Relict olive trees at runoff agriculture remains in Wadi Zetan, Negev Desert, Israel

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Highlights

  • Olive tree in the Negev Desert are relicts of the ancient agricultural landscape.

  • Veteran Olive trees survived in Wadi Zetan in heart of ancient horticulture terroir.

  • The minimum age of one of the trees is 500 years old (based on radiocarbon dating).

  • The trees are rooted sediment dated to the 8th-9th cent. CE (based on OSL dating).

  • DNA profiling indicate that the trees are genetically close to ancient known olives.

Abstract

Olive (Olea europaea) trees in the arid Negev Desert of southern Israel are important relicts on the ancient agricultural landscape. Among them are a cluster of several trees located in Wadi Zetan, at the heart of the Shivta horticulture terroir, with its abundant agricultural runoff remains. Two isolated olive bearing trees stand in a sheltered beneath cliff in the upper part of the wadi. Radiocarbon dating of an internal part of the trunk of one of these living trees estimates its minimum age as the mid-16th – early 17th century CE (∼500 years old). Archaeological excavations conducted beneath the trees and the adjacent dam revealed OSL samples of loess accumulation dated to the Early Islamic period (8th-9th centuries CE). The stratigraphy and chronology of this sediment deposition indicate its rapid and short accumulation. Palynological analysis of the same OSL dated samples indicates that grapevines and olive trees were cultivated in the immediate vicinity of the site during the Early Islamic period. The lack of pollen of cultivated taxa from the latter part of the sequence points to cessation of the agricultural activity, probably a few hundred years later. Leaf samples for DNA profiling of the trees in comparison to other local old olive trees around the country, indicate that the trees in Wadi Zetan are genetically close to a known cultivar common among ancient olive trees. The trees have survived for at least a few hundred years, in an arid area, due to the local conditions and enhanced drainage from the man-made upper runoff system. These old olive trees bear a powerful and symbolic significance, indicating the endurance and sustainability of ancient desert runoff agriculture. Moreover, the survival of their relicts in Wadi Zetan suggests their potential as cultivars greater resilience to the harsh growing conditions of arid environments.

Introduction

The remains of ancient surface runoff agriculture constitute a key component in the cultural landscape of the Negev Desert. These remains include dams, water-harvesting channels and agricultural installations that together provide evidence of complex and intensive farming in an arid environment. This typical runoff agriculture began in the vicinity of Shivta, one of the iconic farming villages of the period, already in the Roman period (second–fourth centuries CE), and was gradually abandoned during the Early Islamic period (seventh–ninth centuries CE). During the Byzantine period (fourth-seventh centuries CE) the area saw major settlement momentum and extensive development of its agricultural hinterland. Not far from Shivta village, in a small and hidden dry riverbed in the upstream of Wadi Zetan, several old olive trees (Olea europaea) have survived to this day within the remnants of this ancient agricultural system (Fig. 1).

The olive trees in Wadi Zetan, which are among the last remnants of the ancient agricultural landscape in the region, continue to grow in this arid landscape and some of which are still bearing fruit, are the subject of the current research. These trees, which have survived outside the normal area of olive cultivation in the region, preserve a unique relict of the complex agricultural system that has allowed their endurance. The original centers of the trees are long-gone and they are estimated to be several centuries old. As such, they preserve a unique genetic fingerprint of heirloom olive cultivars adapted to a hot and arid environment.

In the framework of this research we studied the agricultural system in Wadi Zetan and the cultural history of the olive trees naturally thriving there, with the aim of determining their age and dating the agricultural system within which they have survived. To this end, we surveyed the system above the trees and excavated beneath them near the dam. We retrieved pollen samples from archaeological sections to assess the plant species that had presumably grown in the agricultural plots in the past. The age of the agricultural system was further determined optically stimulated luminescence (OSL) dating of the soil that had accumulated on both sides of the dam and under the roots of the trees. The minimal age of one of the trees was determined by radiocarbon dating of an internal part of the trunk. The results of our research provide important knowledge on the cultural history of these heirloom trees, and provide new insights into traditional and sustainable surface-runoff agriculture, with regard to the cultivation in arid regions of fruit trees in general and of olive trees in particular.

The wild olive tree, which originated in the Mediterranean region (Fig. 2), evolved over millennia along multiple historical pathways, as reflected in the numerous of varieties noted in both historical and modern-day records. It is an easily cultivated tree, well-adapted to harsh growing conditions (Fernández, 2014). Over the course of history, the olive became one of the most important crops in the Mediterranean basin, being both consumed as food and pressed for oil. Genetic analysis provides evidence of two scenarios: an initial, and primarily domestication, center in the northern Levant (Besnard et al., 2018): two independent domestication areas in the Mediterranean basin (Diez et al., 2015). The earliest archaeological, archaeobotanical and palynological evidence for the domestication of the olive in the Mediterranean Basin was found in the southern Levant and is dated to the fifth century BCE. Later, its cultivation spread westward to Greece, Italy and Spain, in a process that led to the development of a variety of cultivars with unique geographical affinities (Langgut et al., 2019).

During the first millennium CE increased demand for olive oil significantly influenced the commercial relationship between the East and the West. It is then when numerous olive presses are found throughout the Mediterranean Basin, many of which bear screw press, indicating the importance of oil production (Ayalon et al., 2009, Frankel, 2010). During that time a commercial hub for olive oil production peaked in Tripolitania in western Libya (Mattingly, 1988, Barker et al., 1996).

