Giora Kidron | The Hebrew University of Jerusalem (original) (raw)

Papers by Giora Kidron

Hydrological Processes, May 1, 2023

Water repellent soils represent some of the most responsive natural surfaces from the point of vi... more Water repellent soils represent some of the most responsive natural surfaces from the point of view of overland flow generation. Measurement of the runoff response of such soils can therefore provide characteristics that can help constrain hydrological models or improve the conceptual models of hillslope runoff generation. We have analysed the overland flow characteristics of water repellent sandy soils at three sites with different dominant vegetation (hereafter denoted as the lichen, moss and herb sites) and following vegetation removal (scalping) during extreme rainfall events created by a rainfall simulator (three consecutive sprinklings at 2.1 mm min−1 for 15 min each with a 5 min hiatus between the sprinklings). Despite the extreme water repellency (WR) and rainfall intensity, on average just up to a half of the rainfall left the plots as an overland flow. Whilst the overland flow mostly generated quickly (on average within 50–120 s), the vegetation substantially delayed its appearance (by approximately 100% compared to scalped plots). The median values of the runoff coefficients were 6% and 49% on the soil with and without vegetation, respectively. Good relationships between the overland flow characteristics and soil moisture were found only for the scalped plots. Although the time to runoff and runoff coefficients after each of the three consecutive sprinklings were not substantially different, the differences between the soil with and without vegetation remained substantial. The results indicated: (a) high variability within each of the sites, including the lichen site that appeared homogenous; (b) all vegetated plots retained a higher amount of water than the scalped plots; (c) although all sites exhibited high WR, the combined influence of preferential flow, higher hydraulic conductivity and specific vegetation (soapwort, black locust) mitigated its effects at the herb site; (d) the relatively lower overland flow at that site may point to subsurface flow.

Land Degradation & Development, Dec 28, 2021

There is no consensus over the factors responsible for dune stabilization in arid regions, with s... more There is no consensus over the factors responsible for dune stabilization in arid regions, with some scholars maintaining that dust (i.e., silt and clay) plays a major role in dune stabilization. Aiming to explore the principal driving factor responsible for dune stabilization in the Negev, we compared various biocrusts having different biomass and compressive strength, and performed surface degradation and illuviation experiments with dust in the presence or absence of biocrusts in order to assess the crust role in impeding wind erosion and dust illuviation. We show that dust cannot be regarded as the primary driving factor for crust strength and subsequently for dune stabilization in the Negev, as suggested in some publications. This function is however fulfilled by extracellular polymeric substances (EPS, mostly polysaccharides), which are excreted by the biocrust (mainly cyanobacteria), and serve as a cementing agent for the establishing crust and therefore for the dust. Exhibiting high water absorption and strong adhering properties, EPS is responsible for granting strength to the crust, impeding wind erosion and dust illuviation, thus providing the necessary cementing agent, which facilitates dune stabilization in the Negev. Global warming which may result in frequent droughts and high input of dust may not contribute to dune stabilization as suggested by some scholars, but rather will negatively affect dune stabilization, as it may result in EPS degradation and subsequently in dune mobilization.

HAL (Le Centre pour la Communication Scientifique Directe), Aug 1, 2021

Geomicrobiology Journal, Feb 21, 2017

ABSTRACT We examined the depthwise distribution of microfungi through 0–40 cm of sandy profiles u... more ABSTRACT We examined the depthwise distribution of microfungi through 0–40 cm of sandy profiles under bare surface and different shrub species at the Nizzana research site (NRS) in the Negev Desert, Israel. A total of 125 species from 61 genera were isolated using the soil dilution plate method. At the topsoil of all profiles melanin-containing species with large multicellular conidia predominated. In the middle depths at the majority of the profiles, mesic group of microfungi, Penicillium spp. substantially increased in abundance. Density of microfungal isolates decreased with depth under shrubs and did not substantially vary in the nonshaded profiles, highly positively correlating with electrical conductivity and organic matter (OM) content. Substantial increase in isolate densities at the undercanopy habitats, especially in the interdune depression with higher substrate stability raising the accumulation of OM, highlights the role of shrubs as “islands of fertility” for microfungal communities at NRS.

