الفهرس 
DiscussionOnly 14 pages are availabe for public view
 |  | from | 273 |  |  |
| | | from | 273 | | |
Abstract
1- This thesis presents an ecological survey of desert
plants in north-west sinai of Egypt to elucidate their
adaptation to environment and ecological relationships
between plant communities and habitats.
2- The study area is a part of south-west Sinai embodying
a number of habitat and vegetation types. For the purpose
of the present study, the area is divided into four
sectors
i- The coastal plain sector.
ii- Ayoun Musa sector.
iii- Wadi Sudr sector.
iv- El-Heitan sector.
3- The course of the study included ·phytosociological
analysis of the main plant communities in the main
habitat types. Ecophysiological studies were carried
out on the dominant species to elucidate their means of
adaptation to their arid and frequently saline
environment.
4- Due to wide variation in the habitat conditions in the
surveyed area, there are numerous plant communities
that may be classified into two categories according to
the salt content of their habitat :
a) Halophytic communities :
These exploit saline habitats and include tl}e
following communities: Juncus rigidus. Cressa cretica,
Alhagi maurorum, Halocnemum strobilaceum, Nitraria retusa
and Tamarix nilotica communities.
b) Glycophytic communities
These are confined to non-saline habitats and include
the following communities: Reaumuria hirtella, Anabasis
setifera. zygophyllum coccineum. Hammada elegans, Anabasis
articulata, Lygos raetam and Tamarix nilotica communities.
5- Part I of the thesis comprises information on Sinai
including geology and geomorphology of Sinai. It
includes also review of literature and a brief
description of the methods of vegetation, plant and
soil danalyses.
6- Part II of the thesis includes information on the study
area and discussion of the climatic features. This part
includes also the results obtained for
phytosociological and ecophysiological studies.
a) The phytosociological studies included analytical and
synthetic characters of the vegetation units (plant
communities). Analysis of the soils associated with the
plant communi ties was investigated to elucidate their
physical and chemic.al characteristics. The habitat
types within the study area were classified into (i)
littoral and inland salt marshes, (ii) swamps, (iii)
sand plains and (iv) wadis.
(i) Littoral and inland salt marshes
The vegetation of littoral salt marsh is dominated by
Halocnemum strobilaceum. This is a highly salt tolerant
species that accumulates high amounts of salt within its
tissue.
The inland salt marshes at Ayoun Mus a are
distinguished into wet and dry salt marshes according to
the gradual rise of level of salt marsh and deeping of the
underground water. The lowest level in the salt marsh is
occupied by a zone of Juncus riqidus community where the
underground water is very shallow and the soil is very
wet. When the level of wet salt marsh gets higher and the
level of underground water becomes deeper (dry salt
marshes) , the vegetation is dominated by cressa cretica,
Alhaqi maurorum, Nitraria retusa and Tamarix nilotica
communities.
(ii) Swamps :
These are created as a result of flow of spring’s
water at Ayoun Musa and ill-drainage. Phragmites australis
and Typha domingensis were recorded in these swamps.
(iii) Sand plains :
The vegetation of the sand plains is dominated by the
two succulent species Zygophyllum coccineum and Anabasis
articulata.
{iv) Wadis :
The vegetation of Wadi Sudr and affluent wadis
crossing Gebel El-Heitan is dominated by Reaumuria hitella
Anabasis setifera. Hammada elegans. Lygos raetam and
Tamarix nilotica.
b) Ecophysiological studies included. the determination of
plant moisture content, degree of succulence, ash
content, elemental composition of the ash as well as
quantitative estimation of carbohydrate fractions,
nitrogenus compounds, amino acids and fatty acids. The
studies were carried out on the dominant species in
winter and summer seasons. The results obtained
revealed that the plants of saline habitats attained
higher values of succulence and moisture content than
non-saline habitats. The ash content of all halophytes
and most of glycophytes was higher in summer than in
winter. This was associated with high acumulation of
Na+, K+, ca++, Mg++, p+++ and Cl.
Meanwhile, glycophytic species attained higher
accumulation of nitrogenous compounds than halophytes.
Total carbohydrates in halophytic and glycophytic species
attained its highest value in winter. The total amino
acids was higher in glycophytes than in halophytes.
Analysis of the fatty acids was carried using G.L.9.
technique and revealed variations between the species of
•
the two ecological groups. The number of fatty acids
ranged from 12 to 20 in glycophytes with linoleic, myristoleic
and myristic as major fatty acids. In halophytes the
number of fatty acids varried between 8 and 17 with
myristic and myrist-oleic as the major fatty acids.
7- Part III of the thesis includes a general discussion of
the results obtained included general remarks about the
aridity of study area, the close relationship between
vegetation and habitats, zonation of salt marsh
vegetation,the inclusion of the vegetation of principal
wadis of well developed climax and subclimax community
types.
Adapatation of glycophytes and halophytes to
environmental factors was discussed in relation to the
role of succulence, ash, minerals, metabolites and fatty
acids.
The last part of the general discussion comprised a
classification of the vegetation of the study area based
on similarity in structure. The different categories
included (a) ground types (Cressa cretica community), (b)
succulent half-shrub types (Zygophyllum coccineum,Anabasis
setifera, ~ articulata.Hammada elegans.Reaumuria hirtella
and Halocnemum strobilaceum comunities), (c) non-succule~t
half-shrub types (Alhagi maurorum community), (d)
succulent shrub types (Nitraria retusa community), (e)
non-succulent shrub types (Lygos ractam and Tamarix
nilotica communities), and (f) rush types (Juncus rigidus
community).