1 .The ”intensiveî direction views grazing on natural pastures as a significant component in the diet of cattle only in the growing season. The available biomass in the growing season (January -May) and it's nutritional value, are key factors in determining the production potential and profitability of the herd.
    Accordingly, the contribution of the dry pasture (from June to December ) to the production cycle is low and can be replaced with cheap supplementary feeds i.e. poultry litter, wheat straw and gin trash. It is preferential to consume the majority of the pasture when green and to supplement feeding in summer and autumn with cheap supplementary feeds.

2. The ìecologicalî direction differs on two main points, the first being the assumption that the dry pasture has no nutritional value. The ìecologicalî direction claims that the dry pasture, especially the seeds and fruits, can fulfill certain requirements of the grazing animal.
    The second difference involves the long term management of the pastures with regards to conserving the production level of the pasture.
    Excessive intensive utilization of the herbaceous pasture during the growing period can be harmful to the pasture for the following reasons:
1) Increase in soil exposure resulting in soil erosion and removal of nutrients.
2) Damage to plants before seed production resulting in reduced capacity for pasture renewal resulting in a possible decrease in pasture yield even when abiotic factors are stable.
3) Due to the selective feeding behavior of the cattle preferred plant species are consumed first. Intensive management encourages high grazing pressure and as a result the preferred species will be consumed at a rate faster than their seed production and dispersal rate. This can result in a change in the botanical composition of the pasture which will progress during the years and can result in a yield decrease in the pasture. This can also result in the exchange of perennial species with annual species, which although more resilient to grazing, have lower nutritional value and dry out at a faster rate.
    Bush invasion is also a danger when the pastoral herbaceous component is reduced. Bushes have lower nutritional value, cover a large areas (preventing herbaceous growth) and can prevent access to areas.

Influence of grazing on pasture primary production

Estimates of primary productivity of grazed rangeland face the double difficulty of determining long term intake of forage by the herd and the challenge of herbage sampling in large, heterogeneous range units. It is therefore not easy to determine quantitatively the degree to which environmental and management factors limit rangeland productivity in different situations. Annual production has been shown to depend on various environmental factors, in particular rainfall and soil moisture (Le Houerou and Hoste, 1977; Murphy, 1970), radiation and temperature (Wallach and Gutman, 1976), combined weather indices like accumulated degree days (George et al., 1988), soil nitrogen and phosphorus (van Keulen, 1975; Penning de Vries and Djiteye, 1982; Benjamin et al., 1982).

Any effects of stocking rate or grazing system on annual herbage production are superimposed on the environmental effects and may interact with them. The effect of defoliation by grazing is dependent not only on the severity of the grazing, but also on the ecology of the habitat. In seasonal ranges, the end of the season can be abrupt when it is caused by photoperiodically induced maturity or by drastic weather change, like the hot, searing winds in the Mediterranean region; or it can be dependent on the availability and rate of depletion of a resource like water or nutrients. In the first case, increasing grazing pressure should, in theory, reduce primary production; in the second case, not necessarily so (Noy-Meir, 1978).

Influence of deferred grazing in botanical composition and pasture primary production

Where the area of rangeland is a limiting factor in animal production, efficient utilization of the available pasture can be influenced by the grazing system. During the early growing phase of a seasonal pasture, grazing, particularly heavy grazing, can delay range readiness and reduce primary production (Smith & Williams, 1973; Noy-Meir, 1975).
    Consequently, deferment of grazing during the critical early phase should allow the vegetation cover to pass a threshold beyond which the rate of biomass accretion from new plant growth will be significantly greater than the loss of biomass to herbivory at a given grazing pressure (Noy-Meir 1975). Intake of forage by grazing livestock should then not be limited by pasture availability. Even where pasture growth is greater than consumption, net biomass accretion and animal production can conceivably be substantially reduced (Noy-Meir, 1978).
    While these are intuitively and theoretically reasonable statements, their generality is difficult to establish, particularly on rangeland where the vegetation is very heterogeneous in structure, phenology and response to grazing stress. Grazing deferment also involves special feeding arrangements for the livestock when they are not on pasture.
    This has logistic and economic consequences that tend to offset advantages that deferment may confer on primary production. These complex interactions make it necessary to test the effectiveness of grazing deferment in specific vegetation types over a range of grazing pressures and within the context of a viable production system (Willoughby, 1959). The present study will be conducted to test the hypothesis that early season deferment of grazing is necessary to maintain acceptable animal production when a Mediterranean type grassland is subjected to relatively heavy grazing pressure.

Objectives of the proposed research

To investigate the influence of grazing pressure and timing on the pastoral botanical composition and on the primary production.

Materials and methods

The experiment will be performed at the Karei Deshe Range Station in the eastern Galilee.

