Sample records for biological soil crusts

  1. Biological soil crust community types differ in key ecological functions

    Pietrasiak, N; Regus, JU; Johansen, JR; LAM, D.; Sachs, JL; Santiago, LS


    Soil stability, nitrogen and carbon fixation were assessed for eight biological soil crust community types within a Mojave Desert wilderness site. Cyanolichen crust outperformed all other crusts in multi-functionality whereas incipient crust had the poorest performance. A finely divided classification of biological soil crust communities improves estimation of ecosystem function and strengthens the accuracy of landscape-scale assessments. © 2013 Elsevier Ltd.

  2. Biological soil crusts in post-mining areas

    Lukešová, Alena; Zahradníková, M.; Frouz, J.

    Boca Raton : Taylor & Francis CRC Press, 2013, s. 53-65. ISBN 978-1-4665-9931-4 Institutional support: RVO:60077344 Keywords : biological soil crusts * post-mining areas Subject RIV: DF - Soil Science

  3. Researchers Reveal Ecological Roles of Biological Soil Crusts in Desert


    @@ Biological soil crust is a complex organic integrity of cyanobacteria, green algae, lichens and mosses, fungi, and other bacteria. This is a common and widespread phenomenon in desert areas all over the world. Biologically,this kind of soil crust differs a lot from physical ones in terms of physical and chemical properties, and become important biological factors in vegetation succession. Despite its unassuming appearance, the crust plays a significant role in the desert ecosystem, involving the process of soil formation, stability and fertility,the prevention of soil erosion by water or wind, the increased possibility of vascular plants colonization, and the stabilization of sand dunes.

  4. Vulnerability of desert biological soil crusts to wind erosion: The influences of crust development, soil texture, and disturbance

    Belnap, J.; Gillette, Dale A.


    Biological soil crusts, consisting of cyanobacteria, green algae, lichens, and mosses, are important in stabilizing soils in semi-arid and arid lands. Integrity of these crusts is compromised by compressional disturbances such as foot, vehicle, or livestock traffic. Using a portable wind tunnel, we found threshold friction velocities (TFVs) of undisturbed crusts well above wind forces experienced at these sites; consequently, these soils are not vulnerable to wind erosion. However, recently disturbed soils or soils with less well-developed crusts frequently experience wind speeds that exceed the stability thresholds of the crusts. Crustal biomass is concentrated in the top 3 mm of soils. Sandblasting by wind can quickly remove this material, thereby reducing N and C inputs from these organisms. This loss can result in reduced site productivity, as well as exposure of unprotected subsurface sediments to wind and water erosion. Actions to reduce impacts to these crusts can include adjustments in type, intensity, and timing of use.

  5. Reconstruction of food webs in biological soil crusts using metabolomics.

    Baran, Richard; Brodie, Eoin L.; Mayberry-Lewis, Jazmine; Nunes Da Rocha, Ulisses; Bowen, Benjamin P.; Karaoz, Ulas; Cadillo-Quiroz, Hinsby; Garcia-Pichel, Ferran; Northen, Trent R.


    Biological soil crusts (BSCs) are communities of organisms inhabiting the upper layer of soil in arid environments. BSCs persist in a dessicated dormant state for extended periods of time and experience pulsed periods of activity facilitated by infrequent rainfall. Microcoleus vaginatus, a non-diazotrophic filamentous cyanobacterium, is the key primary producer in BSCs in the Colorado Plateau and is an early pioneer in colonizing arid environments. Over decades, BSCs proceed through developmental stages with increasing complexity of constituent microorganisms and macroscopic properties. Metabolic interactions among BSC microorganisms probably play a key role in determining the community dynamics and cycling of carbon and nitrogen. However, these metabolic interactions have not been studied systematically. Towards this goal, exometabolomic analysis was performed using liquid chromatography coupled to tandem mass spectrometry on biological soil crust pore water and spent media of key soil bacterial isolates. Comparison of spent vs. fresh media was used to determine uptake or release of metabolites by specific microbes. To link pore water experiments with isolate studies, metabolite extracts of authentic soil were used as supplements for isolate exometabolomic profiling. Our soil metabolomics methods detected hundreds of metabolites from soils including many novel compounds. Overall, Microcoleus vaginatus was found to release and utilize a broad range of metabolites. Many of these metabolites were also taken up by heterotrophs but there were surprisingly few metabolites uptaken by all isolates. This points to a competition for a small set of central metabolites and specialization of individual heterotrophs towards a diverse pool of available organic nutrients. Overall, these data suggest that understanding the substrate specialization of biological soil crust bacteria can help link community structure to nutrient cycling.

  6. Spatial Pattern of Biological Soil Crust with Fractal Geometry

    Ospina, Abelardo; Florentino, Adriana; Tarquis, Ana M.


    Soil surface characteristics are subjected to changes driven by several interactions between water, air, biotic and abiotic components. One of the examples of such interactions is provided through biological soil crusts (BSC) in arid and semi-arid environments. BSC are communities composed of cyanobacteria, fungi, mosses, lichens, algae and liverworts covering the soil surface and play an important role in ecosystem functioning. The characteristics and formation of these BSC influence the soil hydrological balance, control the mass of eroded sediment, increase stability of soil surface, and influence plant productivity through the modification of nitrogen and carbon cycle. This study focus on characterize the spatial arrangements of the BSC based on image analysis and fractal concepts. To this end, RGB images of different types of biological soil crust where taken, each image corresponding to an area of 3.6 cm2 with a resolution of 1024x1024 pixels. For each image and channel, mass dimension and entropy were calculated. Preliminary results indicate that fractal methods are useful to describe changes associated to different types of BSC. Further research is necessary to apply these methodologies to several situations.

  7. Impact of biological soil crusts and desert plants on soil microfaunal community composition

    Darby, B.J.; Neher, D.A.; Belnap, J.


    Carbon and nitrogen are supplied by a variety of sources in the desert food web; both vascular and non-vascular plants and cyanobacteria supply carbon, and cyanobacteria and plant-associated rhizosphere bacteria are sources of biological nitrogen fixation. The objective of this study was to compare the relative influence of vascular plants and biological soil crusts on desert soil nematode and protozoan abundance and community composition. In the first experiment, biological soil crusts were removed by physical trampling. Treatments with crust removed had fewer nematodes and a greater relative ratio of bacterivores to microphytophages than treatments with intact crust. However, protozoa composition was similar with or without the presence of crusts. In a second experiment, nematode community composition was characterized along a spatial gradient away from stems of grasses or shrubs. Although nematodes generally occurred in increasing abundance nearer to plant stems, some genera (such as the enrichment-type Panagrolaimus) increased disproportionately more than others (such as the stress-tolerant Acromoldavicus). We propose that the impact of biological soil crusts and desert plants on soil microfauna, as reflected in the community composition of microbivorous nematodes, is a combination of carbon input, microclimate amelioration, and altered soil hydrology. ?? Springer Science + Business Media B.V. 2009.

  8. Biological soil crusts: a fundamental organizing agent in global drylands

    Belnap, J.; Zhang, Y.


    Ecosystem function is profoundly affected by plant community composition, which is ultimately determined by factors that govern seed retention. Dryland ecosystems constitute ~35% of terrestrial surfaces, with most soils in these regions covered by biological soil crusts (biocrusts), a community whose autotrophs are dominated by cyanobacteria, lichens, and mosses. Studies at 550 sites revealed that plant community composition was controlled by the interaction among biocrust type, disturbance regime, and external morphology of seeds. In bare soils (due to disturbance), all seed types were present in the seedbank and plant community. As biocrusts became better developed (i.e., the cover of lichens and mosses increased), they more strongly filtered out seeds with appendages. Thus, soils under late successional biocrusts contained seedbanks dominated by smooth seeds and vascular plants growing in late successional biocrusts were dominated by those with smooth seeds. Therefore, the tension between the removal of biocrusts by soil surface disturbance and their recovery creates a shifting mosaic of plant patch types in both space and time. Because changes in vascular plant communities reverberate throughout both below ground and above ground food webs and thus affect multiple trophic levels, we propose that biocrusts are a fundamental organizing agent in drylands worldwide. Future increased demand for resources will intensify land use both temporally and spatially, resulting in an increased rate of biocrust loss across larger areas. As a result, we can expect shifts in the composition and distribution of plant communities, accompanied by concomitant changes in many aspects of dryland ecosystems. Conceptual model of shifting dryland plant mosaics through space and time. Within the large circles, soil surface type changes with time in the same space, going from bare uncrusted soil (B) to cyanobacterial biocrust (C) to lichen/moss (L/M) biocrust. Disturbance (D) drives the

  9. Six Siderophore-Producing Microorganisms Identified in Biological Soil Crusts

    Noonan, K.; Anbar, A. D.; Garcia-Pichel, F.; Poret-peterson, A. T.; Hartnett, H. E.


    Biological soil crusts (BSCs) are diverse microbial communities that colonize soils in arid and semi-arid environments. Cyanobacteria in BSCs are pioneer organisms that increase ecosystem habitability by providing fixed carbon (C) and nitrogen (N) as well as by reducing water run-off and increasing infiltration. Photosynthesis and N fixation, in particular, require a variety of metals in large quantities, and yet, metals are predominantly insoluble in the environments where BSCs thrive. Therefore, BSC organisms must have efficient strategies for extracting metals from soil minerals. We hypothesized that BSC microbes, particularly the cyanobacteria, produce siderophores to serve their metal-acquisition needs. Siderophores are small organic compounds that bind Fe with high affinity and are produced by a variety of microorganisms, including cyanobacteria. Most siderophores bind Fe, primarily; however, some can also bind Mo, V, and Cu. Soil siderophores are released by microbes to increase the solubility of metals from minerals and to facilitate microbial uptake. Thus, siderophores serve as chemical weathering agents and provide a direct link between soil microbes and minerals. Studying siderophore production in BSCs provides insight into how BSCs tackle the challenge of acquiring insoluble metals, and may help conservationists determine useful fertilizers for BSC growth by facilitating metal acquisition. Biological soil crusts were collected near Moab, UT. Soil slurries were prepared in deionized water and transferred to modified BG-11 agar plates. The O-CAS agar plate assay was used to screen organisms for siderophore production. Siderophore producing microbes were isolated and identified by16S rRNA gene sequencing. Cultures were then grown in 3 L batch cultures under metal limitation, and siderophore presence was monitored using the traditional liquid CAS assay. After siderophore detection, cells were removed by centrifugation, organic compounds were separated using

  10. Influence of Disturbance on Soil Respiration in Biologically Crusted Soil during the Dry Season

    Wei Feng


    Full Text Available Soil respiration (Rs is a major pathway for carbon cycling and is a complex process involving abiotic and biotic factors. Biological soil crusts (BSCs are a key biotic component of desert ecosystems worldwide. In desert ecosystems, soils are protected from surface disturbance by BSCs, but it is unknown whether Rs is affected by disturbance of this crust layer. We measured Rs in three types of disturbed and undisturbed crusted soils (algae, lichen, and moss, as well as bare land from April to August, 2010, in Mu Us desert, northwest China. Rs was similar among undisturbed soils but increased significantly in disturbed moss and algae crusted soils. The variation of Rs in undisturbed and disturbed soil was related to soil bulk density. Disturbance also led to changes in soil organic carbon and fine particles contents, including declines of 60–70% in surface soil C and N, relative to predisturbance values. Once BSCs were disturbed, Q10 increased. Our findings indicate that a loss of BSCs cover will lead to greater soil C loss through respiration. Given these results, understanding the disturbance sensitivity impact on Rs could be helpful to modify soil management practices which promote carbon sequestration.

  11. The influence of biological soil crusts on mineral uptake by associated vascular plants

    Harper, K.T.; Belnap, Jayne


    Soil surfaces dominated by cyanobacteria and cyanolichens (such as Collema sp.) are widespread in deserts of the world. The influence of these biological soil crusts on the uptake of bioessential elements is reported for the first time for six seed plants of the deserts of Utah. This sample almost doubles the number of species for which the influence of biological soil crusts on mineral uptake of associated vascular plants is known. These new case studies, and others previously published, demonstrate that cyanobacterial or cyanobacteria- Collema crusts significantly alter uptake by plants of many bioessential elements. In studies now available, these crusts always increase the N content of associated seed plants. Uptake of Cu, K, Mg, and Zn is usually (>70% of reported cases) increased in the presence of the biological soil crusts. Soil crusts are generally negatively associated with Fe and P levels in associated seed plant tissue, while plant tissue levels of Ca, Mn, and Na are positively as often as negatively associated with the presence of soil crusts. Increases in bioessential elements in vascular plant tissue from biologically-crusted areas are greatest for short-lived herbs that are rooted primarily within the surface soil, the horizon most influenced by crustal organisms. The mineral content of a deeply rooted shrub (Coleogyne ramosissima) was less influenced by co-occurrence of biological soil crusts.

  12. Biological soil crust succession impact on soil moisture and temperature in the sub-surface along a rainfall gradient

    Zaady, E.; Yizhaq, H.; Ashkenazy, Y.


    Biological soil crusts produce mucilage sheets of polysaccharides that cover the soil surface. This hydrophobic coating can seal the soil micro-pores and thus cause reduction of water permeability and may influence soil temperature. This study evaluates the impact of crust composition on sub-surface water and temperature over time. We hypothesized that the successional stages of biological soil crusts, affect soil moisture and temperature differently along a rainfall gradient throughout the year. Four experimental sites were established along a rainfall gradient in the western Negev Desert. At each site three treatments; crust removal, pure sand (moving dune) and natural crusted were monitored. Crust successional stage was measured by biophysiological and physical measurements, soil water permeability by field mini-Infiltrometer, soil moisture by neutron scattering probe and temperature by sensors, at different depths. Our main interim conclusions from the ongoing study along the rainfall gradient are: 1. the biogenic crust controls water infiltration into the soil in sand dunes, 2. infiltration was dependent on the composition of the biogenic crust. It was low for higher successional stage crusts composed of lichens and mosses and high with cyanobacterial crust. Thus, infiltration rate controlled by the crust is inverse to the rainfall gradient. Continuous disturbances to the crust increase infiltration rates, 3. despite the different rainfall amounts at the sites, soil moisture content below 50 cm is almost the same. We therefore predict that climate change in areas that are becoming dryer (desertification) will have a positive effect on soil water content and vice versa.

  13. [Diversity of nitrogen-fixing microorganisms in biological soil crusts of copper mine wastelands].

    Zhan, Jing; Yang, Gui-De; Sun, Qing-Ye


    Biological soil crusts play an important role in increasing the accumulation of organic matter and nitrogen in re-vegetated mining wastelands. The diversity of nitrogen-fixing microorganisms in three types of biological soil crusts (algal crust, moss crust and algal-moss crust) from two wastelands of copper mine tailings were investigated by polymerase chain reaction-denaturing gradient gel electrophoresis, based on the nifH gene of diazotrophs, to investigate: The diversity of nifH gene in the crusts of mine wastelands, and whether and how the nifH gene diversity in the crusts could be affected by the development of plant communities. The algal crust on the barren area displayed the highest nifH gene diversity, followed by the algal-moss crusts within vascular plant communities, and the moss crust displayed the lowest nifH gene diversity. The diversity of diazotrophs in algal-moss crust within vascular plant communities decreased with the increase of height and cover of vascular plant communities. No significant relationship was found between wasteland properties (pH, water content, contents of organic matter, nitrogen and phosphorus and heavy metal concentration) and nifH gene diversity in the crusts. Sequencing and phylogenetic analysis indicated that most nitrogen-fixing taxa in the crusts of mine wastelands belonged to Cyanobacteria, especially nonheterocystous filamentous Cyanobacteria. PMID:25223036

  14. Discussion on wind factor influencing the distribution of biological soil crusts on surface of sand dunes

    YongSheng Wu; Hasi Erdun; RuiPing Yin; Xin Zhang; Jie Ren; Jian Wang; XiuMin Tian; ZeKun Li; HengLu Miao


    Biological soil crusts are widely distributed in arid and semi-arid regions, whose formation and development have an important impact on the restoration process of the desert ecosystem. In order to explore the relationship between surface airflow and development characteristics of biological soil crusts, we studied surface airflow pattern and development characteristics of biological soil crusts on the fixed dune profile through field observation. Results indicate that the speed of near-surface airflow is the lowest at the foot of windward slope and the highest at the crest, showing an increasing trend from the foot to the crest. At the leeward side, although near-surface airflow increases slightly at the lower part of the slope after an initial sudden decrease at upper part of the slope, its overall trend decreases from the crest. Wind velocity variation coefficient varied at different heights over each observation site. The thickness, shear strength of biological soil crusts and percentage of fine particles at crusts layer decreased from the slope foot to the upper part, showing that biological soil crusts are less developed in high wind speed areas and well developed in low wind speed areas. It can be seen that there is a close relationship between the distribution of biological soil crusts in different parts of the dunes and changes in airflow due to geomorphologic variation.

  15. The microstructure and formation of biological soil crusts in their early developmental stage

    ZHANG Yuanming


    The biological soil crust serves as one of the biological factors contributing to the sand fixation in the Gurbantunggut Desert, the largest fixed and semi-fixed desert in China. This study was conducted to investigate the microstructure and formation of biological soil crusts which develop as a result of occurrence of cryptogams. One year after removal of biological soil crusts, the exposed surface could be fixed by bacteria, which make sand particles cohere by exopolysaccharides. The exopolysaccharides were mainly composed of glucose, mannitol, arabinose and galactose. The intension of pressure for this kind of crust is 13.42±1.38 Pa. After four-year recovery of the exposed sandy surface, the biological soil crust resulting from the colonization of soil surface by communities of filamentous cyanobacteria were mainly dominated by Microcoleus, which occurred as a cluster of filaments surrounded by a gelatinous sheath. At this developmental stage, the main contributors for sand fixation were changed from bacteria to filamentous cyanobacteria. Microscopic examination of this kind of crust revealed an intricate network of filamentous cyanobacteria and extracellular polymer secretions, which binds and entraps mineral particles and finer particles on the filament surface. These effects enhance soil cohesion and resistance to erosion. The intension of pressure for this kind of crust is 32.53±3.08 Pa.

  16. Lichen-moss interactions within biological soil crusts

    Ruckteschler, Nina; Williams, Laura; Büdel, Burkhard; Weber, Bettina


    Biological soil crusts (biocrusts) create well-known hotspots of microbial activity, being important components of hot and cold arid terrestrial regions. They colonize the uppermost millimeters of the soil, being composed of fungi, (cyano-) bacteria, algae, lichens, bryophytes and archaea in varying proportions. Biocrusts protect the (semi-) arid landscape from wind and water erosion, and also increase water holding capacity and nutrient content. Depending on location and developmental stage, composition and species abundance vary within biocrusts. As species live in close contact, they are expected to influence each other, but only a few interactions between different organisms have so far been explored. In the present study, we investigated the effects of the lichen Fulgensia fulgens whilst growing on the moss Trichostomum crispulum. While 77% of Fulgensia fulgens thalli were found growing associated with mosses in a German biocrust, up to 95% of Fulgensia bracteata thalli were moss-associated in a Swedish biocrust. In 49% (Germany) and in 78% (Sweden) of cases, thalli were observed on the moss T. crispulum and less frequently on four and three different moss species. Beneath F. fulgens and F. bracteata thalli, the mosses were dead and in close vicinity to the lichens the mosses appeared frail, bringing us to the assumption that the lichens may release substances harming the moss. We prepared a water extract from the lichen F. fulgens and used this to water the moss thalli (n = 6) on a daily basis over a time-span of three weeks. In a control setup, artificial rainwater was applied to the moss thalli (n = 6). Once a week, maximum CO2 gas exchange rates of the thalli were measured under constant conditions and at the end of the experiment the chlorophyll content of the moss samples was determined. In the course of the experiment net photosynthesis (NP) of the treatment samples decreased concurrently with an increase in dark respiration (DR). The control samples

  17. Chlorophytes of biological soil crusts in Gurbantunggut Desert, Xinjiang Autonomous Region, China


    In this paper, chlorophytes collected from 253 biological soil crust samples in Gurbantunggut Desert in Xinjiang Autonomous Region, China were studied by field investigation and microscopical observation in lab. The flora composition, ecological distribution of chlorophytes in the desert and dynamic changes of species composition of chlorophytes in different developing stages of biological soil crusts are preliminarily analyzed. Results showed that there were 26 species belonging to 14 genera and 10 families, in which unicellular chlorophytes were dominant. There existed some differences in distribution of varied sand dune positions. The taxa of chlorophytes in leeward of sand dunes are most abundant, but the taxa in windward, interdune and the top of sand dunes reduced gradually. Chlorophytes were mainly distributed within the crust and the taxa of chlorophytes decrease obviously under the crust. In the devel-oping stages of the biological soil crust, species diversity of chlorophytes changed a little, but species composition pre-sented some differences. Chlorococcum humicola, Chlorella vulgaris, Chlamydomonas ovalis and Chlamydomonas sp. nearly existed in all developing stages of biological crusts. In several former stages of the biological soil crust there were spherical chlorophytes and filamentous ones. When moss crust formed, filamentous chlorophytes disappeared, such as Microspora and Ulothrix.

  18. Soil nematode communities are ecologically more mature beneath late- than early-successional stage biological soil crusts

    Darby, B.J.; Neher, D.A.; Belnap, J.


    Biological soil crusts are key mediators of carbon and nitrogen inputs for arid land soils and often represent a dominant portion of the soil surface cover in arid lands. Free-living soil nematode communities reflect their environment and have been used as biological indicators of soil condition. In this study, we test the hypothesis that nematode communities are successionally more mature beneath well-developed, late-successional stage crusts than immature, early-successional stage crusts. We identified and enumerated nematodes by genus from beneath early- and late-stage crusts from both the Colorado Plateau, Utah (cool, winter rain desert) and Chihuahuan Desert, New Mexico (hot, summer rain desert) at 0-10 and 10-30 cm depths. As hypothesized, nematode abundance, richness, diversity, and successional maturity were greater beneath well-developed crusts than immature crusts. The mechanism of this aboveground-belowground link between biological soil crusts and nematode community composition is likely the increased food, habitat, nutrient inputs, moisture retention, and/or environmental stability provided by late-successional crusts. Canonical correspondence analysis of nematode genera demonstrated that nematode community composition differed greatly between geographic locations that contrast in temperature, precipitation, and soil texture. We found unique assemblages of genera among combinations of location and crust type that reveal a gap in scientific knowledge regarding empirically derived characterization of dominant nematode genera in deserts soils and their functional role in a crust-associated food web. ?? 2006 Elsevier B.V. All rights reserved.

  19. Impacts of biological soil crust disturbance and composition on C and N loss from water erosion

    Barger, N.N.; Herrick, J.E.; Van Zee, J.; Belnap, J.


    In this study, we conducted rainfall simulation experiments in a cool desert ecosystem to examine the role of biological soil crust disturbance and composition on dissolved and sediment C and N losses. We compared runoff and sediment C and N losses from intact late-successional dark cyanolichen crusts (intact) to both trampled dark crusts (trampled) and dark crusts where the top 1 cm of the soil surface was removed (scraped). In a second experiment, we compared C and N losses in runoff and sediments in early-successional light cyanobacterial crusts (light) to that of intact late-successional dark cyanolichen crusts (dark). A relatively high rainfall intensity of approximately 38 mm per 10-min period was used to ensure that at least some runoff was generated from all plots. Losses of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and ammonium (NH 4+ ) were significantly higher from trampled plots as compared to scraped and intact plots. Sediment C and N losses, which made up more than 98% of total nutrient losses in all treatments, were more than 4-fold higher from trampled plots relative to intact plots (sediment C g/m2, intact = 0.74, trampled = 3.47; sediment N g/m2, intact = 0.06, trampled = 0.28). In light crusts, DOC loss was higher relative to dark crusts, but no differences were observed in dissolved N. Higher sediment loss in light crusts relative to dark crusts resulted in 5-fold higher loss of sediment-bound C and N. Total C flux (sediment + dissolved) was on the order of 0.9 and 7.9 g/m2 for dark and light crusts, respectively. Sediment N concentration in the first minutes after runoff from light crusts was 3-fold higher than the percent N of the top 1 cm of soil, suggesting that even short-term runoff events may have a high potential for N loss due to the movement of sediments highly enriched in N. Total N loss from dark crusts was an order of magnitude lower than light crusts (dark = 0.06 g N/m2, light = 0.63 g/m2). Overall, our

  20. Biological soil crusts in subtropical China and their influence on initial soil erosion

    Seitz, Steffen; Goebes, Philipp; Kühn, Peter; Scholten, Thomas


    Soil is one of the most valuable resources we have on our planet. The erosion of this resource is a major environmental problem, in particular in subtropical China where high rainfall intensity causes severe and continuous soil losses. One of the main mechanisms controlling soil erosion is surface coverage, typically by vegetation, litter, stones and biological soil crusts (BSCs). BSCs play significant functional roles in soil systems, such as accelerating soil formation, changing water and nutrient cycling rates, enhancing soil stability and thus preventing erosion by wind or water. In initial ecosystems, cyanobacteria, algae, fungi, mosses and lichens are the first organisms to colonize the substrate; they form a biological crust within the first millimetres of the surface. BSCs and their effect on erosion are rarely mentioned in literature and most of the work done focussed on arid and semi-arid environments. This study aims to investigate the role of BSCs controlling the amount of runoff generated and sediment detached during soil erosion events in an initial ecosystem in subtropical China. The study took place on a deforested experimental site (BEF China) near Xingangshan, Jiangxi Province, PR China. We used a total number of 350 runoff plots (ROP, 40cmx40cm) to measure sediment discharge and surface runoff. BSC cover in each ROP was determined photogrammetrically in 4 time steps (autumn 2011, spring 2012, summer 2012 and summer 2013). Perpendicular images were taken and then processed to measure the coverage of BSCs using a 1 cm² digital grid overlay. Additionally BSCs were sampled in the field and identified by their taxonomy. In our ROPs we found 65 different moos, algae and lichen species, as well as cyanobacteria's. Mean BSC cover per ROP in 2013 was 17 % with a maximum of 62 % and a minimum of 0 %. Compared to stone cover with 3 %, our findings highlight the role of BSC in soil erosion processes. The total BSC covered area is slightly decreasing since

  1. Dew formation on the surface of biological soil crusts in central European sand ecosystems

    T. Fischer


    Full Text Available Dew formation was investigated in three developmental stages of biological soil crusts (BSC, which were collected along a catena of an inland dune and in the initial substrate. The Penman equation, which was developed for saturated surfaces, was modified for unsaturated surfaces and used for prediction of dewfall rates. The levels of surface saturation required for this approach were predicted using the water retention functions and the thicknesses of the BSCs. During a first field campaign (2–3 August 2011, dewfall increased from 0.042 kg m−2 for the initial sandy substrate to 0.058, 0.143 and 0.178 kg m−2 for crusts 1 to 3, respectively. During a second field campaign (17–18 August 2011, where dew formation was recorded in 1.5 to 2.75-h intervals after installation at 21:30 CEST, dewfall increased from 0.011 kg m−2 for the initial sandy substrate to 0.013, 0.028 and 0.055 kg m−2 for crusts 1 to 3, respectively. Dewfall rates remained on low levels for the substrate and for crust 1, and decreased overnight for crusts 2 and 3 (with crust 3 > crust 2 > crust 1 throughout the campaign. Dew formation was well reflected by the model response. The suggested mechanism of dew formation involves a delay in water saturation in near-surface soil pores and extracellular polymeric substances (EPS where the crusts were thicker and where the water capacity was high, resulting in elevated vapor flux towards the surface. The results also indicate that the amount of dewfall was too low to saturate the BSCs and to observe water flow into deeper soil. Analysis of the soil water retention curves revealed that, despite the sandy mineral matrix, moist crusts clogged by swollen EPS pores exhibited a clay-like behavior. It is hypothesized that BSCs gain double benefit from suppressing their competitors by runoff generation and from improving their water supply by dew collection. Despite higher amounts of dew, the

  2. Dew formation on the surface of biological soil crusts in central European sand ecosystems

    T. Fischer


    Full Text Available Dew formation was investigated in three developmental stages of biological soil crusts (BSC, which were collected along a catena of an inland dune and in the initial substrate. The Penman equation, which was developed for saturated surfaces, was modified for unsaturated surfaces and used for prediction of dewfall rates. The levels of surface saturation required for this approach were predicted using the water retention functions and the thicknesses of the BSCs. During a single event, dewfall increased with crust development from 0.08 kg m−2 for the initial substrate to 0.10, 0.20 and 0.25 kg m−2 for crusts stages 1 to 3, respectively, which was well reflected by the model response. The suggested mechanism of dew formation involves a delay in water saturation in near-surface soil pores and EPS where the crusts were thicker and where the water capacity was high, resulting in elevated vapor flux towards the surface. The results also indicate that the amount of dewfall was too low to observe water flow into deeper soil. Analysis of the soil water retention curves revealed that, despite the sandy mineral matrix, moist crusts with clogged by swollen EPS pores exhibited a clay-like behavior. It is hypothesized that BSCs gain double benefit from suppressing their competitors by runoff generation and from improving their water supply by dew collection. Despite higher amounts of dew, the water availability to the crust community decreases with crust development, which may be compensated by ecophysiological adaptation of crust organisms, and which may further suppress higher vegetation or mosses.

