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АРИДНЫЕ ЭКОСИСТЕМЫ, 2002, том 8, № 16
================== ОТРАСЛЕВЫЕ ПРОБЛЕМЫ ОСВОЕНИЯ ==== ============
ЗАСУШЛИВЫХ ЗЕМЕЛЬ
УДК 632.51 63
РАЗНООБРАЗИЕ СОРНЯКОВ НА НОВЫХ СЕЛЬСКОХОЗЯЙСТВЕННЫХ ЗЕМЛЯХ НА ЗАПАДНОМ И ВОСТОЧНОМ БЕРЕГАХ ОЗЕРА НАССЕР
© 2002 г. А.М. Шаэн
Кафедра ботаники, Асуанский Университет, 81528 Асуан, Египет
Хозяйственная деятельность новых поселенцев на берегах заливов озера Нассер повлекла формирование биотопов, ранее не существовавших в этом регионе. Посадка возле домов тенистых деревьев и регулярная ирригация различных культур на протяжении нескольких лет позволили 96 видам сорных растений освоить эти новые условия обитания, причем 85 из них впервые пришли в подобные биотопы. Остальные 11 видов принадлежат местной флоре пустынных биотопов. Сорные травы поселяются на полях, возделываемых под овощные культуры. Изучаемые сорные виды относятся к 24 семействам и представлены 65 однолетниками (67.7 %) и 31 многолетником (32.3 %), Семейство Gramineae имеет наибольшую долю видов (30.2 %). Сорная флора исследуемой территории включает рудеральные (40.6 %) и пашенные сорняки (58.3 %). Настоящими сорняками являются 88.5 % видов, а 11.5 % — переходные. Судано-Замбезский элемент флоры представлен здесь 28.1 % видов, Палеотропический - 17.7 %, Средиземноморский достигает 5.2 %, и 15.6 % видового состава являются космополитами. Спектр жизненных форм составляют терофиты (69.8 %), геофиты (14.6 %), гемикриптофиты (7.3 %), фанерофиты (6.3 %) и хамефиты (1.04 %). Одни сорные виды, часто встречающиеся в новых биотопах, относятся к местной флоре пустынь и побережий озера. Другие— в первую очередь представители Средиземноморского флористического элемента— пришли из различных сельскохозяйственных районов Египта, имеющих тысячелетнюю земледельческую культуру. Совершенно очевидно, что продолжительное антропогенное воздействие на изучаемую территорию повлечет за собой полную смену естественной растительности сорной.
WEED DIVERSITY OF NEWLY FARMED LAND ON THE SOUTHERN BORDER OF EGYPT (EASTERN AND WESTERN SHORES OF LAKE NASSER)
© 2002. A.M. Shaheen
Botany Department, Faculty of Science, South Valley University 81528
Aswan, Egypt
Introduction
Weeds did not exist before agriculture, but evolved alongside crops. Despite the use of clean seed, ploughing, cultivation, burning, hoeing, hand weeding, managed grazing, smother crops and crop rotation, weeds persist because of our inability to cope with maximum crop production and the massive recycling potentiality of weeds (Sen et al. 1980). The proverb "one year's seeding is seven years weeding" is a recognition of man's role in the control of size of weed populations (Sagar 1982). Losses caused by weeds are well documented in many studies (e.g. King 1966, Reeves 1976, Roberts and Chancellor 1982, Aldrich 1984). Sen et al. (1984) mentioned that the weeds cause more loss to agriculture than all pests put together. Understanding the nature of the weeds is necessary in order to learn how to reduce their effect on crops (Radosevich and Holt 1984).
The main factor that influences native vegetation in the Nile Valley is human interference. The alluvial terraces of the valley have remained under human management for four thousands of years. Hamel and Dansereau (1949) and Curts (1959) classified the vegetation into degraded (where the disturbance of the original community is incomplete and sporadic), and ruderal (where the original community is destroyed and
РАЗНООБРАЗИЕ СОРНЯКОВ НА НОВЫХ СЕЛЬСКОХОЗЯЙСТВЕННЫХ ЗЕМЛЯХ
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a destructive agent is repeatedly applied) and cultivated, (where crops are planted). All the three types of vegetation were be found as a result of human interference.
