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The inventory and mapping of rangeland in West Africa

G. BOUDET *

(*) G. Boudet, Institut d'Elevage et de Médecine Vétérinaire des Pays Tropicaux, 10, rue Pierre-Curie, 94700 Maisons-Alfort, France.


A. Classification and appraisal of rangeland
B. Principles for the development of West African pastures
C. Cartographic work carried out
Bibliography


SUMMARY

Within a case study on western Africa, the author evaluates the surveys and maps made by I.E.M.V.T. Through this study 37 per cent of the Sahelian pastures in the French-speaking countries have been mapped at various scales. The data gathered as a result of the work carried out on natural pastures were also used to elaborate a synoptic report concerning:

- the identification of the principal West African pastures;
- the estimation of the productivity and fodder value of these pastures;
- the principles for the development of these pastures; and
- the basic principles for full-size experimental units.

A rangeland inventory with mapping at different scales was carried out for the eight French-speaking countries of West Africa (Ivory Coast, Dahomey, Mali, Mauritania, Niger, Senegal, Togo and Upper Volta), at the request and on behalf of these countries, by the research workers of I.E.M.V.T., Maisons-Alfort.

The work was principally carried out with the intention of responding to needs either formulated or more imprecisely felt by the responsible authorities, and of improving the presentation of research results for the benefit of those who were to use them.

The objectives of the experts carrying out the inventories were:

- To estimate the potential of the different environments and to specify their limits, with the aim of establishing mappable units of rangeland. The vegetation which reflects the conditions of the environment is a perfect continuum that must be subdivided in a rational manner in order to produce precise results for those who will later make use of them.

- To gauge the resistance or fragility of the types of pasture when subjected to grazing and trampling, and to forecast the probable evolution of the rangeland under different types of use. Traditional use, which represents a veritable "mining operation" adapted to the severe conditions of the environment and to low stocking rates, is inadequate when the pressure of man and stock becomes too great.

- To propose better utilization of the land, taking into consideration its potential in respect of pasture and water, land tenure, known pressure of man and stock, possible methods of exploitation, and techniques available for the improvement and regeneration of the rangeland.

- To establish rangeland maps that would illustrate the results of field research, at scales suited to the aims of the study.

The data gathered during the inventories makes it possible to produce a synopsis of knowledge of West African rangeland:

A. Classification and appraisal of rangeland:

- Sahelian rangeland
- Sudanian rangeland
- Guinean rangeland

B. Principles of development of West African rangeland.

C. Cartographic work carried out.

A. Classification and appraisal of rangeland

From the Tropic of Cancer to the Equator, the climate and the vegetation vary from one extreme to the other, as does the rangeland, which is a reflection of them.

In addition to the various substrata which cause localized differences, the rangeland can be subdivided along a north-south rain intensity scale, according to climatic characteristics that produce locally limiting factors (annual rainfall in semi-arid regions, and the length of the active period of the pasture in humid and semi-humid regions):

- 100 mm isohyet (*): southern limit of the desert,

(*) An isohyet is a line joining geographical locations having the same rainfall.

- 550 mm isohyet: southern limit of the Sahelian zone,

- 5 month active period isopleth (**): northern limit of light forest,

(**) An isopleth is a line joigning geographical locations in which the pasture has an active period of the same length, the active period being the length of time during which the herbaceous cover reaches the end of its vegetative cycle and provides forage.

- 10 month active period isopleth: limit of dense forest.

This gives us for the principal units of pastureland ecosystems (see map):

1) savannah of the Guinean forest sector (7): more than 10-month active period,

2) savannah of the pre-forest sector (6): between 7 and 10 month active period,

3) wooded Savannah, southern Sudanian (5): between 5 and 7 month active period,

4) shrub Savannah, northern Sudanian (4): more than 550 mm annual rainfall and less than 5 month active period,

5) southern Sahelian steppe (3): between 400 and 550 mm annual rainfall,

6) typical Sahelian steppe (2): between 200 and 400 mm annual rainfall,

7) northern Sahelian steppe (1): between 100 and 200 mm annual rainfall,

8) desert area (0): less than 100 mm annual rainfall.

Natural tropical rangeland may thus be divided into three areas: Sahelian area; Sudanian area; and Guinean area. For each area of pastureland the characteristic features are:

- Their floristic groups

Subdivisions can be established for each principal unit of pastureland ecosystems according to the phytoclimatic aspect or the bioclimatic stage, in correlation with the edaphic conditions, and characterized by floristic groups established with the most typical ligneous and herbaceous species of each station.

The relative abundance of each species is symbolized in the summary tables as follows:

o: species found in less than 50 percent of the stations of the ecosystem,

x: species found in more than 50 percent of the stations of the ecosystem in medium-to-great abundance an with specific ground cover of less than 30 percent,

A: species found in more 50 percent of the stations of the ecosystem in medium-to-great abundance and with specific ground cover of more than 30 percent.

!: abundant species with ground cover of more than 30 percent but in less than 50 percent of stations.

(The sign assists in reading the table but has no significance in terms of the presence or abundance of species.)

- Their potential productivity in forage and their carrying capacity.

An estimate of the quantity of forage provided by the cover of Graminaceae is essential in any assessment of the value of an area of rangeland, and it also assists in the evaluation of net primary production of the ecosystem: herbaceous biomass produced during the active period, new growth at different cutting intervals in the rainy season or the dry season. The measurement of the herbaceous biomass is normally carried out on an area of herbaceous Graminaceae cover of sufficient density, at stations which are totally unshaded or which are shaded. The evaluation of the production of the herbaceous Graminaceae cover of an area of rangeland is expressed in dry matter per hectare, taking into consideration any areas of ground denuded or covered by ligneous species. This weighted estimate is the basis of the assessment of overall yield and carrying capacities.

Losses in the biomass of the herbaceous cover, noted during the dry season for pasture protected from grazing, losses through trampling, and the necessity of maintaining some herbaceous cover in order to protect the soil from various causes of erosion, mean that the potential yield, corresponding to the herbaceous biomass produced on land protected from grazing during the active period, may be taken to be approximately 50 percent consumable, taken over the whole year.

The average daily consumption of a bovine is estimated at 2.5 kg of forage dry matter per 100 kg of live weight; and it is thus possible to estimate the capacity of the rangeland for the year in grazing days per 250 kg livestock standard unit (LSU), which consumes 6.25 kg of DM per day:

Obviously the actual carrying capacity of an area of rangeland varies according to the type of exploitation. The estimated capacity corresponds to the actual capacity where there is rational exploitation of the rangeland, but it is very frequently overestimated when the pasture is subjected to the conventional "mining" type of exploitation.

Nevertheless, wherever possible (stock farms, animal production research stations), the systematic checking of stocking rates should be carried out on the main pastureland using cattle whose yield is also controlled (weight gains or milk production).

- The value of the forage produced on the rangeland.

The nutritive value of plants for herbivores is related to three factors:

1) The dry matter content of the forage, since the animals take in each day sufficient forage to enable them to ingest dry matter in proportion to their weight on the hoof (approximately 2.5 kg of DM per 100 kg of live weight for a bovine).

2) The energy value of the forage, which is proportional to the organic matter content (dry matter less mineral matter) and inversely proportional to the cellulose matter content. It is expressed in forage units (FU), one FU corresponding to the energy value of 1 kilogram of barley.

3) The content in digestible nitrogenous matter (dNM), which is proportional to the content in gross nitrogenous matter (gNM) that may be obtained by multiplying the content produced by the Kjeldahl method by the coefficient of 6.25. As an indication, when one kg of DM produces less than 0.45 FU and less than 25 g of dNM, the upkeep of a bovine of 250 kg live weight cannot be assured.

1. Sahelian rangeland

The Sahel is the "cummerbund" of the Sahara, where the desert gradually gives way to the tropical zone, and where well defined seasons exist to which the flora and fauna have adapted.

a) Floristic groups (table 1)

Seven types of ecosystem are distinguishable in the southern and typical Sahel sectors, as against three in the northern Sahel, in terms of topography and nature of the substratum:

hD: highly undulating sand dunes,

sP: sandy peneplains of fairly flat profile,

mP: peneplains of rather sandy/loamy texture,

Mc: low-lying peneplains with depressions of rather loamy/clayey texture,

Mc/R: peneplains with skeletal soil of loamy/ clayey texture on a substratum of rocks or cuirasses,

R: sub-outcrop rocks or cuirasses with or without grit,

S/R: thin spread of sand over a rocky or cuirass substratum.