  3. Geomorphic controls on biological soil crust distribution: A conceptual model from the Mojave Desert (USA)

    Williams, Amanda J.; Buck, Brenda J.; Soukup, Deborah A.; Merkler, Douglas J.


    Biological soil crusts (BSCs) are bio-sedimentary features that play critical geomorphic and ecological roles in arid environments. Extensive mapping, surface characterization, GIS overlays, and statistical analyses explored relationships among BSCs, geomorphology, and soil characteristics in a portion of the Mojave Desert (USA). These results were used to develop a conceptual model that explains the spatial distribution of BSCs. In this model, geologic and geomorphic processes control the ratio of fine sand to rocks, which constrains the development of three surface cover types and biogeomorphic feedbacks across intermontane basins. (1) Cyanobacteria crusts grow where abundant fine sand and negligible rocks form saltating sand sheets. Cyanobacteria facilitate moderate sand sheet activity that reduces growth potential of mosses and lichens. (2) Extensive tall moss-lichen pinnacled crusts are favored on early to late Holocene surfaces composed of mixed rock and fine sand. Moss-lichen crusts induce a dust capture feedback mechanism that promotes further crust propagation and forms biologically-mediated vesicular (Av) horizons. The presence of thick biogenic vesicular horizons supports the interpretation that BSCs are long-lived surface features. (3) Low to moderate density moss-lichen crusts grow on early Holocene and older geomorphic surfaces that display high rock cover and negligible surficial fine sand. Desert pavement processes and abiotic vesicular horizon formation dominate these surfaces and minimize bioturbation potential. The biogeomorphic interactions that sustain these three surface cover trajectories support unique biological communities and soil conditions, thereby sustaining ecological stability. The proposed conceptual model helps predict BSC distribution within intermontane basins to identify biologically sensitive areas, set reference conditions for ecological restoration, and potentially enhance arid landscape models, as scientists address impacts

  4. Effects of Altered Temperature & Precipitation on Soil Bacterial & Microfaunal Communities as Mediated by Biological Soil Crusts

    Neher, Deborah A. [University of Vermont


    With increased temperatures in our original pot study we observed a decline in lichen/moss crust cover and with that a decline in carbon and nitrogen fixation, and thus a probable decline of C and N input into crusts and soils. Soil bacteria and fauna were affected negatively by increased temperature in both light and dark crusts, and with movement from cool to hot and hot to hotter desert climates. Crust microbial biomass and relative abundance of diazotrophs was reduced greatly after one year, even in pots that were not moved from their original location, although no change in diazotroph community structure was observed. Populations of soil fauna moved from cool to hot deserts were affected more negatively than those moved from hot to hotter deserts.

  5. Stabilization of Desert Surfaces and Accumulation of Dust Under Biological Soil Crusts

    Finstad, K. M.; Mcnicol, G.; Pfeiffer, M.; Amundson, R.


    Biological soil crusts (BSC) are known to play a critical role in the stabilization of desert surfaces by helping to protect sediment from wind and water erosion and aiding in the trapping of airborne particles. The crusts are often composed of cyanobacteria, algae, and fungi, and occupy the upper few cm of a soil. Due to their high tolerance of desiccation and ability to utilize fog and dew sources, BSC are able to exist in environments that may otherwise be too dry for vascular plants. In the hyperarid Atacama Desert, decades or more between measurable precipitation events has created a landscape devoid of macroscopic life. While precipitation is rare, coastal fog occurs regularly and microbial communities capable of utilizing fog and dew water are able to persist. Here we found cyanobacteria and lichen living in association with a thin sulfate and dust crust (~2 cm) covering the surface of 'dust plateaus'. Topographically the region is highly irregular and part of a largely erosional landscape. We hypothesized that these flat-topped plateaus are accretionary features that have been able to maintain dust accumulation for thousands of years as a result of the surface crusts. To test this hypothesis we conducted radiocarbon analysis of crusts and soil profiles at two sites approximately 30 km apart, one in a high fog zone and another in lower fog frequency zone. The radiocarbon analysis shows that sediment has been accumulating in the 'plateaus' for the past 15,000 years and that biological activity and rates of C cycling in the crust increase with increasing fog frequency and intensity. The ages of organic material in the dust decrease monotonically with decreasing soil thickness, suggestive of progressive upward growth by dust accumulation. Our data indicate that the BSC are capable of surviving in hyperarid the Atacama Desert, a Mars analogue, through the utilization of fog water, and that their presence can leave a visible geomorphic imprint on the landscape.

  6. Rapid recovery of cyanobacterial pigments in desiccated biological soil crusts following addition of water.

    Raeid M M Abed

    Full Text Available We examined soil surface colour change to green and hydrotaxis following addition of water to biological soil crusts using pigment extraction, hyperspectral imaging, microsensors and 13C labeling experiments coupled to matrix-assisted laser desorption and ionization time of flight-mass spectrometry (MALD-TOF MS. The topsoil colour turned green in less than 5 minutes following water addition. The concentrations of chlorophyll a (Chl a, scytonemin and echinenon rapidly increased in the top <1 mm layer while in the deeper layer, their concentrations remained low. Hyperspectral imaging showed that, in both wet and dehydrated crusts, cyanobacteria formed a layer at a depth of 0.2-0.4 mm and this layer did not move upward after wetting. 13C labeling experiments and MALDI TOF analysis showed that Chl a was already present in the desiccated crusts and de novo synthesis of this molecule started only after 2 days of wetting due to growth of cyanobacteria. Microsensor measurements showed that photosynthetic activity increased concomitantly with the increase of Chl a, and reached a maximum net rate of 92 µmol m-2 h-1 approximately 2 hours after wetting. We conclude that the colour change of soil crusts to green upon water addition was not due to hydrotaxis but rather to the quick recovery and reassembly of pigments. Cyanobacteria in crusts can maintain their photosynthetic apparatus intact even under prolonged periods of desiccation with the ability to resume their photosynthetic activities within minutes after wetting.

  7. A first record of biological soil crusts in the Cape Floristic Region

    Denise M. Mager


    Full Text Available To date, the biological soil crusts (BSCs of southern Africa are thought to be dominated mainly by cyanobacteria, with the exception of the lichen fields of the Namib Desert. Because soil microorganisms can physically modify, maintain or create habitat for other organisms – including soil biota and plants – they have been considered ecosystem engineers. Therefore, the presence of BSCs may be a good indicator of ecosystem resilience. Although BSCs are found throughout the world, recent work has suggested that the absence of BSCs in the fynbos of South Africa may be as a result of the inherent acidity of soils. We surveyed one area within the fynbos biome for the presence of BSCs and determined the relative cover of vegetation and different crust types. We found a widespread presence (up to 80% of surface soil of BSC communities in fynbos soils. We conclude that soil acidity may not be a constraining factor in the development of BSCs in fynbos soils and that previous reports on the absence of BSCs in fynbos soils may have been based on insufficient field observations. We encourage future studies in this region in order to determine the currently unexplored spatial distribution of soil microbial communities and the taxonomic composition of microorganisms in fynbos soils.

  8. Restoring the biological crust cover of soils across biomes in arid North America

    Garcia-Pichel, Ferran; Antoninka, Anita; Bowker, Matthew; Giraldo Silva, Ana; Nelson, Corey; Velasco Ayuso, Sergio; Barger, Nichole; Belnap, Jayne; Reed, Sasha; Duniway, Michael


    Biological soil crust communities provide important ecosystem services to arid lands, particularly regarding soil fertility and stability against erosion. In North America, and in many other areas of the globe, increasingly intense human activities, ranging from cattle grazing to military training, have resulted in the significant deterioration of biological soil surface cover of soils. With the intent of attaining sustainable land use practices, we are conducting a 5-year, multi-institutional research effort to develop feasible soil crusts restoration strategies for US military lands. We are including field sites of varying climatic regions (warm and cold deserts, in the Chihuahuan Desert and in the Great Basin, respectively) and varying edaphic characteristics (sandy and silty soils in each). We have multiple aims. First, we aim to establishing effective "biocrust nurseries" that produce viable and pedigreed inoculum, as a supply center for biocrust restoration and for research and development. Second, we aim to develop optimal field application methods of biocrust inoculum in a series of field trials. Currently in our second year of research, we will be reporting on significant advances made on optimizing methodologies for the large-scale supply of inoculum based on a) pedigreed laboratory cultures that match the microbial community structure of the original sites, and b) "in soil" biomass enhancement, whereby small amounts of local crusts are nursed under greenhouse conditions to yield hundred-fold increases in biomass without altering significantly community structure. We will also report on field trials for methodologies in field application, which included shading, watering, application of chemical polymers, and soil surface roughening. In a soon-to-be-initiated effort we also aim to evaluate soil and plant responses to biocrust restoration with respect to plant community structure, soil fertility, and soil stability, in multi-factorial field experiments. An

  9. Ecological succession, hydrology and carbon acquisition of biological soil crusts measured at the micro-scale.

    Tighe, Matthew; Haling, Rebecca E; Flavel, Richard J; Young, Iain M


    The hydrological characteristics of biological soil crusts (BSCs) are not well understood. In particular the relationship between runoff and BSC surfaces at relatively large (>1 m(2)) scales is ambiguous. Further, there is a dearth of information on small scale (mm to cm) hydrological characterization of crust types which severely limits any interpretation of trends at larger scales. Site differences and broad classifications of BSCs as one soil surface type rather than into functional form exacerbate the problem. This study examines, for the first time, some hydrological characteristics and related surface variables of a range of crust types at one site and at a small scale (sub mm to mm). X-ray tomography and fine scale hydrological measurements were made on intact BSCs, followed by C and C isotopic analyses. A 'hump' shaped relationship was found between the successional stage/sensitivity to physical disturbance classification of BSCs and their hydrophobicity, and a similar but 'inverse hump' relationship exists with hydraulic conductivity. Several bivariate relationships were found between hydrological variables. Hydraulic conductivity and hydrophobicity of BSCs were closely related but this association was confounded by crust type. The surface coverage of crust and the microporosity 0.5 mm below the crust surface were closely associated irrespective of crust type. The δ (13)C signatures of the BSCs were also related to hydraulic conductivity, suggesting that the hydrological characteristics of BSCs alter the chemical processes of their immediate surroundings via the physiological response (C acquisition) of the crust itself. These small scale results illustrate the wide range of hydrological properties associated with BSCs, and suggest associations between the ecological successional stage/functional form of BSCs and their ecohydrological role that needs further examination. PMID:23119058

  10. Effects of altered temperature and precipitation on desert protozoa associated with biological soil crusts

    Darby, B.J.; Housman, D.C.; Zaki, A.M.; Shamout, Y.; Adl, S.M.; Belnap, J.; Neher, D.A.


    Biological soil crusts are diverse assemblages of bacteria, cyanobacteria, algae, fungi, lichens, and mosses that cover much of arid land soils. The objective of this study was to quantify protozoa associated with biological soil crusts and test the response of protozoa to increased temperature and precipitation as is predicted by some global climate models. Protozoa were more abundant when associated with cyanobacteria/lichen crusts than with cyanobacteria crusts alone. Amoebae, flagellates, and ciliates originating from the Colorado Plateau desert (cool desert, primarily winter precipitation) declined 50-, 10-, and 100-fold, respectively, when moved in field mesocosms to the Chihuahuan Desert (hot desert, primarily summer rain). However, this was not observed in protozoa collected from the Chihuahuan Desert and moved to the Sonoran desert (hot desert, also summer rain, but warmer than Chihuahuan Desert). Protozoa in culture began to encyst at 37??C. Cysts survived the upper end of daily temperatures (37-55??C), and could be stimulated to excyst if temperatures were reduced to 15??C or lower. Results from this study suggest that cool desert protozoa are influenced negatively by increased summer precipitation during excessive summer temperatures, and that desert protozoa may be adapted to a specific desert's temperature and precipitation regime. ?? 2006 by the International Society of Protistologists.

  11. Carbon exchange in biological soil crust communities under differential temperatures and soil water contents: implications for global change

    Grote, Edmund E.; Belnap, Jayne; Housman, David C.; Sparks, Jed P.


    Biological soil crusts (biocrusts) are an integral part of the soil system in arid regions worldwide, stabilizing soil surfaces, aiding vascular plant establishment, and are significant sources of ecosystem nitrogen and carbon. Hydration and temperature primarily control ecosystem CO2 flux in these systems. Using constructed mesocosms for incubations under controlled laboratory conditions, we examined the effect of temperature (5-35 1C) and water content (WC, 20-100%) on CO2 exchange in light cyanobacterially dominated) and dark cyanobacteria/lichen and moss dominated) biocrusts of the cool Colorado Plateau Desert in Utah and the hot Chihuahuan Desert in New Mexico. In light crusts from both Utah and New Mexico, net photosynthesis was highest at temperatures 430 1C. Net photosynthesis in light crusts from Utah was relatively insensitive to changes in soil moisture. In contrast, light crusts from New Mexico tended to exhibit higher rates of net photosynthesis at higher soil moisture. Dark crusts originating from both sites exhibited the greatest net photosynthesis at intermediate soil water content (40-60%). Declines in net photosynthesis were observed in dark crusts with crusts from Utah showing declines at temperatures 425 1C and those originating from New Mexico showing declines at temperatures 435 1C. Maximum net photosynthesis in all crust types from all locations were strongly influenced by offsets in the optimal temperature and water content for gross photosynthesis compared with dark respiration. Gross photosynthesis tended to be maximized at some intermediate value of temperature and water content and dark respiration tended to increase linearly. The results of this study suggest biocrusts are capable of CO2 exchange under a wide range of conditions. However, significant changes in the magnitude of this exchange should be expected for the temperature and precipitation changes suggested by current climate models.

  12. Modelling and interpreting biologically crusted dryland soil sub-surface structure using automated micropenetrometry

    Hoon, Stephen R.; Felde, Vincent J. M. N. L.; Drahorad, Sylvie L.; Felix-Henningsen, Peter


    Soil penetrometers are used routinely to determine the shear strength of soils and deformable sediments both at the surface and throughout a depth profile in disciplines as diverse as soil science, agriculture, geoengineering and alpine avalanche-safety (e.g. Grunwald et al. 2001, Van Herwijnen et al. 2009). Generically, penetrometers comprise two principal components: An advancing probe, and a transducer; the latter to measure the pressure or force required to cause the probe to penetrate or advance through the soil or sediment. The force transducer employed to determine the pressure can range, for example, from a simple mechanical spring gauge to an automatically data-logged electronic transducer. Automated computer control of the penetrometer step size and probe advance rate enables precise measurements to be made down to a resolution of 10's of microns, (e.g. the automated electronic micropenetrometer (EMP) described by Drahorad 2012). Here we discuss the determination, modelling and interpretation of biologically crusted dryland soil sub-surface structures using automated micropenetrometry. We outline a model enabling the interpretation of depth dependent penetration resistance (PR) profiles and their spatial differentials using the model equations, σ {}(z) ={}σ c0{}+Σ 1n[σ n{}(z){}+anz + bnz2] and dσ /dz = Σ 1n[dσ n(z) /dz{} {}+{}Frn(z)] where σ c0 and σ n are the plastic deformation stresses for the surface and nth soil structure (e.g. soil crust, layer, horizon or void) respectively, and Frn(z)dz is the frictional work done per unit volume by sliding the penetrometer rod an incremental distance, dz, through the nth layer. Both σ n(z) and Frn(z) are related to soil structure. They determine the form of σ {}(z){} measured by the EMP transducer. The model enables pores (regions of zero deformation stress) to be distinguished from changes in layer structure or probe friction. We have applied this method to both artificial calibration soils in the

  13. Green algae in alpine biological soil crust communities: acclimation strategies against ultraviolet radiation and dehydration

    Karsten, Ulf; Holzinger, Andreas


    Green algae are major components of biological soil crusts in alpine habitats. Together with cyanobacteria, fungi and lichens, green algae form a pioneer community important for the organisms that will succeed them. In their high altitudinal habitat these algae are exposed to harsh and strongly fluctuating environmental conditions, mainly intense irradiation, including ultraviolet radiation, and lack of water leading to desiccation. Therefore, green algae surviving in these environments must ...

  14. Controls of biological soil crust cover and composition shift with succession in sagebrush shrub-steppe

    Dettweiler-Robinson, E.; Bakker, J.D.; Grace, J.B.


    Successional stage may determine strength and causal direction of interactions among abiotic and biotic factors; e.g., species that facilitate the establishment of other species may later compete with them. We evaluated multivariate hypotheses about abiotic and biotic factors shaping biological soil crusts (BSCs) in early and late successional stages. We surveyed vegetation and BSC in the shrub-steppe ecosystem of the Columbia Basin. We analyzed the relationships with bryophyte and lichen covers using structural equation models, and analyzed the relationships with BSC composition using Indicator Species Analysis and distance-based linear models. Cover, indicator species, and composition varied with successional stage. Increasing elevation and bryophyte cover had higher lichen cover early in succession; these relationships were negative in the later successional stage. Lichen cover did not appear to impede B. tectorum cover, but B. tectorum appeared to strongly negatively affect lichen cover in both stages. Biological soil crust composition varied with bunchgrass cover in the early successional stage, but with elevation and B. tectorum cover later in succession. Our findings support the hypotheses that as succession progresses, the strength and direction of certain community interactions shift, and B. tectorum leads to reductions in biological soil crust cover regardless of successional stage.

  15. Biological soil crusts reduce soil erosion in early successional subtropical forests in PR China

    Seitz, Steffen; Goebes, Philipp; Käppeler, Kathrin; Nebel, Martin; Webber, Carla; Scholten, Thomas


    Biological soil crusts (BSCs) have major influences on terrestrial ecosystems and play significant functional roles in soil systems, such as accelerating soil formation, changing water flows or enhancing soil stability. By that, they have the potential to protect soil surfaces against erosive forces by wind or water. However, the effect of BSCs on erosion processes is rarely mentioned in literature and most of the work done focused on arid and semi-arid environments. Furthermore, compared to the structure and function of BSCs, less attention was paid to their temporal and topographical distribution. This study aims to investigate the influence of BSCs on initial soil erosion, and their topographical development over time in initial subtropical forest ecosystems. Therefore, measurements have been conducted within a biodiversity and ecosystem functioning experiment (BEF China) near Xingangshan, Jiangxi Province, PR China. Interrill erosion was measured on 220 microscale run-off plots (ROPs, 0.4 m × 0.4 m) and the occurrence, distribution and development of BSCs within the measuring setup were recorded. BSC cover in each ROP was determined photogrammetrically in four time steps (autumn 2011, summer 2012, summer 2013 and summer 2014). BSC species were identified by morphological characteristics and classified to higher taxonomic levels. Higher BSC cover led to reduced sediment discharge and runoff volume due to its protection against splash energy, the adherence of soil particles and enhanced infiltration. Canopy ground cover and leaf area index had a positive effect on the development of BSC cover at this initial stage of the forest ecosystem. Moreover, BSC cover decreased with increasing slope, as we presume that developing BSCs are washed away more easily at steep gradients. Elevation and aspect did not show an influence. BSCs in this study were moss-dominated and 26 different moos species were found. Mean BSC cover on ROPs was 14 % in the 3rd year of the tree

  16. Species composition,distribution patterns and ecological functions of biological soil crusts in the Gurbantunggut Desert


    As one of the most important biological factors that maintain the stability of the largest fixed and semi-fixed desert in China,the Gurbantunggut Desert,the biological soil crusts (BSCs) develop well and play critical ecological roles in the desert ecosystem. In this paper,we briefly summarize our research findings since 2002 including species composition,distribution pattern and ecological functions of BSCs in the desert. Our results indicate abundant species diversity of BSCs in the Gurbantunggut Desert in comparison to other deserts in China. At the scales of sand dune or whole desert,the distribution patterns of BSCs are location-specific. The existence of BSCs in this desert could:(1) accelerate the formation of desert soil and the weathering of minerals; (2) accumulate organic matter in surface soil through related species in soil crusts; (3) enhance the abilities of sand surface to resist wind erosion; (4) influence seed germination of vascular plants; and (5) enhance the production of dew deposition on sandy soil surface.

  17. Revisiting classic water erosion models in drylands: The strong impact of biological soil crusts

    Bowker, M.A.; Belnap, J.; Bala, Chaudhary V.; Johnson, N.C.


    Soil erosion and subsequent degradation has been a contributor to societal collapse in the past and is one of the major expressions of desertification in arid regions. The revised universal soil loss equation (RUSLE) models soil lost to water erosion as a function of climate erosivity (the degree to which rainfall can result in erosion), topography, soil erodibility, and land use/management. The soil erodibility factor (K) is primarily based upon inherent soil properties (those which change slowly or not at all) such as soil texture and organic matter content, while the cover/management factor (C) is based on several parameters including biological soil crust (BSC) cover. We examined the effect of two more precise indicators of BSC development, chlorophyll a and exopolysaccharides (EPS), upon soil stability, which is closely inversely related to soil loss in an erosion event. To examine the relative influence of these elements of the C factor to the K factor, we conducted our investigation across eight strongly differing soils in the 0.8 million ha Grand Staircase-Escalante National Monument. We found that within every soil group, chlorophyll a was a moderate to excellent predictor of soil stability (R2 = 0.21-0.75), and consistently better than EPS. Using a simple structural equation model, we explained over half of the variance in soil stability and determined that the direct effect of chlorophyll a was 3?? more important than soil group in determining soil stability. Our results suggest that, holding the intensity of erosive forces constant, the acceleration or reduction of soil erosion in arid landscapes will primarily be an outcome of management practices. This is because the factor which is most influential to soil erosion, BSC development, is also among the most manageable, implying that water erosion in drylands has a solution. ?? 2008 Elsevier Ltd.

  18. Rapidly restoring biological soil crusts and ecosystem functions in a severely disturbed desert ecosystem.

    Chiquoine, Lindsay P; Abella, Scott R; Bowker, Matthew A


    Restoring biological soil crusts (biocrusts) in degraded drylands can contribute to recovery of ecosystem functions that have global implications, including erosion resistance and nutrient cycling. To examine techniques for restoring biocrusts, we conducted a replicated, factorial experiment on recently abandoned road surfaces by applying biocrust inoculation (salvaged and stored dry for two years), salvaged topsoil, an abiotic soil amendment (wood shavings), and planting of a dominant perennial shrub (Ambrosia dumosa). Eighteen months after treatments, we measured biocrust abundance and species composition, soil chlorophyll a content and fertility, and soil resistance to erosion. Biocrust addition significantly accelerated biocrust recovery on disturbed soils, including increasing lichen and moss cover and cyanobacteria colonization. Compared to undisturbed controls, inoculated plots had similar lichen and moss composition, recovered 43% of total cyanobacteria density, had similar soil chlorophyll content, and exhibited recovery of soil fertility and soil stability. Inoculation was the only treatment that generated lichen and moss cover. Topsoil application resulted in partial recovery of the cyanobacteria community and soil properties. Compared to untreated disturbed plots, topsoil application without inoculum increased cyanobacteria density by 186% and moderately improved soil chlorophyll and ammonium content and soil stability. Topsoil application produced 22% and 51% of the cyanobacteria density g⁻¹ soil compared to undisturbed and inoculated plots, respectively. Plots not treated with either topsoil or inoculum had significantly lower cyanobacteria density, soil chlorophyll and ammonium concentrations, and significantly higher soil nitrate concentration. Wood shavings and Ambrosia had no influence on biocrust lichen and moss species recovery but did affect cyanobacteria composition and soil fertility. Inoculation of severely disturbed soil with native

  19. Cyanobacterial diversity of western European biological soil crusts along a latitudinal gradient.

    Williams, Laura; Loewen-Schneider, Katharina; Maier, Stefanie; Büdel, Burkhard


    Cyanobacteria associated with biological soil crusts (BSCs) have important attributes, such as nitrogen fixation and soil stabilisation. However, research on these organisms has been minimal, and their diversity and distribution throughout temperate Europe is currently unknown. The SCIN (Soil Crust International) project is a multidisciplinary research initiative that aims to achieve improved understanding of the BSCs of Europe, one facet being an investigation into the cyanobacterial communities of BSCs across a latitudinal gradient. Cyanobacteria assemblages were analysed by both morphological and molecular analysis. Two treatments were applied prior to DNA extraction, continued sample wetting and a dry sample process, and 16S ribosomal RNA (rRNA) amplicons were processed by Illumina MiSeq sequencing. The results reveal high and variable cyanobacterial diversity with each site showing a unique assemblage. Many common cyanobacterial genera, for example Nostoc and Microcoleus, were found in all sites but the abundances of different genera varied considerably. The polyphasic approach was found to be essential in recording the presence of important cyanobacteria that a single method itself did not highlight. The wet and dry treatments showed some differences in diversity, but mainly in abundance, this may suggest how cyanobacterial composition of BSCs changes with seasonal variability. PMID:27411981

  20. Climate change and physical disturbance manipulations result in distinct biological soil crust communities.

    Steven, Blaire; Kuske, Cheryl R; Gallegos-Graves, La Verne; Reed, Sasha C; Belnap, Jayne


    Biological soil crusts (biocrusts) colonize plant interspaces in many drylands and are critical to soil nutrient cycling. Multiple climate change and land use factors have been shown to detrimentally impact biocrusts on a macroscopic (i.e., visual) scale. However, the impact of these perturbations on the bacterial components of the biocrusts remains poorly understood. We employed multiple long-term field experiments to assess the impacts of chronic physical (foot trampling) and climatic changes (2°C soil warming, altered summer precipitation [wetting], and combined warming and wetting) on biocrust bacterial biomass, composition, and metabolic profile. The biocrust bacterial communities adopted distinct states based on the mechanism of disturbance. Chronic trampling decreased biomass and caused small community compositional changes. Soil warming had little effect on biocrust biomass or composition, while wetting resulted in an increase in the cyanobacterial biomass and altered bacterial composition. Warming combined with wetting dramatically altered bacterial composition and decreased Cyanobacteria abundance. Shotgun metagenomic sequencing identified four functional gene categories that differed in relative abundance among the manipulations, suggesting that climate and land use changes affected soil bacterial functional potential. This study illustrates that different types of biocrust disturbance damage biocrusts in macroscopically similar ways, but they differentially impact the resident soil bacterial communities, and the communities' functional profiles can differ depending on the disturbance type. Therefore, the nature of the perturbation and the microbial response are important considerations for management and restoration of drylands. PMID:26276111

  1. Biological Soil Crusts Influence Hydrologic Function Differently in Various Deserts And Future Climate and Land Use will Affect These Relationships

    Belnap, J.; Wilcox, B.; Barger, N.; Herrick, J.; van Soyoc, M.


