Variations in Hillslope Runoff as Detected Using Geological Strata Coupled with Vegetation Patterns- Implications on Spatially Distributed Desert Runoff Agriculture

Contrary to humid areas where runoff takes place following the saturation of the soil column, runoff in arid and semiarid zones takes place when rain intensities exceed the infiltration capability of the upper soil crust, whether physical crust or microbiotic crust (MC). This type of overland flow, known as Hortonian overland flow (HOF), is not fully understood, especially in the case of MC. In particular, little is known regarding the effect of crust thickness and its fine (silt and clay) content on runoff generation, with some scholars claiming that runoff generation is positively correlated with crust thickness and fine content. In an attempt to determine the effect of crust thickness and to assess the role played by the silt and clay on runoff generation, a set of field and lab experiments were undertaken on MCs inhabiting sand dunes in the Negev Desert (Israel). These included sprinkling experiments coupled with measurements of the physical (thickness, silt and clay) and biological (chlorophyll, protein, total carbohydrates) properties of 0.5–10‐mm‐thick crusts. The data showed that runoff generation took place on surfaces as thin as ~0.5–0.7 mm only, and was not correlated with the fine (silt and clay) content. The implications for HOF and for arid ecosystems are discussed. Copyright © 2014 John Wiley & Sons, Ltd.

Spatial evaporation patterns within a small drainage basin in the Negev Desert

Rock slabs were placed from 1991 through 2006 at the bottom of a north- (NFS) and a south-facing (SFS) slope of a first order drainage basin in the Negev Desert Highlands, Israel (P = 95 mm) where natural cobbles have >95% cover of endolithic and epilithic lichens. Periodic measurements of rain, dew and chlorophyll content took place. Lichen cover and the regeneration time were aspect-dependent. Lichen cover was 98% and 61% at NFS and SFS, respectively, while the lichen's recovery time was respectively ∼45 and ∼80 years. The fast regeneration time may have important implications regarding weathering and soil formation.

Flight paths of more than 40,000 nocturnal migrants were collected by tracking radars simultaneously at two sites in spring and autumn. Winds were similar in autumn and spring: i.e., typical, rather weak trade winds with northerly directions below about 1500 m above sea level and with southerly or westerly directions higher up. The tracks of the birds were concentrated around 190° (between S and SSW) in autumn and around 5° (nearly N) in spring. Slight differences between the directional distribution of birds above the Negev Highlands and the Arava Valley could be attributed mainly to local winds and topography. Reversed migration occurring in autumn was at the altitudes of the southwesterly winds. Tracks and headings of different wingbeat classes did not differ significantly, except that birds with low wingbeat frequency and passerine-type flight had more westerly directions in autumn and more easterly directions in spring. Mean groundspeed in autumn was nearly 50 km/h, most birds profiting from...

<p>The concept of whole system approach offers a foundation for ecosystem studies. Identification of the components and interaction demonstrate the challenges in the field of ecology, due to the lack of a conceptual and applied framework. we attend to present a theoretical foundation and a methodology for identifying components and interactions of the whole system approach linking biodiversity and geodiversity processes into ecosystem diversity as a web of interactions (WoI).</p><p>The web of interactions model combines the geodiversity components that include climate, geology, geomorphology, and hydrology processes and their interactions and the biodiversity components that include population, community, ecosystem, and landscape levels of organization and their interactions. Linking biodiversity and geodiversity produces ecosystem diversity, which is represented as a web of diversity interactions that include climate, rock, soil, species, genetic, and functional diversities</p><p>In the talk we will present examples from our long term study in the Negev Highland, an arid water limited environment. The system is characterized by high geodiversity (topographic, geologic, geomorphic, and pedologic diversity) and high biodiversity with many unique and endemic species.</p><p>Our study presents the whole system approach of the Negev Highlands ecosystem as a web of interactions (WoI) among and between the diversity of components that links biotic and abiotic diversities. All the components and their interactions vary in time and space and together determine ecosystem diversity.</p><p>Long term study in the Negev Highland site revealed various of diversities of the ecosystem that can be linked by hydro-geo-ecological components, drivers, and feedbacks that control geodiversity and biodiversity. The main feedbacks are: the hydrological feedback that controlled by rainfall pattern and affects the pedological feedback by runoff generation that accumulates dust and regulates rock-to-soil ratio. These two feedbacks control soil moisture, which links geodiversity with biodiversity components. In addition, an energy and material feedback which is characterized by the producer–consumer and decomposer relationships supports ecosystem engineers that link geo and biodiversity. The functional interactions among the biodiversity and geodiversity components create ecosystem diversity that is the driver of whole system properties.</p><p>We suggest that the web of interaction approach can potentially be applied to understand whole system emergent properties of terrestrial ecosystem.</p>