Along the climatic north-south scale of the Sahelian zone, certain plant species have limited occurrence, others a very widespread occurrence; the latter group may colonize different substrata which are capable of compensating for variations in rainfall. The species having widespread distribution profit from periods of rain to extend their hold, but they are subsequently the species most severely affected during dry seasons. This is the case with the ligneous species (Balanites aegyptiaca, Commiphora africana, Guiera senegalensis) and the perennial Graminacea (Andropogon gayanus).

On the northern Sahelian steppe lands, the vegetation has retreated and is localized on the porous substrata and in topographical situations that favor the gathering of run-off water. In these stations, the herbaceous cover remains scattered, with a predominance of xerophyllous * perennial Graminaceae (Aristida pallida, Panicum turgidum).

(*) Plants whose leaves are suited to a dry climate.

The typical Sahelian steppe lands offer scanty cover consisting of ligneous species with cover of less than 5 percent, with the exception of thickets on loamy/clayey soils, with or without rocks or cuirasses. The herbaceous cover is clearly dominated by xerophyllous annual Graminaceae.

- On the southern Sahelian steppes northern Sudanian ligneous and herbaceous species are found mixed with Sahelian species. The ligneous stratum is still considerable, forming a cover of approximately 15 percent on sandy soils and as much as 60 percent on muddy soils.

- Pasturelands formed on the fall of the major trans-Sahelian rivers are made up of marshy grasslands which are flooded at high water towards the end of the rainy season and the beginning of the dry season.

The level and duration of the flooding and the texture of the soil creates a diversity of flora on these marshy grasslands:

- Grasslands formed of Cynodon dactylon, Andropogon gayanus, Vetiveria nigritana, Oryza barthii (annual), on sandy terraces, where reduced flooding occurs for approximately one month, in the typical Sahel.

- Grasslands of Panicum anabaptistum, Andropogon gayanus, Vetiveria fulvibarbis, on sandy alluvial terraces, with reduced flooding in the southern Sahel.

- Grasslands of Eragrostis barteri with Acroceras amplectens, Echinochloa pyramidalis, Oryza longistaminata (perennial), Vetiveria nigritana on sandy alluvia flooded from 30 to 50 cm for approximately 3 months.

- Grasslands of Brachiaria mutica with Panicum subalbidum, Vossia cuspidata on sandy alluvia flooded up to 1 metre for about three months, but with a fairly strong flow of water. This grassland colonizes in particular the secondary water channels.

- Grasslands (bourgoutières of Echinochloa stagnina and Vossia cuspidata, often with Echinochloa pyramidalis, Oryza longistaminata and Vetiveria nigritana on loamy/sandy-to-clayey alluvia with flooding of the order of 1 metre for three or more months.

b) Productivity and carrying capacity

In the northern Sahelian area, herbaceous cover is nil on skeletal or clayey soils, sparse on sand, where the herbaceous biomass may reach 40 g/m², and more dense on the loamy substratum with a biomass of 50 g/m² (**)

(**) Multiplying the production expressed in g/m² by 10 produces the dry matter yield in kg/ha (50 g/m² = 500 kg/ ha).

In the typical Sahelian areas, it varies on sandy dunes from 200 g/m² on slopes to 300 g/m² in passages between dunes, but almost 30 percent of the soil can remain uncovered, and the average herbaceous biomass is estimated at 100 g/m².

The herbaceous biomass produced on loamy or clayey peneplains is very heterogenous and varies from 100 to 300 g/m², while on skeletal soils it may locally reach 180 g/m²; however, 75 percent remains bare, and the average production is estimated at 80 g/m².

In southern Sahelian areas, the maximum herbaceous phytomass is about 150 g/m² of DM on sandy dunes, 120 g/m² on sandy-to-loamy peneplains, 300 g in loamy/clayey depressions, and 80 g on skeletal soils.

The shrubby ligneous cover does not compete with the herbaceous cover. Indeed, the cast shadow is of low intensity and by filtering creates a microclimate favourable to the growth of special shade Graminaceae with a productivity which may be more than twice that of sunny areas: 160 g/m² in the shade compared with 65 g/m² on sunny dunes in northern Senegal (3).

In marshy grassland the maximum herbaceous phytomass produced in true Echinochloa stagnina bourgoutières may vary from 600 g/m² to 1,700 g/m², including 1,300 g for stalks under water. Whereas the regrowth in the dry season is normally nil, in Sahelian grazed ecosystems in the bourgoutières it reaches 1 g/m²/day on dried-out soil and 0.3 g/m²/day on surface-dried soil.

Overall yield in the Sahel is reduced as a result of the size of denuded areas of soil, but the entire stock of straw produced during the rains may be annihilated by an accidental fire, and the spread of fires is facilitated once the herbaceous phytomass exceeds 100 g/m², so that one rainy year which is favourable to the production of forage, may turn out to be a deficit year for the maintenance of herds, as a result of an abnormally high number of wild fires.

Table 1 - Floristic groups of the Sahelian steppes

Valenza and Fayolle (6) carried out seasonal stocking rate tests in Senegal for a maximum herbaceous phytomass of 130 g/m² of DM. With a low rate of 50 kg/ha of live weight, the daily weight gain was 900 g in August and September. On the same pasture the daily weight gain was 400 g from October to the end of December, for a seasonal rate of 350 kg/ha, and the remaining biomass represented only 40 percent of the October figure. From January to the end of April, the live weight remained constant for a seasonal rate of 80 kg/ha, and the remaining biomass represented 65 percent of the original figure. From January to June inclusive, the daily loss was 170 g for a seasonal rate of 90 kg/ha, and the remaining biomass represented 70 percent of the original. These results demonstrate that there is a difficult period from May to June, but the observations concerning the estimates of phytomass before and after grazing must be aligned with the measurements of biomass carried out in the absence of livestock by Bille (3).

Production

October biomass (base 100)

December (percent of base)

February

Types

biomass

percent of base

Dunes

60 g/m²

91.5

38g/m²

63.5

Shaded

180g/m2

55.5

80g/m2

44 5

Depression

340 g/m2

70.5

220g/m2

64.5

Independently of these results of experiments, which are over-fragmentary, the carrying capacity in the absence of fires is estimated at 60 kg/ha/year in the southern sector, 50 kg in the typical Sahelian sector, and 25 kg/ha/year for the sandy/muddy dunes and peneplains of the northern Sahelian sector; the other substrata offer no significant forage resources. As for the bourgoutières the seasonal carrying capacity between the fall of the water level and the rainy period may reach 2,500 kg/ha of live weight.

c) Forage value of Sahelian pastureland

In the Sahelian area (table 2), annual Graminaceae are preponderant. While their energy value remains at a satisfactory level up to the middle of the dry season, their nitrogen content is insufficient as soon as the rains end, starting with fructification. The various grasses provide an essential nitrogenous supplement beginning with the end of the rains as well as palatable production of ligneous species (leaves, flowers, fruit). Although the whole Acacia husks are rich in nitrogen, their food value remains low in nitrogen, since the seeds which contain this component are digested without being crushed beforehand.

This shows the importance of forage obtained by the ligneous species during the dry season, particularly leaves and fruit.

Rather than prohibiting trimming it would be better to improve trimming techniques by training stock raisers, and to prepare for the foddering of the livestock in the dry season by setting up stocks of leafed branches, trussed after gathering in a favourable season.

The trimming to be envisaged should be applied to only a limited number of branches on each tree in order to ensure its survival. In place of traditional trimming to an umbrella shape by mere hacking at the higher part, efforts should be made to popularize trimming by clean cuts, using a cut half-way through the wood on the lower part of the branch, completed by a cut in the upper part.

2. Sudanian pastureland

Sudanian pastureland corresponds to the northern Sudanian shrub savannah and the southern Sudanian wooded savannah.

a) Floristic groups (table 3)

Sudanian savannah may be classified into four edapho-topographical types for each sector:

(Scs): Vegetation on cuirass skeletal soil in the southern sector, where the smallest deposit of fine elements makes possible the establishment of annual Graminaceae (Loudetia togoensis) and even perennial Graminaceae (Loudetia simplex). In the northern sector the cuirasses carry only plants with a very short cycle, which dry and disappear at the end of the rains.

(Sgs): Savannah on gravelly soils in the southern sector.

(Sgn): Savannah on gravelly soils in the northern sector.

(Ps): Savannah on ferruginous soils on the plateaux of the southern sector.

(Pn): Savannah on ferruginous soils on the plateaux of the northern sector.

(Pc): Savannah on ferruginous soils on the planteaux of the central area.

(Ts): Savannah on ferruginous soils, with deep hydromorphy, of colluvia of terraces in the southern sector.

(Tn): Savannah on ferruginous soils, with deep hydromorphy, of the colluvia of terraces in the northern sector.

