Botanical Features of the Algerian Sahara

Part 1

Illustration: Fig. 1. View of the Oasis of Laghouat

Illustration: Fig. 2. Wood market at Laghouat. Juniper, oak, pine, and other kinds of wood, each bunch a camel load, exposed for sale.

Illustration: Fig. 3. Wood market at Laghouat. Roots of Zizyphus, branches of juniper and pine, and pine bark. The latter is said to be used for staining.]

BOTANICAL FEATURES OF THE ALGERIAN SAHARA

BY WILLIAM AUSTIN CANNON

WASHINGTON, D.C. PUBLISHED BY THE CARNEGIE INSTITUTION OF WASHINGTON 1913

CARNEGIE INSTITUTION OF WASHINGTON PUBLICATION NO. 178

PRESS OF J.B. LIPPINCOTT COMPANY PHILADELPHIA

CONTENTS. * * * * *

PAGE Introduction 1

Geographical Characteristics of Algeria 2

Climate of Algeria 6

Some Characteristics of the Vegetation of the Tell 15

The Forests of Algeria 18

The High Plateau 20

Boghari to Laghouat 20

Djelfa to Laghouat 22

Laghouat 23

The Oasis of Laghouat 24

The Plain 25

The Dunes near Laghouat 27

The Mountains about Laghouat 28

Effects of Grazing on Vegetation near Laghouat 29

From Laghouat to Ghardaia 31

Region of the Dayas 31

Daya of Tilrempt 32

The Chebka 34

Ghardaia 36

Part 2

The Oasis of Ghardaia 38

The Plain (Hamada) of Ghardaia 39

The Mountains about Ghardaia 41

The Valley of the M’Zab 41

Protected Areas near Ghardaia 42

Root-Habits in the Ghardaia Region 44

Leaf-Habits in the Ghardaia Region 49

Growth and Flowering Habits in the Ghardaia Region 49

Ghardaia to Touggourt 50

Ghardaia to Ouargla—Vegetation 53

Ouargla to Touggourt—Vegetation 56

Touggourt to Biskra—Physical Features and Vegetation 58

The Biskra Region 59

Topography 59

Plant Habitats of the Biskra Region 60

Vegetation of the Biskra Region 61

General Summary and Conclusions 66

The Environmental Conditions of Plants in Arid Regions 66

Environmental Features of the Flora of Algeria 69

Some Effects of Temperature and Rainfall in Southern Algeria 71

The Soil Relation in Southern Algeria 73

Root-Characters and Species Distribution in Southern Algeria 76

The Biotic Factor 77

Comparison of Some General Features of the Vegetation of Southern Algeria and of Southern Arizona 79

LIST OF ILLUSTRATIONS. * * * * *

Plate A. Outline map of Algeria, showing main features of surface drainage.

Pl. 1, fig. 1. View of the oasis of Laghouat.

2. Wood market at Laghouat. Juniper, oak, pine, and other kinds of wood, each bunch a camel load, exposed for sale.

Part 3

3. Wood market at Laghouat. Roots of Zizyphus, branches of juniper and pine, and pine bark. The latter is said to be used for staining.

Pl. 2, fig. 4. Shoot-habit of Acanthyllis tragacanthoides. Laghouat.

5. Shoot-habit of Zollikoferia spinosa. Laghouat.

6. Acanthyllis tragacanthoides on sandy plain. Laghouat.

7. Zollikoferia spinosa in habitat, plain (hamada). Laghouat.

Pl. 3, fig. 8. Detail of north slope of Nomad Mountains, where Zollikoferia spinosa is the dominant species. Laghouat.

9. Vegetation of plain (hamada) at Tilrempt. The conspicuous shrub is Haloxylon articulatum.

10. The daya of Tilrempt from the plain, showing the character of the depression.

Pl. 4, fig. 11. Near view of the daya of Tilrempt. The fortified stage station, bordj, and a nomad camp are to be seen. The flattened, level, lower surface of the trees is the effect of grazing, mainly by camels.

12. Jujube (Zizyphus) shrubs and betoum (Pistacia) at the daya of Tilrempt.

Pl. 5, fig. 13. A young specimen of betoum in the midst of a protecting jujube at the daya of Tilrempt.

14. Leaf and shoot habit of the jujube (Zizyphus lotus). Daya of Tilrempt.

15. Leaves of the betoum (Pistacia atlantica) from the daya of Tilrempt.

Pl. 6, fig. 16. South wall of the valley of the Oued M’Zab at Ghardaia.

17. Detail of an eroded bank of the Oued M’Zab at Ghardaia. The overhanging stratum is hardpan similar to the “caliche” of southwestern United States.

Pl. 7, fig. 18. Shoot-habit of Haloxylon articulatum, from the plain near the daya of Tilrempt.

19. Agriculture at Ghardaia. The fields are divided into plots about 3 by 4 feet in size, for the more economical use of water. Young barley is shown growing (November).

Pl. 8, fig. 20. Vegetation in upper part of a “draw” on plain north of the M’Zab Valley, Ghardaia.

21. Situation of square No. 2, on plain north of valley at Ghardaia.

Pl. 9, fig. 22. Capparis spinosa at base of valley wall at Ghardaia.

23. Leaves of Capparis spinosa from Ghardaia.

Pl. 10, fig. 24. Leaf-habit of Dæmia cordata. Ghardaia.