Historical and geographical background

The upper Jordan valley has been used for grazing since prehistoric times. Although throughout the modern period there were developed settlements (Corazim, Tabha), the area of Karei Deshe has been continuously used for seasonal grazing.

Bedouin herds once migrated between the mountains of the Golan to the Corazim Region, utilizing the early pasture, due to the fertile soil and the warmer winter, early in the season until the start of summer. The heavy grazing pressure of the Bedouin animals resulted in almost complete destruction of the natural forest and bushlands with residues only at holy sites and a few isolated places. From these sites it was suggested that the whole area was once similar to the typical forest structure in Yehudiya Park on the other side of the Jordan River.

Climate
Winter temperatures are relatively moderate (multi-year temperature averages calculated) with an average minimum of 7-10 ^o C. In spring and summer the temperatures are relatively high with maximums over 30 ^o C.

Soil and geology
Karei Deshe experimental ranch is situated on the southern tip of a wide basaltic area covered with volcanic rocks from the Miocene period.
    The topography is defined by narrow long valleys running from west to east formed as a result of simultaneous geological events that resulted in a lava stream which covered the red myconian soil and solidified to basalt. The lava stream soquickly and not all the area was covered and between the ridges there remained strips of red soil. The alluvial soil that developed on the young basalt mixed in with the red soil and the valleys became covered with a thick layer of dark red alluvium soil. On the slopes of the valley developed protogromosol soil.

Botanical composition

The area around Karei Deshe lies on the border between the Mediterranean plant and the Irano-Turani plant belts, the majority of segetal plants coming from the Irano-Turani belt, e.g. Prosopis farcata and Gundelia tournefortii. The climax plant composition at Karei Deshe is an open park formation of Quercus ithaburensis similar to that found at Yehudiya park in the Golan Heights, however, today only isolated oak trees are found.

Experimental Site

The trial will be conducted at the Karei Deshe Experimental Range in the lower Galilee of Israel, situated near the Jordan River and the Kinneret Lake (Sea of Galilee), lat. 32°55'N, long. 35°35'E, alt. 150 m. The topography is hilly, with slopes generally less than 10%. The soils are brown basaltic protogrumosols with variable depth but seldom deeper than 60 cm and with a rock cover of about 30% (Gutman, 1977; Gutman and Seligman, 1979). The vegetation is dominated by hemicryptophytes (forbs that have a perennial root system but lose most of the shoot during the dry summer) that include Hordeum bulbosum L., Echinops spp., Psoralea bituminosa L. (Zohary, 1972). There are also many annual species, some of which are palatable pasture plants (Avenasterilis L., Bromus spp., Trifolium spp., Medicago spp., and many others) while others are palatable for only short periods during the early vegetative experiment (e.g. Scolymus maculatus L., Brassica nigra L., Echium plantagineum L.).

Rainfall

The rainy season begins in October-November and ends in April. The pattern of vegetative growth is strongly influenced by rainfall distribution and intensity. Mean annual precipitation (+ S.D.) is 556+169 mm, fluctuating between extremes of 322 and 1029 mm .
    The following pasture parameters will be examined: pasture yield, botanical composition and pasture quality.

Experimental structure

Eight paddocks, in two blocks, are available for the experiment, each 25.5 to 33.0 ha in size and fenced so as to include equivalent proportions of the different range habitats in each paddock (Gutman and Seligman, 1979). Throughout the experimental period, four grazing treatments are replicated twice, once in each block.

Table 1

Table 2

For statistical analyses of the affects each treatment had on the plant composition, the plots and sub-plots were divided into three treatments for each grazing pressure (0.9 or 1.8 Ha/animal)

The area of each plot ranged between 25.5 and 33.8 Ha and the area of each sub-plot ranged between 11.0 and 16.0 Ha. For each treatment there were two replications.

Control Paddock
A paddock of 2.5 Ha size (“ecological plot”), protected from grazing since 1960 will be used as a control.
    The comparison of the ecological plot with the grazing treatments was problematic due to the establishment of a number of species in the ecological plot that rarely appeared in the grazing treatments, such as Polygonum equisetiforme, Cephalaria joppensis, or plants that appeared in much smaller amounts such as Brassica nigra, Isatis lusitanica, Raphanus rostratus and Chaetosciadium trichospernum.
    In each plot where grazing was split, the same order of grazing will be carried out during all the trial years. .
    Grazing started in the sub-plot of early grazing in the first half of January and the herd was moved into the second sub-plot of late grazing at the start of March in the high stocking density treatment (9 R) and at the start of May in the moderate stocking density treatment (1.8 R).
    The current grazing treatments are conducted from January 1994.