    Biological soil crusts (biocrusts) can completely cover plant interspaces in dryland regions, and can constitute 70% or more of the living ground cover. In these areas, where precipitation is low and soils have low fertility, native plants often rely on intact biological soil crusts to provide water and nutrient flow to the broadly scattered vegetation. In cool desert systems, well-developed biocrusts (dominated by lichens and mosses) roughen the soil surface, increasing residence time of surface water flow. This results in increased and relatively homogenous infiltration of water into the soils. Filaments associated with cyanobacteria, fungi, mosses and lichens increase aggregate formation and stabilize soils, thus reducing sediment production, with well-developed biocrusts conferring much more stability on soils than less developed cyanobacterial dominated biocrusts. In hot and hyper-arid desert systems, biocrusts are generally less developed and dominated by cyanobacteria. These biocrusts generally increase runoff from plant interspaces to downslope vegetation. While reduced infiltration may seem to be negative, it can actually be advantageous to the downslope plants, as they may require small watersheds above them to provide the needed amount of water and nutrients required for their growth. Thus, infiltration and nutrient additions are more heterogenous than in cool desert systems. Soil surface disturbance and climate change have the potential to dramatically alter the species composition and thereby function of biological soil crusts in different deserts. Compressional disturbances results in reduced cover and a loss of lichen and moss species. Changes in climate regimes, such as an increase in temperature or a shift in the amount, timing, or intensity of rainfall, will influence the composition and physiological functioning of biological soil crusts, as various crust components have different photosynthetic and respiration responses to temperature and

  2. Identification of factors influencing the restoration of cyanobacteria-dominated biological soil crusts.

    Bu, Chongfeng; Wu, Shufang; Yang, Yongsheng; Zheng, Mingguo


    Biological soil crusts (BSCs) cover >35% of the Earth's land area and contribute to important ecological functions in arid and semiarid ecosystems, including erosion reduction, hydrological cycling, and nutrient cycling. Artificial rapid cultivation of BSCs can provide a novel alternative to traditional biological methods for controlling soil and water loss such as the planting of trees, shrubs, and grasses. At present, little is known regarding the cultivation of BSCs in the field due to lack of knowledge regarding the influencing factors that control BSCs growth. Thus, we determined the effects of various environmental factors (shade; watering; N, P, K, and Ca concentrations) on the growth of cyanobacteria-dominated BSCs from the Sonoran Desert in the southwestern United States. The soil surface changes and chlorophyll a concentrations were used as proxies of BSC growth and development. After 4 months, five factors were found to impact BSC growth with the following order of importance: NH4NO3 ≈ watering frequency>shading>CaCO3 ≈ KH2PO4. The soil water content was the primary positive factor affecting BSC growth, and BSCs that were watered every 5 days harbored greater biomass than those watered every 10 days. Groups that received NH4NO3 consistently exhibited poor growth, suggesting that fixed N amendment may suppress BSC growth. The effect of shading on the BSC biomass was inconsistent and depended on many factors including the soil water content and availability of nutrients. KH2PO4 and CaCO3 had nonsignificant effects on BSC growth. Collectively, our results indicate that the rapid restoration of BSCs can be controlled and realized by artificial "broadcasting" cultivation through the optimization of environmental factors. PMID:24625498

  3. Biological soil crusts emit large amounts of NO and HONO affecting the nitrogen cycle in drylands

    Tamm, Alexandra; Wu, Dianming; Ruckteschler, Nina; Rodríguez-Caballero, Emilio; Steinkamp, Jörg; Meusel, Hannah; Elbert, Wolfgang; Behrendt, Thomas; Sörgel, Matthias; Cheng, Yafang; Crutzen, Paul J.; Su, Hang; Pöschl, Ulrich; Weber, Bettina


    Dryland systems currently cover ˜40% of the world's land surface and are still expanding as a consequence of human impact and global change. In contrast to that, information on their role in global biochemical processes is limited, probably induced by the presumption that their sparse vegetation cover plays a negligible role in global balances. However, spaces between the sparse shrubs are not bare, but soils are mostly covered by biological soil crusts (biocrusts). These biocrust communities belong to the oldest life forms, resulting from an assembly between soil particles and cyanobacteria, lichens, bryophytes, and algae plus heterotrophic organisms in varying proportions. Depending on the dominating organism group, cyanobacteria-, lichen-, and bryophyte-dominated biocrusts are distinguished. Besides their ability to restrict soil erosion they fix atmospheric carbon and nitrogen, and by doing this they serve as a nutrient source in strongly depleted dryland ecosystems. In this study we show that a fraction of the nitrogen fixed by biocrusts is metabolized and subsequently returned to the atmosphere in the form of nitric oxide (NO) and nitrous acid (HONO). These gases affect the radical formation and oxidizing capacity within the troposphere, thus being of particular interest to atmospheric chemistry. Laboratory measurements using dynamic chamber systems showed that dark cyanobacteria-dominated crusts emitted the largest amounts of NO and HONO, being ˜20 times higher than trace gas fluxes of nearby bare soil. We showed that these nitrogen emissions have a biogenic origin, as emissions of formerly strongly emitting samples almost completely ceased after sterilization. By combining laboratory, field, and satellite measurement data we made a best estimate of global annual emissions amounting to ˜1.1 Tg of NO-N and ˜0.6 Tg of HONO-N from biocrusts. This sum of 1.7 Tg of reactive nitrogen emissions equals ˜20% of the soil release under natural vegetation according

  4. Activation of methanogenesis in arid biological soil crusts despite the presence of oxygen.

    Roey Angel

    Full Text Available Methanogenesis is traditionally thought to occur only in highly reduced, anoxic environments. Wetland and rice field soils are well known sources for atmospheric methane, while aerated soils are considered sinks. Although methanogens have been detected in low numbers in some aerated, and even in desert soils, it remains unclear whether they are active under natural oxic conditions, such as in biological soil crusts (BSCs of arid regions. To answer this question we carried out a factorial experiment using microcosms under simulated natural conditions. The BSC on top of an arid soil was incubated under moist conditions in all possible combinations of flooding and drainage, light and dark, air and nitrogen headspace. In the light, oxygen was produced by photosynthesis. Methane production was detected in all microcosms, but rates were much lower when oxygen was present. In addition, the δ(13C of the methane differed between the oxic/oxygenic and anoxic microcosms. While under anoxic conditions methane was mainly produced from acetate, it was almost entirely produced from H(2/CO(2 under oxic/oxygenic conditions. Only two genera of methanogens were identified in the BSC-Methanosarcina and Methanocella; their abundance and activity in transcribing the mcrA gene (coding for methyl-CoM reductase was higher under anoxic than oxic/oxygenic conditions, respectively. Both methanogens also actively transcribed the oxygen detoxifying gene catalase. Since methanotrophs were not detectable in the BSC, all the methane produced was released into the atmosphere. Our findings point to a formerly unknown participation of desert soils in the global methane cycle.

  5. Isolation of a significant fraction of non-phototroph diversity from a desert Biological Soil Crust

    Ulisses eNunes da Rocha


    Full Text Available Biological Soil Crusts (BSCs are organosedimentary assemblages comprised of microbes and minerals in topsoil of terrestrial environments. BSCs strongly impact soil quality in dryland ecosystems (e.g., soil structure and nutrient yields due to pioneer species such as Microcoleus vaginatus; phototrophs that produce filaments that bind the soil together, and support an array of heterotrophic microorganisms. These microorganisms in turn contribute to soil stability and biogeochemistry of BSCs. Non-cyanobacterial populations of BSCs are less well known than cyanobacterial populations. Therefore, we attempted to isolate a broad range of numerically significant and phylogenetically representative BSC aerobic heterotrophs. Combining simple pre-treatments (hydration of BSCs under dark and light and isolation strategies (media with varying nutrient availability and protection from oxidative stress we recovered 402 bacterial and one fungal isolate in axenic culture, which comprised 116 phylotypes (at 97% 16S rRNA gene sequence homology, 115 bacterial and one fungal. Each medium enriched a mostly distinct subset of phylotypes, and cultivated phylotypes varied due to the BSC pre-treatment. The fraction of the total phylotype diversity isolated, weighted by relative abundance in the community, was determined by the overlap between isolate sequences and OTUs reconstructed from metagenome or metatranscriptome reads. Together, more than 8% of relative abundance of OTUs in the metagenome was represented by our isolates, a cultivation efficiency much larger than typically expected from most soils. We conclude that simple cultivation procedures combined with specific pre-treatment of samples afford a significant reduction in the culturability gap, enabling physiological and metabolic assays that rely on ecologically relevant axenic cultures.

  6. Temporal-spatial dynamics of distribution patterns of microorganism relating to biological soil crusts in the Gurbantunggut Desert

    WU Nan; WANG Hongling; LIANG Shaoming; NIE Huali; ZHANG Yuanming


    Biological soil crusts serve as an important biological factor contributing to the sand fixation. This study was conducted to investigate the temporal-spatial variability of microorganism in crusts relating to locations, soil layers of sand dunes and seasons. At moss-dominated inter-dune areas,higher soil nutrient and water concentrations were likely to maintain the microbial activities. Bacteria showed the highest capabilities of settlement and growth in inter-dunes in both spring and autumn. Soil water content reached the highest value in soil crusts in the inter-dune areas, especially in spring. Variations of quantities of actinomyces and fungi basically showed the consistent trend in different locations of sand dunes. With the deepening of soil layers, vertical distribution of quantities of each microorganism group showed different characteristics because environmental factors fluctuated in both spring and autumn. Among different microorganism groups, bacteria were predominant, actinomyces the next and fungi the least in both spring and autumn in all soil layers (0-20 cm). The proportion of bacteria and soil water content were higher in spring than those in autumn in all soil layers (0-20 cm). No consistent trends were found in actinomyces and fungi. The results showed that the quantities of microorganisms were significantly positive correlated with organic matter content,soil water content, total N, total P, available P, available K, pH, electrical conductivity, total salt content,catalase, urease, phosphatase and alkaline phosphatase.

  7. Nitrogen fixation activity in biological soil crusts dominated by cyanobacteria in the Subpolar Urals (European North-East Russia).

    Patova, Elena; Sivkov, Michail; Patova, Anna


    The nitrogen fixation by biological soil crusts with a dominance of cyanobacteria was studied using the acetylene reduction assay in the territory of the Subpolar Urals (65°11' N, 60°18' E), Russia. The field measurements of nitrogen fixation activity were conducted in situ for two different types of soil crusts dominated by Stigonema (V1 type) and Nostoc with Scytonema (V2 type). The nitrogen fixation process had similar dynamics in both crusts but nitrogen fixation rates were different. The crusts of the V2 type showed a significantly higher acetylene reduction activity, with ethylene production rate of 1.76 ± 0.49 g C2H4 m(-2) h(-1) at 15°C, compared with V1-type soil crusts, with a rate of 0.53 ± 0.21 mg C2H4 m(-2) h(-1) at 15°C. The daily value of acetylene reduction activity in V2-type soil crusts was 32.7 ± 6.2 mg C2H4 m(-2) d(-1) and in V1-type crusts, 12.3 ± 1.8 mg C2H4 m(-2) d(-1) After recalculation for N, the daily values of nitrogen fixation were in the range 3.3-22.3 mg N m(-2) d(-1), which is a few times higher than the values of N input from the precipitation to the soil in the studied regions. The dependence of nitrogen-fixation activity on temperature and light intensity of biological soil crusts was investigated. On the basis of temperature models obtained from the dependence, the nitrogen balance was calculated for the growing season (approximately 120 days). The crusts dominated by Stigonema species were fixing 0.3 g N m(-2) (ethylene production rate, 1.10 g C2H4 m(-2)) and crusts dominated by Nostoc and Scytonema were fixing 1.3 g N m(-2) (4.10 g C2H4 m(-2)). PMID:27306556

  8. Biological Soil Crusts from Coastal Dunes at the Baltic Sea: Cyanobacterial and Algal Biodiversity and Related Soil Properties.

    Schulz, Karoline; Mikhailyuk, Tatiana; Dreßler, Mirko; Leinweber, Peter; Karsten, Ulf


    Biological soil crusts (BSCs) are known as "ecosystem-engineers" that have important, multifunctional ecological roles in primary production, in nutrient and hydrological cycles, and in stabilization of soils. These communities, however, are almost unstudied in coastal dunes of the temperate zone. Hence, for the first time, the biodiversity of cyanobacterial and algal dominated BSCs collected in five dunes from the southern Baltic Sea coast on the islands Rügen and Usedom (Germany) was investigated in connection with physicochemical soil parameters. The species composition of cyanobacteria and algae was identified with direct determination of crust subsamples, cultural methods, and diatom slides. To investigate the influence of soil properties on species composition, the texture, pH, electrical conductivity, carbonate content, total contents of carbon, nitrogen, phosphorus, and the bioavailable phosphorus-fraction (PO4 (3-)) were analyzed in adjacent BSC-free surface soils at each study site. The data indicate that BSCs in coastal dunes of the southern Baltic Sea represent an ecologically important vegetation form with a surprisingly high site-specific diversity of 19 cyanobacteria, 51 non-diatom algae, and 55 diatoms. All dominant species of the genera Coleofasciculus, Lyngbya, Microcoleus, Nostoc, Hydrocoryne, Leptolyngbya, Klebsormidium, and Lobochlamys are typical aero-terrestrial cyanobacteria and algae, respectively. This first study of coastal sand dunes in the Baltic region provides compelling evidence that here the BSCs were dominated by cyanobacteria, algae, or a mixture of both. Among the physicochemical soil properties, the total phosphorus content of the BSC-free sand was the only factor that significantly influenced the cyanobacterial and algal community structure of BSCs in coastal dunes. PMID:26507846

  9. Climate change and physical disturbance cause similar community shifts in biological soil crusts.

    Ferrenberg, Scott; Reed, Sasha C; Belnap, Jayne


    Biological soil crusts (biocrusts)—communities of mosses, lichens, cyanobacteria, and heterotrophs living at the soil surface—are fundamental components of drylands worldwide, and destruction of biocrusts dramatically alters biogeochemical processes, hydrology, surface energy balance, and vegetation cover. Although there has been long-standing concern over impacts of physical disturbances on biocrusts (e.g., trampling by livestock, damage from vehicles), there is increasing concern over the potential for climate change to alter biocrust community structure. Using long-term data from the Colorado Plateau, we examined the effects of 10 y of experimental warming and altered precipitation (in full-factorial design) on biocrust communities and compared the effects of altered climate with those of long-term physical disturbance (>10 y of replicated human trampling). Surprisingly, altered climate and physical disturbance treatments had similar effects on biocrust community structure. Warming, altered precipitation frequency [an increase of small (1.2 mm) summer rainfall events], and physical disturbance from trampling all promoted early successional community states marked by dramatic declines in moss cover and increases in cyanobacteria cover, with more variable effects on lichens. Although the pace of community change varied significantly among treatments, our results suggest that multiple aspects of climate change will affect biocrusts to the same degree as physical disturbance. This is particularly disconcerting in the context of warming, as temperatures for drylands are projected to increase beyond those imposed as treatments in our study. PMID:26371310

  10. Ecohydrology of biological soil crusts in arid sand dunes - integration from the micro-scale to the landscape

    Veste, M.; Yair, A.; Breckle, S.-W.; Littmann, T.


    Biological soil crusts are distributed in many ecosystems from the polar, boreal, temperate, and mediterranean to the tropical regions. They are typical in habitats where the vegetation cover is sparse and microclimatic conditions permit their development. They play an important role for ecosystem processes, enhancing surface stability, changing surface properties and influencing hydrological processes and water re-distribution. The spatial distribution and availability of the water resources are the important factors for the vegetation in drylands. Key questions are (i) how the hydrological processes of the BSC are triggering the vegetation pattern on the landscape level and (ii) how we can integrate the hydrological processes on the micro-scale into the landscape processes and patterns? We studied the interrelations between biological soil crusts and vegetation pattern in arid sand dunes of the north-western Negev. Most of the dunes are covered by biological soil crusts and various types can be distinguished in different exposition and along a 40 km geo-ecological gradient. Rainfall increases from approx. 90 mm in the south to 170 mm in the northern dunes. Biological crusts cover nearly 90% of the sand dunes of the northern Haluza sand field, whereas the parts of the southern dune crests are still mobile. Furthermore, soil lichens plays an important role in the northern dunes, covering 30%-90% of the interdune area as well as of the stable north-/northwest slopes. The surrounding dune slopes are covered by a biological crust with cyanobacteria, green algae, mosses. Upon wetting, infiltration decreases and runoff can be observed in crust cover areas, even in sand dunes. Runoff depends on rainfall intensity, soil thickness and composition. The change of surface properties counteracts the effects of increasing rainfall on the vegetation along the geo-ecological gradient. Because of the increase in soil crust thickness the infiltration rates decrease in the dune area

  11. Green algae in alpine biological soil crust communities: acclimation strategies against ultraviolet radiation and dehydration.

    Karsten, Ulf; Holzinger, Andreas


    Green algae are major components of biological soil crusts in alpine habitats. Together with cyanobacteria, fungi and lichens, green algae form a pioneer community important for the organisms that will succeed them. In their high altitudinal habitat these algae are exposed to harsh and strongly fluctuating environmental conditions, mainly intense irradiation, including ultraviolet radiation, and lack of water leading to desiccation. Therefore, green algae surviving in these environments must have evolved with either avoidance or protective strategies, as well as repair mechanisms for damage. In this review we have highlighted these mechanisms, which include photoprotection, photochemical quenching, and high osmotic values to avoid water loss, and in some groups flexibility of secondary cell walls to maintain turgor pressure even in water-limited situations. These highly specialized green algae will serve as good model organisms to study desiccation tolerance or photoprotective mechanisms, due to their natural capacity to withstand unfavorable conditions. We point out the urgent need for modern phylogenetic approaches in characterizing these organisms, and molecular methods for analyzing the metabolic changes involved in their adaptive strategies. PMID:24954980

  12. Weathering of Carbonate Rocks by Biological Soil Crusts in Karst Areas

    Ye Chen; Bin Lian; Zuoying Yin; Yuan Tang


    The weathering of carbonate rocks by biological soil crusts (BSC) in karst areas is very common. It is helpful to understand the weathering mechanisms and processes for avoiding karst rock-desertification. The weathering of carbonate rocks by BSC in karst areas, namely the expansion, contraction and curl resulting from environmental wetting-drying cycles, was investigated and ana-lyzed in this paper. The bulk density, area and thickness of BSC were determined and the weathering amount of limestone and dolomite per unit area of BSC was calculated as 3 700 and 3 400 g·m-2; the amount of biomass on the surface of limestone and dolomite was calculated as 1 146 and 1 301 g·m-2, respectively. Such an increased weathering amount was not only the result of chemical and physical weathering of BSC on carbonate rocks, but also the attachment and cementation of BSC to clay parti-cles, dust-fall, sand particles, solid particles brought by strong air currents, wind and other factors in the surrounding environment, which may also be related to the special environment and the special time period. Based on the results obtained, a weathering mode of BSC is studied, and the mechanisms of weathering by BSC are discussed. In conclusion, we suggest that the mechanical force exerted by the expansion and constriction of gelatinous and mucilaginous substances through wetting and drying of BSC play a significant role in the physical weathering process of the carbonate substrates.

  13. Nutrient availability affects pigment production but not growth in lichens of biological soil crusts

    Bowker, M.A.; Koch, G.W.; Belnap, J.; Johnson, N.C.


    Recent research suggests that micronutrients such as Mn may limit growth of slow-growing biological soil crusts (BSCs) in some of the drylands of the world. These soil surface communities contribute strongly to arid ecosystem function and are easily degraded, creating a need for new restoration tools. The possibility that Mn fertilization could be used as a restoration tool for BSCs has not been tested previously. We used microcosms in a controlled greenhouse setting to investigate the hypothesis that Mn may limit photosynthesis and consequently growth in Collema tenax, a dominant N-fixing lichen found in BSCs worldwide. We found no evidence to support our hypothesis; furthermore, addition of other nutrients (primarily P, K, and Zn) had a suppressive effect on gross photosynthesis (P = 0.05). We also monitored the growth and physiological status of our microcosms and found that other nutrients increased the production of scytonemin, an important sunscreen pigment, but only when not added with Mn (P = 0.01). A structural equation model indicated that this effect was independent of any photosynthesis-related variable. We propose two alternative hypotheses to account for this pattern: (1) Mn suppresses processes needed to produce scytonemin; and (2) Mn is required to suppress scytonemin production at low light, when it is an unnecessary photosynthate sink. Although Mn fertilization does not appear likely to increase photosynthesis or growth of Collema, it could have a role in survivorship during environmentally stressful periods due to modification of scytonemin production. Thus, Mn enrichment should be studied further for its potential to facilitate BSC rehabilitation. ?? 2008 Elsevier Ltd.

  14. Small scale spatial heterogeneity of Normalized Difference Vegetation Indices (NDVIs) and hot spots of photosynthesis in biological soil crusts

    T. Fischer; M. Veste; Andreas Eisele; Oliver Bens; W. Spyra; Reinhard F. J. Hüttl


    Normalized Difference Vegetation Indices (NDVIs) are typically determined using satellite or airborne remote sensing, or field portable spectrometers, which give an averaged signal on centimetre to metre scale plots. Biological soil crust (BSC) patches may have smaller sizes, and ecophysiological, hydrological as well as pedological processes may be heterogeneously distributed within this level of resolution. A ground-based NDVI imaging procedure using low-cost equipment (Olympus Camedia 5000...

  15. The effects of extracellular sugar extraction on the 3D-structure of biological soil crusts from different ecosystems

    Felde, Vincent; Rossi, Federico; Colesie, Claudia; Uteau-Puschmann, Daniel; Felix-Henningsen, Peter; Peth, Stephan; De Philippis, Roberto


    Biological soil crusts (BSCs) play important roles in the hydrological cycles of many different ecosystems around the world. In arid and semi-arid regions, they alter the availability and redistribution of water. Especially in early successional stage BSCs, this feature can be attributed to the presence and characteristics of extracellular polymeric substances (EPS) that are excreted by the crusts' organisms. In a previous study, the extraction of EPS from BSCs of the SW United States lead to a significant change in their hydrological behavior, namely the sorptivity of water (Rossi et al. 2012). This was concluded to be the effect of a change in the pore structure of these crusts, which is why in this work we investigated the effect of the EPS-extraction on soil structure using 3D-computed micro-tomography (µCT). We studied different types of BSCs from Svalbard, Germany, Israel and South Africa with varying grain sizes and species compositions (from green algae to light and dark cyanobacterial crusts with and without lichens and/or mosses). Unlike other EPS-extraction methods, the one utilized here is aimed at removing the extracellular matrix from crust samples whilst acting non-destructively (Rossi et al. 2012). For every crust sample, we physically cut out a small piece (1cm) from a larger sample contained in Petri dish, and scanned it in a CT at a high resolution (voxel edge length: 7µm). After putting it back in the dish, approximately in the same former position, it was treated for EPS-extraction and then removed and scanned again in order to check for a possible effect of the EPS-extraction. Our results show that the utilized EPS-extraction method had varying extraction efficiencies: while in some cases the amount removed was barely significant, in other cases up to 50% of the total content was recovered. Notwithstanding, no difference in soil micro-structure could be detected, neither in total porosity, nor in the distribution of pore sizes, the

  16. Condensation of water vapour on moss-dominated biological soil crust, NW China

    Xin-Ping Wang; Yan-Xia Pan; Rui Hu; Ya-Feng Zhang; Hao Zhang


    Characteristics of water vapour condensation, including the onset, duration, and amount of water vapour condensation on moss-dominated biological soil crust (BSC) and dune sand were studied under simulated conditions with varying air temperature and relative humidity. The simulations were performed in a plant growth chamber using an electronic balance recording the weight of condensation. There was a positive linear correlation between the water vapour condensation and relative humidity while the mean temperature was negatively linearly related to amounts of water vapour condensation for both soil surfaces. The amount of water vapour condensation on BSC and dune sand can be described by the difference between air temperature and dew point with an exponential function, indicating that when the difference of air temperature and dew point exceeds a value of 35.3°C, there will be zero water vapour condensed on BSC. In contrast, when the difference of air temperature and dew point exceeds a value of 20.4°C, the water vapour condensation will be zero for dune sand. In general, when the air is fully saturated with water and the dew point is equal to the current air temperature, the water vapour condensed on BSC attained its maximum value of 0.398 mm, whereas it was 0.058 mm for dune sand. In comparison, water vapour condensed on BSC was at a relatively high temperature and low relative humidity, while we did not detect water vapour condensation on the dune sand under the similar conditions. Physical and chemical analyses of the samples pointed to a greater porosity, high content of fine particles, and high salinity for BSC compared to the dune sand. These results highlight that soil physicochemical properties are the likely factors influencing the mechanism of water vapour condensation under specific meteorological conditions, as onset was earlier and the duration was longer for water vapour condensation on BSC in comparison with that of dune sand. This contributed to

  17. Bacterial diversity and community along the succession of biological soil crusts in the Gurbantunggut Desert, Northern China.

    Zhang, Bingchang; Kong, Weidong; Wu, Nan; Zhang, Yuanming


    Biological soil crusts (BSCs) are common and play critical roles in semi-arid and arid ecosystems. Bacteria, as an important community in BSCs, play critical roles in biochemical processes. However, how bacterial diversity and community change in different successional stages of BSCs is still unknown. We used 454 pyrosequencing of 16S rRNA to investigate the bacterial composition and community, and the relationships between bacterial composition and environmental factors were also explored. In different successional stages of BSCs, the number of bacteria operational taxonomic units (OTUs) detected in each sample ranged from 2572 to 3157. Proteobacteria, Cyanobacteria, Bacteroidetes were dominant in BSCs, followed by Firmicutes, Acidobacteria, and Actinobacteria. At the successional stages of BSCs, bacterial communities, OTU composition and their relative abundance notably differentiated, and Cyanobacteria, especially Microcoleus vaginatus, dominated algal crust and lichen crust, and were the main C-fixing bacteria in BSCs. Proteobacteria and Bacteroidetes increased with the development of BSCs. OTUs related to Planomicrobium Chinese, Desulfobulbus sp., Desulfomicrobium sp., Arthrobacter sp., and Ahhaerbacter sp. showed higher relative abundance in bare sand than other successional stages of BSCs, while relative abundance of Sphingomonas sp. Niastella sp., Pedobacter, Candidatus solobacter, and Streptophyta increased with the development of BSCs. In successional stages of BSCs, bacterial OTUs composition demonstrated strong correlations with soil nutrients, soil salts, and soil enzymes. Additionally, variation of bacterial composition led to different ecological function. In bare sand, some species were related with mineral metabolism or promoting plant growth, and in algal crust and lichen crust, C-fixing bacteria increased and accumulated C to the desert soil. In later developed stage of BSCs, bacteria related with decomposition of organic matter, such as

  18. Climatic and Grazing Controls on Biological Soil Crust Nitrogen Fixation in Semi-arid Ecosystems

    Schwabedissen, S. G.; Reed, S.; Lohse, K. A.; Magnuson, T. S.


