Fruit trees' survival ability in an arid desert environment without irrigation in the Negev Highlands of Southern Israel

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.