species(44 species perennials and 8 annuals) belonging to 19 families have different defensive mechanisms were recorded in the study area.The type ,degree and the percentage of defense, life-forms, and abundance of each species are presented in Table 7. Types of defense, defense percentage, family, growth-form and abundance of the some modified range species in the western coastal region (After Heneidy and Bidak, 1998), W = Woody and P = Perennual.
Aversion factor (AF) was estimated ratio of the relationships between palatability and the degree of protection.The degree of protection acquired by the studied species distinguished into three classes: 100%, 80% and less than 80%.Each of these classes includes three of palatability rates (HP, P, and LP or NP).Table ( 8) shows that 19 species (31%) are of AF =zero, 53% of which is due to protection and 11% is due to palatability while, 36% is due to both.46% of these species are AF = 1 where, 58% is due to protection, 25% is due to palatability, and 17% is due to both.

Browse in grazing lands and types of livestock in Egypt
The role of browse in natural grazing lands varies in importance according to ecological zone.Under temperate climates and in the humid tropics, browse is of limited use in animal production.However, in the Mediterranean isoclimatic zone, the arid and semi-arid tropics and in montane areas, browse plays an essential role in the animal production, and thus greatly contributes to the protein supply of mankind in Africa.For instance, over 250 million heads of domestic animals live in arid, semi-arid and montane zones where browse is an important quantitative component in livestock diets.In the arid zone the main browse species are dwarf shrubs which constitute the bulk of animal feed (Le Houérou, 1980a).
Rangelands in Egypt are dominated by shrubs; most of those are browsed.These "browselands" cover the following surface in 10 3 km 2 (Table 9).In Egypt the main components of rangelands are shrubs, and dwarf shrubs (subshrubs) Heneidy (1992).The area of rangelands in Egypt is about 125.000 km 2 .Houérou, 1980b).
The total area of the rangeland in the western Mediterranean region is about 1.5 million hectare.The number of animals per folks varies among the Bedouin, and between regions in the coastal zone.A herdsize of about 200 head of sheep and 60 head of goats may be reaches to 300 heads (Heneidy 1992).The total number of animals which graze the rangelands is about 1.5 million head where, in Omayed biosphere reserve is about 15,000 head (ratio 3 sheep to 1 goat) Heneidy (1992).Therefore the average stocking rate is one head /ha.Duivebooden (1985) reported that the total number of animals is about 1.2 million head of sheep, 0.9 million head of goats, and 0.2 million head of camels.The stocking rate of Omayed was estimated as about 0.5-0.6 head/ha (Ayyad & Ghabbour, 1977;Ayyad & El-Kady 1982), which is much lower compared to the average for the whole area.The average rate averaged throughout the year at Burg El-Arab varies from 0.75 head/ha to 1.0 or 1.5 head/ha (El-Kady, 1983 andAbdel-Razik et al., 1988a).Further more, the calculated stocking rate in the Omayed by Heneidy (1992) is 0.286 head/ha, is far below the regional average practices.It should be mentioned, however, that the calculated stocking rate holds true only for those animals grazing yearlong on the pasture, while twice as much as the resident animals is removed to the areas of irrigated cultivation for most of the year.Consequently, spatial variation in stocking rate occurs.In addation, variation in time occurs, due to the migration of livestock in summer.Stocking rate may be reaches to 1.2 head/ha at Omayed ( Van Duivenbooden, 1985).There is no consistent range management strategy in control of the season long grazing in the area, which varies mainly with climatic condition, availability of watering points and availability of supplementary feed.Absolutely the stocking rate leads to the problem of overgrazing.Overgrazing has been one of the main factors causing the deterioration of ecosystem productivity in the Mediterranean coastal region.It has resulted in severe reduction of perennial cover, soil erosion and formation of mobile dunes.

Grazing pressure
The pressure of grazing at any given moment is defined as a relationship between demand for by animals and a comination of daily herbage increment and standing crop of vegetation.This function is related only indirectly to number of animals and area of pasture (Heady ,1975).El-Kady (1980) recorded that partial protection and controlled grazing, might be of better consequences than full protection.