In the traditional agriculture of the Mediterranean basin, olive trees grow in marginal soils whose fertility is relatively low, usually on mountainous slopes that are unsuitable for other crops. In Israel, olive trees grow in all types of soil, wherever the multi-annual average rainfall is above 350 mm (Zohary et al., 2012). Drought is the main reason for a decline in olive tree growth and productivity (Ben-Gal et al., 2011).

In all the Mediterranean climate areas north of the Negev, archaeological research has documented numerous installations of oil production (Frankel et al., 1994), along with botanical remains (reviewed in Langgut et al., 2019) that demonstrate the production of olive oil over long periods in these areas. In places where terroirs are optimal, olive trees may live for many years (Zohary et al., 2012:116). A mature olive tree has the unique ability to regenerate after traumatic conditions, such as abandonment, fire, deforestation, overgrazing and drought (Langgut et al., 2014). Determining the age of ancient olive trees, however, is complicated: dendrochronological tools cannot be used because the trees lack regular rings due to the irregular spread of the trunk or branches (Cherubini et al., 2013). The effective means of gauging the age of an olive tree is by radiocarbon dating of the root collar and inner parts of the hollow trunk. Using this approach, for example, revealed that the ancient olive trees in the Garden of Gethsemane in Jerusalem date from the Crusader period and are about 850 years old (Petruccelli et al., 2014).

Section snippets

Olive trees and remnants of ancient agriculture in Wadi Zetan

The dry bed of Wadi Zetan runs from south-east to west near the ancient agricultural settlement of Shivta (347 m asl). The summers there are hot and dry and the winters are cold with little rainfall (a multi-annual average of less than 100 mm a year). The geological setting of the hinterland of Shivta and its unique capabilities to collect runoff is described in Wieler et al. (2016). The few rainy days in winter (less than10 days per year) usually feature heavy rain events. These conditions

Materials and methods

The two olive trees that were studied in our project are numbered I and II for the southern and northern trees, respectively, and the dam (Wall 101) is situated between them (Fig. 7A). Several olive fruit kernels were found near tree No. 2. (Fig. 7B) and a few whole olives on both trees (Fig. 7C), Five archaeological trenches (A1-6) were dug alongside each tree and along the dam wall, between the trees and across the wadi bed: two trenches above the dam and alongside the southern tree (I) and

Results

Trench A1 was excavated on either side of an agricultural boundary wall (W100) parallel to the wadi bed. The wall was constructed of large and medium-size local fieldstones interspersed with a fill of smaller stones. The wall was at least 12 m long with a 3.5 m-long portion of it being unearthed during the excavation. With a width of 1.1–1.2 m, W100 had survived to a height of four courses and was built on bedrock. Above the wall, colluvial brown soil was found, containing numerous small

Discussion

Intensive agriculture, of the type whose remains have been documented on the slopes of Wadi Zetan near Shivta requires extensive knowhow and familiarity with the environmental conditions. In addition, significant wealth and labour must have been invested in the construction of these sophisticated agricultural settings, and the efforts to maintain them must have persisted over a long period of time. In previous research we found that the agricultural system near Shivta dated over a span of

Conclusions

The extensive agricultural systems in the vicinity of Shivta, which peaked at the end of the Byzantine period, reached as far as the southern cliff edge of Wadi Zetan. At that specific location we studied two olive trees and researched the topographical conditions that have enabled their survived in an arid environment. One of the trees has been dated back to about 500 years, while all trees rooted in agricultural soil have been dated back to the Early Islamic period. These remains of runoff

Acknowledgments

This work was supported by the European Research Council under the European Union’s Horizon 2020 Research and Innovation Program Grant 648427 and Israel Science Foundation Grant 340-14. The study was conducted under licenses from the Israel Antiquities Authority (30/2017-G). The radiocarbon research was supported by the Exilarch Foundation for the Dangoor Research Accelerator Mass Spectrometer (D-REAMS) Laboratory and the George Schwartzman Fund. Y. Ehrlich was supported by the Max

References (47)

  • O.z. Barazani et al.

    A comparative analysis of genetic variation in rootstocks and scions of old olive trees–a window into the history of olive cultivation practices and past genetic variation

    BMC Plant Bio.

    (2014)
  • O. Barazani et al.

    Genetic variation of naturally growing olive trees in Israel: from abandoned groves to feral and wild?

    BMC Plant Bio.

    (2016)
  • Barker, G., Gilbertson, D., Jones, B., Mattingly, D. (Eds.), 1996. Farming the Desert: The UNESCO Libyan Valleys...
  • Y. Baumgarten

    Map of Shivta (166)

    (2004)
  • A. Ben-Gal et al.

    The influence of bearing cycles on olive oil production response to irrigation

    Irrigation Sci.

    (2011)
  • Besnard, G., Jean-Frédéric, T., Amandine, C., 2018. On the origins and domestication of the olive: a review and...
  • Bronk, R.C., 2020. OxCal. Available at https://c14.arch.ox.ac.uk/oxcal.html. Accessed April 18,...
  • M. Bernabei

    The age of the olive trees in the Garden of Gethsemane

    J. Archaeol. Sci.

    (2014)
  • P. Cherubini et al.

    Olive tree-ring problematic dating: A Comparative analysis on Santorini (Greece)

    PLoS ONE

    (2013)
  • Colt, H.D., 1962. Excavations at Nessana. Vol. I....
  • C.M. Diez et al.

    Olive domestication and diversification in the Mediterranean Basin

    New Phytol.

    (2015)
  • Y. Ehrlich et al.

    Radiocarbon dating of an olive tree cross-section: New insights on growth patterns and implications for age estimation of olive trees

    Front. Plant Sci.

    (2017)
  • View full text