25. Shoot-habit of Salvia ægyptica. Ghardaia.

26. Upper surface of rocks, showing small incrusting lichens, on a low mountain about 5 km. north of M’Zab Valley, Ghardaia.

Pl. 11, fig. 27. Habitat of Peganum harmala, at Melika, Ghardaia.

28. Shoot and leaf habit of Peganum harmala, from Ghardaia.

Pl. 12, fig. 29. Habit of Henophyton deserti at Ghardaia when growing in a protected situation (cemetery).

30. Leaf-habit of Henophyton deserti. Ghardaia.

Part 4

Pl. 13, fig. 31. View in a cemetery at Ghardaia, to show the relatively abundant vegetation.

32. View in an M’Zabite cemetery, Ghardaia. Haloxylon articulatum is the leading species shown.

Pl. 14, fig. 33. Habit of Deverra scoparia, from plain about 3 km. north of M’Zab Valley, Ghardaia.

34. Root-habit of Gymnocarpos fruticosum, from plain about 3 km. north of M’Zab Valley at Ghardaia.

Pl. 15, fig. 35. Root-habit of a mature specimen of Peganum harmala, from the floor of the M’Zab Valley near Ghardaia. The soil at the place is comparatively deep.

Pl. 15, fig. 36. Root-systems of Helianthemum sessiliflorum (right), Haloxylon articulatum, and Nolletia chrysocomoides (left), from the flood-plain of the Oued M’Zab, Ghardaia.

Pl. 16, fig. 37. Shoot and root habit of Citrullus colocynthis. Oued M’Zab, Ghardaia.

38. Euphorbia guyoniana, in the valley of the Oued M’Zab at Ghardaia.

Pl. 17, fig. 39. Habit of Euphorbia guyoniana. Ghardaia.

40. To the left, shoot of Centaurea sp., showing effect of grazing; to the right, shoots of Teucrium pseudo-chamæpitys. From Ghardaia.

Pl. 18, fig. 41. Habit of Salsola sp. (below) and Echinopsilon muricatus, from the M’Zab Valley, Ghardaia.

42. Ghardaia to Ouargla. View overlooking the hamada about 28 km. from Ghardaia. The relatively abundant vegetation is associated with a light cover of sand over the area shown. The leading species are Aristida, Deverra, and Haloxylon.

Pl. 19, fig. 43. Retama retam, in dunes about 58 km. from Ghardaia.

44. Dates at the Bordj Zolfana, about 58 km. from Ghardaia—one of two wells encountered between Ghardaia and Ouargla.

45. Ghardaia to Ouargla. View overlooking flood-plain of the Oued M’Zab, or a tributary of this oued. The adjacent upland is apparently without plant life.

Pl. 20, fig. 46. Vegetation on edge of the Oued M’Zab, about 63 km. east of Ghardaia, showing habitat of Rhantherium adpressum in foreground.

47. Sandy flood-plain of the Oued M’Zab, about 63 km. from Ghardaia. Retama, Genista, and Ephedra are the leading plants in this place.

48. Habit of Ephedra alata in habitat shown in figure 47. This specimen was 1.5 m. high.

Pl. 21, fig. 49. View of habitat of Ephedra alenda, 138 km. from Ghardaia.

50. Detail of suckering habit of Ephedra alenda, from habitat shown in figure 49.

Pl. 22, fig. 51. Vegetation, mainly Ephedra and Retama, of the western edge of the Chott Mellala.

52. Approach to western edge of the Chott Mellala, showing characteristic rounded hills, or mamelons.

Pl. 23, fig. 53. View between the Ouargla plain and the Chott Mellala, showing characteristic appearance of eroded hills.

54. Looking toward the Ouargla plain (reg).

55. Shallow well about 25 km. north of Ouargla.

Pl. 24, fig. 56. Ouargla to Touggourt. Leaf-habit of Limoniastrum guyonianum. The surface of the leaves is covered with an incrustation of salts.

57. Habit of Limoniastrum guyonianum. About 25 km. north of Ouargla.

Pl. 25, fig. 58. Vegetation of the reg desert, about 25 km. north of Ouargla. Ephedra and Retama are the leading species of the area—a spreading dune.

Part 5

59. Shoot-habit of Halocnemon strobilaceum. About 28 km. north of Ouargla.

Pl. 26, fig. 60. Habit of Halocnemon strobilaceum on the edge of a chott, about 28 km. north of Ouargla.

61. Shoot and leaf habit of Anabasis articulata, about 32 km. north of Ouargla.

Pl. 27, fig. 62. Detail of the shoot-habit of Salsola tetragona?, about 25 km. north of Ouargla.

63. Habit of Nolletia chrysocomoides near the edge of a chott, about 80 km. north of Ouargla.

Pl. 28, fig. 64. Tamarix sp. as a sand-binder near Bled-el-Amar, south of Touggourt.

65. Biskra. Habitat of Euphorbia guyoniana, looking toward the Djebel Maouya, with the Chaine de Sfa in the background.

Pl. 29, fig. 66. Characteristic vegetation on the north slope of the Djebel Bou Rhezal, Biskra. Haloxylon scoparium is a prominent species.

67. North base of Ed Delouatt hills, west of Biskra, showing the low facing dunes. To the right is a glimpse of an oued which pierces the hills in the middle distance.

Pl. 30, fig. 68. Flood-plain of the Oued Hamman es Salahin, Biskra. Halophytes of various species occupy the foreground.

69. Habitat of Phelyæa violacea shown in figure 70.

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