In the northern sector, there is substantial ligneous cover and the shaded areas often occupy more than 30 percent of the soil with localization of sciophilous * Graminaceae (Pennisetum pedicellatum and Pennisetum subangustum towards the south of the sector). The herbaceous cover is dominated by annual Graminaceae (Andropogon pseudapricus, Diheteropogon hagerupii), and the perennial Graminaceae Andropogon gayanus is found localized in deep soils (Tn. Pn) with good water reserves.

(*) Sciophilous: term used to describe plants adapted to a shaded position.

Table 2 - Nutritional value of Sahelian plants

Species - stage - period

Composition as percentage of dry matter

DM percent of forage

Nutritional value of kg of OM

gNm

OM

Cell. M

DNm (g/kg)

FU

Annual Graminaceae

Aristida mutabilis


young growth (July)

7.9

91.9

35.2

32

38

0.55


flowering (September)

7.7

91.1

34.5

33

36

0.56


fructification (September)

4.9

92.0

38.3

60

10

0.46


straw (October to February)

3.9

92.1

39.1

95

1.0

0.44


straw (March to June)

2.1

91.0

41.0

95

tr.

0.36

Cenchrus biflorus


rise (August)

8.6

86.5

34.1

27

45

0.50


regrowth under grazing (September)

16.0

88.2

30.3

23

113

0.64


straw (October to February)

3.1

91.0

38.8

94

tr.



Straw (March to June)

2.6

88 9

39.1

94

tr.

0.37

Schoenefeldia gracilis


rise (August-September)

7.3

91.3

36.1

30

33

0.53


flowering (September)

6.0

90.4

38.5

44

21

0.43


straw (October to February)

3.4

92.8

40.0

95

tr.

0.42


straw (March to June)

1.8

91.6

40.4

94

tr.

0.39

Perennial Graminaceae/flood

Echinochloa stagnina


flowering (October-November)

9.3

87.5

35.8

24

51

0.46


submerged stalks (November)

4.6

91.6

42.3

15

7.5

0.32


straw (April)

2.9

92.6

37.9

92

tr.

0.49


30-day regrowth (May)

14.4

83.3

27.0

27

99

0.64

Other grasses

Alysicarpus ovalifolius


rise (August-September)

17.5

88.7

28.6

24

127

0.70


flowering (September)

18.2

86.3

24.9

35

134

0.75


fructification (October)

13.8

89.1

24.6

41

93

0.80


straw (October to February)

5.2

93.3

30.7

94

13

0.72

Tribulus terrestris


seedlings (July)

14.2

80.4

20.2

23

97

0.77


flowering (September)

15.6

80.7

21.3

26

110

0.75

Zornia glochidiata


rise (August)

15.6

91.8

35.2

22

110

0.75


fructification (September)

16.0

93.4

29.7

32

113

0.75


straw (October)

13.4

90.4

29.2

94

89

0.40

Ligneous species

Acacia albida


leaves (February)

17.8

93.6

17.5

31

130

1.00


whole husks (March)

10.7

95.4

16.8

93

64

1.05


fruit pulp (March)

5.6

95.3

21.8

95

17

0.96


seeds (March)

26.8

96.2

11.0

95

214

1.17

Balanites aegyptiaca


dry leaves/soil (February)

9.5

83.0

11.4

95

53

0.95


young leaves and flowers (April)

20.0

89.1

20.3

35

150

0.90

Pterocarpus lucens


old leaves (November)

19.4

92.7

25.6

42

145

0.83


dry leaves (February)

14.9

93.6

24.0

95


103

Table 3 - Floristic groups of the Sudanian savannahs

For the types of the southern sector (Sgs, Ps, Ts), the ligneous cover tends to evolve towards climax forest, and the cover is all the more substantial since fires are controlled or their action lessened as a result of the disappearance of the combustible material represented by straw, following browsing. When the ligneous cover occupies 60 p. 100 of the soil and over. the shade Graminaceae increase (Andropogon tectorum, Pennisetum subangustum). The herbaceous cover is still dominated by perennial Graminaceae, e.g. on soil with poor water reserves (Andropogon ascinodis. Diheteropogon amplectens) and on soil with good water reserves (Andropogon gayanus).

Light forests occupy an important place in the southern Sudanian sector. The ligneous species in this sector (Isoberlinia doka, Pericopsis laxiflora, Terminalia spp., etc.) with more or less contiguous cymes eliminate most of the savanicultural Graminaceae. I here survives only the sciophilous Graminaceae Andropogon tectorum, which in turn yields to low creeping Graminaceae (Oplismenus burmanii, O. hirtellus) when the density of the ligneous cover accentuates the shade.

The valleys of large rivers often display a high-water bed made up of a low terrace of alluvia, subject to short flooding towards the end of the rainy season. This high-water bed is occupied by a grassy savannah where the Graminaceae are arranged in belts, which are accurate indications of ecological variations: soil texture, length of flooding, or congestion of the profile.

The flood limit is defined by the presence of Hyparrhenia rufa, replacing Andropogon gayanus, which remains fairly localized on the non-floodable terraces.

For the more important flooding periods, the grassy savannah is dominated by perennial Graminaceae:

Anadelphia afzeliana, Andropogon africanus, Andropogon canaliculatus, Elymandra androphila, Panicum fluviicola, Setaria sphacelata, Sorghastrum trichopus.

Flooding which stretches over several months produces marshy grassland, with Brachiaria mutica (sandy soil) and Echinochloa stagnina (loamy/clayey soil).

b) Productivity and carrying capacity

In the northern Sudanian sector, the herbaceous phytomass produced in sunny areas reaches 150200 g/m² on plateaux with deep soil, 80 g/m² on gravelly soil and 250 g/m² on colluvial terraces. On shaded but not brush-covered areas, it is above 300 g/m² of DM. In the dry season, the perennial Graminacea Andropogon gayanus grows again only on low terraces with good water reserves with 0.3 g/ m²/day at the beginning of the season and 0.1 g/m² day in the height of the season.

In the southern Sudanian sector, the maximum herbaceous phytomass produced in sunny areas may reach 300 g/m² of DM on plateaux with deep soils, 200 g/m² on gravelly soils, 150 g/m² on cuirass soils, 800 g/m² on non-floodable colluvial terraces, and 800 g/m² in floodable grassy savannah and watery grassland. In non-brush/covered shaded areas, the biomass of Andropogon tectorum is about 550 g/m² i.e. markedly higher than the sunlit areas; but competition from ligneous species has a sharp effect at the beginning of the dry season, and regrowth is halted at the end of the rains.

On non-floodable terraces, regrowth passes for 60 days of growth from 1.1 g/m²/day in the rainy season to 0.3 g at the beginning of the dry season and 0.1 g in mid-dry season. It falls to 0.1 g/m²/day on plateaux and grit during the month following the end of the rains, and recovers only with the next rains. On the other hand, on watery grassland regrowth remains strong throughout the dry season (1.5 g/m²/day).

The overall yield of Sudanian grazed ecosystems is not limited by the shade of the ligneous species, and only the sunny or denuded areas reduce the production of the herbaceous cover of Graminaceae. The carrying capacity of the pastures is closely dependent on brush fires. If very early fires have a very restricted effect, eliminating only the early-dessicating straw which is of low palatability, if the late fires have only a cleaning-up effect on balance favourable to regrowth at the beginning of the rains, the fires in the height of the dry season have a devastating effect, destroying the whole stock of straw which can be consumed by the livestock.

The livestock carrying capacity is estimated on average at 125 kg of live weight per hectare per year in the southern Sudanian sector, with less than 100 kg/ha/year on gravelly soils and up to 150 kg on terraces. It averages 80 kg of live weight per hectare per year in the northern Sudanian sector with 40 kg on grit and 125 kg on terraces. This capacity may be doubled when the pastures are wholly exploited in the rainy season, but after mid-dry season fires, only the pastures on terraces can still support livestock with, nevertheless, a capacity reduced to the potential for regrowth, estimated at 35 kg of live weight per hectare.

c) Forage value of Sudanian pastures

In the Sudanian area (table 4) annual Graminaceae remain important, particularly in the northern sector. Their regrowth provides good forage up to November, but their straws represent food with bulk but little nutritional value, which has a deficit of nitrogen and energy. The perennial Graminacea Andropogon gayanus produces rich regrowth up to 30 days' growth, but it is poor in nitrogen thereafter. Old production (leaves, inflorescence) is poor in nitrogen but satisfactory in terms of energy.

The nitrogen deficit of Graminaceae production in the dry season is offset by the palatable parts of the herbaceous non-Graminaceae species and the leaves and fruit of ligneous species.