Spatial pattern variation of artificial sand-binding vegetation based on UAV imagery and its influencing factors in an oasis–desert transitional zone

Cyanobacteria are confined to dewless habitats within a dew desert: Implications for past and future climate change for lithic microorganisms

Previous works dealing with the influence of a stone cover on runoff yield showed that runoff, attributed to the sealing effect of the topsoil by raindrops impact, was negatively related to the per cent of stone cover and stone size. These works were conducted on gentle slopes (3–11·5 degree) with a per cent of stone cover generally lower than 50 per cent, and composed of gravels. The present study deals with the runoff yield of steep talus slopes (26–36 degree) whose per cent of stone cover is very high (90–100 per cent), composed of cobbles and boulders. Three stimulated rainstorms were performed at various rainfall. intensities and durations on each one of six plots representative of the North eastern sector of Sinai. Although the contiguous stony cover prevented surface sealing by raindrops impact, runoff developed quite quickly on most slopes, and reached at peak discharge, after approximately ten minutes, up to 56 per cent of the rainfall. Differences between plots, in time lag, peak discharge and other hydrological variables, could be attributed mainly to the properties of the upper stony layer, with stone size as the most influential factor. Contrary to previous works, a positive relationship, was obtained between stone size to runoff yield. The result is explained by the process of water concentration. Each cobble and boulder behaves, on a smaller scale, like a bare rocky surface and yields per unit area water amounts beyond the infiltration rate of the limited uncovered areas. For a given stony cover the effect of water concentration is quicker with the big blocks than with gravels. A series of graphs trying to relate theoretically the relative importance of sealing and water concentration processes in runoff generation, at various conditions of stone cover and stone size, is proposed. The graphs enable to reconcile the results of the present study with those of previous works.

Small herbivores such as rabbits, pika and marmots create spatial patterns in vegetation around their burrows by grazing. This PhD thesis focuses on these refuge-living herbivores.By performing experiments with rabbits, he showed that looking for predators causes the spatial patterns: thiscostsmore foraging time as the burrow is farther, causing a preference for foraging close to the burrow. The animals can stay close to their burrow when the vegetation grows, but are forced to graze larger areas as plant growth declines, and are negatively affected by the seasonal deterioration of plant quality. Models predict that this will have repercussions for population density, but can be countered by large grazers. Ir. Dekker also showed that large grazers also affect refuge living herbivores through changes in vegetation structure: this alters the timing of their activity.The spatial variation in grazing by refuge living herbivores potentially increases variation in structure and diversity in the vegetation. That way, these small, refuge living herbivores are an important addition to large grazers.

The significance of the geological strata on desert runoff agriculture: Indications for stable desert environment over the last 1600 years in southern Israel

<p>Talus-pediment slopes are a common morphologic feature in arid areas and constitute a prominent runoff and sediment source at the watershed and channel scales. The evolution of talus-pediment sequences (talus flatirons) was often linked to climatic cycles, although the physical processes that may account for such a link remained obscure. Our approach is to integrate field measurements, high-resolution radar rainfall data and numerical modeling to link the frequency of storms and the resulted hillslope runoff and sediment transport. We present a quantitative hydrometeorological analysis of rainstorms and their geomorphic impact, potentially involved in the evolution of arid talus-pediment slopes in the Negev desert (Israel). Artificial rainstorms were designed based on intensity-duration-frequency curves and simulated in the field using a rainfall simulator. Then, the obtained experimental results were up-scaled to the entire slope length using a fully distributed hydrological model. In addition, natural storms and their hydro-geomorphic impacts were monitored using X-band radar and time-lapse cameras.</p><p>These integrated analyses constrain the rainfall threshold for local runoff generation at rain intensity of 14-22 mm h<sup>-1</sup> for a duration of 5 min for the study area conditions. We characterized small-scale runoff-generating convective rain cells using an X-band radar and found that small convective cells (~30 km<sup>2</sup>), having extremely high internal spatial gradients in rainfall intensity and low velocity (<10 m s<sup>-1</sup>), have the potential to generate local hillslope runoff. The frequency of local runoff-producing rainstorms is ~1-3 per year, but most of these storms activate only small parts of the hillslope. Modeling results indicate that a full extent hillslope runoff occurs under much rarer rainstorms of at least 100-years return interval (1% or less). During such rainstorms, the shear stress produced by the runoff flow (sheetwash) is capable of transporting surface clasts at a distance of ~80 m downslope. However, transport of coarse clasts in the upper parts of the slopes is most probably gravitationally controlled. The erosion efficiency of discrete rare events (1% or less) on the lower part of the slopes highlights their potential to trigger incision and lead to cliff dissection. This study results support the hypothesis that a climatic shift in terms of the properties and frequency of extreme rainstorms, rather than the common views of it as changing precipitation means, can play an important role in shaping and in transforming landscapes in such arid setting.</p>

