Revue internationale d'écologie méditerranéenne International ...

146
◆ M. A. SHEIKH, M. E. MADY & K. H. SHALTOUT
Rumex dentatus L. -- -- --1-- -------- ------------- -2--------- 101
Setaria viridis (L.) P. Beauv. -- 1- -111- -------- ----1-------- ---1-1-11-- 101
Launaea nudicaulis (L.) Hook. fi l. -- 1- -111- -------- ------------- -11-------- 11000
Otanthus maritimus (L.) Hoffm.&Link -- -- 11-11 -------- ------------1 ----------- 11001
Pancratium maritimum L. -- -- --11- -------- ------------- ----------- 11001
Zygophyllum album L.f. -- -- ---11 -------- ------------- ----------- 11001
Cakile maritima (Scop.) Willd. Nyman -- 1- -1111 -------- ------------- -1--------- 11001
Ziziphus spina-christi (L.) Desf. -- -1 ----- -------- ------------- ----------- 11010
Mesembryanthemum crystallinum L. -- 43 111-1 -----11- ------------- ----------- 11010
Orobanche aegyptiaca Pres. -- -1 ----- -------- ------------- ----------- 11010
Salsola kali L. -- 11 ---11 -----11- ------------- ----------- 11010
Arthrocnemum macrostachyum (L.) Moq. 46 -- -111- -------- ------------- ----------- 11011
Silene succulenta Forssk. 1- -- -1--- -------- ------------- ----------- 11011
Trifolium tomentosum L. -- 1- ----- -----1-- ------------- ----------- 111
TWINISPAN division level 1 11 11 11111 00000000 0000000000000 00000000000
Table 2. Species composition of the six vegetation units (I-VI) identified after the application of TWINSPAN
to the vegetation data of 41 stands along the down-stream part of Wadi Gaza. The cover levels are coded as follows: 1, ≤ 10%; 2, 10-20%;
3, 20-30%; 4, 30-40%; 5, 40-50%; 6, 50-60%; 7, 60-70%; 8, 70-80%; 9, ≥ 90%. Vegetation units are: I: Arthrocnemum macrostachyum,
II. Mesembryanthemum crystallinum, III. Tamarix nilotica – Arundo donax, IV.Tamarix nilotica, V. Alhagi graecorum - Xanthium spinosum,
VI. Centaurea ammocyanus - Atractylis carduus.
life forms, except for the therophytes where the biregionals
were highly represented (fig. 2). The Mediterranean
components were the highest among the monoregionals
(about 25 %) in most life forms, while the Mediterranean-
Irano-Turanian were the highest among the biregionals
(50 %) (table 1).
Fig. 3. Relation between the
six vegetation units resulting
from DCA application. The
eigen values for DCA of axis 1
was 0.763 and for axis 2 was
0.581. Vegetation units are: VGI:
Arthrocnemum macrostachyum;
VGII: Mesembryanthemum
crystallinum; VGIII: Tamarix
nilotica – Arundo donax; VGIV:
Tamarix nilotica; VGV: Alhagi
graecorum - Xanthium spinosum;
VGVI: Centaurea ammocyanus.-
Atractylis carduus.
2 11 00 00000 11111111 1111111111111 00000000000
3 11 00000 11111111 0000000000000 11111111111
4 01111 00000111 0000111111111 0111111111
5 00001 000000001 000000111
6 00000001 011111
TWINSPAN divided the set of 41 stands into six
vegetation units at level 3. They are named after the
characteristic species (which had highest values of presence
percentage and/or cover percentage) as follows:
Arthrocnemum macrostachyum (I), Mesembryanthemum
crystallinum (II), Tamarix nilotica – Arundo donax (III),
ecologia mediterranea, tome 29, fascicule 2, 2003