    Nitrogen, next to water, is believed to be the main limiting resource in arid and semi-arid ecosystems. Biological soil crusts (biocrusts) -a surface community of mosses, lichens and cyanobacteria-have been found to be the main influx of "new" nitrogen (N) into many dryland ecosystems. Controls on biocrust N fixation rates include climate (temperature and moisture), phosphorus availability, and disturbance factors such as trampling, yet a systematic examination of climatic and disturbance controls on biocrusts communities is lacking. Biocrust samples were collected along an elevation gradient in the Reynolds Creek Experimental Watershed near Murphy, Idaho. Four sites were selected from a sagebrush steppe ecosystem with precipitation ranging from ≤250mm/yr to ≥1100mm/yr. Each site included 5 grazed plots and one historic exclosure plot that has been free from grazing for more than 40 years. Five samples each were collected from under plants and from interplant spaces from the grazed plots and exclosures and analyzed for potential N fixation using an acetylene reduction assay. We hypothesized that N fixation rates would be the highest in the exclosures of the two middle sites along the elevation gradient, due to the lack of disturbance and optimal temperature and moisture, respectively. As predicted, results showed higher rates of potential N fixation in exclosures than non-exclosures at a mid-elevation 8.4 ± 3.1 kg N/ha/yr in the exclosures compared to 1.8 ± 1.5 kg N/ha/yr indicating that grazing may reduce N fixation activity. Interestingly, rates were 2-5 times lower under plant canopies compared to interplant spaces at all but the highest elevation site. Findings from our study suggest that biocrust N fixation may be a dominant input of N into theses dryland systems and, in line with our hypotheses, that climate, location within the landscape, and disturbance may interact to regulate the rates of this fundamental ecosystem process.

  19. Common and distinguishing features of the bacterial and fungal communities in biological soil crusts and shrub root zone soils

    Steven, Blaire; Gallegos-Graves, La Verne; Yeager, Chris; Belnap, Jayne; Kuske, Cheryl R.


    Soil microbial communities in dryland ecosystems play important roles as root associates of the widely spaced plants and as the dominant members of biological soil crusts (biocrusts) colonizing the plant interspaces. We employed rRNA gene sequencing (bacterial 16S/fungal large subunit) and shotgun metagenomic sequencing to compare the microbial communities inhabiting the root zones of the dominant shrub, Larrea tridentata (creosote bush), and the interspace biocrusts in a Mojave desert shrubland within the Nevada Free Air CO2 Enrichment (FACE) experiment. Most of the numerically abundant bacteria and fungi were present in both the biocrusts and root zones, although the proportional abundance of those members differed significantly between habitats. Biocrust bacteria were predominantly Cyanobacteria while root zones harbored significantly more Actinobacteria and Proteobacteria. Pezizomycetes fungi dominated the biocrusts while Dothideomycetes were highest in root zones. Functional gene abundances in metagenome sequence datasets reflected the taxonomic differences noted in the 16S rRNA datasets. For example, functional categories related to photosynthesis, circadian clock proteins, and heterocyst-associated genes were enriched in the biocrusts, where populations of Cyanobacteria were larger. Genes related to potassium metabolism were also more abundant in the biocrusts, suggesting differences in nutrient cycling between biocrusts and root zones. Finally, ten years of elevated atmospheric CO2 did not result in large shifts in taxonomic composition of the bacterial or fungal communities or the functional gene inventories in the shotgun metagenomes.

  20. Biological soil crust as a bio-mediator alters hydrological processes in stabilized dune system of the Tengger Desert, China

    Li, Xinrong


    Biological soil crust (BSC) is a vital component in the stabilized sand dunes with a living cover up to more than 70% of the total, which has been considered as a bio-mediator that directly influences and regulates the sand dune ecosystem processes. However, its influences on soil hydrological processes have been long neglected in Chinese deserts. In this study, BSCs of different successional stages were chose to test their influence on the hydrological processes of stabilized dune, where the groundwater deep exceeds 30m, further to explore why occur the sand-binding vegetation replacement between shrubs and herbs. Our long-term observation (60 years) shows that cyanobacteria crust has been colonized and developed after 3 years since the sand-binding vegetation has been established and dune fixation using planted xerophytic shrubs and made sand barrier (straw-checkerboard) on shifting dune surface, lichen and moss crust occurred after 20 years, and the cover of moss dominated crust could reach 70 % after 50 years. The colonization and development of BSC altered the initial soil water balance of revegetated areas by influencing rainfall infiltration, soil evaporation and dew water entrapment. The results show that BSC obviously reduced the infiltration that occurred during most rainfall events (80%), when rainfall was greater than 5 mm or less than 20 mm. The presence of BSC reduced evaporation of topsoil after small rainfall (facilitated topsoil evaporation when rainfall reached 10 mm. The amount of dew entrapment increases with the succession of BSC. Moreover, the effect of the later successional BSC to dew entrapment, rainfall infiltration and evaporation was more obvious than the early successional BSC on stabilized dunes. In general, BSC reduced the amount of rainfall water that reached deeper soil (0.4-3m), which is where the roots of shrubs are primarily distributed. These changes in the soil moisture pattern induced shifting of sand-binding vegetation from

  1. The biological soil crusts of the San Nicolas Island: Enigmatic algae from a geographically isolated ecosystem

    Flechtner, V.R.; Johansen, J.R.; Belnap, J.


    Composite soil samples from 7 sites on San Nicolas Island were evaluated quantitatively and qualitatively for the presence of cyanobacteria and eukaryotic microalgae. Combined data demonstrated a rich algal flora with 19 cyanobacterial and 19 eukaryotic microalgal genera being identified, for a total of 56 species. Nine new species were identified and described among the cyanobacteria and the eukaryotic microalgae that were isolated: Leibleinia edaphica, Aphanothece maritima, Chroococcidiopsis edaphica, Cyanosarcina atroveneta, Hassallia californica, Hassallia pseudoramosissima, Microchaete terrestre, Palmellopsis californiens, and Pseudotetracystis compactis. Distinct distributional patterns of algal taxa existed among sites on the island and among soil algal floras of western North America. Some algal taxa appeared to be widely distributed across many desert regions, including Microcoleus vaginatus, Nostoc punctiforme, Nostoc paludosum, and Tolypothrix distorta, Chlorella vulgaris, Diplosphaera cf. chodatii, Myrmecia astigmatica, Myrmecia biatorellae, Hantzschia amphioxys, and Luticola mutica. Some taxa share a distinctly southern distribution with soil algae from southern Arizona, southern California, and Baja California (e.g., Scenedesmus deserticola and Eustigmatos magnus). The data presented herein support the view that the cyanobacterial and microalgal floras of soil crusts possess significant biodiversity, much of it previously undescribed.

  2. Growth responses of five desert plants as influenced by biological soil crusts from a temperate desert, China

    Zhang, Yuanming; Belnap, Jayne


    In almost all dryland systems, biological soil crusts (biocrusts) coexist alongside herbaceous and woody vegetation, creating landscape mosaics of vegetated and biocrusted patches. Results from past studies on the interaction between biocrusts and vascular plants have been contradictory. In the Gurbantunggut desert, a large temperate desert in northwestern China, well-developed lichen-dominated crusts dominate the areas at the base and between the sand dunes. We examined the influence of these lichen-dominated biocrusts on the germination, growth, biomass accumulation, and elemental content of five common plants in this desert: two shrubs (Haloxylon persicum, Ephedra distachya) and three herbaceous plants (Ceratocarpus arenarius, Malcolmia africana and Lappula semiglabra) under greenhouse conditions. The influence of biocrusts on seed germination was species-specific. Biocrusts did not affect percent germination in plants with smooth seeds, but inhibited germination of seeds with appendages that reduced or eliminated contact with the soil surface or prevented seeds from slipping into soil cracks. Once seeds had germinated, biocrusts had different influences on growth of shrub and herbaceous plants. The presence of biocrusts increased concentrations of nitrogen but did not affect phosphorus or potassium in tissue of all tested species, while the uptake of the other tested nutrients was species-specific. Our study showed that biocrusts can serve as a biological filter during seed germination and also can influence growth and elemental uptake. Therefore, they may be an important trigger for determining desert plant diversity and community composition in deserts.

  3. Biological soil crusts cause subcritical water repellency in a sand dune ecosystem located along a rainfall gradient in the NW Negev desert, Israel

    Keck Hannes; Felde Vincent John Martin Noah Linus; Drahorad Sylvie Laureen; Felix-Henningsen Peter


    The biological soil crusts (BSCs) in the NW Negev cause local water redistribution by increasing surface runoff. The effects of pore clogging and swelling of organic and inorganic crust components were intensively investigated in earlier studies. However, the effect of water repellency (WR) was not addressed systematically yet. This study investigates subcritical WR of BSCs in three different study sites in the NW Negev. For this purpose, three common methods to determine soil WR were used: (...

  4. Molecular and chemical features of the excreted extracellular polysaccharides in Induced Biological Soil Crusts of different ages

    Rossi, Federico; Lanzhou, Chen; Liu, Yongding; Adessi, Alessandra; De Philippis, Roberto


    Biological Soil Crusts (BSCs) are complex microbial associations widely distributed in arid and semiarid environments. These microbial associations have recently been acknowledged as important in restoration ecology (Bowker 2007). The primary colonization of cyanobacteria and other crust organisms after events such as fire or cessation of plowing is considered critical for later vascular plant establishment, due to the control of seed germination and due to the complex pathways that BSCs are capable to establish between plants and crust organisms and exudates (Rossi et al. 2013). In a ten year study carried out in the hyper-arid region of Inner Mongolia (China), introduction of man - made BSCs (induced BSCs, IBSCs) proved to be effective in producing a shift of the ecosystem state from high abiotic to low abiotic stress, evidenced by an increase in photothrophic abundance and subshrub cover. The prerequisite for an efficient exploitation of crust organisms as soil colonizers is their capability to secrete large amount of exopolysaccharides (EPS) which are important, among the reasons, as they lead to soil and BSC stabilization and represent a noticeable source of C that can be respired by the crustal community. By these means, a deep chemical and physiological knowledge concerning these exudates is required. Notwithstanding the large amount of literature available, recently thoroughly reviewed by Mager and Thomas (2011), the chemical characteristics of EPS from BSCs, and in particular from IBSCs, have not been investigated yet. We analyzed the monosaccharidic composition and the molecular weight distribution of two EPS fractions, the more soluble fraction and the fraction more tightly bound to cells, extracted from IBSCs collected in the Inner Mongolian desert, inoculated in different years (namely 4, 6 and 8 years before the sampling), thus characterized by different developmental stages. We thereafter investigated the degradation processes involving EPS

  5. The role of microbial-produced extracellular polymeric matrix in the formation and survival of biological soil crusts

    Rossi, Federico; Adessi, Alessandra; De Philippis, Roberto


    Biological soil crusts (BSCs) are complex communities commonly constituting organo-mineral layers in arid and semiarid environment having a major influence on these ecosystems (Belnap and Lange, 2001). They have high tolerance towards a-biotic stresses and fluctuations in moisture, illumination, salinity and nutrients. The plasticity exhibited by BSCs is hugely contributed by the presence of the extracellular polymeric matrix (EPM) that is synthesized by crustal organisms, notably cyanobacteria and microalgae. This polysaccharidic net plays key roles in biofilm relations with the surrounding constrained environment. Notably, EPM concurs in coping with water scarcity, freezing and salt stress; increases biolayers stability against erosion, and is involved in nutrient provision (Rossi and De Philippis, 2015). We conducted several investigations in a research area located in the Inner Mongolian desert (Inner Mongolia, China) where BSCs were induced over different sites through inoculation-based techniques performed in different years. Our studies were aimed at determining the role of EPM in BSC development and survival in such a hyper-arid system. This presentation will report the results concerning the role of EPM in water capture from non-rainfall sources, water maintenance at the topsoil, and in water infiltrability, the latter being a factor with important ecological implications. In additions we investigated the role of the matrix as a source of carbon for the crustal heterotrophs. Furthermore, EPM was extracted with methods optimized in our lab, aiming at removing tightly bound fractions and loosely bound fractions from BSCs having different ages. The fractions were analyzed in terms of monosaccharidic composition, and molecular weight (MW) distribution. We show how the relative amounts of uronic acids increase in the EPM with the age of the crusts, implying advantages for the community-water relations. In addition, we observed significant differences in MW

  6. Hydraulic and nutritional feedback controls surface patchiness of biological soil crusts at a post-mining site.

    Fischer, Thomas; Gypser, Stella; Subbotina, Maria; Veste, Maik


    , and decreased to BSC2, BSC1 and BSC3. Non-metric multidimensional scaling revealed that the lichens and BSC3 were associated with water soluble nutrients (NO3, NH4, K, Mg, Ca) and with pyrite weathering products (pH, SO4), thus representing a high nutrient low hydraulic feedback mode. The mosses and BSC2 represented a low nutrient high hydraulic feedback mode. These feedback mechanisms were considered as synergic, consisting of run-off generating (low hydraulic) and run-on receiving (high hydraulic) BSC patches. Three scenarios for BSC succession were proposed. (1) Initial BSCs sealed the surface until they reached a successional stage (represented by BSC1) from which the development into either of the feedback modes was triggered, (2) initial heterogeneities of the mineral substrate controlled the development of the feedback mode, and (3) complex interactions between lichens and mosses occurred at later stages of system development. It was concluded that, irrespective of successional pathways, two synergic feedback mechanisms contributed to the generation of self-organized surface patchiness. Such small-scale microsite differentiation with different BSCs has important implications for the vegetation in post-mining sites. Reference Fischer, T., Gypser, S., Subbotina, M., Veste, M. (2014) Synergic hydraulic and nutritional feedback mechanisms control surface patchiness of biological soil crusts on tertiary sands at a post-mining site. Journal of Hydrology and Hydromechanics 62(4):293-302

  7. Development and hydrology of biological soil crusts -- first results from a surface inoculation experiment

    Mykhailova, Larysa; Raab, Thomas; Gypser, Stella; Fischer, Thomas


    Representing a set of various micro-biocoenoses, biocrusts often reside in adjacent patches, which not necessarily relate to structural elements of the habitat, like (micro-) topography or vegetational patterns. Such biocrust patches may become more stable through the formation of mutually dependent ecohydrological regimes. For example, algal patches inhibiting infiltration and generating runoff alternate with runoff-receiving moss patches possessing high water holding capacities. Here, we preliminarily report on a lysimeter field experiment where natural biocrust isolates were used for surface inoculation to (I) prove stochastic vs. deterministic biocrust development and (II) to quantitatively relate biocrust development to soil hydrology. Lysimeter sand was collected from 3-4 m below surface at natural dune outcrops in south-eastern Brandenburg, Germany (Glashütte (GLA) and Neuer Lugteich (LUG)), where biocrust samples were collected at the respective dune bases. The lysimeters were designed to prevent runoff. In a completely randomized full-factorial design, three factors were considered. (A) Inocolum in three treatments (bare control, mosses, algae), (B) mineral substrate texture in two treatments (GLA: 55% and LUG: 79% particles >630 μm), and (C) surface compaction in two treatments (control, 41.5 kN m‑2 for 30 seconds). The samples were kept dry and re-moistened to -60 hPa two days before inoculation. After a species inventory, the inoculate was isolated by gently washing off sand particles from the biocrust samples. Algal/lichen crusts were dominated by Zygogonium ericetorum and Cladonia sp. at both sites. All moss crusts were dominated by Polytrichum piliferum and Ceratodon purpureus, whereas Brachythecium albicans was present at GLA only. 20 g of homogenized moist inoculate were spread over the surface of each lysimeter (Ø 19 cm, 22 cm depth). We performed autochthonous inoculation, i.e. biocrust isolates collected from GLA were used for inoculation

  8. Climate and Physical Disturbance Effects on the Spectral Signatures of Biological Soil Crusts: Implications for Future Dryland Energy Balance

    Rutherford, W. A.; Flagg, C.; Painter, T. H.; Okin, G. S.; Belnap, J.; Reed, S.


    Drylands comprise ≈40% of the terrestrial Earth surface and observations suggest they can respond markedly to climate change. A vital component of dryland ecosystems are biological soil crusts (biocrusts) - a network of surface soil lichens, mosses, and cyanobacteria - that perform critical ecosystem functions, such as stabilizing soil and fixing carbon and nitrogen. Yet, our understanding of the role biocrusts play in dryland energy balance remains poor. Changes in climate can rapidly affect biocrust communities and we have long known that biocrusts respond dramatically to physical disturbance, such as human trampling and grazing animals. Associated changes in biocrust cover often result in increased bare soil; creating higher surface reflectance. We used spectral solar reflectance measurements in two manipulative experiments to compare the effects of climate and physical disturbance on biocrusts of the Colorado Plateau We measured reflectance at two heights: at crust surface and 1 m above. The climate disturbance site has four treatments: control, warming (4°C), altered precipitation, and warming plus altered precipitation. The physical disturbance site was trampled by foot annually since 1998. At the climate experiment, the largest change in reflectance was in the altered precipitation treatment (35% increase) at the surface-level, and the smallest difference was in the warmed (17% increase) at the meter-level. Physical disturbance differences were 10% at meter-level and 25% at surface-level. Unexpectedly, these results suggest that, via effects on biocrust communities, climate change could have a larger effect on dryland energy balance relative to physical disturbance, and result in more radiation from drylands returned to the atmosphere. Biocrusts cover large portions of the Earth's surface and, to our knowledge, these are the first data showing climate-induced changes to biocrust reflectance, with negative feedback in the global energy balance.

  9. Key Factors Controlling the Growth of Biological Soil Crusts: Towards a Protocol to Produce Biocrusts in Greenhouse Facilities

    Velasco Ayuso, Sergio; María Giraldo Silva, Ana; Nelson, Corey; Barger, Nichole; Antoninka, Anita; Bowker, Matthew; Garcia-Pichel, Ferran


    Biological soil crusts (= biocrusts) are topsoil communities comprise of, but not limited to, cyanobacteria, algae, lichens, and mosses that grow intimately associated with soil particles in drylands. Biocrusts have central ecological roles in these areas as sources of carbon and nutrients, and efficiently retain water and prevent soil erosion, which improves soil structure and promotes soil fertility. However, human activities, such as cattle grazing, hiking or military training, are rapidly striking biocrusts. Although it is well known that the inoculation with cyanobacteria or lichens can enhance the recovery of biocrusts in degraded soils, little is known about the factors that control their growth rates. Using soil and inocula from four different sites located in one cold desert (Utah) and in one hot desert (New Mexico), we performed a fractional factorial experiment involving seven factors (water, light, P, N, calcium carbonate, trace metals and type of inoculum) to screen their effects on the growth of biocrusts. After four months, we measured the concentration of chlorophyll a, and we discovered that water, light and P, N or P+N were the most important factors controlling the growth of biocrusts. In the experimental treatments involving these three factors we measured a similar concentration of chlorophyll a (or even higher) to this found in the field locations. Amplification of the 16S rRNA gene segment using universal bacteria primers revealed a microbial community composition in the biocrusts grown that closely corresponds to initial measurements made on inocula. In summary, based on our success in obtaining biocrust biomass from natural communities in greenhouse facilities, without significantly changing its community composition at the phylum and cyanobacterial level, we are paving the road to propose a protocol to produce a high quality-nursed inoculum aiming to assist restoration of arid and semi-arid ecosystems affected by large-scale disturbances.

  10. Relationship between the herbaceous and woody vegetation caracteristics and biological soil crusts distribution in fallow and rangeland across a latitudinal gradient in Sahelian Western Niger

    Malam Issa, O.; Hiernaux, P.; Kalilou, A.; Rajot, J. L.; Languille, J.


    Biological soil crusts (BSC) are common soil feature in the Sahel, in Western Niger. They occur in association with various types of physical soil crusts in fallow, rangeland and 'tiger bush' biomes (landscape with a typical pattern consisting of alternating dense thicket bands composed of shrubs and small trees, and bare soil bands). Despite their widespread occurrence, little research has focussed on the spatial extent of microbiotic soil crusts at regional scale in Sahel. Moreover, little is known about the interrelations between the occurrence of those crusts and the characteristics of the vegetation. In this paper, field data on the distribution of biological soil crusts and some characteristics (cover, composition, mass) of herbaceous and woody vegetation co-occurring in fallows and rangelands are presented and analysed. The study was performed in ten sites selected in Western Niger along a south-north climatic gradient between 650 to 300 mm of annual rainfall. The soil surfaces features, specifically physical and biological soil crusts, were surveyed twice in july-october 2009 and October-november 2011. The second survey combined the assessment of soil surfaces features with systematic observations of vegetation. Herbaceous cover, mass and species composition were assessed by stratified sampling along a 200 meter axis. PCQ distance method was used to characterise the density, cover and species composition of the woody plant population. The extends of BSC observed in the 10 sites in 2011 are in the same order as those observed in 2009, i.e. ranging between 4 and 59% in 2009 vs 1.5 and 48 % in 2011. The results showed a significant increase of BSC coverage with increasing annual rainfall towards the south of the gradient. The actual cover of herbaceous vegetation, taking the extends of bare soil patches in account, averages 14.2 % over the different sites. Similarly to BSC repartition, a slight increase of herbaceous cover is observed from the northern dryer

  11. Elevated CO2 did not mitigate the effect of a short-term drought on biological soil crusts

    Wertin, Timothy M.; Phillips, Susan L.; Reed, Sasha C.; Belnap, Jayne


    Biological soil crusts (biocrusts) are critical components of arid and semi-arid ecosystems that contribute significantly to carbon (C) and nitrogen (N) fixation, water retention, soil stability, and seedling recruitment. While dry-land ecosystems face a number of environmental changes, our understanding of how biocrusts may respond to such perturbation remains notably poor. To determine the effect that elevated CO2 may have on biocrust composition, cover, and function, we measured percent soil surface cover, effective quantum yield, and pigment concentrations of naturally occurring biocrusts growing in ambient and elevated CO2 at the desert study site in Nevada, USA, from spring 2005 through spring 2007. During the experiment, a year-long drought allowed us to explore the interacting effects that elevated CO2 and water availability may have on biocrust cover and function. We found that, regardless of CO2 treatment, precipitation was the major regulator of biocrust cover. Drought reduced moss and lichen cover to near-zero in both ambient and elevated CO2 plots, suggesting that elevated CO2 did not alleviate water stress or increase C fixation to levels sufficient to mitigate drought-induced reduction in cover. In line with this result, lichen quantum yield and soil cyanobacteria pigment concentrations appeared more strongly dependent upon recent precipitation than CO2 treatment, although we did find evidence that, when hydrated, elevated CO2 increased lichen C fixation potential. Thus, an increase in atmospheric CO2 may only benefit biocrusts if overall climate patterns shift to create a wetter soil environment.

  12. Influence of biological soil crusts at different successional stages in the implantation of biogeochemical cycles in arid and semiarid zones

    Gil-Sotres, F.; Miralles, I.; Canton-Castilla, Y.; Domingo, F.; Leiros, M. C.; Trasar-Cepeda, C.


    Influence of biological soil crusts at different successional stages in the implantation of biogeochemical cycles in arid and semiarid zones I. Miralles1, F. Gil-Sotres2, Y. Cantón-Castilla3, F. Domingo1, M.C. Leirós2, C. Trasar-Cepeda4 1 Experimental Estation of Arid Zones (CSIC), E-04230 La Cañada de San Urbano, Almería, Spain. 2 Departamento Edafología y Química Agrícola, Grupo de Evaluación de la Calidad del Suelo, Unidad Asociada CSIC, Facultad de Farmacia, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela, Spain. 3 University of Almería, Departamento de Edafología y Química Agrícola, E-04230-La Cañada de San Urbano, Almería, Spain. 4 Departamento Bioquímica del Suelo, IIAG-CSIC, Apartado 122, E-15708 Santiago de Compostela, Spain. Crusts (BSCs) are formed by a close association between soil particles and cyanobacteria, algae, lichens, bryophytes and microfungi in varying proportions. Their habitat is within or immediately on top of the uppermost millimetres of the soil and are the predominant surface cover in arid and semiarid zones. Among the diverse functions developed by BSCs in the ecosystem (hydrology, erosion, soil properties, etc.), one of the most important is its role in nutrient cycling. Within arid and semiarid environments, BSCs have been termed 'mantles of fertility' being considered hotspots of biogeochemical inputs, fixing C, N and P above- and below-ground. However, there are differences in N and C fixation rates between BSCs types. Early successional BSCs, dominated by cyanobacterial species, fix lower quantities of C and N than mature BSCs dominated by lichens. Although the positive effects of BSCs on biogeochemical soil cycles are widely accepted, no previous studies have evaluated the activities of the enzymes involved in C, N and P cycles of BSCs and how they are affected by the successional stage of the BSC. In this work, performed in the Tabernas desert (SE Spain), we studied the hydrolase enzymes

  13. Prioritizing conservation effort through the use of biological soil crusts as ecosystem function indicators in an arid region

    Bowker, M.A.; Miller, M.E.; Belnap, J.; Sisk, T.D.; Johnson, N.C.


    Conservation prioritization usually focuses on conservation of rare species or biodiversity, rather than ecological processes. This is partially due to a lack of informative indicators of ecosystem function. Biological soil crusts (BSCs) trap and retain soil and water resources in arid ecosystems and function as major carbon and nitrogen fixers; thus, they may be informative indicators of ecosystem function. We created spatial models of multiple indicators of the diversity and function of BSCs (species richness, evenness, functional diversity, functional redundancy, number of rare species, number of habitat specialists, nitrogen and carbon fixation indices, soil stabilization, and surface roughening) for the 800,000-ha Grand Staircase-Escalante National Monument (Utah, U.S.A.). We then combined the indicators into a single BSC function map and a single BSC biodiversity map (2 alternative types of conservation value) with an unweighted averaging procedure and a weighted procedure derived from validations performance. We also modeled potential degradation with data from a rangeland assessment survey. To determine which areas on the landscape were the highest conservation priorities, we overlaid the function- and diversity-based conservation-value layers on the potential degradation layer. Different methods for ascribing conservation-value and conservation-priority layers all yielded strikingly similar results (r = 0.89-0.99), which suggests that in this case biodiversity and function can be conserved simultaneously. We believe BSCs can be used as indicators of ecosystem function in concert with other indicators (such as plant-community properties) and that such information can be used to prioritize conservation effort in drylands. ?? 2008 Society for Conservation Biology.

  14. Dryland biological soil crust cyanobacteria show unexpected decreases in abundance under long-term elevated CO2

    Steven, Blaire; Gallegos-Graves, La Verne; Yeager, Chris M.; Belnap, Jayne; Evans, R. David; Kuske, Cheryl R.


    Biological soil crusts (biocrusts) cover soil surfaces in many drylands globally. The impacts of 10 years of elevated atmospheric CO2 on the cyanobacteria in biocrusts of an arid shrubland were examined at a large manipulated experiment in Nevada, USA. Cyanobacteria-specific quantitative PCR surveys of cyanobacteria small-subunit (SSU) rRNA genes suggested a reduction in biocrust cyanobacterial biomass in the elevated CO2 treatment relative to the ambient controls. Additionally, SSU rRNA gene libraries and shotgun metagenomes showed reduced representation of cyanobacteria in the total microbial community. Taxonomic composition of the cyanobacteria was similar under ambient and elevated CO2 conditions, indicating the decline was manifest across multiple cyanobacterial lineages. Recruitment of cyanobacteria sequences from replicate shotgun metagenomes to cyanobacterial genomes representing major biocrust orders also suggested decreased abundance of cyanobacteria sequences across the majority of genomes tested. Functional assignment of cyanobacteria-related shotgun metagenome sequences indicated that four subsystem categories, three related to oxidative stress, were differentially abundant in relation to the elevated CO2 treatment. Taken together, these results suggest that elevated CO2 affected a generalized decrease in cyanobacteria in the biocrusts and may have favoured cyanobacteria with altered gene inventories for coping with oxidative stress.