3. Guinean pastures

Outside the forested massifs proper, the action of repeated fires and the poverty of the soils promote the herbaceous non-Graminaceae species and the form of pseudo-climax or fire-climax.

a) Floristic groups (table 5)

Four types of grazeable Guinean ecosystems may be identified, including one in forested sectors on sandy soils (Sf); and three in pre-forest sectors; on sandy soils (Sp); on skeletal soils with little thickness and with fer-ruginized grit (C); and on deep loamy/clayey soils (D).

Table 4 - Nutritional value of Sudanian plants

Species - stage - period

Composition as percentage of dry matter

DM percent of fodder

Nutritional value in kg of DM

gNm

OM

Cell. M

dNM (g/kg)

FU

Annual Graminaceae


(Pennisetum subangustum)


rainy season:



20-day regrowth (September)

13.8

85.8

24.6

14.0

93

0.75

dry season:








regrowth (November)

15.2

87.3

32.2

21.3

106

0.57


straw (March)

1.5

92.5

43.8

85.3

tr.

0.30

Perennial graminaceae


(Andropogon gayanus)


rainy season:



25-day regrowth

10.4

91.9

33.2

21.3

61

0.62


60-day regrowth

4.6

94.1

37 6

29.9

7.5

0.51

dry season:








inflorescences (October)

4.3

93.1

35.1

44.8

4.7

0.59


old leaves (November)

4.2

91.9

34.5

36.9

3.8

0.58


dry leaves (March)

2.3

92.7

34.8

89.3

tr.

0.58

30-day regrowth

9.1

84.6

25.5

38.2

49

0.71

Other grasses (dry season)


Borreria stachydea



fructification (October)

12.1

87.7

23.7

16.3

77

0.80


infructescences (December)

8.3

89.5

26.8

86.6

42

0.76

Cassia mimosoides








inflorescences (October)

15.3

96.1

23.2

36.8

107

0.93

Ligneous species


Daniellia oliveri



young leaves (March)

12.8

95.1

18.7

23.4

84

1.02


young fruit/soil (March)

8.7

95.7

31.0

26.9

46

0.74

Pterocarpus erinaceus



young leaves (March)

16.9

92.4

24.4

26.8

122

0.86


young fruit/soil (March)

14.3

91.8

29.4

20.5

98

0.72

Table 5 - Floristic groups of the Guinean savannah

Ecosystems

D

G

Sp

Sf

Species

Ligneous:

Albizia zygia

O

-

x

-

Crossopteryx febrifuga

x

x

x

-

Annona senegalensis ssp. Oulotricha

x

x

x

x

Bridelia ferruginea

-

x

x

x

Hymenocardia acida

-

x

x

-

Piliostigma thonningii

-

x

x

-

Lophira laneeolata

-

-

x

-

Parinari curatellifolia

-

-

x

-

Daniellia oliveri

-

-

x

-

Borassus aethiopium

-

-

O

-

Perennial Graminaceae:

Andropogon macrophyllus

!

-

-

-

Hyparrhenia rufa

!

-

-

-

Hyparrhenia diplandra

A

x

x

A

Panicum phragmitoides

O

x

x

-

Hyparrhenia smithiana

-

x

x

-

Loudetia arundinacea

-

x

-

-

Schizachyrium sanguineum

-

x

-

-

Elymandra androphila

-

!

-

-

Hyparrhenia subplumosa

-

O

-

-

Andropogon schirensis

-

O

-

-

Loudetia simplex

-

-

x

-

Andropogon ascinodis

-

-

x

x

Brachiana brachylopha

-

-

x

x

Imperata cylindrica

-

-

-

A

The ligneous cover is of little importance, and is generally less than 5 percent of the soil, but it may reach 10 to 15 percent on certain sandy slopes (Sp.). Trees are rare (Lophira Lanceolata, Daniellia oliveri), and the shrubs are often twisted under the influence of the violence of fires.

The Graminaceae cover is made up basically of perennials in clumps generally well spaced, the stubble of which meets in a practically continuous layer at the moment of the rise in the water level.

Hyparrhenia diplandra is still the dominant species, associated with: Hyparrhenia rufa on deep soils in high-altitude regions (Adamaoua in Cameroun); Loudetia arundinacea on gravelly soils (middle Ivory Coast, CAR); and Imperata cylindrica in forest sectors (Congo, Ivory Coast, Gabon, southern CAR, Zaire).

The shade of arborescent ligneous species of savannahs is often colonized by a highly palatable sciophilous perennial Graminacea, Beckeropsis uniseta.

The edges of sheets of water and calm rivers may be colonized by marshy grassland with Echinochloa pyramidalis (muddy/clayey soils) or Brachiaria mutica (sandy soils).

b) Productivity and carrying capacity

On sand or grit, the phytomass produced during the rainy season is estimated at between 250 and 300 g per m² of dry matter (DM). On deep soils, that of Hyparrhenia diplandra reaches 1,300 g/m² of DM.

In the rainy season the regrowth after cutting varies especially with length of the period of growth between two successive cuttings. On deep soils it varies from 0.8 g/m²/day of DM for a period of 21 days to 1.2 g/m²/day for intervals of 30 days and 2 g/m²/day for intervals of 60 days. The result is phytomass exported during the period of active life varying from 277 g/m:, with cutting intervals of 21 days to 312 g/m² for 60 days, while the maximum herbaceous biomass reaches 402 g/m²

For a maximum phytomass of 300400 g/m² of DM a formation with Imperata cylindrica gives production of 1.5 g/m²/day for cutting intervals of 6 days and 3.3 g/m²/day for intervals of 18 days.

In the dry season the regrowth varies little, whatever the prior clearing treatment (fire or cutting). For an interval of 30 days between two cuttings, the production is 0.5 g/m²/day of DM on gravelly soils and 0.7 g/m²/day on deep soils.

This herbaceous production makes it possible to maintain livestock either during the period of growth or throughout the year, with a carrying capacity estimated at between 125 and 175 kg of live weight per hectare per year, which may correspond to seasonal stocking rates of 250-500 kg of live weight per hectare during the period of growth of the pastures.

c) Forage value of Guinean pastures

For different durations of growth, the regrowths of Graminaceae provide forage of variable quality.

Table 6 - Nutritive value of Guinean plants

Species - stage - Period (perennial graminaceae)

Composition as percent of dry matter

DM percent of fodder

Nutritive value of kg of DM

gNM

OM

Cell. M.

gNM (g/kg)

FU

Hyparrhenia diplandra

rainy season:








20-day regrowth

8.1

93.1

36.4

28.1

40

0.54


30-day regrowth

7.8

93.0

36.7

27.7

37

0.52


60-day regrowth

5.8

93.6

38.2

31.0

19

0.50

dry season








40-day regrowth

8.4

92.7

36.0

27.8

43

0.55


60-day regrowth

5.6

93.8

35.2

39.8

17

0.59

Imperata cylindrica

(dry season)








6-day regrowth

11.2

91.6

39.1

24.4

69

0.43


18-day regrowth

8.7

92.7

40.3

29.2

46

0.40

Panicum phragmitoides


40-day regrowth








rainy season

8.4

94.3

35.0

28.3

43

0.60


dry season

7.4

94.0

35.9

345

34

0.57

The cellulose element content is generally high in Graminaceae of the Guinean area. Whatever the season, the energy value is adequate for the maintenance of a bovine, even at 60 days' growth, but the nitrogen content becomes insufficient after 40 days. For Imperata cylindrica the young regrowth is rich in nitrogen, but the energy value is still insufficient.

B. Principles for the development of West African pastures

The rigorous conditions in the Sahel make this ecological zone a region with a "pastoral vocation ", in view of the impossibility of its being used for any other purpose. However, the activity of livestock raising is not carried out there without risks - hence the need for the integration of Sahelian livestock raising in more favoured, complementary ecological zones. The potential for realization varies by country (table 7), and moreover the complementarity of ecological zones is difficult to plan, as each zone develops independently of its neighbours and fundamental obstacles must be surmounted in advance of any project for the harmonization of the development of the various ecological zones.

Sahelian livestock raisers could produce young animals which would later be raised in the northern Sudanian zone by agriculturalists, but first it would be necessary to reduce transhumance movements from the Sahel southwards. While the transhumance permits contracts for the manuring of fields in exchange for cereals, it also leads to the ruthless consumption of crop residues (haulm, canes) so that no forage remains for the animals kept by the agriculturalists.

Failing expensive chemotherapeutic protection, the zebu bovine cannot live beyond the 5-month isopleth, where the risks of trypanosomiasis become too great, and it usually yields to taurine bovines, which have the reputation of being trypanotolerant.