Stocking rate
The total area of the rangeland in the western Mediterranean region is about 1.5 million hectare.Therefore the average stocking rate is one head /ha.The stocking rate of Omayed was estimated as about 0.5-0.6 head/ha (Ayyad & Ghabbour, 1979;Ayyad & El-Kady 1982), which is much lower compared to the average for the whole area.The average rate averaged throughout the year at Burg El-Arab varies from 0.75 head/ha to 1.0 or 1.5 head/ha (El-Kady, 1983 andAbdel-Razik et al., 1988a).Further more, the calculated stocking rate in the Omayed by Heneidy (1992) is 0.286 head/ha, is far below the regional average practices.It should be mentioned, however, that the calculated stocking rate holds true only for those animals grazing yearlong on the pasture, while twice as much as the resident animals is removed to the areas of irrigated cultivation for most of the year.There is no consistent range management strategy in control of the season long grazing in the area, which varies mainly with climatic condition, availability of watering points and supplementary feed.
Absolutely the stocking rate leads to the problem of overgrazing.Overgrazing has been one of the main factors causing the deterioration of ecosystem productivity in the Mediterranean coastal region.It has resulted in severe reduction of perennial cover, soil erosion and formation of mobile dunes.

Forage consumption
Heneidy (1992) reported that the annual consumption of forage by the grazing animals is about 619 kg/ head (average of 1.696 kg/ head/ day).If this value of annual consumption is multiplied by the calculated stocking rate of grazing animals, the consumption rate would be about 0.485 kg/ha/day which is well below the total accessible forage production of different habitats in Omayed.Normally, browse (grazing on shrubs) is supplementary to a herbage based system.It may serve to raise the protein intake for all or part of the year, or it may be essential that animals subsist on browse during cold or dry periods, so that they survive to utilize and breed on the herbage at other times of the year.This indicates the importance of browse species in the area.Taking into consideration that subshrubs constitute the bulk of feed of grazing animals.Such shrubs are therefore valuable in tiding over the periods of limited forage supply.Combining this with the high production levels of woody species, may reflect the importance of such species in arid rangelands.It should be added that the relatively high production levels of some of the perennial herbs ensure a good supply of standing dead material during the dry period that is selected by grazing animals with even higher priority than the available green.The consumption rate of dry matter in the three habitats of the study area (non-saline depression, the ridge, and the inland plateau) is about 0.53, 0.36, and 0.47 kg/ha/day respectively.
The total phytomass accessible to grazing animals (gm dy weight/m 2 ) varied remarkably with season and habitat, from 30.8 gm/m 2 in the ridge habitat in autumn to 154.3 gm/m 2 in the habitat of inland plateau in spring.The total livestock offtake is estimated to be on the order of 6% of primary production in the study area.Therefore, it seems unlikely that livestock exert a major control on plant biomass.
The monthly variations in the species composition of the daily diet of animals in different habitats are presented in Seasonality in consumption behavior of grazing animals in the Omayed site is mainly a function of: (1) variation in the availability of consumable parts of species and their relative palatability, (2) the phenological stages of plants having different nutritional status and characterized their specific chemical composition in energy and mineral elements, (3) the relative need for drinking water, (4) climatic factors, and (5) structure and size of the flock.
The interplay between the previously mentioned three factors let the grazing animal spend periods of voluntary walk over distances that vary between 20 km/day during winter and 9 km/day during summer.These walking experiences represent a transect of about 15 km in length in winter and 7 km in length during summer (Heneidy, 1992).The corresponding grazing time averages about 9 hours/day during winter and 7 hours/day during summer( at the rate of 2.22 and 1.29 km/hour during winter and summer respectively) Ayyad, (1978) reported that in the Mediterranean desert ecosystem variable input of rain would be matched, under relatively light usage, by the supply of forage, but heavy stocking might so damage the grazing that there would be an enfprced decrease in cattle numbers when the rains failed.If the damage were severe, neither forage no cattle numbers could recover and there would be a sustained fall in yield.Grazing tends to damage the most palatable first and then progressively less palatable species, so reducing their frequency in the community.Not all palatable species, however, need be decreases: some may actually thrive on grazing.In the present study some species exhibited a negative response to protection.These species may have been either of low play abilities and were deprived of light nibbling and removal of standing dead shoot, a practice which usually promotes vigour and growth or they may have been unpalatable and due to competition by the protected palatable species became of lower potential for productivity.