  15. Rain pulse response of soil CO2 exchange by biological soil crusts and grasslands of the semiarid Colorado Plateau, United States

    Bowling, David R.; Grote, E.E.; Belnap, J.


    Biological activity in arid grasslands is strongly dependent on moisture. We examined gas exchange of biological soil crusts (biocrusts), the underlying soil biotic community, and the belowground respiratory activity of C3 and C4 grasses over 2 years in southeast Utah, USA. We used soil surface CO2 flux and the amount and carbon isotope composition (δ13C) of soil CO2 as indicators of belowground and soil surface activity. Soil respiration was always below 2 μmol m-2s-1 and highly responsive to soil moisture. When moisture was available, warm spring and summer temperature was associated with higher fluxes. Moisture pulses led to enhanced soil respiration lasting for a week or more. Biological response to rain was not simply dependent on the amount of rain, but also depended on antecedent conditions (prior moisture pulses). The short-term temperature sensitivity of respiration was very dynamic, showing enhancement within 1-2 days of rain, and diminishing each day afterward. Carbon uptake occurred by cyanobacterially dominated biocrusts following moisture pulses in fall and winter, with a maximal net carbon uptake of 0.5 μmol m-2s-1, although typically the biocrusts were a net carbon source. No difference was detected in the seasonal activity of C3 and C4 grasses, contrasting with studies from other arid regions (where warm- versus cool-season activity is important), and highlighting the unique biophysical environment of this cold desert. Contrary to other studies, the δ13C of belowground respiration in the rooting zone of each photosynthetic type did not reflect the δ13C of C3 and C4 physiology.

  16. Some Like it High! Phylogenetic Diversity of High-Elevation Cyanobacterial Community from Biological Soil Crusts of Western Himalaya

    Čapková, Kateřina; Hauer, Tomáš; Řeháková, Klára; Doležal, Jiří


    Roč. 71, č. 1 (2016), s. 113-123. ISSN 0095-3628 R&D Projects: GA ČR GA13-13368S Institutional support: RVO:67985939 Keywords : Soil crusts * Cyanobacterial diversity * Western Himalayas Subject RIV: EH - Ecology, Behaviour Impact factor: 2.973, year: 2014

  17. Some like it high! Phylogenetic diversity of high-elevation cyanobacterial community from biological soil crusts of Western Himalaya.

    Čapková, K.; Hauer, T.; Řeháková, Klára; Doležal, J.


    Roč. 71, č. 1 (2016), s. 113-123. ISSN 0095-3628 Institutional support: RVO:60077344 Keywords : soil crusts * cyanobacterial diversity * Western Himalayas * high -elevation * desert * phosphorus Subject RIV: EH - Ecology, Behaviour Impact factor: 2.973, year: 2014

  18. Effects of Re-vegetation on Herbaceous Species Composition and Biological Soil Crusts Development in a Coal Mine Dumping Site

    Zhao, Yang; Zhang, Peng; Hu, Yigang; Huang, Lei


    Despite the critical roles of plant species' diversity and biological soil crusts (BSCs) in arid and semi-arid ecosystems, the restoration of the diversity of herbaceous species and BSCs are rarely discussed during the process of vegetation restoration of anthropogenically damaged areas in these regions. In this study, the herbaceous plant species composition, along with the BSCs coverage and thicknesses, was investigated at six different re-vegetation type sites, and the natural vegetation site of the Heidaigou open pit coal mine in China's Inner Mongolia Autonomous Region was used as a reference. The highest total species richness (16), as well as the species richness (4.4), occurred in the Tree and Herbaceous vegetation type site. The species composition similarities between the restored sites and the reference site were shown to be very low, and ranged from 0.09 to 0.42. Also, among the restored sites, the similarities of the species were fairly high and similar, and ranged from 0.45 to 0.93. The density and height of the re-vegetated woody plants were significantly correlated with the indexes of the diversity of the species. The Shrub vegetation type site showed the greatest total coverage (80 %) of BSCs and algae crust coverage (48 %). The Shrub and Herbaceous type had the greatest thicknesses of BSCs, with as much as 3.06 mm observed, which was followed by 2.64 mm for the Shrub type. There was a significant correlation observed between the coverage of the total BSCs, and the total vegetation and herbaceous vegetation coverage, as well as between the algae crust coverage and the herbaceous vegetation coverage. It has been suggested that the re-vegetated dwarf woody plant species (such as shrubs and semi-shrubs) should be chosen for the optimal methods of the restoration of herbaceous species diversity at dumping sites, and these should be planted with low density. Furthermore, the effects of vegetation coverage on the colonization and development the BSCs

  19. Three distinct clades of cultured heterocystous cyanobacteria constitute the dominant N2-fixing members of biological soil crusts of the Colorado Plateau, USA

    Yeager, C.M.; Kornosky, J.L.; Morgan, R.E.; Cain, E.C.; Garcia-Pichel, F.; Housman, D.C.; Belnap, J.; Kuske, C.R.


    The identity of the numerically dominant N2-fixing bacteria in biological soil crusts of the Colorado Plateau region and two outlying areas was determined using multiple approaches, to link the environmental diversity of nifH gene sequences to cultured bacterial isolates from the regions. Of the nifH sequence-types detected in soil crusts of the Colorado Plateau, 89% (421/473) were most closely related to nifH signature sequences from cyanobacteria of the order Nostocales. N2-fixing cyanobacterial strains were cultured from crusts and their morphotypes, 16S rRNA gene and nifH gene sequences were characterized. The numerically dominant diazotrophs in the Colorado Plateau crusts fell within three clades of heterocystous cyanobacteria. Two clades are well-represented by phylogenetically and morphologically coherent strains, corresponding to the descriptions of Nostoc commune and Scytonema hyalinum, which are widely recognized as important N2-fixing components of soil crusts. A third, previously-overlooked clade was represented by a phylogenetically coherent but morphologically diverse group of strains that encompass the morphogenera Tolypothrix and Spirirestis. Many of the strains in each of these groups contained at least two nifH copies that represent different clusters in the nifH environmental survey. ?? 2007 Federation of European Microbiological Societies.

  20. The stability and the hydrological behavior of biological soil crusts is significantly affected by the complex nature of their polysaccharidic matrix

    De Philippis, Roberto


    Biological crusts (BSCs) are complex microbial associations constituted by cells and microbial filaments embedded in a polysaccharidic matrix (EPS) that binds them together and with soil particles. EPSs of BSCs play a key role in structuring the soil and in affecting the hydrological processes taking place at the topsoil in desert environments. Recently, the amphiphilic nature of the EPSs, due to the contemporaneous presence in the macromolecules of hydrophilic and hydrophobic constituents, was put in relation with their capability to contribute to the structuring of the soil particles in BSCs and to hydrological behavior of the crusts. Indeed, in the EPSs the hydrophobicity due to the non-polar constituents (i.e. deoxysugars, ester-linked fatty acids, non polar aminoacids) was associated with the adhesion of the microbial cells to solid surfaces and to the clogging of micropores in the crusts. On the other hand, the hydrophilic constituents of the EPSs (i.e. acidic sugars, ketal-linked pyruvic acid, sulphate groups etc) were suggested to determine the final water content and distribution in the soil. The presence of BSCs facilitates the uptake of moisture from the atmosphere and at the same time contributes to enriching the soils with organic matter. In this lecture, the role of the EPSs in affecting the hydrological behavior of BSCs will be discussed by comparing the results obtained with natural and artificially induced BSCs also in relation with the texture of the soils. Furthermore, the contribution to the structuring of the soils of the polysaccharidic matrix of the crusts will be discussed moving from the different characteristics of two operationally-defined EPS fractions, the colloidal (C-EPS) and the EDTA extractable (tightly bound, TB-EPS) fractions. In BSCs, C-EPSs are loosely bound to cells and sediments while TB-EPSs are tightly bound to the crustal biotic and abiotic constituents of the crusts. The results obtained in a recent study suggest that the

  1. Biological Soil Crusts are Ecohydrological Hotspots in Dryland and Subhumid Regions

    Belnap, J.; Chamizo de la Piedra, S.


    Dry and subhumid lands cover ~41% of Earth's terrestrial surface and biocrusts are often a dominant lifeform in these regions. These soil surface communities are known to be critical component in determining dryland hydrologic cycles by altering infiltration, runoff and evaporation processes; thus, they create a hotspot for ecohydrologic processes. Biocrust properties, such as micro-topography and the spatial distribution of overall cover and individual species, are believed to be the most influential; these properties vary with climate. Across the gradient from higher potential evapo-transpiration (PET; lower rainfall/higher temperatures such as hyper-arid deserts) to lower PET (higher rainfall/lower temperature such as semi-arid steppe), the external morphology of biocrusts generally goes from very smooth to highly roughened, with water residence time thus increasing as well. This change in PET is also accompanied by increasing species number and biomass; while these changes increase water absorption, they also clogs soil pores. It has long been believed that as biocrust roughness, species, and biomass increases, so does water infiltration and retention. However, the majority of these studies have occurred at a very small (dogma holds: smooth biocrusts with low biomass decrease infiltration and increase runoff, whereas roughened ones with higher biomass increase infiltration. However, studies done at larger spatial scales across a gradient of roughness, species composition, and biomass, show biocrusts almost always increase infiltration and decrease runoff, regardless of biocrust characteristics. This finding runs counter to long-held views regarding the role of biocrusts in hydrologic cycles. These findings have large implications for modelling of soil moisture cycles in drylands under current and future conditions and the concept of ecohydrologic hotspots and hot moments in drylands.

  2. The effect of lichen-dominated biological soil crusts on growth and physiological characteristics of three plant species in a temperate desert of northwest China.

    Zhuang, W W; Serpe, M; Zhang, Y M


    Biocrusts (biological soil crusts) cover open spaces between vascular plants in most arid and semi-arid areas. Information on effects of biocrusts on seedling growth is controversial, and there is little information on their effects on plant growth and physiology. We examined impacts of biocrusts on growth and physiological characteristics of three habitat-typical plants, Erodium oxyrhynchum, Alyssum linifolium and Hyalea pulchella, growing in the Gurbantunggut Desert, northwest China. The influence of biocrusts on plant biomass, leaf area, leaf relative water content, photosynthesis, maximum quantum efficiency of PSII (F(v)/F(m)), chlorophyll, osmotic solutes (soluble sugars, protein, proline) and antioxidant enzymes (superoxide dismutase, catalase, peroxidase) was investigated on sites with or without biocrust cover. Biomass, leaf area, leaf water content, photosynthesis, F(v)/F(m) and chlorophyll content in crusted soils were higher than in uncrusted soils during early growth and lower later in the growth period. Soluble sugars, proline and antioxidant enzyme activity were always higher in crusted than in uncrusted soils, while soluble protein content was always lower. These findings indicate that biocrusts have different effects on these three ephemeral species during growth in this desert, primarily via effects on soil moisture, and possibly on soil nutrients. The influence of biocrusts changes during plant development: in early plant growth, biocrusts had either positive or no effect on growth and physiological parameters. However, biocrusts tended to negatively influence plants during later growth. Our results provide insights to explain why previous studies have found different effects of biocrusts on vascular plant growth. PMID:26084731

  3. High rates of denitrification and nitrous oxide emission in arid biological soil crusts from the Sultanate of Oman

    Abed, Raeid M M; Lam, Phyllis; De Beer, Dirk;


    layer and thus apparently originated from incomplete denitrification. Using quantitative PCR, denitrification genes were detected in both the crusts and were expressed either in comparable (nirS) or slightly higher (narG) numbers in the cyanobacterial crusts. Although 99% of the nirS sequences in the...

  4. Biological soil crusts cause subcritical water repellency in a sand dune ecosystem located along a rainfall gradient in the NW Negev desert, Israel

    Keck Hannes


    Full Text Available The biological soil crusts (BSCs in the NW Negev cause local water redistribution by increasing surface runoff. The effects of pore clogging and swelling of organic and inorganic crust components were intensively investigated in earlier studies. However, the effect of water repellency (WR was not addressed systematically yet. This study investigates subcritical WR of BSCs in three different study sites in the NW Negev. For this purpose, three common methods to determine soil WR were used: (i the repellency index (RI method (ii the water drop penetration time (WDPT test and (iii the Wilhelmy plate method (WPM. Furthermore, the potential influence of WR on local water redistribution is discussed and the applied methods are compared. We found the BSC to be subcritically water repellent. The degree of WR may only affect water redistribution on a microscale and has little influence on the ecosystem as a whole. The RI method was clearly the most appropriate to use, whereas the WDPT and the WPM failed to detect subcritical WR.

  5. Dynamics of cover, UV-protective pigments, and quantum yield in biological soil crust communities of an undisturbed Mojave Desert shrubland

    Belnap, J.; Phillips, S.L.; Smith, S.D.


    Biological soil crusts are an integral part of dryland ecosystems. We monitored the cover of lichens and mosses, cyanobacterial biomass, concentrations of UV-protective pigments in both free-living and lichenized cyanobacteria, and quantum yield in the soil lichen species Collema in an undisturbed Mojave Desert shrubland. During our sampling time, the site received historically high and low levels of precipitation, whereas temperatures were close to normal. Lichen cover, dominated by Collema tenax and C. coccophorum, and moss cover, dominated by Syntrichia caninervis, responded to both increases and decreases in precipitation. This finding for Collema spp. at a hot Mojave Desert site is in contrast to a similar study conducted at a cool desert site on the Colorado Plateau in SE Utah, USA, where Collema spp. cover dropped in response to elevated temperatures, but did not respond to changes in rainfall. The concentrations of UV-protective pigments in free-living cyanobacteria at the Mojave Desert site were also strongly and positively related to rainfall received between sampling times (R2 values ranged from 0.78 to 0.99). However, pigment levels in the lichenized cyanobacteria showed little correlation with rainfall. Quantum yield in Collema spp. was closely correlated with rainfall. Climate models in this region predict a 3.5-4.0 ??C rise in temperature and a 15-20% decline in winter precipitation by 2099. Based on our data, this rise in temperature is unlikely to have a strong effect on the dominant species of the soil crusts. However, the predicted drop in precipitation will likely lead to a decrease in soil lichen and moss cover, and high stress or mortality in soil cyanobacteria as levels of UV-protective pigments decline. In addition, surface-disturbing activities (e.g., recreation, military activities, fire) are rapidly increasing in the Mojave Desert, and these disturbances quickly remove soil lichens and mosses. These stresses combined are likely to lead to

  6. Evolution of Fractal Parameters through Development Stage of Soil Crust

    Ospina, Abelardo; Florentino, Adriana; Tarquis, Ana Maria


    Soil surface characteristics are subjected to changes driven by several interactions between water, air, biotic and abiotic components. One of the examples of such interactions is provided through biological soil crusts (BSC) in arid and semi-arid environments. BSC are communities composed of cyanobacteria, fungi, mosses, lichens, algae and liverworts covering the soil surface and play an important role in ecosystem functioning. The characteristics and formation of these BSC influence the soil hydrological balance, control the mass of eroded sediment, increase stability of soil surface, and influence plant productivity through the modification of nitrogen and carbon cycle. The site of this work is located at Quibor and Ojo de Agua (Lara state, Venezuela). The Quibor Depression in Venezuela is a major agricultural area being at semi-arid conditions and limited drainage favor the natural process of salinization. Additionally, the extension and intensification of agriculture has led to over-exploitation of groundwater in the past 30 years (Méndoza et al., 2013). The soil microbial crust develops initially on physical crusts which are mainly generated since wetting and drying, being a recurrent feature in the Quíbor arid zone. The microbiotic crust is organic, composed of macro organisms (bryophytes and lichens) and microorganisms (cyanobacteria, fungi algae, etc.); growing on the ground, forming a thickness no greater than 3 mm. For further details see Toledo and Florentino (2009). This study focus on characterize the development stage of the BSC based on image analysis. To this end, grayscale images of different types of biological soil crust at different stages where taken, each image corresponding to an area of 12.96 cm2 with a resolution of 1024x1024 pixels (Ospina et al., 2015). For each image lacunarity and fractal dimension through the differential box counting method were calculated. These were made with the software ImageJ/Fraclac (Karperien, 2013

  7. Effects of nitrogen deposition and soil fertility on cover and physiology of Cladonia foliacea (Huds.) Willd., a lichen of biological soil crusts from Mediterranean Spain

    Ochoa-Hueso, Raul, E-mail: raul.ochoa@ccma.csic.e [Instituto de Recursos Naturales, Centro de Ciencias Medioambientales, Consejo Superior de Investigaciones Cientificas, C/Serrano 115 bis, 28006 Madrid (Spain); Manrique, Esteban [Instituto de Recursos Naturales, Centro de Ciencias Medioambientales, Consejo Superior de Investigaciones Cientificas, C/Serrano 115 bis, 28006 Madrid (Spain)


    We are fertilizing a thicket with 0, 10, 20 and 50 kg nitrogen (N) ha{sup -1} yr{sup -1} in central Spain. Here we report changes in cover, pigments, pigment ratios and FvFm of the N-tolerant, terricolous, lichen Cladonia foliacea after 1-2 y adding N in order to study its potential as biomarker of atmospheric pollution. Cover tended to increase. Pigments increased with fertilization independently of the dose supplied but only significantly with soil nitrate as covariate. {beta}-carotene/chlorophylls increased with 20-50 kg N ha{sup -1} yr{sup -1} (over the background) and neoxanthin/chlorophylls also increased with N. (Neoxanthin+lutein)/carotene decreased with N when nitrate and pH seasonalities were used as covariates. FvFm showed a critical load above 40 kg N ha{sup -1} yr{sup -1}. Water-stress, iron and copper also explained variables of lichen physiology. We conclude that this tolerant lichen could be used as biomarker and that responses to N are complex in heterogeneous Mediterranean-type landscapes. - Research highlights: We are providing evidence of the potential use of the crust-forming lichen Cladonia foliacea as biomarker of atmospheric pollution in Mediterranean ecosystems of Europe, which are understudied with regard to this topic. Pigment concentration increased with N addition and FvFm, used as indicator of physiological status, showed a critical load above 20 kg N ha{sup -1} y{sup -1}. Soil nitrate and pH were important in modulating responses to simulated N pollution and other soil parameters (micro-nutrients, water content...) also explained variables of lichen physiology. We conclude that Cladonia foliacea could be used as biomarker and that responses to N are complex in heterogeneous Mediterranean-type landscapes. - Nitrogen deposition and soil variables affect the physiology of terrestrial Mediterranean lichens.

  8. 黄土丘陵区生物结皮对土壤可蚀性的影响%Effects of biological soil crust on soil erodibility in Hilly Loess Plateau Region of Northwest China

    高丽倩; 赵允格; 秦宁强; 张国秀


    在采样分析生物结皮对土壤理化属性影响的基础上,采用EPIC模型估算与模拟降雨试验相结合的方法,研究了黄土丘陵区不同生物量、不同土壤质地和不同季节的生物结皮对土壤可蚀性(K值)的影响.结果表明:生物结皮显著降低了土壤可蚀性,生物结皮层土壤可蚀性较下层土壤降低17%;土壤可蚀性随生物结皮生物量的增加呈降低趋势,藓结皮土壤可蚀性K值较藻结皮土壤降低21%;生物结皮土壤可蚀性在不同季节因其生物活性不同而存在差异,雨季中显著高于雨季前和雨季末;不同质地土壤上生物结皮对可蚀性的影响不同,可蚀性K值为砂壤>粉壤>砂土;模拟降雨条件下测定表明,生物结皮的发育使土壤可蚀性较对照(下层5~10 cm土壤)降低约90%.%Based on the analysis of the effects of biological soil crust (biocrust) in re-vegetated grasslands on soil physical and chemical properties, and by using EPIC estimation model in combi-ning with simulated rainfall trials, this paper studied the effects of biocrust with different biomass and different soil texture on the soil credibility (K value) in Hilly Loess Plateau Region of North-west China in different seasons. The results showed biocrust could significantly decrease soil erod-ibility, with the K value of biocrust soil decreased by about 17% , compared with subsoil. The soil erodibility decreased with the increasing biomass of biocrust. The K value of moss crust soil de-creased by 21% , compared with cyanobacteria crust soil. The erodibiliy of biocrust soil differed with different seasons, being significantly higher in rainy season than before or after the rainy season due to the differences in the biological activity of the biocrust organisms. The erodibilty of biocrust soil with different texture also varied significantly, with the K value in the order of sandy loam soil > silt soil > sandy soil. The measurement under simulated

  9. The dual role of soil crusts in desertification

    Assouline, S.; Thompson, S. E.; Chen, L.; Svoray, T.; Sela, S.; Katul, G. G.


    Vegetation cover in dry regions is a key variable in determining desertification. Soils exposed to rainfall by desertification can form physical crusts that reduce infiltration, exacerbating water stress on the remaining vegetation. Paradoxically, field studies show that crust removal is associated with plant mortality in desert systems, while artificial biological crusts can improve plant regeneration. Here it is shown how physical crusts can act as either drivers of or buffers against desertification depending on their environmental context. The behavior of crusts is first explored using a simplified theory for water movement on a uniform, partly vegetated slope subject to stationary hydrologic conditions. Numerical model runs supplemented with field data from a semiarid Long-Term Ecological Research site are then applied to represent more realistic environmental conditions. When vegetation cover is significant, crusts can drive desertification, but this process is potentially self-limiting. For low vegetation cover, crusts mitigate against desertification by providing water subsidy to plant communities through a runoff-runon mechanism.

  10. Living in biological soil crust communities of African deserts-Physiological traits of green algal Klebsormidium species (Streptophyta) to cope with desiccation, light and temperature gradients.

    Karsten, Ulf; Herburger, Klaus; Holzinger, Andreas


    Green algae of the genus Klebsormidium (Klebsormidiales, Streptophyta) are typical members of biological soil crusts (BSCs) worldwide. The phylogeny and ecophysiology of Klebsormidium has been intensively studied in recent years, and a new lineage called superclade G, which was isolated from BSCs in arid southern Africa and comprising undescribed species, was reported. Three different African strains, that have previously been isolated from hot-desert BSCs and molecular-taxonomically characterized, were comparatively investigated. In addition, Klebsormidium subtilissimum from a cold-desert habitat (Alaska, USA, superclade E) was included in the study as well. Photosynthetic performance was measured under different controlled abiotic conditions, including dehydration and rehydration, as well as under a light and temperature gradient. All Klebsormidium strains exhibited optimum photosynthetic oxygen production at low photon fluence rates, but with no indication of photoinhibition under high light conditions pointing to flexible acclimation mechanisms of the photosynthetic apparatus. Respiration under lower temperatures was generally much less effective than photosynthesis, while the opposite was true for higher temperatures. The Klebsormidium strains tested showed a decrease and inhibition of the effective quantum yield during desiccation, however with different kinetics. While the single celled and small filamentous strains exhibited relatively fast inhibition, the uniserate filament forming isolates desiccated slower. Except one, all other strains fully recovered effective quantum yield after rehydration. The presented data provide an explanation for the regular occurrence of Klebsormidium strains or species in hot and cold deserts, which are characterized by low water availability and other stressful conditions. PMID:26422081

  11. Habitat stress initiates changes in composition, CO2 gas exchange and C-allocation as life traits in biological soil crusts.

    Colesie, Claudia; Green, T G Allan; Haferkamp, Ilka; Büdel, Burkhard


    Biological soil crusts (BSC) are the dominant functional vegetation unit in some of the harshest habitats in the world. We assessed BSC response to stress through changes in biotic composition, CO2 gas exchange and carbon allocation in three lichen-dominated BSC from habitats with different stress levels, two more extreme sites in Antarctica and one moderate site in Germany. Maximal net photosynthesis (NP) was identical, whereas the water content to achieve maximal NP was substantially lower in the Antarctic sites, this apparently being achieved by changes in biomass allocation. Optimal NP temperatures reflected local climate. The Antarctic BSC allocated fixed carbon (tracked using (14)CO2) mostly to the alcohol soluble pool (low-molecular weight sugars, sugar alcohols), which has an important role in desiccation and freezing resistance and antioxidant protection. In contrast, BSC at the moderate site showed greater carbon allocation into the polysaccharide pool, indicating a tendency towards growth. The results indicate that the BSC of the more stressed Antarctic sites emphasise survival rather than growth. Changes in BSC are adaptive and at multiple levels and we identify benefits and risks attached to changing life traits, as well as describing the ecophysiological mechanisms that underlie them. PMID:24694713

  12. Soil crusts to warm the planet

    Garcia-Pichel, Ferran; Couradeau, Estelle; Karaoz, Ulas; da Rocha Ulisses, Nunes; Lim Hsiao, Chiem; Northen, Trent; Brodie, Eoin


    Soil surface temperature, an important driver of terrestrial biogeochemical processes, depends strongly on soil albedo, which can be significantly modified by factors such as plant cover. In sparsely vegetated lands, the soil surface can also be colonized by photosynthetic microbes that build biocrust communities. We used concurrent physical, biochemical and microbiological analyses to show that mature biocrusts can increase surface soil temperature by as much as 10 °C through the accumulation of large quantities of a secondary metabolite, the microbial sunscreen scytonemin, produced by a group of late-successional cyanobacteria. Scytonemin accumulation decreases soil albedo significantly. Such localized warming had apparent and immediate consequences for the crust soil microbiome, inducing the replacement of thermosensitive bacterial species with more thermotolerant forms. These results reveal that not only vegetation but also microorganisms are a factor in modifying terrestrial albedo, potentially impacting biosphere feedbacks on past and future climate, and call for a direct assessment of such effects at larger scales. Based on estimates of the global biomass of cyanobacteria in soil biocrusts, one can easily calculate that there must currently exist about 15 million metric tons of scytonemin at work, warming soil surfaces worldwide

  13. Development of Soil Crusts Under Simulated Rainfall and Crust Formation on a Loess Soil as Influenced by Polyacrylamide

    HU Xia; LIU Lian-You; LI Shun-Jiang; CAI Qiang-Guo; L(U) Yan-Li; GUO Jin-Rui


    This study evaluated the morphological characteristics and dynamic variation in characteristics of soil crust and identified the relationships between soil crust and splash erosion under simulated rainfall.The effect of polyacrylamide (PAM) on soil aggregate stabilization and crust formation was also investigated.A laboratory rainfall simulation experiment was carried out using soil sample slices.The slices were examined under a polarized light microscopy and a scanning electron microscope (SEM).The results revealed that the soil crusts were thin and were characterized by a greater density,higher shear strength,finer porosity,and lower saturated hydraulic conductivity than the underlying soil.Two types of crusts,i.e.,structural and depositional crusts,were observed.Soil texture was determined to be the most important soil variable influencing surface crust formation; depositional crust formation was primarily related to the skeleton characteristics of the soil and happened when the soil contained a high level of medium and large aggregates.The crust formation processes observed were as follows:1) The fine particles on the soil surface became spattered,leached,and then rough in response to raindrop impact and 2) the fine particles were washed into the subsoil pores while a compact dense layer concurrently formed at soil surface due to the continual compaction by the raindrops.Therefore,the factors that influenced structural crust formation were a large amount of fine particles in the soil surface,continual impact of raindrops,dispersion of aggregates into fine particles,and the formation of a compact dense layer concurrently at the soil surface.It was concluded that the most important factor in the formation of soil crusts was raindrop impact.When polyacrylamide (PAM) was applied,it restored the soil structure and greatly increased soil aggregate stabilization.This effectively prevented crust formation.However,this function of PAM was not continuously effective and


    Luigi Cavazza


    Full Text Available Soil surface crusting has severe agricultural and environmental effects. The action of beating rains can destroy soil surface structure and in some cases lead to surface sealing and crusting which, in turn, reduce soil conductivity, seed emergence and increase the runoff hazard. The susceptibility of different soils to crusting was studied by a new experimental apparatus and model. A micro rain – simulator mounted on a rotating disc sprinkles water on soil sample and after a certain time (or revolutions of the disc the water ponded on soil surface completely percolates and water is again applied to the soil surface. The model was used to follow the variation of soil hydraulic conductivity as a function of time or total water applied during the crust formation. The effects of soil sieved crumbs and duration of pre-saturation were investigated during the crust formation. For some soils crusting decreases along the sprinkling events, with the diameter of aggregates presenting high values; sometimes significant structural deterioration in the aggregate of higher diameter occurs after a initial resistance to crusting as evidenced by a sharp reduced hydraulic conductivity. The role of the pre-saturation time seem more important for less resistant soils.