The alluvial terraces of the Nile Valley in Upper Egypt and the desert outskirts of the farmland of the Nile Delta are the subject of active land desert annuals ranged from 18 species in North Aswan to 42 species in the eastern and western outskirts of the Nile Delta. Older fields contained fewer desert populations which became gradually replaced by weed assemblages of the old farmland.
Agrestal and ruderal constitute the bulk of the flora of farmland (El-Hadidi 1994-95). These were the subject of the detailed studies by El Amary (1981) in Sharqiya governorate. Shaheen (1987) in Aswan governorate, Mahgoub (1993) in Beheira governorate. Their studies showed that assemblages are related to season, type of soil and geographical range (Upper or Lower Egypt).
According to El-Hadidi (1993a), the percentage of Sahelian and Sudanian taxa (sensu Wickens, 1976) is the highest in upper Egypt, decreasing gradually northwards in the Nile Delta. The percentage of Mediterranean taxa is highest in the Nile Delta and this decreases gradually southward in upper Egypt. A major percentage of the weed flora is represented by the widely spread Cosmopolitan, Paleotropical and Pantropical taxa.
The new farmed lands around the Lake Nasser khors have created new habitats that never previously existed in the area. Planting of small gardens near houses and the constant irrigation of crops two or five years ago enabled many weeds to penetrate these habitats.
In this article, a list of weeds in agrestal and ruderal conditions at newly farmed land is presented. The study area is located on the southern Egyptian border 200-300 km south of the High Dam (Eastern and Western Desert) (Fig. 1). This area was classic desert which has been promoted for cultivation. A documentary study of the flora of that region was indubitably required.
Study area
The study area is located on the perimeter of Aswan governorate, 300 km south of the High Dam. It extends from the Eastern Desert (Absco and Tuorgomi) to the Western Desert (Gharf Hussein, Kalabsha, El-Subai) across Lake Nasser. It represents a transitional zone between the adjoining desert and the shore of Lake Nasser. It was a part of the Nubian Eastern and Western Desert but is now under reclamation (two to five years old).
It is characterised by numerous wadis, or intermittent stream channels, which run through Egypt's Southern and Western Desert to the shores of the Lack Nasser. The wadis extend for more than 400 km south, deep into Sudanese territory. Lake Nasser is a vast man-made water body upstream of the Aswan High Dam on the Nile, which reached its maximum height in 1998. Research suggests that the new Lake has had a considerable impact on the overall physical environment of the areas around it, including that of the study area. This area has highest range summer temperatures of 40 to 50C, and mean annual precipitation 5 to 50 mm, with rain events occurring only about once in every five years.
Methods:
Data and records were derived from newly farmed fields (two to five years old). Some fields were located in the Eastern Desert (Absco and Tuorgomi) and others in the Western Desert (Gharf-Hussein, Kalabsha and El-Subai). Seventy-five sampling stands were selected to cover the farmed lands. Each stand was 20m wide but lengths varied from 20m to 40m. The stands were the basic unit for description of plant life and comparison of the vegetation in different fields. The quotient of similarities between the different sites were calculated according to Sorensen (1948).
A list of weed species was monitored seasonally in each stand between 2000-2001. This was undertaken from just after was sown the crop until its harvest. The recorded species were identified and arranged according to El-Hadidi, (1994-95). For each species the most important collections are cited and are being kept in the Aswan herbarium (ASW). Floristic categories and life form spectrum for all the species are those applied by Wickens (1976) and Runnkiaer (1934) respectively.