Grazing behavior of animals
Grazing animals do not graze continuously .They have specific periods during the 24 hours daily cycle, when ingestive intake is very high and others when grazing is punctuated by ruminating resting and idling.In the coastal Mediterranean region the grazing times varied between 7 and 9 hours with the increase occurring from summer to winter, and with small differences between animals in their annual grazing time spent on different life forms.) In general, there are two periods of grazing activity of domestic animals in Omayed area one in the morning and one in the afternoon, with a resting period in between.The peak of grazing activity differs with season and habitat, but it usually occurs either in the early morning or the late afternoon, particularly during summer.In spring and winter, the peak activity may occur towards mid-day.
In general, the grazing activity during the day stats at six in the morning, and ends at six in the afternoon during autumn and spring, while, in summer it starts at eight, and in winter it starts one hour later and ends one hour earlier.The resting period for grazing animals starts at 12 noon, and lasts for two hours during winter and spring, four hours during autumn, and seven hours during summer.
The annual pasture can be divided into two periods: the wet grazing period (winter, spring) and the dry grazing period (summer, autumn).The effective wet grazing period is that period when green pasture availability is sufficient for the animals to satisfy their appetite and meet all nutritional requirements (about 4 or 5 months) depending on the amount and distribution of rainfall.Seligman and Spharim (1987) indicate that, this green period in arid rangelands of the Middle East lasts only 3 months from December till March.In the rainy season most species are in vegetative stage and furnish an adequate supply of forage to the grazing animals.Some species start activity for a few months when the soil moisture is available, after which they go to dormancy or inactivity.
including, with the exception of phosphorus, more than adequate minerals and are available throughout the year.
Many physical and chemical factors influence palatability of plant species, of which animal behavior and chemical composition are the most important.The contents of chemical constituents in plants and their digestibility vary independendently between different organs and according to plant age (Le Houéou, 1980a andHeneidy, 1992).Of these, crude protein (CP) is viewed classically as an indicator of the nutritional value of food for ruminants.Abdel-Razik et al. (1988 a,b) reported that the analysis of samples which represent the diet selected by the herbivores indicated that the grazeable proportion of the phytomass of most species had in general, higher nutrient concentration than the nongrazeable proportion.Crude protein was a highest concentration early in the growing season, and was lowest at the end of the dry season.The concentration of total nonstructural carbohydrates (TNC) and in the grazeable parts varied also with life-forms and habitats and crude fibers was lower in the wet season in the young parts.The concentration of lipids in the grazeable parts of different species slightly higher in winter and does not exhibit notable differences between habitats (Heneidy, 1992).Heneidy (1992) reported that the percentage of digestible crude protein( DCP) in Omayed area is 4.9%, while Heneidy and Bidak (1996) reported that it reached 6.9%.DCP content of the forage in the coastal region at Omayed area is ranked good according to the scale suggested by Boudet & Riviere (1980) who consider a fair DCP percentage between 2.5 and 3.4.
Total digestible nutrients (TDN) is reported by Abdel-Salam (1985) in the coastal Mediterranean region as about 66% DM, while Abdel-Razik et al (1988b) reported annual average value of TDN for consumable forage as 75% DM and Heneidy (1992) reported the annual average of TDN in coastal region as about 67% DM.Heneidy and Bidak (1996) reported that TDN in the saline depression habitat in the coastal region as about 66.2%.Accordingly the energy content in the coastal Mediterranean region equals 0.76 SFU of the halophytes species, while it was estimated by El-Kady (1983) at Omayed as 0.3 SFU.In general, the nutritive value of forage decreases with advancing maturity of plants.This decrease is mainly due to the decrease in protein content together a concomitant increase in the fiberous components and general lignification.

Recommendations and some suggestions
1. Degradation of vegetation and even the whole ecosystem due to overgrazing is manifest in almost all the localities in the protectorate.The communal system of grazing www.intechopen.com

Fig. 2 .
Fig. 2. (A) Different percentages of life forms in the study area.(B) Life form spectrum of the two seasons winter and spring (1992 and 2000) for the ploughed stripes.(C) Life form spectrum of the two seasons winter and spring (1992 and 2000) for the unploughed stripes.

137 Land use area in global dry lands
Some of most common rangeland species in the Mediterranean coastal region are Anabasis articulata, A. oropediorum, Artemisia monosperma, A. herba-alba, Asphodelus ramosis.

Table 1 .
Wild plant species recorded in Omayed Biosphere Reserve.

Table 3 .
The total standing crop phytomass (old organs + new-growths) and below-ground biomass (gm/dr.wt/m 2 ) of different organs of species in the different habitats at Omayed.Above-ground (old organs + new growths), Bold value = New growths (grazeable parts).

Table 4 .
Total above-ground (TAG) biomass and accessible biomass (mean ± standard error (SE) kg ha -1 ) in different habitats during the two seasons.

Table 11 .
Variations in the daily consumption rate (gm dry wt/head/day) in the different habitats at Omayed.