الفهرس 
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Abstract
The Egyptian Western Desert covers two-thirds of the total area
of Egypt. Western Desert is also characterized by sand seas and sand
dunes, a burning sun, winds and sandstorms, springs and wells, mountains
and rocks, minerals and stones, plants and animals and a multitude of
fossils. Sand dunes at different stages of development are numerous in the
oases of the Western Desert. The significant oases in the Western Desert
are (Siwa, Bahariya, Farafra, Dakhla and Kharga). Dakhla Oasis is one of
the seven oases of Egypt’s Western Desert. Dakhla Oasis is located in the
New Valley Governorate, 350 km from the Nile and between the Farafra
and Kharga Oasis, which is about 190 km from Kharga. It is about 10-20
km from east to west and 250 km from north to south. Weather: 22°C, Wind
N at 14 km/h, 24% Humidity. Dakhla Oasis extends between 25.5°N
latitude and 29°E east longitude, and is 110-140 meters above sea level.
During the growing seasons of 2017, vegetation was sampled from
47 permanently visited stands situated along N-S line transect across
Dakhla Oasis, and extending for about 185 km to cover as much as
possible the physiognomic variation in habitats. All the stands
studied were geo-referenced using GPS technique. Four habitats were
recognized in this study; from inner to outer zones: farmlands and palm
orchards represent the inner zone, the waste-salinized lands (not
saltmarshes) in the middle, and the surrounding (bounding) desert in the
outer zone. The farmlands included the major crops, wheat (Triticum
aestivum L.), millet (Sorghum halepens L.) Moench, and the perennial alfaalfa (Medicago sativa L.). In each of the studied stand, presence or absence
of plant species was recorded using a number of permanent stands
randomly positioned and representing the variation in the floristic
composition of these habitats. The studied stands covered the 4 recognized
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habitats, and distributed as follows: 24 in farmlands, 11 in palm orchards, 4
in waste-saline lands and 8 in the out-skirting deserts. Presence percentages
(P%) of each species in each habitat was calculated as the total number of
stands where species recorded divided by the total number of monitored
stands inside the habitat. The vegetation of the Dakhla Oases is essentially
halophytic. Weeds of cultivated land represent the most ephemeral of plant
communities for, although they are the initial stage of plant succession.
Weeds will usually have, with few exceptions, short vegetative phase, high
reproductive output, and capable of limiting the crop yields. Weeds
represent a highly specific and important biological component of their
environments. The distribution of weed communities is mostly dependent
on climatic conditions; seasonal rainfall and temperature have important
roles in weed distribution. Weeds of Egyptian croplands differ from season
to season because of their ecological requirements. Ecological and
phytosociological studies of weeds are necessary for understanding the
relationship between crops and their weed flora. At each of the 47 stands,
three soil samples (0 - 50 cm) were collected from each stand and
mechanical and chemical analyses were carried out.