Result and discussion
Ninety-six weed species belonging to 24 families were recorded from the study area during the period from March 2000 to March 2001 (Table 1). This area had a remarkably uniform flora whereas
considerable difference in the floral composition has been noticed northwards and southwards of this area. Boulos (1966, 1967) recorded during the springs of 1963 and 1964 about 180 species of phanerogams in
the Egyptian Nubia including Aswan (67 from Nubia). A near figure of 170 species was given by Abdallah et al. (1972a) from the same area, also during the spring of 1963 and 1964. El-Haddid recorded over 200 species during two visits to Nubia in 1963, 1964 (unpublished reports) and a summer visit to Aswan area in 1963 (El Hadidi and Ghabbour 1968). A near figure of over 200 species was given by Shaheen (1987) from north Aswan only. An early stage for the establishment of the riverian of the Nubia was studied by El-Hadidi (1976) in the Daboud area which is located about 10km south of the High Dam. The few species recorded (about 15) belong to: the adjacent desert, floating seeds, aerially dispersed fruits and some inundated species.
Table 1. Floristic composition of weeds (%) associated to the newly farmed land;, T: Tuorgomi, A: Absco, K: Kalabsha, G: Gharf-Hussein, S: El-Subai, G: Geophytes, TH: Therophytes, H: Hemicryptophytes, PH: Phanerophytes, CH: Chamaephtes, COSM: Cosmopolitan, PAL; Palaeotropic, PAN: Pantropic, S-Z: Sudano-Zambesian, ME: Mediterranean, SA-SI: Saharo Sindian L.F.: Life form, Fl. Cat.: Florstic categoriesand P (%): total percentage of species. Таблица 1. Флористический состав сорных видов (%), встречающихся на новых сельскохолзяйственных землях. Земли: Т-Тургоми, А-Абско, К-Калабша, G-Гарф Хессин, S-Эль-Субуа. Жизненные формы: ТН-Терофиты, Н-Гемикриптофиты, РН-фанерофиты, СН-хамефиты. Флористические элементы: COSM-космополиты, PAL-палеотропический, PAN-Пантропический, S-Z-Судано-Замбезский, МЕ-Средиземноморский, SA-SI-Caxapo-Синдский. L.F. — жизненные формы, FI. Cat — флористические категории, Р(%) - общая доля видов.
L.F Species Виды растений Ruderal Рудеральные P% Agrestal пашенные P% Fl.Cat.
T А К GS T А К GS
G Panicum repens + + 40 COSM
ТН Avena fatua + 20 COSM
ТН Tribulus terrestris + + 40 COSM
ТН Solarium nigrum + + + + + 100 COSM
ТН Portulaca oleracea + + + + 80 COSM
ТН Polypogon monspeliensis + + + + + 100 COSM
ТН Brassica nigra + + + 60 COSM
ТН Chenopodium album + + + + + 100 COSM
ТН С murale + + + + + 100 COSM
ТН Sonchus oleraceus + + + + + 100 COSM
ТН Eragrostis cilianensis + + + + 80 COSM
ТН E. aspera + + + + 80 COSM
ТН Anagallis arvensis + + + 60 COSM
ТН Phalaris canariensis + 20 COSM
ТН Setaria viridis + + + + + 100 COSM
ТН Amaranthus viridis + 40 PAL
ТН Melilotus indicus + + + 60 PAL
ТН Digitaria sanguinalis + + + 60 PAL
ТН D. ciliaris + + 40 PAL
ТН Dactyloctenium aegyptium + 40 PAL
G Eleusine indica + 20 PAL
G Diplachne fusca + 20 PAL
Н Glinus lotoides + + + + + 100 PAL
ТН Chloris virgata + 20 PAL
ТН Heliotropium ovalifolium + 20 PAL
G Dichanthimum annulatum + 20 PAL
ТН Conyza bonariensis + 40 PAL
ТН Convolvulus arvensis + 20 PAL
G Paspalidium geminatum + + 40 PAL
G Paspalum paspalodes + + 40 PAL
ТН Hibiscus trionum + 20 PAL
ТН Xanthium strumarium + 20 PAL
G Cyndon dactylon + + + + + 100 PAN
ТН Echinochloa crusgalli + + + 60 PAN
ТН E. colona + + 40 PAN
ТН Corchorus olitorius + + 40 PAN
ТН Aster squamatus + + 40 PAN
ТН Datura stramonium + 20 PAN
ТН D. innoxia + 20 PAN
РАЗНООБРАЗИЕ СОРНЯКОВ НА НОВЫХ СЕЛЬСКОХОЗЯЙСТВЕННЫХ ЗЕМЛЯХ 89 Table 1. (continuation). Таблица 1. (продолжение).
