Search

Start Over Creator Kidron, Giora J. Language Slovak

2. Linking surface and subsurface properties of biocrusted and non-biocrusted habitats of fine-grained fluvial sediments (playas) from the Negev Desert

Creator:
Kidron, Giora J.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
available water content, loess, and soil moisture
Language:
Slovak
Description:
With biocrusts playing a cardinal role in C and N fixation in arid zones, information regarding the factors that determine their limits of growth is of uttermost importance for the study of ecosystem structure and function. This is also the case in the western Negev dunefields, where although abundant on the sandy surfaces, biocrusts are scarce on finegrained (mainly loessial) sediments, termed playas. In the Nizzana research site (NRS), visibly distinct surfaces, with and without biocrusts were noted within a single playa. In an attempt to characterize these distinct surfaces, a set of random measurements were carried out, which included measurements of crack density, microrelief and chlorophyll content of the upper 0-1 cm. Following a cluster analysis, four distinct types of surfaces (hereafter habitats) were defined, one with substantial amount of chlorophyll content which can be regarded as biocrust (P4), and three non-crusted surfaces (P1- P3). Within each type, two 50 cm-deep pits were dug and the pH, electrical conductivity (EC) and fine (silt and clay) content (FC) of samples collected at 1-5, 5-10, 10-20, 20-30, 30-40 and 40-50 cm-depth were analyzed. In addition, periodical moisture measurements were carried out (in pairs) to a depth of 0-20 cm at each surface type during 2013/14. All non-crusted habitats (P1-P3) were characterized by loessial subsurface sediments. Conversely, P4 was either characterized by loessial subsurface sediments (and in this case it was characterized by a slightly concave surface) or having a sandy subsurface (at ~5-10 cm depth). While the non-crusted surfaces exhibited low moisture content, P4 exhibited deeper and higher moisture content explained either by the more sandy sediments or by lower water loss through runoff. The findings point to the close link between surface and subsurface properties and indicate that water availability may explain biocrust establishment and growth also at the loessial playa surfaces. Biocrusts may thus serve as bioindicators for habitats with high moisture content.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

3. Lithobiont-dependent ionic composition in runoff water

Creator:
Kidron, Giora J. and Starinsky, Abraham
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
cyanobacteria, dew, lichens, magnesium, potassium, and Negev desert
Language:
Slovak
Description:
Rock dwelling organisms (lithobionts) such as cyanobacteria (prokaryotes) and chlorolichens (eukaryotes) abound in the Negev Desert, where they cover almost all calcareous bedrocks and rock particles (cobbles, boulders). In a small limestone watershed in the Negev Highlands, cyanobacteria inhabit the south-facing (SF) bedrocks, epilithic lichens (accompanied by endolithic lichens) inhabit the north-facing (NF) bedrocks, while endolithic lichens cover most of the cobbles and boulders in both aspects. In order to study their contribution to runoff water, a pair of runoff plots was established on habitats with cyanobacteria, endolithic lichens, and epilithic lichens. Rain and runoff were collected during the hydrological year 2006/07, and the chemical composition (Ca, Mg, Na, K, Cl, SO4, HCO3, Si) of the rain and runoff water was analyzed. Several patterns were observed: (a) as indicated by Si, more dust accumulated on the bedrocks; (b) all substrates exhibited high amounts of Ca, and HCO3; (c) while SF-bedrocks showed enrichment in K, both bedrocks (and especially the NF bedrocks), as well as the NF boulders showed an enrichment in Mg. While the enrichment in Ca and HCO3 can be explained by the contribution of the limestone parent material, the enrichment in K and Mg can be explained by the contribution of the living lithobionts, with K being mainly contributed by the cyanobacteria and Mg mainly by the epilithic lichens. Ion enrichment may therefore be aspect-dependent, reflecting the lithobiont distribution within the drainage basin, partially explaining the enrichment in K and Mg previously recorded in runoff water from the Negev.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

4. Sink plot for runoff measurements on semi-flat terrains: preliminary data and their potential hydrological and ecological implications

Creator:
Kidron, Giora J.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
infiltration, playa surfaces, sand dunes, and Negev Desert
Language:
Slovak
Description:
In arid and semiarid regions where water is the main limiting factor, water redistribution is regarded as an important hydrological process of great ecological value. By providing additional water to certain loci, moist pockets of great productivity are formed, characterized by high plant biomass and biological activity. These moist pockets are often a result of runon. Yet, although runoff may take place on semi-flat undulating surfaces, runoff measurements are thus far confined to slopes, where a sufficient gradient facilitates downslope water harvesting. On undulating surfaces of mounds and depressions, such as in interdunes, no quantification of the amount of water reaching depressions is feasible due to the fact that no reliable method for measuring the runoff amounts in semi-flat terrains is available. The current paper describes specific runoff plots, designed to measure runoff in depressions (sinks). These plots, termed sink plots (SPs), were operative in the Hallamish dunefield (Negev Desert, Israel). The paper presents measurements of runoff yield that were carried out between January 2013 and January 2014 on SPs and compared them to runoff obtained from crusted slope plots and fine-grained (playa) surfaces. The potential hydrological and ecological implications of water redistribution within semi-flat terrains for this and other arid ecosystems are discussed.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5. The role of biocrust-induced exopolymeric matrix in runoff generation in arid and semiarid zones - a mini review

Creator:
Kidron, Giora J.
Format:
počítač and online zdroj
Type:
model:article and TEXT
Subject:
biological soil crusts, extracellular polymeric substances, pore clogging, hydrophobicity, infiltration-excess overland flow, and water repellency
Language:
Slovak
Description:
Although playing an important role in shaping the environment, the mechanisms responsible for runoff initiation and yield in arid and semiarid regions are not yet fully explored. With infiltration-excess overland flow, known also as Hortonian overland flow (HOF) taking place in these areas, the uppermost surface 'skin' plays a cardinal role in runoff initiation and yield. Over large areas, this skin is composed of biocrusts, a variety of autotrophs (principally cyanobacteria, green algae, lichens, mosses) accompanied by heterotrophs (such as fungi, bacteria, archaea), which may largely dictate the infiltration capability of the surface. With most biocrust organisms being capable of excreting extracellular polymeric substances (EPS or exopolymers), and growing evidence pointing to the capability of certain EPS to partially seal the surface, EPS may play a cardinal role in hindering infiltration and triggering HOF. Yet, despite this logic thread, great controversy still exists regarding the main mechanisms responsible for runoff generation (runoff initiation and yield). Elucidation of the possible role played by EPS in runoff generation is the focus of the current review.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public