This study investigates the impact of crude oil contamination on the fungal community dynamics in the Evrona Nature Reserve, situated in Israel’s hyper-arid Arava Valley. The reserve experienced petroleum-hydrocarbon-spill pollution at two neighboring sites in 1975 and 2014. The initial contamination was left untreated, providing a unique opportunity to compare its effects to those of the second contamination event. In 2022, soil samples were collected from both contaminated areas and nearby clean (control) sites, 47 and 7 years after the spills. The taxonomic diversity of fungal community and functional guilds, as well as various properties of the soil, were analyzed. We focused on three functional groups within fungal communities: saprotrophs, symbiotrophs, and pathotrophs. The results revealed a significant decrease in number of fungal species in the contaminated samples over time. Consequently, prolonged effect of crude oil-contaminated soils can facilitate the development of a distinct fungal community, which has adapted to the conditions of oil contamination. This study aims to elucidate the dynamics of fungal communities in oil-contaminated soils, contributing to a better understanding of their behavior and adaptation in such environments.

On April 10, 2023, exceptional weather conditions over southern Israel produced an extreme rainstorm. The peak precipitation, with a maximum rainfall depth of 62 mm and rain intensities exceeding 50 mm h⁻¹, fell over the hyper-arid southern Negev and Arava Valley and generated a mega flash flood in Wadi Zihor. This ephemeral stream channel supported a comparatively dense cover of vegetation, predominated by Acacia raddiana, Acacia pachyceras, Tamarix nilotica, and Tamarix aphylla. To determine the properties of the flash flood, we used post-flood ground-based measurements and calculations of shear stress and peak discharge along the wadi. Also, we used pre- and post-flood satellite images to assess the flood’s impact on woody vegetation cover along the ∼17 km-long wadi bed. Calculations based on data collected by the Israel Water Authority implied a peak discharge of 585 m³/s at the wadi outlet, indicating a low-frequency flash flood of less than once in 150 years. The pre-flood’s 12.7 % vegetation cover throughout the wadi bed decreased to 7.5 % after the flood, corresponding to a 41 % net loss. To detect differences in tree removal extent along the wadi, we divided its entire length into 24 equal segments, and separately assessed the vegetation cover before and after the flood. Vegetation cover loss was 10.8 % in the wadi’s uppermost segment, whereas its lowermost segment lost 51.6 %. Overall, a significant and strongly positive (r = 0.88) correlation was recorded between the accumulated watershed area (downstream) and the extent of tree cover loss. Among other factors, this effect seems to be predominantly determined by the increasing shear stress and peak discharge downstream. Forecasted climatic change scenarios, with increasing magnitude and frequency of extreme rainstorms and floods across the world’s drylands, highlight the need for more data collecting and analyzing of those events impact as described in this study.

Ancient stone terrace walls aimed at harvesting water runoff and facilitating crop production are widespread across the drylands of the Middle East and beyond. In addition to retaining the scarce water resource, the terrace walls also conserve soil and thicken its profile along ephemeral stream channels (wadis) by decreasing fluvial connectivity and mitigating erosional processes. In this study, we created hydrological models for three wadis with ancient stone terrace walls in the arid northern Negev of Israel, where the predominant geophyte species is Asphodelus ramosus L. A two-dimensional (2D) rain-on-grid (RoG) approach with a resolution of 2 m was used to simulate the rain events with return periods of 10, 20, 50, and 99 % (10-y, 5-y, 2-y, and yearly, respectively) based on the Intensity-Duration-Frequency rain curves for the region. To evaluate the effect of stone terrace walls on fluvial hydrology and geomorphology, the ground level was artificially elevated by 20 cm at the wall locations in a digital terrain model (DTM), using the built-in HEC-RAS 2D terrain modification tool. Our results showed that the terraced wadis have a high capacity to mitigate runoff loss, but a lesser capacity to delay the peak flow. Yet, for all rainstorm return periods, peak flow mitigation was positively related to the number of terrace walls along the stream channel. Field surveys in two of the studied wadis demonstrated that the A. ramosus clones were found in proximity to the stone terrace walls, presumably due to the greater soil–water content there. The results thus suggest that the terrace walls provide improved habitat conditions for these geophytes, supporting their growth and regulating their distribution along the wadi beds.