L.F Species Виды растений Ruderal Рудеральные P% Agrestal пашенные P% Fl.Cat.
ТН Mentha microphylla + 20 PAN
ТН Fimbristylis bis-umbellata + + 40 PAN
G Imperata cylindrica + + + + 80 PAN
G Sida alba + + 40 PAN
G Cyperus rotunds + + 40 PAN
G C. longus + + 40 PAN
Н.Н Phragmites australis + + + 60 PAN
РН Ricinus communis + 20 PAN
РН Sesbania sesban + + + 60 S-Z
ТН Senecio aegyptius + 20 S-Z
ТН Cornulaca moncantha + 20 S-Z
ТН Vigna membranacea + 20 S-Z
ТН Stipagrostis plumosa + + 40 S-Z
ТН Reseda pruinosa + 20 S-Z
G Sorghum sudunese + 20 S-Z
ТН Rhynchosia minima + 20 S-Z
ТН Conyza aegyptiaca + + 40 s-z
сн Aerva javanica + + + 60 s-z
н Crotalaria thebaica + + + 60 s-z
н Morettia philaeana + 20 s-z
G Panicum coloratum + + 40 s-z
ТН Cajanus cajan + 20 s-z
ТН Echium rauwolfii + + 40 S-Z
ТН Lolium temulentum + + 40 s-z
н Fagonia indica + + + + 80 s-z
ТН Hyoscyamus muticus + + + + + 100 s-z
ТН Cotula anthemoides + 20 s-z
РН Caltropis procera + 20 SA-AI
ТН Astragalus hamosus + 20 SA-ST+S-Z
ТН A. vogelii + 20 SA-SI+S-Z
РН Ziziphus spina-christi + 20 SA-ST+S-Z
н Pulicaha arabica + + + 60 SA-ST+S-Z
РН Tamara nilotica + + + 60 SA-ST+S-Z
РН Salsola baryosma + + + + 80 SA-ST+TR-TR
ТН Emex spinosa + + + 60 ME
ТН Ammi majus + + ++ 80 ME
ТН Lepidium sativum + 20 ME
ТН Cichohum pumilum + 20 ME
ТН Ambrosia maritima + 20 ME
G Saccharum spontaneum + 20 ME+S-Z
н Citrullus colocynthis + + + + 80 ME+SA-ST
ТН Ammi visnaga + 20 ME+TR-TR
ТН Brachiaria eruciformis + 20 ME+TR-TR
ТН Amaranthus lividus + + ++ 80 ME+TR-TR
ТН A. graecizans + + ++ 80 ME+TR-TR
н polygonum equisetiforme + + 20 ME+TR-TR
ТН phalaris minor + + + 60 ME+TR-TR
ТН Malva parviflora + + + + + 100 ME+TR-TR
ТН Trifolium resupinatum + + + 60 ME+TR-TR+ER-SR
ТН Sisymbrium irio + + + 60 ME+TR-TR+ER-SR
ТН Lactuca serriola + 20 ME+TR-TR+ER-SR
ТН Poa annua + + 40 ME+TR-TR+ER-SR
ТН Heliotropium europaeum + + + 60 ME+TR-TR+ER-SR
ТН Beta vulgaris + + + 60 ME+TR-TR+ER-SR
ТН Coronopus squamatus + 20 ME+TR-TR+ER-SR
ТН Trigonella hamosa + + + + + 100 ME+TR-TR+S-Z
ТН Rumex dentatus + + + 60 ME+TR-TR+S-Z
The most represented families are Gramineae (30.2%), Compositae (11.3%), Leguminosae (10.3%), and Chenopodiaceae (5.2%). The annuals represent 65 species (67.7%) and perennials 31 species (32.3%). The agrestals form 59.4% and ruderals 40.6%.