    The term "Soil Biology", the study of organism groups living in soil, (plants, lichens, algae, moss, bacteria, fungi, protozoa, nematodes, and arthropods), predates "Soil Ecology", the study of interactions between soil organisms as mediated by the soil physical environment. oil ...

  16. The impact of soil crusts on overland flow and soil degradation processes in Souss valley, South Morocco

    Giudici, Christiane; Peter, Klaus Daniel; Schneider, Raimund; Ries, Johannes B.; Aït Hssaïne, Ali


    sample. Moreover, a connection between micromorphology and runoff could be established. Platy structure and vesicles led to a high and very high runoff, while vegetation cover, biological crusts, vertical pore continuity and connectivity was linked with middle and low runoff rates. On the levelled areas, platy structure and vesicles dominated, probably due to the use of heavy land levelling machines. The crusts on the un-levelled areas showed different and more variable microstructures. Biological soil crusts lowered the runoff, however,especially pronounced in combination with vertical pore continuity and connectivity. Vegetation cover was the most effective protection against soil degradation.

  17. Effects of physical soil crusts on infiltration and splash erosion in three typical Chinese soils

    Chong-feng BU; Shu-fang WU; Kai-bao YANG


    Physical soil crusts likely have significant effects on infiltration and soil erosion, however, little is known on whether the effects of the crusts change during a rainfall event. Further, there is a lack of discussions on the differences among the crusting effects of different soil types. The objectives of this study are as follows: (i) to study the effects of soil crusts on infiltration, runoff, and splash erosion using three typical soils in China, (ii) to distinguish the different effects on hydrology and erosion of the three soils and discuss the primary reasons for these differences, and (iii) to understand the variations in real soil shear strength of the three soils during rainfall events and mathematically model the effects of the crusts on soil erosion. This study showed that the soil crusts delayed the onset of infiltration by 5 to 15 min and reduced the total amount of infiltration by 42.9 to 53.4%during rainfall events. For a purple soil and a loess soil, the initial crust increased the runoff by 2.8%and 3.4%, respectively, and reduced the splash erosion by 3.1% and 8.9%, respectively. For a black soil, the soil crust increased the runoff by 42.9%and unexpectedly increased the splash erosion by 95.2%. In general, the effects of crusts on the purple and loess soils were similar and negligible, but the effects were significant for the black soil. The soil shear strength decreased dynamically and gradually during the rainfall events, and the values of crusted soils were higher than those of incrusted soils, especially during the early stage of the rainfall. Mathematical models were developed to describe the effects of soil crusts on the splash erosion for the three soils as follows:purple soil, 0.384Fc =0.002t− ; black soil, 3.060Fc =−0.022t+ ; and loess soil, Fc =0.233 ln t−1.239 . Combined with the equation 1)Rc=Fc⋅(Ruc− , the splash erosion of the crusted soil can be predicted over time.


    Tongxin ZHU


    Soil crusting may have significant impacts on infiltration, runoff generation and erosion in agricultural lands or semi-arid and arid soils. The previous investigations on soil crusting were often conducted under simulated rainfall conditions. This study aims to evaluate the effects of soil crusting on soil moisture during inter-storm periods and soil and water losses during storm periods under natural rainfalls. The study site was located in the Loess Plateau of China. Four plots with a uniform slope and size were selected. Soil crusts were kept intact on the two plots throughout the monitoring periods of 1999 and 2000,but were broken after each rain storm event on the other two plots. Soil moisture was measured on all plots with an interval of one week at three depths and total event runoff and sediment discharges were measured in each storm. It was found that no marked difference in soil moisture and runoff exists between the crusted and uncrusted plots. This is because the rapid development of new crusts on the uncrusted plots during the storm events. However, the erosion rate on the uncrusted plots was significantly higher than that on the crusted plots, which was mainly caused by the disturbance of the surface soils on the uncrusted plots. This study questions the effectiveness of a common agricultural practice in the Loess Plateau, hoeing lands after rainfall, in reducing runoff and erosion.

  19. La costra biológica del suelo: Avances recientes en el conocimiento de su estructura y función ecológica Biological soil crusts: Recent advances in our knowledge of their structure and ecological function



    estructura y funcionamiento de los ecosistemas en los que se encuentran.Biological soil crusts (BSCs result from an intimate association between soil particles and cyanobacteria, algae, microfungi, lichens, and bryophytes. These crusts are widespread in many type of soils and in almost all plant communities where sunlight can reach the soil surface. However, BSCs are particulary dominant in environments with low productivity such as arid, semi-arid, alpine and polar areas. Biological soil crusts affect soil nutrient cycling, influence the local hidrological cycle, increase soil stability, and affect the establisment and performance of vascular plants. The knowledge on the biology, ecology and physiology of BSCs has substantially increased in recent years. However, there are important gaps in our knowledge concerning the influence of BSCs on biogeochemical cycles, particularly of phosphorus and carbon, as well as on many aspects related to biotic interactions among BSC components, and between these components and microorganisms, vascular plants and invertebrates. It is necessary to expand current research efforts to other parts of the world, as most studies have been conducted mainly in arid and semi-arid areas of USA, Israel, Australia and China. Of particular concern is the lack of studies from Central and South America, despite BSCs must be a key biotic component in countries such as Chile, Argentina, Peru and Mexico. With the aim of increasing the interest of the scientific community of Spanish-speaking countries about this important group of organisms, in this review we illustrate recent advances on the importance of BSCs to maintain the structure and functioning of those ecosystems in which they are present. We also highlight the main gaps in our knowledge on the ecology of these organisms, and discuss key areas for future research.

  20. Comparison of diurnal dynamics in evaporation rate between bare soil and moss-crusted soil within a revegetated desert ecosystem of northwestern China

    Ya-Feng Zhang; Xin-Ping Wang; Yan-Xia Pan; Rui Hu


    Effects of biological soil crusts (BSCs) on soil evaporation is quite controversial in literature, being either facilitative or inhibitive, and therein few studies have actually conducted direct evaporation measurements. Continuous field measurements of soil water evaporation were conducted on two microlysimeters, i.e., one with sand soil collected from bare sand dune area and the other with moss-crusted soil collected from an area that was revegetated in 1956, from field capacity to dry, at the southeastern edge of the Tengger Desert. We mainly aimed to quantify the diurnal variations of evaporation rate from two soils, and further comparatively discuss the effects of BSCs on soil evaporation after revegetation. Results showed that in clear days with high soil water content (Day 1 and 2), the diurnal variation of soil evaporation rate followed the typical convex upward parabolic curve, reaching its peak around midday. Diurnal evaporation rate and the accumulated evaporation amount of moss-crusted soil were lower (an average of 0.90 times) than that of sand soil in this stage. However, as soil water content decreased to a moderately low level (Day 3 and 4), the diurnal evaporation rate from moss-crusted soil was pronouncedly higher (an average of 3.91 times) than that of sand soil, prolonging the duration of this higher evaporation rate stage; it was slightly higher in the final stage (Day 5 and 6) when soil moisture was very low. We conclude that the effects of moss crusts on soil evaporation vary with different evaporation stages, which is closely related to soil water content, and the variation and transition of evaporation rate between bare soil and moss-crusted soil are expected to be predicted by soil water content.

  1. Impact of Biological Soil Crust on Soil Physical Properties in the Hilly Loess Plateau Region,China%黄土丘陵区生物结皮对土壤物理属性的影响

    高丽倩; 赵允格; 秦宁强; 张国秀; 杨凯


    Biological soil crusts(biocrusts) are ubiquitous living surface covers in many arid and semi-arid regions.It has been demonstrated that the coverage of biocrusts was over 70% in the hilly Loess Plateau region of China and it played many important roles,such as exerting observably impact on soil properties and improving soil antierodibility.But the response of soil physical properties to the development of biocrusts has been unclear so far.The objective of the study was to determine the impact of development of biocrusts(i.e.with variable biomass) on soil physical properties in hilly Loess Plateau region.In this study,soil samples were collected after biocrusts and vegetation coverage survey,and the soil physical properties including soil bulk density,soil porosity,field water holding capacity,cohesion and hardness of biocrusts in different developmental stages were determined.The results showed: 1) Fine particles content increased due to the development of biocrusts.The content of coarse sand decreased by 86% while fine sand increased by 45% with biocrusts developing from cyanobacteria dominated to moss dominated(biomass of moss was 4.31±0.12 g/dm^2).2) With the development of biocrusts,soil bulk density and hardness were reduced while field water holding capacity,soil porosity and cohesion were increased significantly.Along with the development of biocrusts,soil bulk density was dropped by 15%.Soil hardness of biocrusts in later development stage was reduced by 68% compared with the early stage.Field water holding capacity was increased to 57%,adding about 36% compared with the early stage,while soil porosity gone up to 58%,increasing by about 14%.Cohesion of biocrusts was 6 or 7 times as much as that of subsurface soil(0-2 cm).3) Impact of biocrusts on soil physical properties was closely related to biocrusts'biomass.When biomass of moss in biocrusts was to 2.91±0.12 g/dm^2,soil physical properties changed no longer significantly.4

  2. Responses of biological soil crust to and its relief effect on raindrop kinetic energy%生物土壤结皮对雨滴动能的响应及削减作用

    秦宁强; 赵允格


    Based on the field investigation and by the method of simulated single-drop rain, this pa-per studied the responses of different types of biological soil crusts ( biocrusts) in the wind-water erosion interleaving region of Loess Plateau to and their relief effect on the kinetic energy of rain-drops. The responses of the biocrusts to raindrop kinetic energy had close relations with their biolog-ical composition. The cyanobacteria-dominated biocrusts with a thickness of 1 cm and the moss-dominated biocrusts with the coverage of 80% could resist in 0.99 J and 75. 56 J of cumulative rain drop kinetic energy, respectively, and the potential resistance of the biocrusts with the same biologi-cal compositions was relative to the biomass of the biological compositions, i. e. , the larger the bio-mass , the higher the resistance. As the chlorophyll a content of cyanobacteria- dominated biocrusts (which characterizes the cyanobacterial biomass) increased from 3. 32 to 3. 73μg · g-1, the resist-ance of the biocrusts against the cumulative raindrop kinetic energy increased from 0. 99 to 2. 17 J; when the moss biomass in the moss- dominated biocrusts increased from 2.03 to 4. 73 g · dm-2, the resistance of the crusts increased from 6. 08 to 75. 56 J. During the succession of the biocrusts, their responses to the raindrop kinetic energy presented an "S" pattern. No significant differences in the resistance against raindrop cumulative kinetic energy were observed between the cyanobacte-ria-dominated biocrusts with variable biomass, but the resistance of moss-dominated biocrusts in-creased significantly as their biomass per unit area increased. The resistance of moss-dominated bio-crusts increased linearly when their biomass increased from 2.03 g ·dm-2 to 4. 73g·dm-2. The moss-dominated biocrusts could resist in 62.03 J of raindrop kinetic energy when their biomass was up to 3.70 g · dm-2. Biocrusts had obvious effects in relieving raindrop kinetic energy, and the re

  3. 黄土丘陵区不同降水量带生物结皮对土壤氮素的影响%Impacts of biological soil crusts on soil nitrogen in different rainfall regions in hilly areas of the Loess Plateau, China

    明姣; 赵允格; 许明祥; 杨丽娜; 王爱国; 姚春竹


    黄土丘陵区生物结皮广泛发育,可通过固氮作用影响土壤氮素水平,但该区生物结皮对土壤氮素水平的影响鲜见报道.本文通过野外调查结合采样分析,研究了黄土丘陵区不同降水量带生物结皮组成、覆盖度差异及其对土壤氮素水平的影响.结果表明,1)黄土丘陵区不同降水量带生物结皮覆盖度无显著差异,但组成有差别;2)不同降水量带土壤氮素含量剖面分布具有明显的分层特征,生物结皮显著增加了结皮层土壤氮素含量,对下层土壤影响较小,结皮层下0-2 cm、2-5 cm、5-10 cm土层中氮素含量差异不显著;3)生物结皮层土壤全氮、碱解氮及微生物氮在不同降水量带差异不显著,而0-2 cm、2-5 cm、5-10 cm土壤全氮、碱解氮及土壤微生物氮含量在200~300 mm降水量带小于300~600 mm降水量带.研究结果揭示了黄土丘陵区生物结皮对土壤氮素的贡献,而不同降水量带生物结皮对土壤氮素的贡献差异不显著的原因有待于进一步研究.%Biocrusts ( biological soil crusts) , as ubiquitous living covers on soil surface of the revegetated grasslands in the hilly Loess Plateau regions, are potential influence factors on soil nitrogen contents. However, studies on the influence of biocrusts on soil nitrogens in this region were fresh. The objective of the paper was to determine the impact of biological soil crusts on soil nitrogen contents. Field investigation was conducted, and the contents of soil total nitrogen, soil alkali-hydrolyzable nitrogen and soil microbial nitrogen in different soil layers from various rainfall regions were analyzed. The results show that the coverage of biocrusts in different rainfall regions have no significant differences, while the compositions of biocrusts are different. The formation of the biocrusts enriched nitrogen (soil total nitrogen, alkali-hydrolyzable nitrogen and soil microbial nitrogen) in the upper layers of soils

  4. 黄土丘陵区不同演替阶段生物结皮对土壤CO2通量的影响%Effects of biological soil crust at different succession stages in hilly region of Loess Plateau on soil CO2 flux

    王爱国; 赵允格; 许明祥; 杨丽娜; 明姣


    生物结皮是土壤表面具有光合活性的致密复合层,是土-气界面CO2通量的影响因子之一.本文采用改进的Li-8100土壤碳通量测量系统,研究了黄土丘陵区退耕地上不同演替阶段生物结皮对土壤CO2通量的影响.结果表明:光照条件下,生物结皮土壤CO2通量较除去生物结皮显著下降,其中藻结皮和藓结皮分别下降了92%和305%;生物结皮对土壤CO2通量的降低程度与其生物组成和生物量有关,深色藻结皮和藓结皮土壤CO2通量较裸地分别降低了141%和484%.生物结皮土壤CO2通量的日变化呈降低-升高-降低的趋势,而裸地CO2通量日变化趋势为单峰曲线,藻结皮、藓结皮的碳吸收峰值分别出现在8:00和9:00前后,其CO2通量分别为0.13和-1.02 μmol CO2·m-2·s-1;藻结皮24 h CO2通量排放总量较裸地增加7.7%,而藓结皮减少了29.6%.生物结皮对土壤CO2通量的影响显著,在评价退耕地土壤碳循环时,应考虑生物结皮的影响.%Biological soil crust ( biocrust) is a compact complex layer of soil, which has photosyn-thetic activity and is one of the factors affecting the CO2 flux of soil-atmosphere interface.In this paper, the soil CO2 flux under the effects of biocrust at different succession stages on the re-vegetated grassland in the hilly region of Loess Plateau was measured by a modified LI-8100 automated CO2 flux system.Under light condition, the soil CO2 flux under effects of cyanobacteria crust and moss crust was significantly decreased by 92% and 305% , respectively, as compared with the flux without the effects of the biocrusts.The decrement of the soil CO2 flux by the biocrusts was related to the biocrusts components and their biomass.Under the effects of dark colored cyanobacteria crust and moss crust, the soil CO2 flux was decreased by 141% and 484% , respectively, as compared with that in bare land.The diurnal curve of soil CO2 flux under effects of biocrusts presented a

  5. Physical characterization, spectral response and remotely sensed mapping of Mediterranean soil surface crusts

    Jong, S.M. de; Addink, E.A.; Duijsing, D.; Beek, L.P.H. van


    Soil surface crusting and sealing are frequent but unfavorable processes in Mediterranean areas. Soil crust and seals form on bare soil subject to high-intensity rainfall, resulting in a hard, impenetrable layer that impedes infiltration and hampers the germination and establishment of plants. The a

  6. Soil Crust Changes due to Wetting and Drying Analyzed by Non-Invasive Images

    In this work a γ-ray computed tomography (CT) scanner was used to evaluate soil crust changes due to wetting and drying (W-D) cycles. Changes in soil porous system (SPS) due to W-D cycles of samples with crust have important practical consequences, because they can affect the soil water retention curve (SWRC) representativeness. CT data allowed detailed analyses of the soil bulk density (db) for thick layers, which cannot be achieved by traditional methods commonly used in soil physics. It was also possible to observe a decrease in db in the crust region. These results show that important changes can occur in SPS during SWRC evaluations.

  7. Process and Mechanism for the Development of Physical Crusts in Three Typical Chinese Soils

    BU Chong-Feng; W.J.GALE; CAI Qiang-Guo; WU Shu-Fang


    To compare the development of physical crusts in three typical cultivated soils of China,a black soil (Luvic Phaeozem),a loess soil (Haplic Luvisol),and a purple soil (Calcaric Regosol) were packed in splash plates with covered and uncovered treatments,and exposed to simulated rainfall.Meshes covered above the surfaces of half of soil samples to simulate the effects of crop residue on crusting.The results indicated a progressive breakdown of aggregates on the soil surface as rainfall continued.The bulk density and shear strength on the surface of the three soil types increased logarithmically as rainfall duration increased.During the first 30 min of simulated rainfall,the purple soil developed a 7-8 mm thick crust and the loess soil developed a 3-4 mm thick crust.The black soil developed a distinguishable,but still unstable,crust after 80 min of simulated rainfall.Soil organic matter (SOM) content,the mean weight diameter (MWD) of soil aggregates,and soil clay content were negatively correlated with the rate of crust formation,whereas the percentage of aggregate dispersion (PAD),the exchangeable sodium percentage (ESP),and the silt and sand contents were positively correlated with crusting.Mechanical breakdown caused by raindrop impact was the primary mechanism of crust formation in the black soil with more stable aggregates (MWD 25.0 mm,PAD 3.1%) and higher SOM content (42.6 g kg-1).Slaking and mechanical eluviation were the primary mechanisms of crust formation in the purple soil with low clay content (103 g kg-1),cation exchange capacity (CEC,228 mmol kg-1),ESP (0.60%),and SOM (17.2 g kg-1).Mechanical breakdown and slaking were the most important in the loess soil with low CEC (80.6 mmol kg-1),ESP (1.29%),SOM (9.82 g kg-1),and high PAD (71.7%) and MWD (4.6 mm).Simulated residue cover reduced crust formation in black and loess soils,but increased crust formation in purple soil.

  8. Spectroscopic surrogates of soil organic matter resilience in crusted semiarid Mediterranean ecosystems

    Miralles Mellado, Isabel; Almendros, Gonzalo; Ortega, Raúl; Cantón, Yolanda; Poveda, Francisco; van Wesemael, Bas


    Arid and semiarid ecosystems represent nearly a third of the Earth's total land surface. In these ecosystems, there is a critical balance between C sequestration and biodegradation that could easily be altered due to human disturbance or global change. These ecosystems are widely characterized by the presence of biological soil crusts (BSCs) which play the most important role in the C-cycle in arid and semiarid areas. Consequently, soil organic matter (SOM) characteristics of crusted soil could readily reflect important information on the resilience of SOM in response to any global temperature increase or to inappropriate soil management practices. In this research, representative BSCs and underlying soils were studied in two different semiarid ecosystems in Southern Spain, i.e., Amoladeras (located in Cabo de Gata Natural Park), and El Cautivo (located in Tabernas desert). Chemical fractionation and characterization of the SOM in BSCs and underlying soils were carried out in order to assess not only the total amount of organic C sequestered but mainly the quality of humic-type organic fractions. After isolating the major organic fractions (particulate fraction, humic acid-like (HA), alkali-extracted fulvic acid (FA) and H3PO4-FAs), the macromolecular, HA fraction was purified and studied by derivative visible spectroscopy and resolution-enhanced infrared (IR) spectroscopy. Our results show differences in the structural characteristics of the HA-type substances, interpreted as progressive stages of diagenetic transformation of biomacromolecules. Amoladeras showed higher SOM content, and higher values of HA and HA/FA ratio than El Cautivo, with lower SOM content in BSCs and underlying soils. The latter site accumulates SOM consisting mainly of comparatively less recalcitrant organic fractions with small molecular sizes (H3PO4-FAs and FAs). Moreover HAs in samples from Amoladeras showed higher condensation and aromaticity (higher E4, lower E4/E6 ratio), pointing to

  9. Experimental investigation of the early interaction between cyanobacterial soil crusts and vascular plants

    Klemens Zaplata, Markus; Veste, Maik; Pohle, Ina; Schümberg, Sabine; Abreu Schonert, Iballa; Hinz, Christoph


    While there are hints that biological soil crusts (BSCs) can constitute physical barriers for the emergence of vascular plants, a conceptual approach for the quantitative evaluation of these effects is still missing. Here we present an experimental design to test the emergence of seedlings in situ with (i) capping natural intact, (ii) destroyed and (iii) removed BSC. The selected field site is directly adjacent to the constructed Hühnerwasser catchment (Lusatia, Germany). This site exists since the end of 2008 and consists of loamy sand. Serving as proxy for seedling thrust, we inserted pre-germinated seeds of three confamiliar plant species with different seed masses (members of the Fabaceae family: Lotus corniculatus L., Ornithopus sativus Brot., and Glycine max (L.) Merr.). In each treatment as well as in the control group planting depths were 10 mm. We took care that experimental plots had identical crust thickness, slightly less than 4 mm, serving as proxy for mechanical resistance. A plot became established as follows: Firstly, the pristine crusted surface was vertically cut. To the windward side the BSC remained intact (i: "with BSC" stripe). To the downwind side soil material was temporarily excavated for laterally inserting the seeds beneath the surface of the first stripe. Then at the thereby disturbed second stripe pulverised BSC material became filled as a top layer (ii: "BSC mix" stripe). From the next stripe the BSC was removed (iii: "no BSC" stripe). Thus each plot had each experimental group in spatial contiguity (within 50 cm × 50 cm). The overall 50 plots were distributed across an area of 40 m × 12 m. When individuals of a species either emerged at all stripes, "× × ×", or at no stripe of a plot, "- - -", there was no reason to suppose any effect of a crust. The "- × ×" emergence pattern (depicting the appearance of seedlings in both stripes possessing manipulated surfaces) points towards hindrance more clearly than "- × -" or "- -

  10. Cyanobacterial community composition in Arctic soil crusts at different stages of development

    Pushkareva, E.; Pessi, I. S.; Wilmotte, A.; Elster, Josef


    Roč. 91, 12 fiv143 (2015), s. 1-10. ISSN 0168-6496 Institutional support: RVO:67985939 Keywords : soil crust * Arctic * cyanobacteria Subject RIV: EH - Ecology, Behaviour Impact factor: 3.568, year: 2014

  11. Potential methanotrophic and methanogenic activity of soil crusts in semi-arid Tabernas region

    Macková, Jana; Macek, P.; Pugnaire, F.I.; Šimek, Miloslav

    Dijon : INRA, 2014. s. 484. [Global Soil Biodiversity Conference. Assessing soil biodiversity and its role for ecosystem services /1./. 02.12.2014-05.12.2014, Dijon] Institutional support: RVO:60077344 Keywords : methane oxidation and production * soil crusts * semi-arid zone * nutrient content Subject RIV: EH - Ecology, Behaviour

  12. 黄土丘陵区生物结皮对土壤磷素有效性及碱性磷酸酶活性的影响%Impacts of biological soil crust on availability of phosphorus and phosphatase activity in hilly regions of the Loess Plateau, China

    张国秀; 赵允格; 许明祥; 高丽倩


    Biocrusts (biological soil crusts ), as ubiquitous living covers on soil surface of the revegetated grasslands in hilly regions of the Loess Plateau, are potential influence factors on the availability of soil P (phosphorus). However, researches focus on the relationship between soil P availability and development of biocrusts were still fresh so far. Impacts of biocrusts on soil total P, available P and phosphatase activity were investigated in revegetated grasslands at different stages of biocrusts developed after the survey of biocrusts distribution. The objects of the study were to determine the influences of biocrusts development on the availability of soil P in the region. The results show that the biological crusts could significantly improve soil total phosphorus contents in the biocrusts layers, while the contents of total phosphorus in 0-10 cm layers are not significant. Soil available phosphorus contents of the biocrusts in the study area are in the range of 3.27-5.87 mg/kg, which are accounting for O. 57%-0. 95% of total P in the same layer. The alkaline phosphatase activities in biocrusts are significantly higher than those of the lower soils (0-10 cm) 3-81 times. The effects of biological crusts on the availability of soil P and phosphatase activity are related to the developmental stages of biocrusts. The biological crusts increase availability alkaline phosphatase activity and organic matter, of soil phosphorus. These results suggest that and reduce the crusts on soil pH, finally improve the availability of soil P could be significantlyenhanced for the formation of biocrusts.%黄土丘陵区生物结皮广泛发育,可影响土壤磷素有效性。目前鲜见生物结皮对土壤磷素有效性的研究报道。本文以该区不同年限退耕地的生物结皮为研究对象,通过野外调查和室内分析,研究了生物结皮对土壤全磷、有效磷及碱性磷酸酶活性的影响。结果表明,1)生物结皮的形

  13. Soil crusting regulator characteristics of some allic humid tropical soils from Colombia

    It was collected soil samples within 5 cm of the surface from Amazonia soils in Caqueta (Macagual); Orinoquia in Meta (Carimagua), Casanare (Matazul) and Vichada (La Primavera); and in Andean region in Cauca (San Isidro) and Valle (CIAT, Palmira). In each of those sites, the International Center for Tropical Agriculture (CIAT) has many experiments to know the impact of land husbandry, leguminous associations and rotations and mulches on natural system. After evaluating weighed particle size, sand particle size, soil organic matter, iron, aluminum and silicon oxides, and fertility, it could cluster in three groups according to those characteristics and their importance in governing soil hazard crusting: la Primavera and Carimagua (high organic matter, oxides and fine sand but low in clay); Matazul and Macagual (low in organic matter, oxides and clay but variable sand values); and San Isidro (the greatest in Al2O3 concentrations, high in Fe2O3 clay and fine sand but the poorest in soil organic matter). Soil organic matter contents were significantly associated with the kind of management

  14. Nitrogenase activity of biological soil crusts and its response to hydrothermic factors in the Shapotou region of northern China%沙坡头地区生物土壤结皮的固氮活性及其对水热因子的响应

    张鹏; 李新荣; 贾荣亮; 胡宜刚; 黄磊


    Aims In arid and semi-arid environments such as deserts, nitrogen is often the most limiting nutrient for biological activity. Biological soil crusts (BSCs) are an important component of vegetation in the Shapotou region in the Tengger Desert, northern China. However, their importance as contributors to soil fertility such as nitrogen fixation is relatively unknown. This study was conducted to quantify the potential nitrogenase activity (NA) of different types of BSCs in artificial vegetation areas, as well as their responses to variation in moisture and temperature.Methods Algae crust, lichen crust and moss crust were collected from an artificial vegetation area in the Shapotou region, and were incubated under three gradients of moisture (3, 5 and 10 mm simulated rainfall) and temperature in open-top growth chambers from June to October. The NA was measured using acetylene reduction assay. One-way ANOVA and general linear models (GLM) procedure were applied to compare NA between treatments and interactions between type of BSCs, water and temperature.Important findings NA for each type of BSC was highly variable, ranging from 2.5 × 103 to 6.2 × 104 nmol C2H4·m-2·h-1. The NA of algae crust was higher than that of lichen crust and moss crust (2.8 vs. 2.4 and 1.4 × 104 nmol C2H4·m-2·-1, respectively). The three types of BSCs under the 3 mm simulated rainfall reached the maximum rate of nitrogen fixation, but > 3 mm did not affect NA. Significant negative correlation was observed between NA of all three types of BSCs and temperature. The optimal temperature for NA in algae crust, moss crust and lichen crust were 25-30 ℃, 25-30 ℃ and 20-30 ℃, respectively.%氮是除水分之外影响干旱区生态系统生物活性的关键因子.生物土壤结皮是干旱半干旱荒漠地表景观的重要组成部分,也是荒漠生态系统氮素的主要贡献者.通过野外调查采样,利用开顶式生长室,模拟不同降水梯度,采用乙炔还原法连续

  15. Microbial exopolysaccharides as determinants of geomorphological, hydrological and optical properties of soil crusts from the Precambrian till today

    Garcia-Pichel, F.


