Pistacia atlantica trees have a very limited distribution in wadis in the central Negev highlands, and erosive processes may have a negative impact on the recruitment and survival of the trees. We measured the sizes of the trunks of adult trees, the condition of their canopies, fruit density, insect herbivory, and soil parameters--both in eroded and noneroded habitats. This was to determine the habitat soil quality and how it relates to the demographic disposition and vitality of these trees. The results revealed irregular size/age distribution and possible poor recruitment. There were no differences in fruit density between trees in eroded and noneroded habitats. However, analysis on gall density per branch revealed that Slavum wertheimae prefer host plants in relatively uneroded habitats. Analysis of water-holding capacity, soil organic carbon content, and pH revealed significant differences, with better soil quality existing in noneroded areas.
Twenty-three olive trees were found to grow in traditional orchard sites in the Negev Highlands desert, southern Israel. Their location was marked on maps, and their growth, morphology, biology, preservation and survival was monitored. Some of them are presently maintained by the Bedouin population of the Negev, whereas others seemed to have survived from earlier periods. The average annual rainfall in this region is 90–130 mm. Most of the orchards were deliberately planted in pre-existing agricultural plots, built during the Byzantine and Early Muslim era (3rd–8th centuries CE). They were irrigated by harvesting runoff water. The Byzantine era was the most populated period in the Negev Highlands, when wine and olive oil were the main horticultural products. A variety of domesticated fruit trees are found in the present abandoned orchards: olive, fig, grapevine, pomegranate, almond, date palm, carob, pistachio and bitter orange. The trees have not been artificially irrigated for at least seven decades. Nevertheless, most of them continue to flourish and bear fruit. We focused on understanding the abandoned olive trees’ survival and adaptation mechanisms. Olive trees growing was a favorite crop to Byzantine farmers due to the significant economic value of olive oil and good adaptation to the environmental conditions in the Negev Highlands.
More than a hundred abandoned but presently maintained fruit trees are scattered in the Negev Desert Highlands in Southern Israel. Most of the older groves were planted by Bedouins in pre-existing agricultural systems built in the distant past, mainly during the Byzantine era, mostly during the sixth and seventh centuries AD. In these groves a variety of domesticated fruit trees such as date palms, figs, pomegranates, almonds, carobs, pistachios, bitter oranges, grapevines and olives have been planted. The trees growing in these abandoned sites throughout the Negev Highland region are strictly rain-fed and dependent on the amount of runoff water accumulating from the surrounding old runoff harvesting systems with no modern artificial irrigation at least for the past several decades. Despite the lack of active irrigation, some of the trees of all species continue to flourish and even persist in bearing fruit to this day. The trees growing in the Negev Highlands can be divided into several planting periods. The oldest olive trees are apparently descendants of trees planted in the area during the Byzantine period (sixth and seventh centuries AD), while the youngest consist of varieties and species recently planted by Bedouins, until 1948. The factors affecting the survival of the trees are mainly of a geological nature, especially the rock types and their spatial distribution that contribute to the potential of runoff water. Topographic layouts are also critical for enhancing water runoff, as well as various soil parameters, such as water-holding capacity, depth, salinity, and organic matter content. A significant impact on the trees’ condition and survival depends also on the preservation state of the ancient terraces in which they were planted and the level of horticultural expertise of the Bedouins in growing fruit trees. During this study we characterized the geographical, geological and topographical conditions enabling the survival of different fruit trees with no artificially added irrigation in various locations within the Southern Israeli desert. Apparently no specific genotypes were required and involved in the survival of the various fruit trees, but the microconditions at each tree's location were found to be critical.