The most common weeds (p = 100%) are: Solarium nigrum, Polypogon monspeliensis, Chenopodium album, С. murale, Sonchus oleraceus, Setaria viridis as Cosmopolitan elements; Glinus lotoides as Paleotropical; Cynodon dactylon as Pantropical; Hyoscyamus muticus as Sudano-Zambizian and Malva parviflora and Trigonella hamosa as Mediterranean elements. The wide distribution of some weeds may be interpreted by the view that these weeds often are uniquitous. Species with large amplitude (Cyndon dactylon, Solatium nigrum) are often caused by phenotypic plasticity and heterogeneity (Shaltout and Sharaf El-Din 1988). Weeds of moderate occurrence (p = 60%) are: Rumex dentatus, Anagallis arvensis, Melilotus indicus, Beta vulgaris, Sisymbrium irio, Trifolium respinatum and Emex spinosa. The restriction of distribution (e.g Lepidium sativum, Cichorium pumilum, Avena fatua, Ambrosia maritima, Diplachne fusca) may be related to the need for special habitat "thermic preferability".
The Tuorgomi site has highest value of species richness (62.5%) in the reclaimed land. This could be due to the distance of cultivation and method of weed control. On the other hand, Kalabsha site has the lowest species richness (26.04%) which may be due to the use of the herbicides.
There is a moderate similarity between the floristic composition of Tuorgomi vs Absco (72.7%), Tuorgomi vs El-Subai (62.6%), Absco vs El-Subai (60.7%), Gharf- Hussein vs El-Subai (57.8%) and Kalabsha vs El-Subai (56.3%) (Table 2). The most lowest similarities are: Kalabsha vs Gharf-Hussein (42.1%) and Absco vs Gharf-Hussein (43.7%).
Table 2. Matrix of Sorenson similarity coefficient (Sorenson 1948) calculated between each pair of localities, bold number: number of species/locality, practice number: values of species for pairs of locations. Таблица 2. Коэффициент сходства (формула Соренсона (1948), расчитанный между каждой парой участков: реальное количество: число видов на каждом участке, практическое количество: ценность видов для участков.
locations Tuorgomi Absco Kalabsha Gharf- Huessin El-Subai
N. of species 60 50 25 51 39
Т 72.7 44.7 50.5 62.6
А (40) 45.3 43.7 60.7
К (19) (17) 42.1 56.3
G (28) (22) (16) 57.8
S (31) (27) (18) (26)
Sudano-Zambasian elements include 19 mono-regional (typically) as well as eight bi-regional species. Among these Senecio aegyptica and Conyza aegyptiaca were endemic to Egypt and Pulicaria arabica, Vigna membranacea and Rhynchosia minima were locally endemic to Nubia. The bi-regional species are primarily Sudano-Zambasian which were penetrating to the southern tributaries of Egypt. Shaheen (1987) recorded 29 species in Aswan (north) which were typically mono-regional Sudano-Zambasian taxa. These results are more in agreement with El-Hadidi (1994-95 ), who reported that the percentage of Sahelian and Sudanian taxa is highest in Upper Egypt.
Cosmopolitan species include 15 annual species, among which five species lives in ruderal condition (Panicum repens, Avena fatua, Polypogon monspeliensis, Phalaris canariensis and Setaria viridis) and the ten species consider as agrestals weeds. Shaheen (1987) recorded 29 Cosmopolitan species from north Aswan.
Paleotropical elements include 15 annuals as well as two perennials. Six species belonging to this group were collected from ruderal habitat and eleven were from agrestals. The most limited species are the pantropical elements where only fifteen species were recorded: six ruderal and nine agrestal. Shaheen (1987) recorded 28 paleotopical and 38 pantropical elements in north Aswan.
Mediterranean elements include five mono-regional (all agrestal), nine binoregional (seven agrestal and two ruderal)) as well as nine pluri-regional (all agrestal). Shaheen (1987) recorded 27 Mediterranean species from north Aswan. These results are more in agreement with El-Hadidi (1993a) who reported that the percentage of Mediterranean taxa is lowest in the govemorates of Upper Egypt.