Cover cropping is practiced in conservation agriculture to preserve soil and water resources, alleviate soil compaction, sequester organic carbon, and control weeds. Meanwhile, cover cropping is rarely used in forestry, probably due to the lack of awareness of this management practice. In this short essay, we discuss the concept of utilizing cover crops to prepare degraded lands for afforestation or reforestation projects. The benefits of this practice are similar to those in agriculture. The risks of this practice are mostly related to plant-plant interactions, and particularly, to the potential competition for resources with the target trees. As such, this practice should be implemented cautiously, to prevent adverse impacts on the forest system. Also, attention should be paid to ensure the delivery of ecosystem services and functions by the target land. Further, the co-use of complementary practices may be considered to accelerate the success rate of cover cropping in degraded lands designated for afforestation and reforestation. Among these practices, application of soil additives, such as composts, manures, and biochars, may be useful in increasing soil concentrations of organic carbon and nutrients, thus improving soil quality and fertility. Additional complementary active practices may be the direct seeding or planting of nurse shrubs and trees, as well as the inoculation of soil surface with biocrust slurries, aimed to increase ecosystem complexity by forming a multi-story vegetation structure. Recommendations and guidelines for implementing cover crops in forestry should be site-specific and case-dependent, and consider both the desired benefits and potential risks.

The Saint Catherine region of southern Sinai Peninsula’s drylands encompasses a unique combination of geophysical conditions. These features have formed highly diverse habitats, which support extremely complex plant communities. Throughout history, the local Bedouin population has used many of these plants for therapeutic purposes. The objectives of this study were to document the medicinal knowledge for as many as possible plant species, evaluate this ethnobotanic knowledge against a modern biomedical database, and identify links between the two disciplines. On-site gathering of information, through structured interviews with two local key informants, revealed the traditional use of 90 native vegetation species for a range of therapeutic purposes. Surveying the modern biomedical uses of these plant species in the PubMed database revealed medicinal use for 41 of them, as well as other plant species without known traditional therapeutic uses. Of the 41 plant species, in-depth integration of traditional and modern knowledge was implemented for 20 species, for which sufficient information was found in the PubMed. The results highlight the common ground between the two disciplines, and propose bridges between traditional and modern medicines. The study stresses the need for additional research in ethnobotany, which may assist in developing new plant-based medications.

Forestry has long been considered an effective means of restoring degraded drylands worldwide. Often, afforestation in such lands relies on the establishment of runoff harvesting systems that are formed as contour bench terraces on hillslopes, increasing water availability for the planted trees and shrubs. The construction of terraces requires intensive earthworks by heavy machinery. This study assessed the long-term (>10 yrs) effects of forestry-related land-use change on soil properties and herbaceous vegetation in 16-year-old and 12-year-old afforestation sites (established in 2005 and 2009), and in nearby control (“natural”) areas in the semi-arid northern Negev, Israel. Mean herbaceous vegetation height in the 2005 afforestation sites (12.1 cm) was significantly (P = 0.0009) and 23% greater than in the control areas (9.8 cm), whereas in the 2009 afforestation sites (6.2 cm) it was 37% lesser than in the control areas. Mean herbaceous vegetation aboveground biomass was similar in the 2005 afforestation (0.39 Mg ha⁻¹) and control areas (0.38 Mg ha⁻¹), and almost significantly (P = 0.0510) and twofold greater than in the 2009 afforestation sites (0.19 Mg ha⁻¹). The effect of hillslope aspect on these variables was substantial; their mean values were higher in the northern (mesic) hillslopes than in the southern (xeric) hillslopes. Soil samples were obtained from depths of 0–5 and 5–10 cm and physio-chemo-biological properties were assessed in the laboratory. The overall soil quality – as calculated by two soil quality indices (SQIs), including the generalized SQI (SQI_gen) and the minimum dataset SQI (SQI_MDS) – was significantly (P < 0.0001 for both indices) and 13–22% greater in the control areas (0.52 and 0.61, respectively) than that in the afforestation treatments (0.44–0.46 and 0.50–0.51, respectively). These results are generally attributed to the removal of soil's A-horizon during earthworks, and the exposure of the underlying B-horizon. The similar SQI values of both hillslope aspects, as well as of both soil depths, indicate the generally degraded state of the entire region. In conclusion, while contour bench terracing may facilitate the recovery of herbacaeous vegetation to some extent, the effectiveness of this practice for soil restoration is questionable. Overall, insights of this study demonstrate a caveat that converting natural drylands to forestry systems may not yield sufficient ecological benefits, and therefore should be implemented with caution.

In drylands, particularly in sandy environments, clonal plants occasionally develop into ring patterns that slowly expand radially, leaving bare soil in the ring's center. Several mechanisms have been suggested to explain ring formation, and yet it is very difficult to find out the dominant driving mechanism for each specific ecosystem. This study is the first to assess the rings of Stipagrostis obtusa in the north-eastern Negev of Israel, an arid region with mean annual precipitation of ≈65 mm. Our results propose that S. obtusa rings form in response to the infiltration feedback, which is enhanced by microtopography; the rings developed on small mounds due to continuous deposition of sand and dust. The infiltration feedback is caused by the sharp contrast in water infiltrability between the rings and the inter-ring spaces, where infiltration is lower. In addition, during heavy rainstorms, runoff generated in the inter-ring spaces partially percolates in the rings’ periphery and enhances radial expansion. These source–sink relations increase water availability for the S. obtusa plants, increasing their resilience to the harsh dryland conditions.