We explored the temporal and spatial variations in airborne Alternaria spore quantitative and phenological features in Europe using 23 sites with annual time series between 3 and 15 years. The study covers seven countries and four of the main biogeographical regions in Europe. The observations were obtained with Hirst-type spore traps providing time series with daily records. Site locations extend from Spain in the south to Denmark in the north and from England in the West to Poland in the East. The study is therefore the largest assessment ever carried out for Europe concerning Alternaria. Aerobiological data were investigated for temporal and spatial patterns in their start and peak season dates and their spore indices. Moreover, the effects of climate were checked using meteorological data for the same period, using a crop growth model. We found that local climate, vegetation patterns and management of landscape are governing parameters for the overall spore concentration, while the annual variations caused by weather are of secondary importance but should not be neglected. The start of the Alternaria spore season varies by several months in Europe, but the peak of the season is more synchronised in central-northern Europe in the middle of the summer, while many southern sites have peak dates either earlier or later than northern Europe. The use of a crop growth model to explain the start and peak of season suggests that such methods could be useful to describe Alternaria seasonality in areas with no available observations.

In terrestrial ecosystems of Maritime Antarctica (King George Island), the transference of primary marine production to the land promoted by penguins ( Pygoscelis adeliae) and other birds, appears to influence soil formation and chemical weathering to a greater extent than formerly predicted. This paper summarizes the results of pedological investigations on the vicinity of the American Pieter J. Lenie Field Station (62°10′ S, 58°28′ W), discussing soil formation processes related to vegetation succession in the studied area. Soil organic matter (SOM) accumulation and associated phosphatization are marked soil‐forming processes in ice‐free areas once colonized by penguins. Also there is a high correlation between soil development and vegetation patterns. Nutrient supply in these cryogenic soils is affected by low pH following nitrification and high contents of P, K, Ca, and Mg due to seabirds' inputs. Lithic Umbriturbels and Glacic Haploturbels are the most common ornithogenic soils, followed by Lithic Fibristels and Psammentic Aquiturbels. In all soils phosphatization and ornithogenesis occurs in varying degrees. However, the recent Gelisols order of Soil Taxonomy does not consider the influence of ornithogenesis or phosphatization in its framework, so that a more detailed classification of such soils is not possible.

Determination, localized and frequency control and distribution condition of Gastropod species in several sedimentary environment in Miankaleh territory, and their temporal and spatial variation by Caspian rapid sea level change are the main targets in this research. By selecting 8 measuring transects along the study area, 24 sediment samples and 8 water samples have been taken for biofacies and chemical properties analysis. At parallel of above mentioned subject, deformation and displacement degree of shore line of theCaspian Seaduring 38 years was evaluated by remote sensing and GIS modeling. The results show that the most important species of Gastropod totally include: 10 species associated to 3 genera of two family of Prosobranshia. Also some species of Gastropod was selected due to sedimentary environment bioindicators. Water chemical quality and quantity indicate that the salinity, EC, pH degree is different in several parts of study area. Sediments grain size gradually has decreased from the West to East region of Miankaleh territory. Instead of in the same direction near to Gorgan Golf shore line the sediment particles size have been increased. Gastropod species accumulation and concentration tendency convert to high population in saline low land and lagoon with shallow depth and gentle slope of bottom. The correlation of information layers of Gastropod species location map with shore line displacement in GIS modeling indicate vital variation more in the central and east part of Miankaleh.

Vegetation plays a very important role of carbon (C) sinks in the global C cycle. With its complex terrain and diverse vegetation types, the Lancang River Basin (LRB) of southwest China has huge C storage capacity. Therefore, understanding the spatial variations and controlling mechanisms of vegetation C storage is important to understand the regional C cycle. In this study, data from a forest inventory and field plots were used to estimate and map vegetation C storage distribution in the LRB, to qualify the quantitative relationships between vegetation C density and altitude at sublot and township scale, and a linear model or polynomial model was used to identify the relationship between C density and altitude at two spatial scales and two statistical scales. The results showed that a total of 300.32 Tg C was stored in the LRB, an important C sink in China. The majority of C storage was contributed by forests, notably oaks. The vegetation C storage exhibited nonlinear variation with latitudinal gradients. Altitude had tremendous influences on spatial patterns of vegetation C storage of three geomorphological types in the LRB. C storage decreased with increasing altitude at both town and sublot scales in the flat river valley (FRV) region and the mid-low mountains gorge (MMG) region, and first increased then decreased in the alpine gorge (AG) region. This revealed that, in southwest China, altitude changes the latitudinal patterns of vegetation C storage; especially in the AG area, C density in the mid-altitude (3100 m) area was higher than that of adjacent areas.