Genet Resour Crop Evol (2007) 54:465–481 DOI 10.1007/s10722-006-9205-2 RESEARCH ARTICLE Mountain oases in northern Oman: An environment for evolution and in situ conservation of plant genetic resources Jens Gebauer Æ Eike Luedeling Æ Karl Hammer Æ Maher Nagieb Æ Andreas Buerkert Received: 11 September 2006 / Accepted: 13 December 2006 / Published online: 28 February 2007 Ó Springer Science+Business Media B.V. 2007 Abstract Several botanical studies have been of species at all oases. However, the number of conducted in different parts of Oman, but knowl- species varied significantly between sites. Fruit edge about agro-biodiversity in the rapidly decay- species diversity and homogeneity of distribution ing ancient mountain oases of this country remains of individual fruit species was highest at Balad scarce. To fill this gap we assessed the genetic Seet and lowest at Maqta as indicated by respec- resources of three mountain oases in the al-Hajar tive Shannon indices of 1.00 and 0.39 and evenness range using a GIS-based field survey and farmer values of 32% and 16%. Century plant (Agave interviews. While arid conditions prevail through- americana L.), faba bean (Vicia faba L. var. minor out the mountain range, the different elevations of Peterm. em. Harz) and lentil (Lens culinaris Balad Seet (950–1020 m a.s.l.), Maqta Medik.) were identified as relict crops, supporting (930–1180 m a.s.l.) and Al Jabal al Akhdar oral reports of past cultivation and providing (1750–1930 m a.s.l.) provide markedly differing evidence of genetic erosion. Some species, such as agro-climatic conditions. Overall, 107 different the temperate fruits of Al Jabal al Akhdar, were crop species were identified belonging to 39 exclusively found at the coolest site, while others families. Species number was highest among fruits only occurred at the hotter locations. Overall (33 spp.), followed by vegetables (24 spp.). Inten- greatest species similarity was found between sive irrigation allows cultivation of a broad range Balad Seet and Al Jabal al Akhdar as indicated by a Sørensen coefficient of similarity of 67%. At all oases a multilayered vegetation structure Dedicated to the memory of Richard N. Lester (1937– dominated with a canopy, an understory and a 2006), keen researcher of plant genetic resources. ground layer. Greatest species richness was J. Gebauer (&) Á E. Luedeling Á M. Nagieb Á recorded in the lowest stratum. Overall the study A. Buerkert shows a location-specific but surprisingly diverse Department of Organic Agriculture and mosaic of crops in Omani mountain oases which Agroecosystems Research in the Tropics and merits further studies and conservation efforts. Subtropics, Institute of Crop Science, University of Kassel, Steinstr. 19, Witzenhausen 37213, Germany e-mail: [email protected] Keywords Agroforestry systems Á Arabian Peninsula Á Arabic ethnobotany Á Crop K. Hammer diversity Á Cultivated flora Á Genetic erosion Á Department of Agrobiodiversity, Institute of Crop Science, University of Kassel, Steinstr. 19, Home gardens Á Indigenous knowledge Á Witzenhausen 37213, Germany Multicropping systems 123 466 Genet Resour Crop Evol (2007) 54:465–481 Introduction supplying about one third of the country’s water demand. Situated at the eastern edge of the Arabian Several botanical studies have been conducted Peninsula, the infrastructure of the Sultanate of in different parts of the country (e.g., Mandaville Oman, like that of other oil producing countries 1977, 1985; Radcliffe-Smith 1980; Cope 1988; in the Middle East, is developing rapidly (Minis- Miller and Morris 1988; Ghazanfar 1992; Gha- try of National Economy 2004). Asphalt roads, zanfar and Rappenho¨ ner 1994; Ghazanfar 2003; housing and other amenities are being built to Patzelt 2004; Gebauer et al. 2006b). However, fulfill the needs of a fast growing nation. information about agro-biodiversity, especially in Due to the hyper-aridity of its climate, agri- the complex mountain oasis systems of northern culture in Oman depends heavily on irrigation Oman remains scarce (Guarino 1990a, b; Ham- (Norman et al. 1998). Currently, only 0.3% of mer et al. 2004). This is perhaps because culti- Oman’s surface is used for crop production (FAO vated plants are usually neglected by botanists 2006). Which is dominated by two types of and collectors of crop genetic resources, who intensive irrigation agriculture. About 74% of often follow crop-specific programs and are the total agricultural land is irrigated by sprinkler therefore less interested in the wealth of species systems, which are located in the Batinah region found (Hammer 1991). To fill this gap of knowl- near the northeastern coast (Victor and Al-Farsi edge and to determine the status quo of cultivated 2001). In contrast in the mountain region of species, this study summarizes survey data from northern Oman, a completely