In the Sudanian area, which has substantial if not dominant agricultural activity, sedentary agriculturalists are already numerous, sometimes too numerous, and the areas inhabited have remained inhabited only as a result of obstacles to human settlement (poor soil fertility, bare rock, lateritic cuirasses, grit), the absence of water in certain seasons, preventing any permanent human occupation, and uncontrolled endemic diseases (onchocerciasis, trypanosomiasis).

The development of water points and the eradication of endemic diseases could, in the near future, open up vast spaces. These regions could be settled, after planning on a national scale, either by moving agriculturalists from over-populated areas or by introducing livestock raisers to the sedentary way of life. At the same time plans should be made for the establishment of ranches to lessen grazing pressure in the Sahel "re-rearing", short-fattening) as a part of the planned development of these virgin territories.

Table 7 - Distribution of West African rangelands (Area in thousands of km²)

This development of vacant spaces cannot alone solve the problem of the integration of the major ecological regions. Within the agricultural zones, it remains necessary to programme development of livestock locally, but also to link it up with "re-rearing" and fattening of Sahelian livestock in harmony with the expansion of intensified agriculture. This presupposes a coherent policy on brush fires.

In Sahelian pastures the fire is harmful, as it destroys the forage reserves constituted during the rains, and the risk of early fires rises as soon as the herbaceous biomass produced during the active period exceeds 1 t/ha of dry matter.

In northern Sudanian pastures, the annual Graminaceae are very inflammable and a fire in mid-dry season is both devastating and difficult to control.

When fire protection is difficult to carry out, as in underpopulated regions, it would be better to generalize very early fires, which spare the shade Graminaceae and eliminate the Graminaceae on sunny areas whose straw is often poorly palatable, while constructing a proper network of fire breaks.

In southern Sudanian pastures, the absence of fires throughout the dry season should be envisaged wherever possible, particularly on grassy fallow land.

The late end-of-dry-season fire and the delayed fire after the first rains (after about 50 mm rainfall) makes possible economical clearing of the land to be ploughed and the pastures, which then produce delayed grazeable regrowth at an advanced stage of the rainy season.

An early fire clears the pastures of their straw and promotes the departure of young growth, whose production does not exceed 3 kg/ha/day of DM as long as the soil's water reserves permit it; and 10 ha are then necessary for the maintenance of one LSU of 250 kg during the dry season.

While a mid-dry season fire maintains best the balance between the ligneous and herbaceous strata, it ensures practically no Graminaceae regrowth, and the pasture remains unproductive until the rains.

In addition, a better distribution of human activities over the territory is needed to increase the space exploitable by the herds, and that presupposes a fundamental condition: assignment, in a manner to be determined, of the land (ploughable land or pasture) to the users, with the onus on them to be fully responsible for it and to ensure its sound management in accordance with the advice which should be given to them by means of a basic, close-knit framework.

This redistribution of the territory on the basis of modern development techniques presumes that the techniques to be popularized will have been tested beforehand on a full scale on pilot experimental plots both in the Sahelian and in the Sudanian areas.

a. Sahelian area (figure 1)

The pilot experimental unit should:

- Be viable and be able to survive deficit years. It can be envisaged only under adequate average rain fall (more than 300 mm) and with satisfactory pastures.

- Ensure better use of water, whatever its source (run-off water, temporary or permanent standing water, rivers, wells, boreholes).

- Tend towards a reorganization of the rural environment by rationalizing and improving the transhumance phenomenon to the point of reducing it to a light coming-and-going between rainy-season pasture and dry-season pasture.

- Seasonal exploitation of the pastures so that some of them are always used in the rainy season and others in the dry season, this being done to benefit from the evolution of the pastures under the effect of browsing in the rainy season, where the annual Graminaceae are replaced by short-cycle species which are rich and well consumed, but which disappear and turn to dust as soon as the dry season begins.

- Improve the conditions for the exploitation of forage, herbaceous, ligneous, natural or introduced resources, while maintaining the production potential.

- Develop a sound exploitation system for ligneous production (sound trimming technique, placing of leaf fodder in reserve before the fall of the leaves).

- Improve herd management and raise production (milk, meat).

- Be oriented towards obtaining results exploitable for training and popularization.

- Tend towards a final objective, that of maintaining the human population at all levels, improving their standard of living and health, and integrating them into the national and international economic circuit.

The unit should therefore be centred on a permanent water point with a flow sufficient to meet, in the dry season, requirements estimated at more than 200 m³ per day, a village centre of 350 persons comprising the livestock raisers, and the livestock concerned being estimated at 7,000 livestock standard units = unités bétail tropical (1 LSU = 1 UBT = 1 horse = 1 "camel " = 1 adult tropical bovine; 1 ovine = 1 caprine = 0.12 LSU).

The dry-season pasture, centred round the water point, would represent a circle of 10 km radius (31,500 ha) corresponding to the requirements of the livestock concerned, with a supplement of one fifth in reserve during rainy years for exploitation in deficit years. The pasture exploited in the rainy season would be located beyond, with about 8,500 ha served by 10 stretches of standing water remaining wet, without interruption, during the rainy season. These temporary water points for the rainy season would be equipped fully on a favourable site, by collecting rain water or by deepening of transitory pools.

While deep boreholes have improved opportunities for watering in the dry season, the use of temporary standing water remains necessary in the rainy season, but the number and especially the distribution of such stretches of water are unsuited to the needs of today's livestock. For better exploitation of Sahelian pastures, artificial temporary areas of standing water that remain wet throughout the rainy season should be set up, taking into account the quality of the pastures and the development of the Sahelian area. However, techniques for watering at these areas of water should be modified. Currently, the animals enter the water directly and soil it with their dejecta. Trampling all around the water area facilitates the carrying-off of the soil by erosion in patches or in ravines, and colluvial deposition in the water is accelerated. It would be essential to popularize techniques for exploiting areas of water without contaminating it. The Borana of southern Ethiopia have respect for water, and their animals never enter surface water. If they do, an ox belonging to the guilty owner is sacrificed and eaten by the group of raisers together. The raisers prepare on the edge of the water small earth barriers which the animals must not step over, and piles of branches prevent the herd from gaining access to the water. The animals are led in small groups to water at this device. After watering, the faeces are removed by the livestock raiser who has led his animals to drink, in order to avoid contamination in the event the water level rises. New devices are installed as the area of water shifts.

The shorter length of exploitation in the rainy season and the precautions adopted for watering would reduce the danger of parasitic infestation and would limit criticism of the use of areas of water by those responsible for the health of the livestock.

The rainy-season pasture would be put into operation as soon as the watering areas had been supplied with water. One fifth of the areas of water would be left aside, with the pasture served at the end of a month if the rainfall was more than 30 percent above normal (need for a rain gauge to be at the disposal of a permanent staff member).

At the beginning of the dry season, each herd grazing around an area of water would be brought back within the dry-season area. One fifth of the pastures would be put into reserve if the rainfall of the rainy season was more than 30 percent above normal.

If this setting aside could be repeated for 2 or 3 years, it would allow good regeneration of the herbaceous cover and, most importantly, would constitute a genuine reserve on a pluri-annual basis comparable with that produced by the inermous cactus in a Mediterranean climate, thanks to the development towards the bottom of leafed branches of Balanites aegyptiaca, Cadaba glandulosa, Maerua crassifolia, and Ziziphus mauritiana.

The herds would first take up position towards the outside, the calves being kept close to the settlement. The herds would go to drink each day at the central well, taking paths which would constitute actual fire breaks and would form, with the pastures exploited in the rainy season, a network of fire breaks naturally maintained. (It is in fact very difficult and expensive to maintain effective fire breaks throughout the Sahel. These fire breaks require early scraping or burning over a width of about 10 m.) In March or April, the settlement would be shifted to 5 km from the central well to reduce the movements in hot seasons. Unfortunately, it is the opposite which is usually practiced at the moment, and often tired animals no longer bother to go to the pasture, which is too far away at the end of the dry season; they lie down in the shade of a tree near the well and await the next watering there. The dry-season pasture must therefore move in a centripetal manner towards the water point, whereas the movement is traditionally centrifugal.

Improvements to the pasture could be reduced initially as a result of this rotation (rainy season dry season) with areas set aside in years with surplus rainfall (abandonment of an area of water in August, then of the corresponding section of the dry-season pasture).

On areas of warped soil, with disappearance of the herbaceous cover and death of the ligneous species, this setting-aside should be accompanied by working of the soil, following contours every 50 or 100 metres (scarifier with flexible teeth, and if possible a subsoil plough tooth). This loosening of the soil in parallel strips might be followed by sowing of local pioneer species: Cenchrus biflorus, Schoenefeldia gracilis, Zornia glochidiata.

