الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
Abstract
Al-Jabal Al-Akhdar Mountain is the richest vegetation and highest species diversity in Libya. The Al-Jabal Al- Akhdar region islayingbetween latitude 32° and 33° North and 20° to 23° East; it is about 360 km long and 60 km in width on the Mediterranean coast. This region is very important due to it is distinct environmental characteristics associated with being the only evergreen forest of its kind in the region along the Mediterranean from the Atlas Mountains to the Levant. Also, it has an environment similar to other regions in Southern Europe such as Italy the Greek islands and Turkey.
Environmental condition and different types of human impacts including urbanization, agriculture, mining and quarrying, over collection, and overcutting of woody species have a significant influence on diversity and distribution of threatened, endemic, and medicinal plants in Al-Jabal Al- Akhdar.
Soil factors play an important role in growth, chemical composition and distribution of plants under different ecosystems in Al-Jabal Al- Akhdar. In the present work, 63 soil sample supporting the growth of the different studied species (especially the twelve selected endangered plant species), were collected from seven site located along the Al-Jabal Al- Akhdar.
Soil reaction (pH) is slightly alkaline for all the studied stands. While, electrical conductivity (E.C) showed the lowest value in all wadis of Al-Jabal Al- Akhdar.
The study area which is represented by the seven wadis (Al-Marj-Al-Baida motorway, El-Beida, Jardas Jerrari, Shahat, Sidi Ahmad Al-Hemery, Susah and Wadi El-Kouf) is the habitat of 91 species, belonging to 85 genera and
44 families. Twelve of the recorded species (target species*) are of medicinal value, endemic and endangered plants: (*Arbutus pavariiPamp., *Cupressus sempervirens L.var. horizontalis (Mill.) Gord., *Ceratonia siliqua L., *Juniperus phoenicea L., *Laurus nobilis L., *Olea europaea L., *Pinus halepensis Miller., *Pistacia lentiscus L., *Querecus coccifera L., *Seriphidium herba-alba (Asso) Soják., *Thymus capitatus (L.) Hoffmanns. & Link. and *Ziziphous lotus (L.) Lam.
Regarding the number of species within each family, the abundant families were Asteraceae which has the highest contribution to the total number of the recorded species (comprising sixteen species with ratio 18%), followed by Lamiaceae comprising twelve species (14%), Fabaceae comprising five species (6%), Apiaceae comprising four species (5%) and Poaceae comprising three species (3 %).
Phanerophytes (Ph) were the abundant life-form in the study area and represented by 28 species of about 31 %, followed by Chamaephytes (26%), Therophytes (21 %), Hemicryptophytes (13 %) and finally Geophytes (9 %). Considering the global floristic distribution, the monoregional elements recorded the highest species number among the classes of chorotypes, especially Mediterranean chorotype which increased northward and comprise48 species (52 %), the endemic elements in dude 20 species (22%), the biregional elements attain 11 species (12 %), the pluriregional elements comprise7 species (8 %) and the Cosmopolitan elements attained the lowest species number among the five classes of chorotypes, where it includes five species (6 %).
The phytosociological study of these wadis was based on the analysis of vegetation in 63 sampled stands using Braun-Blanquet scheme. In Al-
Jabal Al-Akhdar, theapplication of the Two-Way Indicator Species Analysis (TWINSPAN) to the data set of cover estimated of 91 species in 63 stands resulted in agglomerating of seven major groups at the 3rd cut level of classification. Application of the Detrended Correspondence Analysis (DECORANA) indicated reasonable segregation among these vegetation groups. Dominant species areSeriphidium herba-alba for groups A and B, Seriphidium herba-alba and Thymus capitatus for group C, Arbutus pavarii for group E and Juniperus phoenicea for groups D, F and G.
The ordination diagram produced by CCA indicated that the most important correlation of environmental variables correlated with species distribution in Al-Jabal Al- Akhdar wadis are pH, CI , Na⁺, K⁺, Ca⁺², clay, HCO3ˉ, and Mg⁺², silt and sand.
The population structure of the twelve endangered species was evaluated in term size distribution along the three elevation levels (down-stream, mid-stream and up-stream) at the sevenwadis in Al-Jabal Al- Akhdar. The number of individuals of each species was counted while the height (H) and mean crown diameter (D) were measured. The present study indicated that the height to diameter ratio was less than unity for some of the recorded species such as Pistacia lentiscus, Seriphidium herba-alba, Thymus capitatus and Ziziphus lotus, and others exceed the unity such as Arbutus pavarii, Cupressus sempervirens, Ceratonia siliqua, Juniperus phoenicea, Laurus nobilis, Olea europaea, Pinus halepensis and Querecus coccifera.
The diagrams illustrating the size distribution of twelve examined species approximate one of the following size distributions: More or less inverse J-shape distribution,positively skewed distribution towards the small size, more or less J-shaped distribution, more or less stationary size distribution
and more or less symmetrcal distribution (i.e bell shaped). The obtained results showed that density histograms of size distributions are good indicators of future trends in population number for the studied species, especiallyJuniperus phoenicea and Arbutus pavarii. All the studied species showed a ”reverse-J” size structure, which is usually taken as an indicator of self-replacing populations.The negative skewed distribution of Ceratonia siliqua, Laurus nobilis,Querecus coccifera and Pinus halepensis indicated the dominance of mature individuals over the juvenile ones. This distribution characterizes a declining population; because the population has a large proportion of larger individuals than smaller ones (i.e. limited regeneration capacity). This may indicate that the recruitment of these species is restricted which may be related to hyper-aridity and low fertility.
Branch dieback ofJuniperus phoenicea trees in a natural growing area on (Al-Marj-Al-Baida motorway) in the Al-Jabal Al-Akhdar, during 2015 and 2016. Fungal isolates obtained from symptomatic twigs and branches showing dieback and bark necrosis. The present study showed that Ascotricha chartarum is directly involved in theetiology of branch dieback and mortality of Juniperus phoenicea trees