different form of three ancient oases in the western and eastern agriculture has persisted for millennia (Nagieb part of the al-Hajar mountain range of northern et al. 2004). Agricultural and horticultural crops Oman. such as alfalfa (Medicago sativa L.), date palm Our underlying hypothesis was that mountain (Phoenix dactylifera L.), garlic (Allium sativum oases in the extremely xeric northern Oman are L.), lime (Citrus aurantiifolia [L.] Swingle), oats rich in crop diversity and that they differ greatly (Avena sativa L.), onion (Allium cepa L.), sor- in species richness and composition. ghum (Sorghum bicolor [L.] Moench) and wheat The study did not aim to collect seeds for (Triticum aestivum L.) are intensively cultivated future storage in a genebank. Instead its objective (Buerkert et al. 2005) in traditional, mainly sub- was to assess the current species composition of sistence-oriented oasis systems. Fields consist of sustainable cropping systems in specific areas of small man-made terrace systems, which are often northern Oman thereby providing baseline data squeezed between cliffs. for future work. This will allow future analysis of Due to their green vegetation, pleasant micro- time-related changes (Bruelheide et al. 2003) and climate and availability of fresh water, these oases assessment of the degree of genetic erosion contrast strikingly with the dry and rough land- (Hammer and Laghetti 2005; Buerkert et al. scape of northern Oman, and have in recent years 2006). It may also provide criteria to select gained increasing attractiveness for tourism specific oasis systems for in situ on farm conser- (Rienhardt 2006). vation of crop germplasm. The crops of the oases are surface-irrigated by elaborate canal systems called aflaj (singular falaj; Wilkinson 1977; Norman et al. 1998) in Arabic, Materials and methods which are fed by natural springs. This irrigation system has been investigated by several authors Study sites (Abdel-Rahman and Omezzine 1996; Omezzine and Lokman 1998; Al-Marshudi 2001). Once the Our survey was conducted in the al-Hajar moun- falaj system has been established, irrigation water tains (Fig. 1), the main mountain range in north- flow is ensured by gravity and does not require ern Oman. At Jabal Shams, this range reaches direct energy inputs. Shahalam (2001) estimated approximately 3,000 m above sea level. At the that 4,000 aflaj exist in the Sultanate of Oman upper altitudes, the climate is distinctly cooler 123 Genet Resour Crop Evol (2007) 54:465–481 467 Fig. 1 Map of Oman indicating the locations of the three mountain oases of Balad Seet, Maqta and Al Jabal al Akhdar, where the vegetation surveys were conducted and more humid than in the lowlands. Neverthe- as Acacia ehrenbergiana Hayne, Acacia tortilis less, the climatic conditions of the whole moun- (Forssk.) Hayne, Nerium mascatense DC., tain range are arid to semi-arid with a potential Prosopis cineraria (L.) Druce and Ziziphus spin- evapotranspiration of more than 2,000 mm year–1 a-christi (L.) Desf. (below 1,000 m a.s.l.), Acrido- (Nagieb et al. 2004) and even in the higher parts carpus orientalis A. Juss., Dyerophytum indicum of the mountains, mean annual precipitation does (Gibs. ex Wight) Kuntze, Ficus palmata Forssk., not exceed 400 mm (Mandaville 1977). Occa- Grewia erythraea Schweinf. and Moringa pere- sional torrential rainfalls in winter can lead to grina (Forssk.) Fiori (1000–2000 m a.s.l.), Dodo- flash floods that rush through the barren wadis. naea viscosa Jacq., Juniperus excelsa M. Bieb. The sparse natural vegetation in the al-Hajar subsp. polycarpos (K. Koch) Takhtajan, Olea range is characterized by different plant commu- europaea L. subsp. cuspidata (Wall. ex G. Don) nities dominated by tree and shrub species, such Ciferri, Sageretia thea (Osbeck) M.C. Johnst. Fig. 2 Study oases Balad Seed (a), Maqta (b) and Al Jabal al Akhdar in northern Oman 123 468 Genet Resour Crop Evol (2007) 54:465–481 Table 1 Characteristics Characteristics Balad Seet Maqta Al Jabal al Akhdar of the three study oases in northern Oman Type of oasis Core oasis Scattered oasis Core oasis Altitude (m a.s.l.) 950–1020 930–1180 1750–1930 Mean annual rainfall (mm) 100 148a 336 Rainfall range (mm) 30–240 42–255a 128–901 Mean Temperature (°C) 23 b 19 Temperature range (°C) 3–43 b –4c–32 Terraced land (ha) 13.48 4.40 13.92 Number of springs 12 22 2 a Based on records from Available water (m3 d–1) 601 115 856 Ibra (2003–2005), 48 km Water m3 ha–1 d–1 44.8 25.6 65.6 west of Maqta Number of houses 120 73 147 b No data available Number of inhabitants 650 200 330 c Number of households 80 73 45 According to World Number of survey plots 385 agricultural 130 agricultural 375 agricultural Conservation Union fields and 3 fields and 17 fields and (1987, quoted in Guarino palm groves palm groves 1017 orchard terraces 1990b) and Sideroxylon mascatense (A.