Journal of Hydrology, May 1, 2017

Journal of Hydrology, Aug 1, 2023

Ecohydrology, Feb 22, 2023

Soil biocrusts abound in deserts, but yet little agreement exists regarding their water sources. ... more Soil biocrusts abound in deserts, but yet little agreement exists regarding their water sources. Most researchers regard non‐rainfall water (NRW), particularly dew as an important water source for soil biocrusts, but nevertheless, evidence from the Negev suggests that following the nocturnal soil heat efflux, NRW is drastically reduced. The possible contribution of NRW to 3‐ to 5‐mm‐tall lichens, which are less impacted by the warm nocturnal surface temperatures, poses an additional challenge. For this end, NRW obtained by cloths attached to the soil surface and cloths located at a 5‐mm height above ground were measured, accompanied by periodic temperature measurements. As for the cyanobacteria and the 1‐mm‐tall lichens, NRW did not reach the necessary threshold required for the performance of net photosynthesis by cyanobacterial (0.1 mm) or chlorolichens (0.05 mm) but was occasionally reached at 5‐mm height above ground. Nevertheless, when the average amount obtained at 1‐mm intervals (mimicking the length of the lichen thallus) along the 5‐mm height was calculated, it either fell below the necessary threshold or was too low during daytime to compensate for the carbon loss during nighttime respiration. The apparent incapability of NRW to provide sufficient water to sustain the 3‐ to 5‐mm‐tall lichens in the Negev Highlands is supported by the confinement of these lichens to north‐facing rock terraces (ledges), where they may benefit from additional water through runoff. One may therefore conclude that NRW may not be regarded as a meaningful water source for the Negev biocrusts, whether composed of cyanobacteria or of 1‐ to 5‐mm‐tall lichens.

Applied Soil Ecology, Nov 1, 2022

한국토양비료학회 학술발표회 초록집, Jun 1, 2014

Advances in Astronomy, Oct 17, 2020

Earth-Science Reviews, Aug 1, 2022

Ecohydrology, 2021

Long‐term field campaigns in the Negev observed wet–dry cycles (WDCs) following rain events, prin... more Long‐term field campaigns in the Negev observed wet–dry cycles (WDCs) following rain events, principally on sand. Aiming to assess the relevant mechanism (whether dewfall, water capillarity or distillation derived by temperature‐induced vapor flux [TIVF] which stems from the soil), a set of outdoor experiments was conducted on sand and loess. They included nonrainfall water (NRW) and temperature measurements during the rainless dry seasons (summer, fall) and during the winter, which was divided to a wet (following rain) and dry periods. Dew measurements were conducted on cloths, whether directly attached to the soil or located at 0.5 cm above ground, aiming to eliminate capillarity and assessing the possible contribution of dewfall and TIVF‐induced distillation. Our findings show that (a) WDCs were only observed following rainstorms, particularly on sand, (b) WDCs could not have been explained by capillarity (they continued at the presence of an air gap), (c) significantly lower min...

Microorganisms

We examined fungal communities in soil profiles of 0–10 cm depth along the altitudinal gradient o... more We examined fungal communities in soil profiles of 0–10 cm depth along the altitudinal gradient of 250–530–990 m.a.s.l. at the Central Negev Desert, Israel, which benefit from similar annual precipitation (95 mm). In the soil samples collected in the summer of 2020, a mycobiota accounting for 169 species was revealed by both culture-dependent and culture-independent (DNA-based) methodologies. The impact of soil depth on the variations in fungal communities was stronger than the impact of altitude. Both methodologies displayed a similar tendency in the composition of fungal communities: the prevalence of melanin-containing species with many-celled large spores (mainly Alternaria spp.) in the uppermost layers and the depth-wise increase in the proportion of light-colored species producing a high amount of small one-celled spores. The culturable and the DNA-based fungal communities had only 13 species in common. The differences were attributed to the pros and cons of each method. Never...

Journal of Hydrology and Hydromechanics

With dew serving as an important water source for various small organisms and plants in deserts, ... more With dew serving as an important water source for various small organisms and plants in deserts, knowledge regarding the spatial distribution of dew (which constitutes an important fraction of the non-rainfall water, NRW) is of prime importance. This is also the case for the Negev dew desert. According to the classical model, local nocturnal katabatic winds that descend down the slopes during the night to the wadi beds are responsible for the accumulation of cold air, subsequently triggering dew formation in the wadis. Nevertheless, NRW measurements that were conducted in a one-order drainage basin in the Negev during the dewy season (late summer and fall) yielded half the amount in the wadi bed in comparison to the hilltop, attributed to the sheltered position of the wadi from the cooling effect of the regional (sea-breeze) winds, which are not considered by the classical model. Hypothesizing that the classical model may however take place at wide wadi where the sea breeze winds ar...