    The presence of microbial extracellular polysaccharides (EPS) in the soil solution and/or in association with particular microbial types can impart novel properties to biological soil crust (BSC), and hence to soil surfaces. For the most part these properties are of a geobiological relevance that exceeds what one could surmise from its relatively low specific mass content. I will review some examples that range from the mundane to the unexpected. EPS associated with filamentous cyanobacteria can effectively and in the long term stabilize the soil surface against erosive forces, even after the microbes are long gone. Electrostatic interactions between EPS and blowing dust may help retain dust particles, enriching the soil with new nutrient sources. In a telltale sign of BSC presence, EPS is the agent that allows sandy soils to fold and curl-up, to form pee-tee's and elephant-skin surfaces, and to crack into polygons like clays would. EPS in large quantities in flat crusts can retain fluids (both liquid and gaseous) resulting in the alteration of hydrological flow and in the formation of internal vesicular horizons, gas bubbles, pock-marked surfaces and other characteristic structures. Yet, in some settings, EPS plays an architectural role in creating a "spongy" texture that increases hydraulic conductivity. This architectural role can indirectly result in significant increases of a crust's albedo. While the diversity of consequences of EPS presence is far from understood, evidence for its sustained role through Earth's history can be found in the form of sedimentary bio-signatures as far back as the Proterozoic.

  16. Potential fate of SOC eroded from natural crusted soil surface under simulated wind driven storm

    Xiao, Liangang; Fister, Wolfgang; Greenwood, Philip; Hu, Yaxian; Kuhn, Nikolaus J.


    Improving the assessment of the impact of soil erosion on carbon (C) cycling requires a better understanding of the redistribution of eroded sediment and associated soil organic carbon (SOC) across agricultural landscapes. Recent studies conducted on dry-sieved aggregates in the laboratory demonstrated that aggregation can profoundly skew SOC redistribution and its subsequent fate by accelerating settling velocities of aggregated sediment compared to mineral grains, which in turn can increase SOC mineralization into greenhouse gases. However, the erodibility of the soil in the field is more variable than in the laboratory due to tillage, crus formation, drying-wetting and freeze-thaw cycles, and biological effects. This study aimed to investigate the potential fate of the SOC eroded from naturally developed soil surface and to compare the observations with those made in the laboratory. Simulated, short, high intensity wind driven storms were conducted on a crusted loam in the field. The sediments were fractionated with a settling tube according to their potential transport distances. The soil mass, SOC concentration and cumulative 80-day CO2 emission of each fraction were identified. The results show: 1) 53% of eroded sediment and 62% of eroded SOC from the natural surface in the field would be deposited across landscapes, which is six times and three times higher compared to that implied by mineral grains, respectively; 2) the preferential deposition of SOC-rich fast-settling sediment potentially releases approximately 50% more CO2 than the same layer of the non-eroded soil; 3) the respiration of the slow-settling fraction that is potentially transported to the aquatic systems was much more active compared to the other fractions and the bulk soil. Our results confirm in general the conclusions drawn from laboratory and thus demonstrate that aggregation can affect the redistribution of sediment associated SOC under field conditions, including an increase in

  17. Surface disturbance of cryptobiotic soil crusts: nitrogenase activity, chlorophyll content, and chlorophyll degradation

    Belnap, Jayne; Harper, Kimball T.; Warren, Steven D.


    Cryptobiotic soil crusts are an important component of semiarid and arid ecosystems. An important role of these crusts is the contribution of fixed nitrogen to cold‐desert ecosystems. This study examines the residual effects of various intensities and combinations of different surface disturbances (raking, scalping, and tracked vehicles) on nitrogenase activity, chlorophyll content, and chlorophyll degradation in these soil crusts. Nine months after disturbance chlorophyll content of disturbed soils was not statistically different from undisturbed controls, except in the scalped treatments, indicating recovery of this characteristic is fairly quick unless surface material is removed. Differences in chlorophyll degradation among treatments were not statistically significant. However, nitrogenase activity in all treatments showed tremendous reductions, ranging from 77–97%, when compared to the control, indicating this characteristic is slow to recover. Consequently, assessment of crustal recovery from disturbance must include not only visual and biomass characteristics but other physiological measurements as well. Areas dominated by these crusts should be managed conservatively until the implications of crustal disturbance is better understood.

  18. Spectra and vegetation index variations in moss soil crust in different seasons, and in wet and dry conditions

    Fang, Shibo; Yu, Weiguo; Qi, Yue


    Similar to vascular plants, non-vascular plant mosses have different periods of seasonal growth. There has been little research on the spectral variations of moss soil crust (MSC) over different growth periods. Few studies have paid attention to the difference in spectral characteristics between wet MSC that is photosynthesizing and dry MSC in suspended metabolism. The dissimilarity of MSC spectra in wet and dry conditions during different seasons needs further investigation. In this study, the spectral reflectance of wet MSC, dry MSC and the dominant vascular plant (Artemisia) were characterized in situ during the summer (July) and autumn (September). The variations in the normalized difference vegetation index (NDVI), biological soil crust index (BSCI) and CI (crust index) in different seasons and under different soil moisture conditions were also analyzed. It was found that (1) the spectral characteristics of both wet and dry MSCs varied seasonally; (2) the spectral features of wet MSC appear similar to those of the vascular plant, Artemisia, whether in summer or autumn; (3) both in summer and in autumn, much higher NDVI values were acquired for wet than for dry MSC (0.6 ∼ 0.7 vs. 0.3 ∼ 0.4 units), which may lead to misinterpretation of vegetation dynamics in the presence of MSC and with the variations in rainfall occurring in arid and semi-arid zones; and (4) the BSCI and CI values of wet MSC were close to that of Artemisia in both summer and autumn, indicating that BSCI and CI could barely differentiate between the wet MSC and Artemisia.

  19. Vietnam workshop on soil quality: Soil biology and chemistry

    G. B. Reddy


    This presentation was presented during the Soil Quality workshop held at Nong Lam University, June 2007. It shows the importance of biological diversity as a gauge of good soil quality. Furthermore, criteria of healthy chemical balances in soil is also explained. Simple measures of biological and chemical indices of soil health are summarized.

  20. Experimental design to model infiltration into a water repellent soil using a crust-type infiltration equation

    Adnès, Cyriel; Morschel, Jean; Darboux, Frédéric


    The combustion of vegetation during forest fires can lead to the condensation of hydrophobic compounds on mineral matter near the soil surface. The resulting water repellent layer then inhibits water infiltration by altering soil hydraulic conductivity and the water content–soil matric suction relationship. This situation resembles that of a crust or seal capped soil, where a thin layer of reduced hydraulic conductivity overlays a more permeable soil. Although the physical processes leading t...

  1. Transient Liquid Water as a Mechanism for Induration of Soil Crusts on Mars

    Landis, G. A.; Blaney, D.; Cabrol, N.; Clark, B. C.; Farmer, J.; Grotzinger, J.; Greeley, R.; McLennan, S. M.; Richter, L.; Yen, A.


    The Viking and the Mars Exploration Rover missions observed that the surface of Mars is encrusted by a thinly cemented layer tagged as "duricrust". A hypothesis to explain the formation of duricrust on Mars should address not only the potential mechanisms by which these materials become cemented, but also the textural and compositional components of cemented Martian soils. Elemental analyzes at five sites on Mars show that these soils have sulfur content of up to 4%, and chlorine content of up to 1%. This is consistent with the presence of sulfates and halides as mineral cements. . For comparison, the rock "Adirondack" at the MER site, after the exterior layer was removed, had nearly five times lower sulfur and chlorine content , and the Martian meteorites have ten times lower sulfur and chlorine content, showing that the soil is highly enriched in the saltforming elements compared with rock.Here we propose two alternative models to account for the origin of these crusts, each requiring the action of transient liquid water films to mediate adhesion and cementation of grains. Two alternative versions of the transient water hypothesis are offered, a top down hypothesis that emphasizes the surface deposition of frost, melting and downward migration of liquid water and a bottom up alternative that proposes the presence of interstitial ice/brine, with the upward capillary migration of liquid water.

  2. Highlights on progress in forest soil biology

    Uroz, S.; Bispo, A; Buee, M.; Cebron, A.; Cortet, J.; Decaens, T.; Hedde, M.; Peres, G; Vennetier, M.; Villenave, C.


    Determining the identity and function of forest soil organisms is essential to understand their relative roles, but also to determine their resilience after environmental perturbations. These characteristics are scientific challenges because of the high biological diversity of forest soil organisms, but also because many of them currently remain unknown. In this context, this review presents a snapshot of the difficulty associated with soil organism characterization, the uniqueness of forest ...

  3. Dynamic effects of wet-dry cycles and crust formation on the saturated hydraulic conductivity of surface soils in the constructed Hühnerwasser ("Chicken Creek") catchment

    Hinz, Christoph; Schümberg, Sabine; Kubitz, Anita; Frank, Franzi; Cheng, Zhang; Nanu Frechen, Tobias; Pohle, Ina


    Highly disturbed soils and substrates used in land rehabilitation undergo rapid changes after the first wetting events which in turn can lead to ecosystem degradation. Such changes were detected during the early development of the constructed Hühnerwasser ("Chicken Creek") catchment in Lusatia, Germany. Surface substrates consisting of quaternary sandy sediments formed surface seals during the first rainfall events leading to reduced infiltration and substantially increased surface runoff. Subsequently biological soil crusts formed and stabilised the surface. The aim of this study is to investigate the factors that cause the hydraulic conductivity to decrease using undisturbed and disturbed soil samples. Based on the hypothesis that physical and biological crusts lower the hydraulic conductivity, the first set of experiments with undisturbed soil cores from the Hühnerwasser catchment were carried out to measure the saturated hydraulic conductivity using the constant head method. Measurements were done with intact cores and repeated after the surface crust was removed. As the quaternary glacial sediments tend to display hard setting behaviour, we further hypothesised that the mobilisation of fine particles within the cores lead to pore clogging and that wet-dry cycles will therefore decrease hydraulic conductivity. A second set of experiments using the same methodology consisted of five repeated measurements of hydraulic conductivity after each drying cycle. These measurements were done with undisturbed core samples as well as repacked cores in order to assess how dry packing affects the dynamics of the hydraulic conductivity somewhat similar to the situation during the first wetting after completion of the catchment construction. For all experiments, the temporal evolution of hydraulic conductivity was measured and the turbidity of the effluent was recorded. The results clearly demonstrated that the substrate is highly unstable. The first set of experiments

  4. Response of Surface Soil Hydrology to the Micro-Pattern of Bio-Crust in a Dry-Land Loess Environment, China.

    Wei Wei

    Full Text Available The specific bio-species and their spatial patterns play crucial roles in regulating eco-hydrologic process, which is significant for large-scale habitat promotion and vegetation restoration in many dry-land ecosystems. Such effects, however, are not yet fully studied. In this study, 12 micro-plots, each with size of 0.5 m in depth and 1 m in length, were constructed on a gentle grassy hill-slope with a mean gradient of 8° in a semiarid loess hilly area of China. Two major bio-crusts, including mosses and lichens, had been cultivated for two years prior to the field simulation experiments, while physical crusts and non-crusted bare soils were used for comparison. By using rainfall simulation method, four designed micro-patterns (i.e., upper bio-crust and lower bare soil, scattered bio-crust, upper bare soil and lower bio-crust, fully-covered bio-crust to the soil hydrological response were analyzed. We found that soil surface bio-crusts were more efficient in improving soil structure, water holding capacity and runoff retention particularly at surface 10 cm layers, compared with physical soil crusts and non-crusted bare soils. We re-confirmed that mosses functioned better than lichens, partly due to their higher successional stage and deeper biomass accumulation. Physical crusts were least efficient in water conservation and erosion control, followed by non-crusted bare soils. More importantly, there were marked differences in the efficiency of the different spatial arrangements of bio-crusts in controlling runoff and sediment generation. Fully-covered bio-crust pattern provides the best option for soil loss reduction and runoff retention, while a combination of upper bio-crust and lower bare soil pattern is the least one. These findings are suggested to be significant for surface-cover protection, rainwater infiltration, runoff retention, and erosion control in water-restricted and degraded natural slopes.

  5. Biological treatment: Soil impacted with crude oil

    Biological land treatment proved to be a successful way to manage contamination at a California oil and gas production property. During the project, approximately 120,000 yards of contaminated soil was treated in the treatment plots to below the cleanup goals of 1,000 milligrams per kilograms (mg/kg) total petroleum hydrocarbons. In general, remaining hydrocarbon levels in treated soil were the 200 mg/kg total petroleum hydrocarbons range or lower. Cleanup goals were achieved in less than 2 months for each lift of soil treated. The treated soil was used as fill material in the excavation. No significant odor problems occurred during the project. Groundwater monitoring confirmed that no impact to groundwater occurred due to the biological land treatment process. Design of the treatment plan and regulatory requirements are also discussed

  6. Microbiotic crusts on soil, rock and plants: neglected major players in the global cycles of carbon and nitrogen?

    W. Elbert


    Full Text Available Microbiotic crusts consisting of bacteria, fungi, algae, lichens, and bryophytes colonize most terrestrial surfaces, and they are able to fix carbon and nitrogen from the atmosphere. Here we show that microbiotic crusts are likely to play major roles in the global biogeochemical cycles of carbon and nitrogen, and we suggest that they should be further characterized and taken into account in studies and models of the Earth system and climate.

    For the global annual net uptake of carbon by microbiotic crusts we present a first estimate of ~3.6 Pg a−1. This uptake corresponds to ~6% of the estimated global net carbon uptake by terrestrial vegetation (net primary production, NPP: ~60 Pg a−1, and it is of the same magnitude as the global annual carbon turnover due to biomass burning. The estimated rate of nitrogen fixation by microbiotic crusts (~45 Tg a−1 amounts to ~40% of the global estimate of biological nitrogen fixation (107 Tg a−1. With regard to Earth system dynamics and global change, the large contribution of microbiotic crusts to nitrogen fixation is likely to be important also for the sequestration of CO2 by terrestrial plants (CO2 fertilization, because the latter is constrained by the availability of fixed nitrogen.

  7. Effect of rainfall and tillage direction on the evolution of surface crusts, soil hydraulic properties and runoff generation for a sandy loam soil

    Ndiaye, Babacar; Esteves, Michel; Vandervaere, Jean-Pierre; Lapetite, Jean-Marc; Vauclin, Michel


    The study was aimed at evaluating the effect of rainfall and tillage-induced soil surface characteristics on infiltration and runoff on a 2.8 ha catchment located in the central region of Senegal. This was done by simulating 30 min rain storms applied at a constant rate of about 70 mm h -1, on 10 runoff micro-plots of 1 m 2, five being freshly harrowed perpendicularly to the slope and five along the slope (1%) of the catchment. Runoff was automatically recorded at the outlet of each plot. Hydraulic properties such as capillary sorptivity and hydraulic conductivity of the sandy loam soil close to saturation were determined by running 48 infiltration tests with a tension disc infiltrometer. That allowed the calculation of a mean characteristic pore size hydraulically active and a time to ponding. Superficial water storage capacity was estimated using data collected with an electronic relief meter. Because the soil was subject to surface crusting, crust-types as well as their spatial distribution within micro-plots and their evolution with time were identified and monitored by taking photographs at different times after tillage. The results showed that the surface crust-types as well as their tillage dependent dynamics greatly explain the decrease of hydraulic conductivity and sorptivity as the cumulative rainfall since tillage increases. The exponential decaying rates were found to be significantly greater for the soil harrowed along the slope (where the runoff crust-type covers more than 60% of the surface after 140 mm of rain) than across to the slope (where crusts are mainly of structural (60%) and erosion (40%) types). That makes ponding time smaller and runoff more important. Also it was shown that soil hydraulic properties after about 160 mm of rain were close to those of untilled plot not submitted to any rain. That indicates that the effects of tillage are short lived.

  8. Salt crust development in paddy fields owing to soil evaporation and drainage : contribution of chloride and deuterium profile analysis

    Grunberger, Olivier; Macaigne, P.; Michelot, J. L.; Hartmann, Christian; Sukchan, S.


    In Northeast Thailand lowlands with shallow saline watertable, rainfed paddy fields often present high salt concentration in the dry season, forming patches or spots of salt crusts on the soil surface. In this context, the mechanisms implied in salt concentration during dry season were studied by establishing salt budget with evaporation and drainage estimates inside and outside a saline patch. Drainage was estimated by Hydrus-1D modelling constrained by an hydrodynamic characterization and t...

  9. Advances in Soil Biology: What does this mean for assessing soil change?

    Black, Helaina; Mele, Pauline


    Our interests in soil change are moving away from soil properties and increasingly towards changes in the processes and functioning of soils. Soil organisms are fundamental to dynamics and change in soils through their fundamental role in soil processes [1]. However it is only with recent technical and theoretical advances that we have started to establish quantitative relationships between soil biology and soil change (c.f. [2]). It is this predictive understanding that will enable us to fully integrate soil biology into the effective monitoring and sustainable management of soils. This paper outlines some of the recent advances in soil biology and discusses their relevance to monitoring and management.

  10. Soil biodiversity assessment, biological indicators and soil ecosystem services - an overview of European approaches

    CREAMER, Rachel; Hamer, Ute; Helder, Johannes; Pelosi, Céline; Pérès, Guénola; Rutgers, Michiel


    Soil biota are essential for many soil processes and functions, yet there are increasing pressures on soil biodiversity and soil degradation remains a pertinent issue. The sustainable management of soils requires soil monitoring, including biological indicators, to be able to relate land use and management to soil functioning and ecosystem services. Since the 1990s, biological soil parameters have been assessed in an increasing number of field trials and monitoring programmes across Europe....

  11. Understanding and Enhancing Soil Biological Health: The Solution for Reversing Soil Degradation

    R Michael Lehman; Cynthia A. Cambardella; Diane E. Stott; Veronica Acosta-Martinez; Manter, Daniel K; Buyer, Jeffrey S.; Jude E. Maul; Smith, Jeffrey L.; Harold P. Collins; Halvorson, Jonathan J.; Kremer, Robert J.; Lundgren, Jonathan G.; Tom F. Ducey; Jin, Virginia L.; Douglas L. Karlen


    Our objective is to provide an optimistic strategy for reversing soil degradation by increasing public and private research efforts to understand the role of soil biology, particularly microbiology, on the health of our world’s soils. We begin by defining soil quality/soil health (which we consider to be interchangeable terms), characterizing healthy soil resources, and relating the significance of soil health to agroecosystems and their functions. We examine how soil biology influences soi...

  12. Distribution and floristics of moss- and lichen-dominated soil crusts in a patterned Callitris glaucophylla woodland in eastern Australia

    Eldridge, David J.


    The distribution and abundance of soil crust lichens and bryophytes was examined in a patterned Callitris glaucophylla woodland in eastern Australia. Twenty-one lichen species and 26 bryophyte species were collected within thirty quadrats along a sequence of runoff, interception and runoff zones. Crust cover was significantly greatest in the interception zones (79.0 %), followed by the runoff zones (24.0 %), and lowest in the groved, runon zones (6.6 %). Lichens and bryophytes were distributed across all geomorphic zones, and, although there were significantly more moss species in the interception zones (mean = 9.1) compared with either the runoff (4.2) or runon (3.2) zones, the number of lichen species did not vary between zones. Ordination of a reduced data set of 32 species revealed a separation of taxa into distinct groups corresponding to the three geomorphic zones. Canonical correspondence analysis (CCA) of the 32 species and thirteen environmental variables revealed that the most important factors associated with the distribution of species were sheet and scarp erosion, soil stability and coherence, litter cover and crust cover. Surface cracking, microtopography and plant cover were of intermediate importance. The CCA biplot revealed that the timbered runon zones (groves) were dominated by `shade-tolerant' mosses Fissidens vittatus and Barbula hornschuchiana, whilst the heavily eroded runoff zones supported sparse populations of `erosion tolerant' lichens ( Endocarpon rogersii) and mosses (Bryum argenteum and Didymodon torquatus). Interception zones supported a rich suite of `crust forming' mosses and lichens capable of tolerating moderate inundation by overland flow. Two other groups of taxa were identified by this analysis: the `pioneer' group, comprising mainly nitrogen-fixing lichens which occupy the zone of active erosion at the lower edge of the groves, and the `opportunists' dominated by liverworts, occupying the shallow depressions or bays at the

  13. Understanding and Enhancing Soil Biological Health: The Solution for Reversing Soil Degradation

    R. Michael Lehman


    Full Text Available Our objective is to provide an optimistic strategy for reversing soil degradation by increasing public and private research efforts to understand the role of soil biology, particularly microbiology, on the health of our world’s soils. We begin by defining soil quality/soil health (which we consider to be interchangeable terms, characterizing healthy soil resources, and relating the significance of soil health to agroecosystems and their functions. We examine how soil biology influences soil health and how biological properties and processes contribute to sustainability of agriculture and ecosystem services. We continue by examining what can be done to manipulate soil biology to: (i increase nutrient availability for production of high yielding, high quality crops; (ii protect crops from pests, pathogens, weeds; and (iii manage other factors limiting production, provision of ecosystem services, and resilience to stresses like droughts. Next we look to the future by asking what needs to be known about soil biology that is not currently recognized or fully understood and how these needs could be addressed using emerging research tools. We conclude, based on our perceptions of how new knowledge regarding soil biology will help make agriculture more sustainable and productive, by recommending research emphases that should receive first priority through enhanced public and private research in order to reverse the trajectory toward global soil degradation.

  14. Biological and biochemical properties in evaluation of forest soil quality

    Błońska Ewa; Lasota Jarosław


    The aim of this study was to assess the possibility of using biological and biochemical parameters in the evaluation of forest soil quality and changes caused by land use. The study attempted to determine a relationship between the enzymatic activity of soil, the number of earthworms and soil physico-chemical properties. The study was carried out in central Poland in adjoining Forest Districts (Przedbórz and Smardzewice). In soil samples taken from 12 research plots, basic physico-chem...

  15. Chemical and biological rhizosphere interactions in low zinc soils

    Duffner, A.


    Abstract of the PhD thesis entitled “Chemical and biological rhizosphere interactions in low zinc soils” by Andreas Duffner Soil provides ecosystem services critical for life. The availability of micronutrients, such as zinc (Zn), in soils is an essential factor for normal healthy growth and reproduction of plants. Zinc deficiency is, however, a global problem in crop production due to low Zn bioavailability in soils to plants. The bioavailable Zn fraction in soils is controlled ...

  16. Biological framework for soil aggregation: Implications for ecological functions.

    Ghezzehei, Teamrat; Or, Dani


    Soil aggregation is heuristically understood as agglomeration of primary particles bound together by biotic and abiotic cementing agents. The organization of aggregates is believed to be hierarchical in nature; whereby primary particles bond together to form secondary particles and subsequently merge to form larger aggregates. Soil aggregates are not permanent structures, they continuously change in response to internal and external forces and other drivers, including moisture, capillary pressure, temperature, biological activity, and human disturbances. Soil aggregation processes and the resulting functionality span multiple spatial and temporal scales. The intertwined biological and physical nature of soil aggregation, and the time scales involved precluded a universally applicable and quantifiable framework for characterizing the nature and function of soil aggregation. We introduce a biophysical framework of soil aggregation that considers the various modes and factors of the genesis, maturation and degradation of soil aggregates including wetting/drying cycles, soil mechanical processes, biological activity and the nature of primary soil particles. The framework attempts to disentangle mechanical (compaction and soil fragmentation) from in-situ biophysical aggregation and provides a consistent description of aggregate size, hierarchical organization, and life time. It also enables quantitative description of biotic and abiotic functions of soil aggregates including diffusion and storage of mass and energy as well as role of aggregates as hot spots of nutrient accumulation, biodiversity, and biogeochemical cycles.

  17. Influence of humic acid applications on modulus of rupture, aggregate stability, electrical conductivity, carbon and nitrogen content of a crusting problem soil

    Gümüş, İ.; Şeker, C.


    Soil structure is often said to be the key to soil productivity since a fertile soil, with desirable soil structure and adequate moisture supply, constitutes a productive soil. Soil structure influences soil water movement and retention, erosion, crusting, nutrient recycling, root penetration and crop yield. The objective of this work is to study humic acid (HA) application on some physical and chemical properties in weakly structured soils. The approach involved establishing a plot experiment in laboratory conditions. Different rates of HA (control, 0.5, 1, 2 and 4 %) were applied to soil during three incubation periods (21, 42 and 62 days). At the end of the each incubation period, the changes in physicochemical properties were measured. Generally, HA addition increased electrical conductivity values during all incubation periods. HA applications decreased soil modulus of rupture. Application of HA at the rate of 4 % significantly increased soil organic carbon contents. HA applications at the rate of 4 % significantly increased both mean soil total nitrogen content and aggregate stability after three incubation periods (p < 0.05). Therefore, HA has the potential to improve the structure of soil in the short term.

  18. Biological treatment of oil-contaminated soils in bioreactors

    In Germany, biological soil treatment is practiced in most cases by using the window technique, where more and more the process takes place inhouse. This paper reports that biological soil treatment in closed reactors is more frequently considered. The reactors are more costly to run and should be used in those cases where the window technique is not satisfactory. Closed reactor treatment is appropriate when; higher standards are needed for the emission control of the volatile components; some organics are difficult to degrade; soil with a higher clay content must be treated; and naturally occurring biological processes must be enhanced. To operate biological soil treatment under optimum conditions and to discover the treatment limits, the specific factors of influence have to be determined in advance by using a series of laboratory-scale experiments

  19. Relationship between Mineral Soil Surface Area and the Biological Degradation of Biosolids Added to Soil

    Dongqi Wen


    Full Text Available Geochemical and biological processes that operate in the soil matrix and on the soil surface are important to the degradation of biosolids in soil. Due to the large surface area of soils it is assumed that the microbial ecology is associated with mineral soil surface area. The total mineral surface areas were determined for soils from eight different fields selected from a long term study (1972–2006 of annual biosolids application to 41 fields in central Illinois varying in size from 3.6 to 66 ha. The surface areas for the soils varied from 1 to 9 m2/g of soil. The biological degradation rates for the eight soils were determined using a biological degradation rate model (DRM and varied from 0.02 to 0.20/year−1. Regression analysis revealed that the degradation rate was positively associated with mineral soil surface area (1 m2/g produces 0.018 year−1 increase in the degradation rate. The annual soil sequestration rate was calculated to increase from 1% to 6% when the soil total surface area increased from 1 to 9 m2/g of soil. Therefore, land application of biosolids is an effective way to enhance carbon sequestration in soils and reduce greenhouse gas emissions.