Preliminary results

Treatment influence on the major plant species:
    Tall grasses . High grazing pressure resulted in a cover reduction in these species and a cover increase in late grazing plots, especially under moderate grazing pressure (1.8 Ha/animal).
    This applied to all the plants in the group and stood out for certain plants in the group.
In the late grazing plot, the plants were protected from grazing all the growing season (until the start of may), allowing the ripening and dispersal of most of the seeds before grazing.
    Continuous grazing at high grazing pressure and early grazing reduced tall species cover, although there existed variable sensitivity within the four major plants of this group (tall grasses).
    The species most resilient to grazing was Hordeum bulbosum , perhaps the most important pasture component. The cover of this perennial plant, which sprouts strongly with the first rains and possesses multiple spikes, was significantly reduce d in the early, heavy grazing treatment (9E). (Table 2). There was a cover reduction for Hordeum spontaneum under early grazing especially under heavy grazing pressure (9E)., but cover was stable under late grazing.
    There was a strong increase in Triticum dicoccoide s cover in the late, moderate grazing treatment (18L) (table 4). There was also a reduction in wheat cover in the late, heavy grazing treatment (9L), suggesting that Triticum dicoccoides was also sensitive to grazing at the later stages of the growing season. This may be due to the protection offered to Hordeum bulbosum, Hordeum spontaneum under early grazing especially under heavy grazing pressure (9E)., but cover was stable under and Avena sterilis by the ìhairsî on the spikes which prevent their consumption and is not prominent with Triticum dicoccoides.. These results confirmed previous observations where the prevention of grazing caused an increase in Triticum dicoccoides cover.

In Avena sterilis, similar to the three other species, there was a cover increase in the late, moderate grazing treatment (18L) (table 5).
Treatments influence on dwarf shrubs (Psoralea bituminosa and Echinops viscosus)
The influence of grazing on these species was relatively small.
Psoralea bituminosa (table 6) is a perennial legume that is not eaten by cattle when there is plenty of herbaceous pasture. Under early grazing conditions (treatment 9R, early grazing sub - paddock) it was strongly grazed by the cattle at the start of the season but recovered after the cessation of grazing when the cattle was moved to the late grazing sub - paddock.

Echinops viscosus is a thorny plant not eaten by cattle, however in the late grazing treatments (18L) (table 7) there was a decrease in Echinops viscosus cover. This was probably because Echinops viscosus competed with the herbaceous species for space, nutrients and water, whilst in the other treatments, especially in the heavy grazing treatments at the start of the grazing season, Echinops viscosus had an advantage because tcattle preferred tastier, herbaceous species. Table 7 portrays this effect clearly.

In treatments with high grazing pressure there was an increase in low plant species cover along with the decrease in tall grasses. The major low species in this group are common Aloecurus articulatus (table 8) and Trifolium pilulare (table 9). Common fox tail cover increased with increasing grazing pressure (table 8) and the highest common Aloecurus articulatus cover was found with the continuous, heavy grazing treatment (9C).

When the cover of the dominant species, sensitive to grazing, decreased, their place was taken by a number of smaller species. Hence there were more species under strong grazing, especially with continuous grazing. This effect resulted in an increase in biological variation under strong grazing compared with moderate grazing. Species diversity is important in enriching the available food variety in the pasture and in terms of conservation.

Botanical diversity

The number of species was highest under continuous grazing with a trend for more species under heavy grazing (table 10). Amongst the treatments, the lowest species numbers appeared under moderate and delayed (late) grazing. Under these conditions, the tall grains were protected from grazing during the growth season and were able to produce and disperse seeds before the effect of grazing.

The early, heavy grazing treatment with a instantaneous stocking rate of 0.45 ha/animal (9E), due to all the cattle grazing on one half of the plot, had results that did not follow the expected trend. A possible explanation for this could be that after 45 days the available pasture was consumed and the cattle were moved to the second half of the plot (9L) and during the rest of the growth season the pasture in the first half of the plot recovered.

Under strong, continuous grazing (9C), the effect of grazing on the plants was stronger because of the existence of continuous cattle grazing for the duration of all the growing season. A similar results were found with early, moderate grazing treatments (18E). This could be a possible explanation of the relatively small differences between the treatments.

Conclusion

Mediterranean herbaceous plants are resistant to heavy grazing in the growing season and only extreme grazing pressures were able to affect the botanical composition.
    Grazing pressures of 1.8 ha/animal are considered to be high in Israel and exist in very few ranches.
    The effect of early, moderate grazing in the deferred grazing treatments (1.8 Ha/animal) was similar to continuous, strong grazing pressure (9 Ha/animal). It seems that that early grazing in the growing season has the strongest effect on plant composition and hence the similarity in the results between the two treatments.

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