Close to the boundaries of the desert, and within these farmed land, species of xerophytic nature grow among the weeds of cultivation. These included Morettia philaeana, Cornulaca monacantha, Reseda pruinosa, pulicaria arabica, Salsola baryosma, Citrullus colocynthis, Hyoscyamus muticus, Fagonia indica and Crotalaria thebaica. This indicates that these plant species are native to the desert and are remaining after the reclamation processes. On the other hand, a major group of weed species are distributed in the newly
РАЗНООБРАЗИЕ СОРНЯКОВ НА НОВЫХ СЕЛЬСКОХОЗЯЙСТВЕННЫХ ЗЕМЛЯХ 91
farmed land (Portuiaca oleracea, Cynodon dactylon, Aster squmatus, Ammi mqjus, Trifolium resupinatum, Malvaparviflora, Solatium nigrum). This sugests that land reclamation entails weed species replacing natural plant communities (Stainforth and Scott 1991, Bazzaz 1996). Introduced species must be capable of establishing themselves in areas of natural habitats (Mcdonald 1989) and may alter the native habitat in such way that all the native species are pushed out.
The most of the perennial weeds of the newly farmed land are represented by a central core of large shrubs of Tamarix nilotica, Sesbania sesban, Ricinus communis, Ziziphus spina-christi and Phragmites australis, which must have existed before the reclamation, when these farms were part of the Eastern and Western Deserts. Respectively a few specimens of the desert perennials, Hyoscyamus muticus, Aerva javanica, Salsola baryosma, Pulicaria arabica and Morettia philaeana, are also recorded. The perennials have the lowest value here (32.3%) and this trend is dissimilar to the spectra reported for Egyptian flora as a whole (Hassib 1951).
In both ruderal and agrestal conditions, there are zones of annual weeds which were associated with vegetable fields. Annual growth occurs in rows identical to the treat of water at regular intervals (irrigation pipes). The annuals constitute the majority of the species in the study area (67.7%). The short life cycle of annuals as well as prevailing climatic conditions and water availability lead to their frequent occurrence (Shaltout and El-Fahar 1991). The dominance of annuals could be attributed to the fact that annuals have higher reproductive capacity and ecological, morphological and genetic plasicity under high level of disturbance (Grime 1979).
The life form spectra showed that, the recorded species comprise 69.8% therophytes, 14.6% geophytes, 7.3% hemicryptophtes, 6.3% phanerophytes while chamaeophytes represent only 1.04% of the life form spectrum. A near figure of same data was given by Shaheen (1987) from north Aswan (old cultivated land).
The weeds of irrigated agricultural crops in the southern border of Egypt grow in habitats that never previously existed in the area. Some of these weeds are plants from the local flora of the region. Among them are plants which were typical to ruderal habitats in deserts and make use of environmental conditions which are similar to their typical niche, and other species such as Imperata cylindrica which were normally confined to desert. Mostly, they have wind dispersed diaspores that reach the constantly irrigated plots and establish themselves there. Species such as Hyoscyamus muticus grow regularly in desert wadies and establish themselves at the margins of irrigated plots where it is not too wet.
Many of these weeds species, such as Ammi majus, Convolvulus arvensis Sisymbrium iro, Cichorium pumilum, Trifolium resupinatum, Melilotus indicus, Trigonella hamosa, Portuiaca oleracea and Brassica nigra, were derived from other agricultural areas in Egypt (the Delta) where the plants, seeds, manure and agricultural equipment originated. The other weeds were from the local flora of the desert and lake shore habitats that can withstand the new environment. These species grow in the relatively dry microhabitats near the fields or establish themselves in the abandoned fields.
Acknowledgement
The author would like to acknowledge the financial support provided by prof. Ahmed Esmat Belal and Prof. Irina Springuel, Directors of the USED, South Valley University , Aswan, Egypt through Allagi Project.
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