Water loss through surface runoff is a significant constraint for rainfed agricultural lands across the Mediterranean region. Using straw-mulch cover (SMC) as a runoff mitigator has been successfully utilized to negate the impact of raindrop splashing. However, this practice is uncommon due to the high demand for crop residue as feed or fodder for livestock. Therefore, the application of synthetic polyacrylamide (PAM) has become a common practice. Although many studies have shown the positive impact of PAM on runoff control, most were conducted under laboratory conditions, where interactions with crop phenology and runoff dynamics were disregarded. In this study, on-site rainfall simulation was used to determine the efficiency of PAM and SMC to control runoff from foxtail millet (Setaria italica) fields under three seasonal conditions: (1) high-intensity rainfall, characteristic of autumn, on bare soil surfaces; (2) moderate-intensity rainfall, characteristic of winter, following crop tillering; and (3) high-intensity rainfall, characteristic of spring, following the flowering phase. The effect of SMC during the autumn and spring simulations was significantly better than that of the PAM and control treatments. For the winter simulation, runoff rates and runoff ratios were similar for all treatments. The most prominent finding was obtained for the spring simulation, where SMC yielded no runoff, whereas the PAM and control treatments yielded similar runoff rates and runoff ratios.

Shrubs, encompassing important ecosystem engineers in dryland environments, have experienced mass mortality due to long-term droughts across the northwestern Israeli Negev. This massive die-back, which has particularly affected the predominant shrub species Noaea mucronata, predominates edaphically homogeneous (low geodiversity) hillslopes, and is minor in edaphically heterogeneous (high geodiversity) hillslopes. While the homogeneous hillslopes encompass a thick and non-stony soil layer, the heterogeneous hillslopes are composed of a thin, stony layer that overlies weathered, chalky bedrock. The objective of this geophysical study was to assess the subsurface and bedrock characteristics, and its effect on shrub durability vs. mass mortality in a dryland ecosystem. A combination of 2D and 3D Ground Penetrating Radar (GPR) imaging and Frequency Domain Electromagnetics (FDEM) was applied. For the GPR procedure, the 2D and 3D reflection imaging was dominated by different dielectric permittivities (dielectric constants) of layers and changes in soil-rock-water content. For the FDEM procedure, the soil-rock electrical properties, alongside the concentration of dissolved salts, determined the measured electrical conductivity (EC). The results show substantial differences in EC values between the homogeneous and heterogeneous hillslopes, which are attributed to differences in the soil-rock interface, soil-water content, and salts concentration. Overall, the much greater EC values of the soil-rock interface in the heterogeneous hillslopes are expected to adversely affect shrub vitality. However, the greater shrub vitality in these hillslopes is likely attributed to the fractured and weathered chalky underground, which retains moisture in pockets or micro-aquicludes that increase water availability for the shrubs. Under these better habitat conditions of the heterogeneous hillslopes, the high EC values do not limit shrub survival or growth. At the same time, the absence of such water pockets in the thick soil layer of the homogeneous hillslopes imposes severe stress under long-term drought conditions, resulting in shrub die-off. This study illustrates the vital role of subsurface geodiversity in determining the resilience of dryland ecosystems to droughts and climatic change.

Land degradation and desertification are widespread across the world’s drylands. These processes are substantially affected by climatic change, with long-term and severe droughts on the one hand, and high intensity rainstorms and devastating floods on the other hand. Simultaneously, land-use change and mismanagement practices have led to processes of accelerated soil erosion, depletion of soil organic carbon pools, and the degradation of extensive drylands. Forestry has been accepted as an effective means for restoring degraded drylands, and for attaining a range of regulating, provisioning, supporting, and cultural ecosystem services. Specifically, forestry is widely perceived as an effective means for soil erosion control, organic carbon sequestration, microclimate improvement, and climate change mitigation. However, forestry in drylands often proves to generate substantial environmental challenges, resulting in deterioration of ecosystem functions and health. The objective of this essay is to review the challenges and opportunities induced by dryland afforestation and reforestation, and highlight the need to attain climate-smart strategies for establishing and managing these land-uses. Particularly, tree species invasion and allelopathy, which are common in dryland forestry projects, jeopardize species richness and diversity of native vegetation communities. Further, the challenges linked with tree invasiveness necessitate predicting the distribution of potentially invasive species and foreseeing their impacts on the recipient ecosystems under projected climate change scenarios. The effect of allelopathy is significant under limited water availability conditions and is expected to be determined by the expanding drylands and intensifying aridity worldwide. Therefore, judicious selection of tree species should not only focus on ones with high water-use efficiency, low flammability, high pest resistance, and fast growth, but also on low invasiveness and allelopathic capacities. Insights of this essay may be used by land managers, stakeholders, and policy makers involved in environmental development of drylands.