Organic and mineral growing media are commonly used in horticultural soilless systems for vegetable cropping in greenhouses and net-houses. However, extraction of these materials adversely affects environmental quality. The objective of this study was to assess the horticultural potential of biochar and compochar (a mix of biochar and compost) growing media—both produced from human (domestic) sewage sludge—as an alternative to tuff/tephra (light porous medium formed by consolidation of volcanic ash). The study was conducted in the Israeli drylands, where lettuce and cherry tomato were grown in a net-house under deficit nutrient management (50% of the recommended rate). The biochemical properties of the three substrates ((i) 100% biochar; (ii) compochar (50% biochar+50% compost); and (iii) 100% commercial tuff) and productivity of the two crops were assessed. For the two crops, the nutrient status of biochar and compochar were similar, and different from that of tuff. In the lettuce, mean values of substrate general quality index (SQIgen) and substrate quality index minimum dataset (SQIMDS) were similar for biochar and compochar (0.550 and 0.541, respectively, for SQIgen; 0.614 and 0.613, respectively, for SQIMDS), and significantly greater than that of tuff (0.337 for SQIgen; 0.310 for SQIMDS). In the cherry tomato, a similar trend was recorded, with significantly greater means for biochar and compochar (0.499 and 0.497, respectively, for SQIgen; 0.436 and 0.482, respectively, for SQIMDS) than those of tuff (0.320 for SQIgen; 0.192 for SQIMDS). In terms of crop yields, mean productivity of lettuce followed the trend of compochar>biochar>tuff, whilst cherry tomato yields followed the trend of biochar>compochar>tuff. Thus, biochar and compochar can be recommended as viable, sustainable alternatives in soilless horticulture systems. Further, insights of this study highlight the climatic change mitigation and adaptation capacities of biochar and compochar when used as horticultural growing media.

The loess plains cover approximately 2000.00 km² of the northern Negev Desert, accounting for about 9% of Israel’s total land area. As elsewhere, the loess in the Negev Desert is composed of wind-transported dust and sand particles that have been deposited in sink sites. The loess deposits are characteristically covered by biocrusts, which constitute a substantial share of the region’s primary productivity. The biocrusts regulate the vascular vegetation communities, including herbaceous and woody plants, many of which are endemic and/or endangered plant species. Throughout history, the region’s main land-uses have been based on extensive livestock grazing and runoff-harvesting agriculture, which both still exist to some extent. These land-uses did not challenge the sustainability of the geo-ecosystems over centuries and millennia. At present, predominant land-uses include intensive rangelands (1016.81 km², encompassing 51% of the loess plains’ area), croplands (encompassing both rainfed and irrigated cropping systems: 930.92 km², 47% of the loess plains’ area), and afforestation lands (158.75 km²). These current land-uses impose substantial challenges to the functioning of the loess plains. Further, urban and rural settlements have expanded considerably in the last decades (158.45 km²), accompanied by mass construction of infrastructures. Altogether, these new land-uses have caused widespread soil erosion, soil structure deformation, depletion of soil organic carbon, environmental contamination, native vegetation removal, invasion of plant species, and habitat fragmentation. Recent climate change has intensified these stressors, exacerbating adverse impacts and forming feedback loops that intensify land degradation and desertification. The declining ecosystem functioning over recent decades emphasizes the urgent need for passive and active restoration schemes. While some of these efforts have proven to be successful, other have failed. Therefore, proactive policy making and environmental legislation are needed to plan and develop schemes aimed at halting land degradation, while simultaneously maximizing nature conservation and restoration of degraded lands across the loess plains. Such actions are expected to increase the regions’ capacity for climate change mitigation and adaptation.

Petroleum pollution has become a substantial challenge in soil ecology. The soil bacterial consortia play a major role in the biodegradation of petroleum hydrocarbons. The main objective of this study was to assess changes in bacterial composition and diversity in oil-contaminated dryland soils. The Illumina MiSeq high-throughput sequencing technique was used to study the bacterial diversity and structural change in hyper-arid oil-contaminated soil in the Arava Valley of Israel. The diversity and abundance of soil bacteria declined significantly following oil pollution. The dominant phyla in the petroleum-contaminated soils were Proteobacteria (~33% higher vs. control soil) and Patescibacteria (~2.5% higher vs. control soil), which are oil-associated and hydrocarbon-degrading bacteria. An opposite trend was found for the Actinobacteria (~8%), Chloroflexi (12%), Gemmatimonadetes (3%), and Planctomycetes (2%) phyla, with the lower abundances in contaminated soil vs. control soil. Investigation of long-term contaminated sites revealed significant genus-level taxonomic restructuring in soil bacterial communities. The most evident changes were observed in Mycobacterium, Alkanindiges, and uncultured bacterium-145, which showed marked abundance shifts between spill and control soils across decades. Particularly, hydrocarbon-degrading genera such as Pseudoxanthomonas demonstrated persistent dominance in contaminated sites. While some genera (e.g., Frigoribacterium, Leifsonia) declined over time, others—particularly Nocardioides and Streptomyces—exhibited substantial increases by 2014, suggesting potential ecological succession or adaptive selection. Minor but consistent changes were also detected in stress-tolerant genera like Blastococcus and Quadrisphaera. The effect of oil contamination on species diversity was greater at the 1975 site compared to the 2014 site. These patterns highlight the dynamic response of bacterial communities to chronic contamination, with implications for bioremediation and ecosystem recovery. The study results provide new insights into oil contamination-induced changes in soil bacterial community and may assist in designing appropriate biodegradation strategies to alleviate the impacts of oil contamination in drylands.

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.

Continual land degradation processes adversely affect the functioning of dryland ecosystems. In recent decades, extensive afforestation activities have been undertaken in marginal lands of the semiarid northern Negev region of southern Israel to mitigate such degradation processes. However, the long-term impacts of these actions in drylands, subjected to long-term drought episodes, remain unknown. We investigated the impact of landuse change from natural lands to afforestation runoff-harvesting systems—through intensive earthworks (landforming) to establish a contour bench terrace during long-term drought—on herbaceous vegetation productivity, and assessed its temporal dynamics across the multi-aged Ambassadors’ Forest. The MODIS MOD13Q1 and MYD13Q1 maximum value composite products were used to calculate normalized difference vegetation index (NDVI) data for the hydrological years 2000 to 2020. For this study, implemented in 2021, we selected three locations within the Ambassadors’ Forest: (1) 15-year-old afforested hillslopes, (2) 11-year-old afforested hillslopes, and (3) 4-year-old afforested hillslopes. We further delineated undisturbed hillslopes near these sites as a reference treatment. We found high spatiotemporal variability in vegetation cover. Over the short term, and specifically in the first hydrological year following the establishment of the water-harvesting systems, a substantial reduction in mean annual NDVI was observed, with values ranging from 30% to 65% lower compared to the reference sites. However, the negative impact of landuse change diminished over time, suggesting that (1) self-restoration processes occurred over a longer term after landuse changes were implemented, and (2) the establishment of water-harvesting systems improve the conservation of runoff water at the hillslope. This effect was observed for the 11- and 15-year-old afforestation sites, where vegetation productivity was 8.9% and 31.0% greater, respectively, than in the respective reference sites (p < 0.05). Although the long-term drought occurred during the construction of the water-harvesting systems, these findings are in agreement with previous studies. Specifically, this study suggests that ecological self-restoration processes in semiarid regions occur approximately a decade after runoff-harvesting systems are established through earthworks.

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.