Leguminous forage crops might be envisaged subsequently in the dry season area on favourable sites (sandy/loamy to clayey depressions) for grazing on the hoof in the dry season: Dolichos lablab, Centrosema pubescens, Stylosanthes humilis.

A piece of land with food crops would be set up near the village on a favourable site; passage between dunes, loamy/sandy depression. An auxiliary irrigation system might be envisaged in the case of mechanical pumping out. Small millet canes would be consumed by the livestock in the dry season. Acacia albida would be planted on the crop area and their fruit consumed later by the livestock.

The supply of wood for heating to the village would be programmed by means of placing areas invaded by young bush plants outside the pasture area.

If opportunities for the development of standing water turned out to be inadequate, a long-distance transhumance herd would be sorted at the beginning of the rainy season (oxen, cows without milk) and sent to far-off transhumance pastures, most often located in the subdesert Sahel and set up as a part of regional development. Each year, the surplus animals would be eliminated from the area by marketing or sent to centres (co-operatives or other types), either in the Sahel or in the Sudanian zone. These transactions should initiate commercial activity in the village (co-operative shop to supply essential products: cloth, tea, sugar, flour, cereals, etc.).

Sudanian area (figure 2)

The pilot experimental unit should be adapted to the land of a village whose population is favourable to the project and is integrated into it.

After a property survey of the land, the experiment should:

- Be centred on the development of crop land, with regrouping, testing of an adequate rotation system and an anti-erosion device, improvement of methods of work (animal-drawn cultivation, etc.);

- Integration of forage production into food and cash crop cultivation: forage-producing fallow land, intercalated strips sown with grass seed to be grazed using stakes or to be mown, planting, on ridges following contours of perennial forage plants for cutting (Andropogon, Pennisetum, Angola peas, Leucaena);

- Development and exploitation of natural pastures. The regrouping of individual fields should free deep soils. In these soils would be delimited the pasture sector for the herds of the village, and the herds of sedentarized transhumants could be integrated into those herds. The soils of these Sudanian pastures are generally poorly structured, and trampling throughout the rainy season leads to damage to the soil, with glazing of the soil and denudation by asphyxiation of the perennial Graminaceae. It is therefore necessary to plan simple rotation of the pastures in three sections:

Rainy season


Dry season

Beginning

middle

end

Section 1

Rest

Pasture

Light pasture

Section 2

Pasture

Rest

Light pasture

Section 3

Rest

Light pasture (Fires)

Section 3, set aside during the rains, would be turned over to grazing in the dry season, at the same time as the two others, then cleared with a fire at the beginning of the rains (after 30 mm of rain). The following year, it would become section 1, with grazing in the second half of the rainy season; section 1 would then become 2, and section 2, 3.

In the pasture sector, a forage crop of Stylosanthes guianensis would be established on the damp soils close to the water course. It would be grazed at night, in the dry season, in a night area, with all-round closure if possible.

The pasture sector should not burn from the beginning to the end of the dry season. A cultivated fire break might be planned on the edge of the section in the rainy season rest period, to protect it against uncontrolled external fires. Fifty metres in width, it might be cultivated by the agriculturalists or the sedentary livestock raisers with short-cycle crops such as small millet and groundnuts. There would thus be one year of crops for two years of fallow. Along the other two sections, the rainy season night areas would be established in order to manure the land, reduce herbaceous production, and at the same time keep up the fire break.

The neighbouring gritty plateau, separating two areas of village land, could be grazed in the rainy season, with watering in temporary standing water by a herd made up of beeves, dry cows, and growing young. This very extensive pasture could be exploited in rotation with grazing for one month, rest for one month, by moving the herd on two main areas of water. At the beginning of the dry season, the herd would be moved together with the dairy cattle, and the plateau would be set on fire as counter-fire protection.

C. Cartographic work carried out

As of 1974, the work on rangeland inventory and mapping published by IEMVT made up a total of 64 reports, with 57 maps at various scales (see annexed list). This covers almost 1,400,000 km²) including more than a million in intertropical Africa, with 150,000 km: in southern Ethiopia and almost 900,000 km²) in French-speaking central and western Africa.

Areas (km²)

Areas of zones

Mapped by I.E.M.V.T.

Zones

large scale
1/10 to 1/50,000

medium scale 1/100,000 - 1/200,00

small scale
1/400 to 1/1,000,000

areas mapped

Sahelian

2,000,000

2,240

125,320

631,620

759,180

Sudanian

1,766,000

1,240

72,415

36,000

109,655

Guinean

661,000

3,130

11,000

-

14,130

Totals

4,427,000

6,610

208,735

667,620

882,965

In West Africa, the areas mapped (table 8) cover more than 680,000 km²) including 500,000 on a small scale.

The Sahelian region has been particularly well studied, with mapping of more than 600,000 km²) representing 37 percent of the 1,615,000 km²) of Sahelian land within the five French-speaking states concerned.

The published maps are designed to illustrate and provide a synthesis of the data gathered in the field study.

The choice of scales depends on the objectives of the studies, the area involved, and also the cost (see paper by G. de Wispelaere, item 5-4).

The exploitation of aerial photographs at appropriate scales (1/25,000 and 1/50,000) is essential to the generalization of the fragmentary observations made during the visits. A key list of criteria is defined in order to establish a relationship between the types of pasture to be mapped and certain aspects of the photos perceptible for stereoscopic examination. The form of the land is a geomorphological characteristic which supplies the majority, but not the totality, of the criteria of the key for photointerpretation of the pastures, since certain representative aspects of the plant cover, and in particular the ligneous cover, are basic and relatively accurate.

The cartographic document has the advantage of presenting, in the form of a synthesis, the geographical distribution of the various individualized pastures and their relative importance. It should summarize all the data concerning the pastures of a region and reflect the state of the pastures and their carrying capacity at the moment of the study. Since a pasture is made up of a population of plant species in perpetual imbalance due to the action of climatic vagaries and changes in the stocking rate, the cartographic representation should make it possible to situate the state of the pasture within a series of probable evolution, a specific series of edapho-climatic conditions of each of the major units of the pastures.

The technical realization of the map and the choice of colours should tend to improve the legibility of the document and illustrate the " pasture " theme, while at the same time maintaining the interest of the topographical background (paper by G. Lamarque, item 5-3).

Table 8 - Rangeland mapped in West Africa (Areas in km²)

Bibliography

1. BOUDET. G. - Manuel sur les pâturages tropicaux et les cultures fourragères (2e édition). Ministère de la Coopération. Institut d'Elevage et de Médecine vétérinaire des Pays Tropicaux, 1974 (à paraître).

2. BOUDET, G., RIVIERE, R. - Emploi pratique des analyses fourragères pour l'appréciation des pâturages tropicaux. Revue d'Elevage et de Médecine Vétérinaire des Pays Tropicaux, 1968, 21 (2): 227-66.

3. BOURLIERE et al. - Recherches écologiques sur une

1. Bille, J.C., Lepage, M., Morel, G., Poupon, H. - Présentation de la région.
2. Bille, J.C., Poupon, H. - Description de la végétation.
3. Bille, J.C., Poupon, H. - Biomasse végétale et production primaire nette.
4. Lepage, M. - Données préliminaires sur l'écologie des termites.
5. Morel, G., Morel, M.Y. - Les oiseaux. 6. Poulet, A.R. - Les mammifères.
La Terre et la Vie, 1972, 26 (3): 325-472.

4. F.A.O. - Annuaire de la production 1972, 26. F.A.O. Division de la Statistique, 1973.

5. LE HOUEROU, H.N. - Contribution à une bibliographie des phénomènes de désertisation, de l'écologie végétale des pâturages et du nomadisme dans les régions arides de l'Afrique et de l'Asie du Sud-Ouest. Rome, F.A.O., Division de la Production végétale et de la protection des plantes, 1973: 120 p.

6. VALENZA, J., FAYOLLE, F. - Note sur les essais de charge de pâturage en République du Sénégal. Revue d'Elevage et de Médecine Vétérinaire des Pays Tropicaux, 1965, 18 (3): 321-7.

7. WHYTE, R.O. - Tropical grazing lands; communities and constituent species. The Hague, Junkw. publisher, 222 p., 24 fig., 15 tab.

ANNEX: LIST OF INVENTORIES AND MAPS PREPARED BY I.E.M.V.T.

I. ETUDES AGROSTOLOGIQUES

1. GILLET, H. - Oct. 1961. Pâturages sahéliens Le ranch de l'Ouadi Rimé. 1 vol.: 210 p., 21 pl. phot. h.t., 7 c. 10 fig., 10 tab. Paris, Journ. Agric. Trop. Bot. Appl. 8: 465-536; 557-692.

2. BOUDET, G. et DUVERGER, E. - Nov. 1961. Etude des pâturages naturels sahéliens. Le Hodh (Mauritanie). Paris, Vigot, 1 vol.: 160 p., 52 phot., 1 c. h.t.

3. MOSNIER, M. - Déc. 1961. Pâturages naturels sahéliens. Région de Kaedi (Mauritanie). Miméogr.: 169p.; 1 c. coul. au 1/200 000 en deux feuilles (24 500 km²).

4. MOSNIER, M. - Fév. 1963. Etude agrostologique des fermes du Service de l'Agriculture de la République du Tchad. Miméogr. : 80 p.

5. PEYRE DE FABREGUES B. - Juil. 1963. Etude des pâturages naturels sahéliens - Ranch de Nord-Sanam (Rép. du Niger). Miméogr.: 132 p.; 1 c. coul. au 1/100000 (3450 km²).

6. BOUDET G. - Juil. 1963. Pâturages et plantes fourragères en République de Côte-d'Ivoire. Miméogr.: 102 p.; 1 c.

7. BOUDET, G. - Juil. 1963. Etude et cartographie des pâturages en République de Côte-d'Ivoire. Miméogr.: 20 p.; 1 c. coul. au 1/25 000 (150 km²).

8. AUDRU J. et BOUDET, G. - Juin 1964. Pâturages de la zone Sud de la République Centrafricaine. Miméogr.: 213 p.; 1 c. coul. au 1/50 000 (335 km²).

9. BILLE, J.C. - Déc. 1964. Pâturages du secteur occidental d'élevage de la République Centrafricaine. Miméogr.: 286 p.; 2 c. coul. au 1/200 000 (11000 km²). et 1/25000 (160 km²).

10. PEYRE DE FABREGUES, B. - Juin 1965. Etude des pâturages naturels sahéliens de la région de Nord-Gouré (Rép. du Niger). Miméogr.: 163 p.; 1 c. coul. au 1/100000 (4180 km²).

11. GASTON, A. - Mars 1966. Etude agrostologique du Kanem (Rép. du Tchad). Miméogr.: 176 p., 1 c. coul. au 1/400 000 (22 268 km²).

12. PEYRE DE FABREGUES, B. - Fév. 1966. Les cactées fourragères dans le Nord-Est brésilien. Miméogr.: 80 p.

13. FOTIUS, G. et VALENZA, J. - Avril 1966. Etude des pâturages naturels du Ferlo-oriental (Rép. du Sénégal). Miméogr. : 180 p.; 1 c. coul. au 1/200 000 en deux feuilles (20 000 km²).

14. BOUDET, G. - Sept. 1966. Etude agrostologique du ranch de Sipilou (Rép. de Côte-d'Ivoire). Miméogr.: 150 p.; 1 c. coul. au 1/25 000 (95 km²).

15. AUDRU, J. - Oct. 1966. Etude des pâturages naturels et des problèmes pastoraux dans le delta du Sénégal. Définition d'une politique de l'élevage. Miméogr., 2 vol.: 359 p.; 1 c. coul. au 1/100000 (2200 km²).

16. AUDRU, J. - Déc. 1966. Ensemble pastoraux du Logone et du Moyen Chari (Rép. du Tchad). Miméogr.: 210 p.; 1 c. coul. au 1/400000 (36000 km²).

17. PEYRE DE FABREGUES, B. - Janv. 1967. Etude agrostologique des pâturages de la zone nomade de Zinder (Rép. du Niger). Miméogr.: 188 p.; 1 c. coul. au 1/400 000 (14 000 km²).

18. MOSNIER, M. - Juin 1967. Les pâturages naturels de la région de Gallayel (Rép. du Sénégal). Miméogr.: 137 p.; 1 c. coul. au 1/100000 (1790 km²).

19. GASTON, A. - Juin 1967. Etude agrostologique du Kanem - Préfecture du Kanem au Sud du 16e parallèle et Préfecture du Lac (Rép. du Tchad). Miméogr.: 147 p.; 1 c. coul. au 1/500 000 (75 750 km²).

20. GASTON, A. - Juin 1967. Etude agrostologique des pâturages de la zone de transhumance de l'Ouadi Haddad (Rép. du Tchad). Miméogr.: 64 p.; 1 c. au 1/500 000 (13 000 km²).

21. BILLE J.C. - Avril 1967. Expérimentation agrostologique en République Centrafricaine. Miméogr.: 246 p.

22. BILLE, J.C. - Déc. 1967. Note sur les stations d'élevage de la République Centrafricaine. Miméogr.: 31 p.

23. DIALLO, A.K. - Mai 1968. Pâturages naturels du Ferlo Sud (Rép. du Sénégal). Miméogr.: 173 p.; 1 c. coul. au 1/200 000 (4 015 km²).

24. BILLE, J.C. - Mai 1968. Etude agrostologique des pâturages de la région des savanes (Rép. du Togo). Miméogr.: 108 p.; 1 c. au 1/65 000; 1 c. coul au 1/50 000 en 7 feuilles (441 km²).

25. DELHAYE, R. et GRANIER P. - 1968. Etude des pâturages naturels de Madagascar en vue de l'aménagement de zones d'embouche pour bovins. Miméogr., 10 fasc.; 8 c. coul. au 1/50 000 (2 400 km²).

26. BOUDET, G. - Avril 1969. Etude des pâturages naturels du Dallol-Maouri (Rép. du Niger). Miméogr.:

27. BOUDET, G. - Mai 1970. Pâturages naturels de Haute et Moyenne Casamance (Rép. du Sénégal). Miméogr.: 240 p. phot.; 1 c. coul. au 1/200 000 en deux feuilles (20 500 km²).

28. PEYRE DE FABREGUES, B. - Juil. 1970. Pâturages naturels sahéliens du Sud Tamesna (Rép. du Niger). Miméogr.: 200 p.; 1 c. coul. au 1/500 000 (23 600 km²).

29. BOUDET, G. - Juil. 1970. Etude agrostologique pour la création d'une station d'embouche dans la région de Niono (Rép. du Mali). Miméogr.: 268 p., 8 ph., 1 c. coul. au 1/500 000 (8 000 km²). 1 c. coul. au 1/50 000 (110 km²). 1 c. coul. au 1/100 000 (1300 km²). et 1 c. coul. Au 1/200000 (1000 km²).

30. BOUDET, G. et ELLENBERGER, J.F. - Juin 1971. Etude agrostologique du berceau de la race N'Dama dans le cercle de Yanfolila (Rép. du Mali). Miméogr.: 174 p., 8 phot., 6 fig., 13 tab., 1 c. coul. au 1/50 000 (220 km²).

31. GASTON, A. et BOTTE F. - Juil. 1971. Etude agrostologique de la Réserve dé Tin Arkachen (Rép. de Haute Volta). Miméogr.: 146 p., tab.; 1 c. coul. au 1/100 000 (3 000 km²).

32. PEYRE DE FABREGUES, B. - Déc. 1971. Evolution des pâturages naturels sahéliens du Sud Tamesna (Rép. du Niger). Miméogr.: 135 p., 9 fig., 19 tab.; 4 c. coul. au 1/50 000 (1 000 km²).

33. RIPPSTEIN, G. et PEYRE DE FABREGUES, B. - Janv. 1972. Modernisation de la zone pastorale du Niger. Miméogr.: 306 p., 8 ph. 38 tab., 9 fig., 1 c. coul. au 1/1000 000 en deux feuilles (360 00;) km²).

34. VALENZA, J. et DIALLO, A.K. - Juin 1972. Etude des pâturages naturels du Nord-Sénégal. Miméogr.: 311 p., 8 fig., 11 phot., 44 tab., 1 c. coul. au 1/200000 en trois feuilles (34 500 km²).

35. AUDRU, J. - Sept 1972. Etude de factibilité des ranches d'Abokouamékro et de Sipilou (Rép. de Côte d'Ivoire). Miméogr.: 145 p., tab. cartes; 1 c. coul. au 1/25 000 (120 km²).

36. RIPPSTEIN, G. - Juil. 1972. Projet de développement de l'élevage au Ghana- Etude de factibilité de quatre ranches. Miméogr.: 178 p., cartes et tab.

37. BOUDET, G. - Sept. 1972. Projet de développement de l'élevage dans la région de Mopti (Rép du Mali). Miméogr.: 309 p., 21 tab., 12 phot., 5 c. au 1/2000000 et 1 c. coul. au 1/1000 000 (88 000 km²).

38. AUDRU, J. - Févr. 1973. L'élevage bovin dans les régions de Biankouma et de Touba (Rép. de Côte d'Ivoire). Miméogr.: 155 p., 4 tab., 1 c. au 1/200 000.

39. AUDRU, J. - Mars 1974. Inventaire des parcours de la région Ouest de Bodokro pour l'installation d'un élevage naisseur en secteur paysannal (Rép. de Côte d'Ivoire). Maisons-Alfort I.E.M.V.T., Miméogr.: 110 p.; 1 c. coul. au 1/20000 (50 km²).

40. TOUTAIN, B. - Juil. 1974. Etude agrostologique préalable à l'implantation d'un ranch d'embouche dans la région de Léo (Rép. de Haute-Volta). Maisons-Alfort I.E.M.V.T.; miméogr. : 149 p.; 1 c. coul. au 1/50 000 (460 km²). 1 c. coul. au 1/100000 (2500 km²).

41. GASTON, A. - Juil. 1974. Etude agrostologique des pâturages du projet Assalé-Serbewel (Rép. du Tchad Rép. Unie du Cameroun). Miméogr.: 143 p.; 1 c. au 1/200 000 (9 700 km²).

42. PEYRE DE FABREGUES, B. - Mars 1975. Etude de la piste à bétail Ati-N'Djamena (Rép. du Tchad). Miméogr.: 101 p.; 1 c. coul. au 1/50000 (400 km²).

II. AGROSTOLOGICAL WORK (Subcontracted)

1. MORDANT, J. - Fév. 1967. Plan de développement des ressources en terre et en eau pour les îles d'Aruba, Bonaire et Curaçao (Antilles Néerlandaises). S.O.G.R.E.A.H. (Grenoble)/I.E.M.V.T. Miméogr.: 114 p.

2. MOSNIER, M. - Fév. 1968. Les terrains de parcours de la zone V (Arabie Saoudite). S.O.G.R.E.A.H. (Grenoble) / I.E.M.V.T. Miméogr.: 42 p.; 1 c. au 1/500000 (85 000 km²).

3. MOSNIER, M. - Juil. 1968. Etude des pâturages naturels en Arabie Saoudite - Projet pilote de la zone VI. S.O.G.R.E.A.H. (Grenoble) / I.E.M.V.T. Miméogr.: 50 p. 1 c. au 1/500 000, 2 feuilles (245 000 km²).

4. MOSNIER, M. - Déc. 1968. Projet-pilote d'élevage de la plaine côtière de la Mer Rouge - Région de Saadiyah (Arabie Saoudite). S.O.G.R.E.A.H. (Grenoble) / I.E.M. V.T. Miméogr.: 113 p.; 1 c. au 1/50000 (1700 km²).

5. MOSNIER, M. - Janv. 1969. Les terrains de parcours du territoire côtier de la Mer Rouge (Arabie Saoudite). S.O.G.R.E.A.H. (Grenoble)/I.E.M.V.T. Miméogr.: 142 p.

6. BILLE, J.C. - Fév. 1969. Etude agrostologique de la plaine du Gondo (Vallée du Sourou, Rép. de Haute-Volta). B.D.P.A. (Paris) / I.E.M.V.T. Miméogr.: 76 p.; 1 c. au 1/200 000 (6 900 km²).

7. GASTON, A. - Juin 1969. Etude des pâturages de la zone sud de Tarif-Djebel Dana - Trucial State (Abu Dhabi). S.O.G.R.E.A.H. (Grenoble)/I.E.M.V.T. Miméogr.: 33 p., 1 flor., 1 c. au 1/100 000 (9 000 km²).

8. MORDANT J. - Déc. 1970. Projet d'amélioration pastorale des régions arides et semi-arides du Maroc. Min. Aff. Etr. (Paris) / I.E.M.V.T. Miméogr.: 231 p., 1 c., bibl., flor.

9. BOUDET, G., CORTIN, A., MACHER, H. - 1971. Esquisse pastorale et esquisse de transhumance de la région du Gourma (Rép. du Mali). DIWI (Essen)/I.E.M. V.T. (DIWI Gesellschaft für ingennieurberatung, Essen, Allemagne). Miméogr.: 283 p., tabl., graph., 12 ph., 1 c. 1 atlas polychrome au 1/200 000 (39 600 km²).

10. BOUDET, G. - 1972. Rapport de consultant pour l'étude SATEC de mise en valeur de la Zor Zériba de Bouira en Grande Kabylie (Algérie). SATEC (Paris)/ I.E.M.V.T. Miméogr.: 15 p.

11. ELLENBERGER, J.F. - Septembre 1972. Possibilité d'intensification de l'exploitation des pâturages dans la pampa-isla d'Ixiamas - Province Itturalde (Bolivie). AGRAR und HYDROTECK (Essen) / I.E.M.V.T. Miméogr.: 91 p., 6 ph.

12. ELLENBERGER, J.F. - Octobre 1972. Quelques indications sur les possibilités d'affouragement du bétail en sec dans la zone du projet Abapo-Izozog (Bolivie). AGRAR und HYDROTECK (Essen) / I.E.M.V.T.. Miméogr.: 54 p., 3 ph.

13. GRANIER, P. - Décembre 1972. Problèmes posés par le développement de l'élevage bovin dans le Brésil Central (Mission Condepe n° 1). F.A.O.-B.I.R.D./I.E.M. V.T. Miméogr.: 58 p., 2 fig.

14. BOUDET, G. - Janvier 1973. Aperçu sur les pâturages de la Vallée du Fafan et de la Basse Vallée du Wabi Shabelli (Ogaden - Ethiopie). B.C.E.O.M. (Paris)/I.E.M. V.T. Miméogr.: 75 p., 3 pl., ph., 1 plan de sit.

15. PEYRE DE FABREGUES, B. - Mai 1973. Synthèse des études de la zone de modernisation pastorale du Niger. Amélioration de l'exploitation pastorale. S.E. D.E.S. (Paris) / I.E.M.V.T. Miméogr.: 50 p.

16. AUDRU, J. et DEMANGE, R. - Juin 1973. Etude agrostologique et problèmes de nutrition au Sud Mali. S.E.D.E.S. (Paris) / I.E.M.V.T. Miméogr., 2 vol.: 562 p., 1 c. couleur au 1/200000 (11000 km²).

17. BOUDET, G., RIPPSTEIN, G. et coll. - Juillet 1973. Southern rangeland livestock development project Ecological range survey (Ethiopie). AGROTEC (Rome), C.R.G. (Florence), S.E.D.E.S. (Paris)/I.E.M.V.T. Miméo.: 175 p., 15 tabl., 3 fig., 8 ph., 1 maquette au 1/250 000 en 20 feuilles (160 000 km²). et 1 maquette au 1/50 000 (770 km²).

18. ELLENBERGER, J.F. - Novembre 1973. Selection of perimetres in Garhyan province (Libya). S.A.T.E.C. (Paris) / I.E.M.V.T. Miméogr.: 19 p., 5 c. au 1/50000.

19. DIALLO, A.K. - Janvier 1974. Pâturages naturels et alimentation du cheptel dans l'Unité Expérimentale de Koumbidia (Rép. du Sénégal). I.R.A.T. (Bambey) / I.E.M.V.T. Miméogr.: 44 p., 15 tabl., 1 c. coul. au 1/20000 (120 km²).

20. GASTON, A. - 1973. Esquisse de reconnaissance des groupements végétaux de la zone de recherches écologiques intensives du projet Quelea-Quelea (Région de N'Djamena). Etude des potentialités grainières de certains groupements végétaux. P.N.U.D.-F.A.O. (Rome)/ I.E.M.V.T. Miméogr.: 122 p., 1 c. au 1/50 000 (1 100 km²). cartons au 1/10 000 (30 km²).

21. PEYRE DE FABREGUES, B. - 1974. Problèmes posés par le développement de l'élevage bovin dans le Brésil Central. Mission Condepe nº 2. Min. Aff. Etr. (Paris)/ I.E.M.V.T. Miméogr.: 50 p.

22. GRANIER, P. - Janvier 1974. Rapport agrostologique sur la factibilité de deux ranches au Niger. S.E.D.E.S. (Paris) / I.E.M.V.T. Miméogr.: 40 p., 8 graph.

23. BILLE, J.C. - Mars 1974. Développement agro-pastoral de l'Ubangui - Etude des pâturages (Rép. du Zaïre). SOGELERG (Paris) / I.E.M.V.T. Miméogr.: 46 p., 1 c. au 1/100000 (2500 km²).

Figure a

Figure b

Figure c

Figure d


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