  20. Book review: Soil biology guide, Daniel L. Dindal, ed.

    Arnett, Ross H.


    Under the skillful direction of Professor Dindal of Syracuse University, the work of 54 authors, 11 years in the making, is blended into one large, useful volume treating the systematics and biology of all organisms involved in the soil ecology of North America, north of Mexico. The separate authors treat their special groups following a similar format throughout, covering the biology, taxonomy, and ecology of each soil biotic group. The amount of data presented varies with the extent of know...

  1. Chemical and biological rhizosphere interactions in low zinc soils

    Duffner, A.


    Abstract of the PhD thesis entitled “Chemical and biological rhizosphere interactions in low zinc soils” by Andreas Duffner Soil provides ecosystem services critical for life. The availability of micronutrients, such as zinc (Zn), in soils is an essenti

  2. Biological detoxification of a hydrocarbon contaminated soil

    The soil quality of an industrial site chronically contaminated by 39000 mg/kg of oil was detrimentally affected. Soil treatments by bio-pile and land-farming resulted in a reduction of the level of contamination exceeding 90% of the original values, but without reaching regulatory limits. However, the bio-remediation treatments dramatically reduced the mobility of the contaminants and, accordingly, microbial tests clearly indicate that the soil quality improved to acceptable levels, similar to those typically observed in unaltered soils. Hydrocarbon mobility was estimated by the use of water and mild extractants (methanol and sodium dodecyl sulphate) to leach the contaminants from the soil; soil quality was evaluated by comparing the values of selected microbial and enzymatic parameters of the treated soil samples to reference values determined for natural soils. Microbial assessments included: measurement of the nitrification potential, dehydrogenase activity, measures of respiration and lipase activity, microbial counts (MPN on rich media) and MicrotoxTM assays of the water elutriate. Dermal absorption potential was evaluated using absorption on C18 disks

  3. Biological detoxification of a hydrocarbon contaminated soil

    Fabbri, F.; Lucchese, G.; Nardella, A. [E. Ramarini Eni Technologie, Monterotondo (RM), Roma (Italy)


    The soil quality of an industrial site chronically contaminated by 39000 mg/kg of oil was detrimentally affected. Soil treatments by bio-pile and land-farming resulted in a reduction of the level of contamination exceeding 90% of the original values, but without reaching regulatory limits. However, the bio-remediation treatments dramatically reduced the mobility of the contaminants and, accordingly, microbial tests clearly indicate that the soil quality improved to acceptable levels, similar to those typically observed in unaltered soils. Hydrocarbon mobility was estimated by the use of water and mild extractants (methanol and sodium dodecyl sulphate) to leach the contaminants from the soil; soil quality was evaluated by comparing the values of selected microbial and enzymatic parameters of the treated soil samples to reference values determined for natural soils. Microbial assessments included: measurement of the nitrification potential, dehydrogenase activity, measures of respiration and lipase activity, microbial counts (MPN on rich media) and Microtox{sup TM} assays of the water elutriate. Dermal absorption potential was evaluated using absorption on C{sub 18} disks.

  4. The mechanisms whereby the green alga Chlorella ohadii, isolated from desert soil crust, exhibits unparalleled photodamage resistance.

    Treves, Haim; Raanan, Hagai; Kedem, Isaac; Murik, Omer; Keren, Nir; Zer, Hagit; Berkowicz, Simon M; Giordano, Mario; Norici, Alessandra; Shotland, Yoram; Ohad, Itzhak; Kaplan, Aaron


    Excess illumination damages the photosynthetic apparatus with severe implications with regard to plant productivity. Unlike model organisms, the growth of Chlorella ohadii, isolated from desert soil crust, remains unchanged and photosynthetic O2 evolution increases, even when exposed to irradiation twice that of maximal sunlight. Spectroscopic, biochemical and molecular approaches were applied to uncover the mechanisms involved. D1 protein in photosystem II (PSII) is barely degraded, even when exposed to antibiotics that prevent its replenishment. Measurements of various PSII parameters indicate that this complex functions differently from that in model organisms and suggest that C. ohadii activates a nonradiative electron recombination route which minimizes singlet oxygen formation and the resulting photoinhibition. The light-harvesting antenna is very small and carotene composition is hardly affected by excess illumination. Instead of succumbing to photodamage, C. ohadii activates additional means to dissipate excess light energy. It undergoes major structural, compositional and physiological changes, leading to a large rise in photosynthetic rate, lipids and carbohydrate content and inorganic carbon cycling. The ability of C. ohadii to avoid photodamage relies on a modified function of PSII and the dissipation of excess reductants downstream of the photosynthetic reaction centers. The biotechnological potential as a gene source for crop plant improvement is self-evident. PMID:26853530

  5. Biological Dimensions of Crack Morphology in Dryland Soils

    DeCarlo, K. F.; Spiegel, M.; Caylor, K. K.


    Macropores and cracks have an integral role in soil hydrology, and the physicochemical factors that induce them have been the subject of much laboratory research. How these processes translate to field soils, however, is often obfuscated by the biological elements present that complicate its formation and dynamics. In this study, we investigated the biological influence of herbivores and vegetation on 3D crack morphology in a dryland swelling soil (black cotton/vertisol). Fieldwork was conducted at and near the Kenya Long-Term Exclosure Experiment (KLEE) plots in Mpala, central Kenya, where three different soil regions were identified: highly vegetated areas, animal trails, and termite mounds. Crack networks were physically characterized by pouring liquid resin into the soil and excavating them when dry, after which they were imaged and quantified using medical magnetic resonance imaging (MRI). Cracking intensity of each cast was corrected via soil moisture and bulk density measurements at 5 cm intervals over 30 cm. 3D characterization of the soil system shows that mechanical compaction is a major influence in the formation of extensive and deep cracks in animal trails, with megaherbivores (e.g. elephants) inducing the most extreme cracks. Bioturbation is seen as a major influence in the formation of shallower cracks in termite mounds, as termites loosen and aerate the soil and reduce the soil's cohesive properties. Highly vegetated soils show a large degree of variability: small, disconnected soil patches induced by vegetative cover and a larger root network results in smaller and shallower cracks, but full vegetative cover induces deep and irregular cracks, possibly due to diverted rainfall. Our results highlight the intricate connections between the biology and physics that dictate soil processes in a complex soil system at the field scale.

  6. Relationship between Mineral Soil Surface Area and the Biological Degradation of Biosolids Added to Soil

    Dongqi Wen; Wenjuan Zhai; Demetrios Moschandreas; Guanglong Tian; Noll, Kenneth E.


    Geochemical and biological processes that operate in the soil matrix and on the soil surface are important to the degradation of biosolids in soil. Due to the large surface area of soils it is assumed that the microbial ecology is associated with mineral soil surface area. The total mineral surface areas were determined for soils from eight different fields selected from a long term study (1972–2006) of annual biosolids application to 41 fields in central Illinois varying in size from 3.6 to ...

  7. Soil biological activity at European scale - two calculation concepts

    Krüger, Janine; Rühlmann, Jörg


    The CATCH-C project aims to identify and improve the farm-compatibility of Soil Management Practices including to promote productivity, climate change mitigation and soil quality. The focus of this work concentrates on turnover conditions for soil organic matter (SOM). SOM is fundamental for the maintenance of quality and functions of soils while SOM storage is attributed a great importance in terms of climate change mitigation. The turnover conditions depend on soil biological activity characterized by climate and soil properties. To assess the turnover conditions two model concepts are applied: (I) Biological active time (BAT) regression approach derived from CANDY model (Franko & Oelschlägel 1995) expresses the variation of air temperature, precipitation and soil texture as a timescale and an indicator of biological activity for soil organic matter (SOM) turnover. (II) Re_clim parameter within the Introductory Carbon Balance Model (Andrén & Kätterer 1997) states the soil temperature and soil water to estimate soil biological activity. The modelling includes two strategies to cover the European scale and conditions. BAT was calculated on a 20x20 km grid basis. The European data sets of precipitation and air temperature (time period 1901-2000, monthly resolution), (Mitchell et al. 2004) were used to derive long-term averages. As we focus on agricultural areas we included CORINE data (2006) to extract arable land. The resulting BATs under co-consideration of the main soil textures (clay, silt, sand and loam) were investigated per environmental zone (ENZs, Metzger et al. 2005) that represents similar conditions for precipitation, temperature and relief to identify BAT ranges and hence turnover conditions for each ENZ. Re_clim was quantified by climatic time series of more than 250 weather stations across Europe presented by Klein Tank et al. (2002). Daily temperature, precipitation and potential evapotranspiration (maximal thermal extent) were used to calculate

  8. Impact of temperature on the biological properties of soil

    Borowik, Agata; Wyszkowska, Jadwiga


    The aim of the study was to determine the response of soil microorganisms and enzymes to the temperature of soil. The effect of the temperatures: 5, 10, 15, 20, and 25°C on the biological properties of soil was investigated under laboratory conditions. The study was performed using four different soils differing in their granulometric composition. It was found that 15°C was the optimal temperature for the development of microorganisms in soil. Typically, in the soil, the highest activity of dehydrogenases was observed at 10-15°C, catalase and acid phosphatase - at 15°C, alkaline phosphatase at 20°C, urease and β-glucosidase at 25°C. The highest colony development index for heterotrophic bacteria was recorded in soils incubated at 25°C, while for actinomycetes and fungi at 15°C. The incubation temperature of soil only slightly changed the ecophysiological variety of the investigated groups of microorganisms. Therefore, the observed climate changes might have a limited impact on the soil microbiological activity, because of the high ability of microorganisms to adopt. The response of soil microorganisms and enzymes was more dependent on the soil granulometric composition, organic carbon, and total nitrogen than on its temperature.

  9. Behavior of oxyfluorfen in soils amended with different sources of organic matter. Effects on soil biology.

    Gómez, Isidoro; Rodríguez-Morgado, Bruno; Parrado, Juan; García, Carlos; Hernández, Teresa; Tejada, Manuel


    We performed a laboratory study on the effect of oxyfluorfen at a rate of 4lha(-1) on biological properties of a soil amended with four organic wastes (two biostimulants/biofertilizers, obtained from rice bran, RB1 and RB2; municipal solid waste, MSW; and sheep manure, SM). Soil was mixed with SM at a rate of 1%, MSW at a rate of 0.52%, RB1 at a rate of 0.39% and RB2 at a rate of 0.30%, in order to apply the same amount of organic matter to the soil. The enzymatic activities and microbial community in the soil were determined during the incubation times. The application of RB1 and RB2 to soil without oxyfluorfen increased the enzymatic activities and biodiversity, peaking at day 10 of the incubation period. This stimulation was higher in the soil amended with RB2 than in that amended with RB1. In SM and CF-amended soils, the stimulation of enzymatic activities and soil biodiversity increased during the experiment. The application of herbicide in organic-amended soils decreased the inhibition of soil enzymatic activities and soil biodiversity. Possibly the low molecular weight protein content easily assimilated by soil microorganisms and the higher fat content in the biostimulants/biofertilizers are responsible for the lower inhibition of these soil biological properties. PMID:24742665

  10. Evaluation of Pigeon Pea Lines for Biological Soil Decompaction

    Rodolfo Godoy


    Full Text Available Soil decompaction is generally achieved through mechanical cultivation practices; however biological processes can significantly add to this process through root growth, development, and later senescence. This study was carried out in Piracicaba, SP, Brazil and had the purpose of selecting, among forty one pure pigeon pea lines, the most efficient genotypes that promote soil decompaction by roots penetrating compacted soil layers. Utilizing artificially compacted 30 mm high soil blocks, in a series of experiments, these lines were compared to the cultivar Fava Larga taken as a standard. Three lines were preliminarily selected out of the initial group, and afterwards, in more detailed screenings by monitoring soil resistance to penetration and also evaluating the behavior of Tanzania grass plants seeded after pigeon pea, two of them, g5-94 and g8-95, were selected as possessing the most fit root system to penetrate compacted soil layers.

  11. Light-induced changes within photosystem II protects Microcoleus sp. in biological desert sand crusts against excess light.

    Itzhak Ohad

    Full Text Available The filamentous cyanobacterium Microcoleus vaginatus, a major primary producer in desert biological sand crusts, is exposed to frequent hydration (by early morning dew followed by desiccation during potentially damaging excess light conditions. Nevertheless, its photosynthetic machinery is hardly affected by high light, unlike "model" organisms whereby light-induced oxidative stress leads to photoinactivation of the oxygen-evolving photosystem II (PSII. Field experiments showed a dramatic decline in the fluorescence yield with rising light intensity in both drying and artificially maintained wet plots. Laboratory experiments showed that, contrary to "model" organisms, photosynthesis persists in Microcoleus sp. even at light intensities 2-3 times higher than required to saturate oxygen evolution. This is despite an extensive loss (85-90% of variable fluorescence and thermoluminescence, representing radiative PSII charge recombination that promotes the generation of damaging singlet oxygen. Light induced loss of variable fluorescence is not inhibited by the electron transfer inhibitors 3-(3,4-dichlorophenyl-1,1-dimethylurea (DCMU, 2,5-dibromo-3-methyl-6-isopropylbenzoquinone (DBMIB, nor the uncoupler carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP, thus indicating that reduction of plastoquinone or O(2, or lumen acidification essential for non-photochemical quenching (NPQ are not involved. The rate of Q(A (- re-oxidation in the presence of DCMU is enhanced with time and intensity of illumination. The difference in temperatures required for maximal thermoluminescence emissions from S(2/Q(A (- (Q band, 22 degrees C and S(2,3/Q(B (- (B band, 25 degrees C charge recombinations is considerably smaller in Microcoleus as compared to "model" photosynthetic organisms, thus indicating a significant alteration of the S(2/Q(A (- redox potential. We propose that enhancement of non-radiative charge recombination with rising light intensity may reduce

  12. Soil biology and carbon in dryland agriculture

    The goal of this paper is to explore potential management strategies in dryland agriculture that can promote soil health and crop productivity. Traditional crop production in the semiarid Great Plains consists of conventional tillage management of winter wheat (Triticum aestivum L.) - summer fallow....

  13. Crusted scabies

    Karthikeyan Kaliaperumal


    Full Text Available Crusted scabies is a rare manifestation of scabies characterized by uncontrolled proliferation of mites in the skin. In immunocompromised patients, this infestation is characterized by crusted lesions. The occurrence of the disease in human immunodeficiency virus-infected patients and the widespread use of immunosuppressive agents has led to a renewed interest in the disease. Early recognition and treatment is necessary to avoid an outbreak of scabies. This review highlights the pathogenesis, predisposing factors, clinical features and treatment of crusted scabies.

  14. Soil crusts on Mars

    Moore, H. J.


    Three distinct soillike materials sampled by the Viking landers (VL) on Mars are (in order of increasing strength): (1) drift; (2) crusty to cloddy; and (3) blocky. Relative strengths of these materials are manifested by footpad penetrations during landing (VL 1), depths of deep holes, motor currents during sampling, sampler backhoe penetrations, comminutor motor currents, impact pits, trench tailings, and successful acquisitions of the coarse fraction (only blocky material). Cementation by S Cl compounds probably contributes to the relative strengths. This is shown where the weight pct. of SO3 + Cl of each material is plotted against their relative strengths. A similar result is obtained using SO3 alone, but not with Cl which is deficient in VL 2 samples.

  15. Biological decomposition of aqueous solutions from soil cleaning

    The biological cleaning of process water from soil cleaning and from contaminated groundwater required the development of new types of reaction systems. With the introduced membrane biofilm reactor, even substances difficult to decompose can be removed from contaminated water. Previous investigations of the elimination of pyrene in the presence of n-hexadecane show an optimum temperature at 30 C. An increase of scale is possible based on the invesstigations carried out on the aerobic biological decomposition of polycyclic aromatic hydrocarbons. (orig.)

  16. The biological factors influence on the conversion of mineral components of Extremely Arid Desert Soils (Kazakhstan)

    Kutovaya, Olga; Vasilenko, Elena; Lebedeva, Marina; Tkhakakhova, Azida


    Extremely arid soils of stony deserts (hamadas) along the southern periphery of the Ili Depression are considered to be analogous to extremely arid soils of Mongolia, also named as "ultra-arid primitive gray-brown soils." In general, the morphology of extremely arid soils of hamadas in the Ili Depression is similar to that of the soils of stony deserts in other parts of the world, including the Gobi, Atacama, and Tarim deserts. The diagnostics of the active communities of microorganisms were performed according to the method of Rybalkina-Kononenko. The exact identification of the living forms of microorganisms to the species level is not always possible with the use of this method. However, it allows us to study the physiological role of the microorganisms and their ecological functions, including the relationships with the soil matrix and other organisms. In particular, it is possible to estimate the contribution of the microorganisms to the transformation of mineral soil components. The obtained materials allow us to conclude that the extremely arid desert soils are characterized by the very high biological activity during short periods of the increased soil moistening after rare and strong rains. The diversity of living forms is very considerable; both prokaryotes (cyanobacteria, actinomycetes, and iron bacteria) and protists (green algae, diatoms, and dinoflagellates) are developed in the soil. Thus, during a short period after the rains, these microorganisms pass from the stage of anabiosis to the stage of active growth and reproduction. Then, upon drying of the soil, the biotic activity of the soil slows down and, finally, terminates. The organisms remain in the state of anabiosis until the next rain. During the period of active growth, the microorganisms compose a specific consortium of different species and exert a profound impact on the soil properties. They participate in the transformation of the soil minerals with the formation of amorphous substances

  17. Actual laser removal of black soiling crust from siliceous sandstone by high pulse repetition rate equipment: effects on surface morphology

    Iglesias-Campos, M. A.


    Full Text Available This research project studies the role of pulse repetition rate in laser removal of black soiling crust from siliceous sandstone, and specifically, how laser fluence correlates with high pulse repetition rates in cleaning practice. The aim is to define practical cleaning processes and determine simple techniques for evaluation based on end-users’ perspective (restorers. Spot and surface tests were made using a Q-switched Nd:YAG laser system with a wide range of pulse repetition rates (5–200 Hz, systematically analysed and compared by macrophotography, portable microscope, stereomicroscope with 3D visualizing and area roughness measurements, SEM imaging and spectrophotometry. The results allow the conclusion that for operation under high pulse repetition rates the average of total energy applied per spot on a treated surface should be attendant upon fluence values in order to provide a systematic and accurate description of an actual laser cleaning intervention.En este trabajo se estudia el papel de la frecuencia de repetición en la limpieza láser de costras de contaminación sobre una arenisca silícea, y concretamente, como se relaciona fluencia y frecuencias elevadas en una limpieza real. Se pretende definir un procedimiento práctico de limpieza y determinar técnicas sencillas de evaluación desde el punto de vista de los usuarios finales (restauradores. Para el estudio se realizaron diferentes ensayos en spot y en superficie mediante un equipo Q-switched Nd:YAG con un amplio rango de frecuencias (5–200 Hz, que se analizaron y compararon sistemáticamente mediante macrofotografía, microscopio portátil, estereomicroscopio con visualización 3D y mediciones de rugosidad en área, imágenes SEM y espectrofotometría. Los resultados permiten proponer que, al trabajar con altas frecuencias, la media de la energía total depositada por spot en la superficie debería acompañar los valores de fluencia para describir y comprender mejor una

  18. Effects of Soil and Water Conservation of Algae Crust in Hilly and Gully Regions on Loess Plateau%黄土高原沟壑区藻类结皮的水土保持效应

    康磊; 孙长忠; 殷丽; 汤志敏; 贺淑霞


    The effect of soil and water conservation of algae crust widespread in hilly and gully regions on Loess Plateau had been researched from two aspects which were rainfall infiltration-runoff and evaporation of soil water.The results were as follows: ①Algae crust could increase the 0-10 cm depth soil porosity.The maximum increase of total porosity was 7.4%,and the capillary was 14.2%.Algae crust had no significant effect on the soil porosity of the deeper layer.②In wasterland,mongolian scotch pine and Chinese pine forest,the runoff between the algae crust and non-crust had a significant difference.Compared with the runoff of non-crust,the runoff of algae crust in the three types of vegetation reduced by 28.1%~32.5%,34.4%~43.1% and 30.8%~31.6%.③In the three types vegetation,the amount of soil erosion between algae crust and non-crust had a significant difference.Compared with the amount of soil erosion of non-crust,the amount of soil erosion of algae crust in the three types of vegetation reduced by 58.8%~70.6%,48.9%~62.6% and 38.3%~57.1%.④By stepwise regression analysis,the different regression equations between runoff,soil erosion of algae crust and rainfall factor in different vegetation types could be obtained.⑤The soil moisture of 20-60 cm depth could be affect by algae crust.In this depth the soil moisture of algae crust was significantly higher than non-crust zone.%从降雨径流、水分蒸发两方面探讨黄土高原沟壑区藻类结皮的水土保持效应。结果表明:①藻类结皮可显著增加0-10cm土层内土壤孔隙度,最大增加幅度总孔隙度为7.4%,毛管孔隙度为14.2%;对更深土层的土壤孔隙度无显著影响。②荒草坡、樟子松林和油松林3种植被类型下,有藻类结皮试验区径流量与无结皮对照区有显著差异,径流量分别减少了28.1%~32.5%、34.4%~43.1%和30.8%~31.6%。③3种植被类型下,藻类结皮的土壤侵蚀量与无结皮对照土壤侵蚀量有

  19. Application of the biological forced air soil treatment (BIOFAST trademark) technology to diesel contaminated soil

    A subsurface Biological Forced Air Soil Treatment (BIOFAST trademark) system was constructed at the Yellow Freight System, Inc. (Yellow Freight) New Haven facility in Connecticut as a means of expediting the remediation of soils impacted by a diesel fuel release. Prior to beginning construction activities the soils were evaluated for the feasibility of bioremediation based on soil characteristics including contaminant degrading bacteria, moisture content, and pH. Based on results of stimulant tests with oxygen and nutrients, the addition of fertilizer during the construction of the cell was recommended. Following the removal of underground storage tanks, the bioremediation cell was constructed by lining the enlarged excavation with high density polyethylene (HDPE) and backfilling alternating layers of nutrient-laden soil and pea gravel. Passive and active soil vapor extraction (SVE) piping was included in the gravel layers and connected to a blower and vapor treatment unit, operated intermittently to supply oxygen to the subsurface cell. Operating data have indicated that the bacteria are generating elevated levels of CO2, and the SVE unit is evacuating the accumulated CO2 from the soils and replacing it with fresh air. These data suggest that the bioremediation process is active in the soils. Soil samples collected from within the soil pit subsequent to installation and again after 10 months of operation indicate that TPH concentrations have decreased by as much as 50%

  20. Biological activity of soil contaminated with cobalt, tin, and molybdenum.

    Zaborowska, Magdalena; Kucharski, Jan; Wyszkowska, Jadwiga


    In this age of intensive industrialization and urbanization, mankind's highest concern should be to analyze the effect of all metals accumulating in the environment, both those considered toxic and trace elements. With this aim in mind, a unique study was conducted to determine the potentially negative impact of Sn(2+), Co(2+), and Mo(5+) in optimal and increased doses on soil biological properties. These metals were applied in the form of aqueous solutions of Sn(2+) (SnCl2 (.)2H2O), Co(2+) (CoCl2 · 6H2O), and Mo(5+) (MoCl5), each in the doses of 0, 25, 50, 100, 200, 400, and 800 mg kg(-1) soil DM. The activity of dehydrogenases, urease, acid phosphatase, alkaline phosphatase, arylsulfatase, and catalase and the counts of twelve microorganism groups were determined on the 25th and 50th day of experiment duration. Moreover, to present the studied problem comprehensively, changes in the biochemical activity and yield of spring barley were shown using soil and plant resistance indices-RS. The study shows that Sn(2+), Co(2+), and Mo(5+) disturb the state of soil homeostasis. Co(2+) and Mo(5+) proved the greatest soil biological activity inhibitors. The residence of these metals in soil, particularly Co(2+), also generated a drastic decrease in the value of spring barley resistance. Only Sn(2+) did not disrupt its yielding. The studied enzymes can be arranged as follows for their sensitivity to Sn(2+), Co(2+), Mo(5+): Deh > Ure > Aryl > Pal > Pac > Cat. Dehydrogenases and urease may be reliable soil health indicators. PMID:27277093

  1. Biological soil disinfestation : a safe and effective approach for controlling soilborne pests and diseases

    Lamers, J.G.; Wanten, P.J.; Blok, W.J.


    Biological soil disinfestation (bsd) is an environmentally friendly method to disinfest the soil from soilborne fungi and nematodes. With biological soil disinfestation a green manure crop (40 tonnes per ha) or other green biomass is homogeneously incorporated into the soil layer that has to be disi


    Radu Lacatusu


    Urban soil is an material that has been manipulated, disturbed or transported by man’s activities in the urban environment and is used as a medium for plant growth and for constructions. The physical, chemical, and biological properties are generally less favorable as a rooting medium than soil found on the natural landscape. The main characteristics of urban soils are: great vertical and spatial variability; modified soil structure leading to compaction; presence of a surface crust; modified...

  3. Biological residues define the ice nucleation properties of soil dust

    F. Conen


    Full Text Available Soil dust is a major driver of ice nucleation in clouds leading to precipitation. It consists largely of mineral particles with a small fraction of organic matter constituted mainly of remains of micro-organisms that participated in degrading plant debris before their own decay. Some micro-organisms have been shown to be much better ice nuclei than the most efficient soil mineral. Yet, current aerosol schemes in global climate models do not consider a difference between soil dust and mineral dust in terms of ice nucleation activity. Here, we show that particles from the clay and silt size fraction of four different soils naturally associated with 0.7 to 11.8 % organic carbon (w/w can have up to four orders of magnitude more ice nuclei per unit mass active in the immersion freezing mode at −12 °C than montmorillonite, the most efficient pure clay mineral. Most of this activity was lost after heat treatment. Removal of biological residues reduced ice nucleation activity to, or below that of montmorillonite. Desert soils, inherently low in organic content, are a large natural source of dust in the atmosphere. In contrast, agricultural land use is concentrated on fertile soils with much larger organic matter contents than found in deserts. It is currently estimated that the contribution of agricultural soils to the global dust burden is less than 20 %. Yet, these disturbed soils can contribute ice nuclei to the atmosphere of a very different and much more potent kind than mineral dusts.

  4. Soil organic components distribution in a podzol and the possible relations with the biological soil activities

    Alvarez-Romero, Marta; Papa, Stefania; Verstraeten, Arne; Curcio, Elena; Cools, Nathalie; Lozano-Garcia, Beatriz; Parras-Alcántara, Luis; Coppola, Elio


    the different fractions of the SOC. It can form the base study for evaluation of changes in some biological activity along soil profile.

  5. Biological attributes of rehabilitated soils contaminated with heavy metals.

    Valentim Dos Santos, Jessé; Varón-López, Maryeimy; Fonsêca Sousa Soares, Cláudio Roberto; Lopes Leal, Patrícia; Siqueira, José Oswaldo; de Souza Moreira, Fatima Maria


    This study aimed to evaluate the effects of two rehabilitation systems in sites contaminated by Zn, Cu, Pb, and Cd on biological soil attributes [microbial biomass carbon (Cmic), basal and induced respiration, enzymatic activities, microorganism plate count, and bacterial and fungal community diversity and structure by denaturing gradient gel electrophoresis (DGGE)]. These systems (S1 and S2) consisted of excavation (trenching) and replacement of contaminated soil by uncontaminated soil in rows with Eucalyptus camaldulensis planting (S1-R and S2-R), free of understory vegetation (S1-BR), or completely covered by Brachiaria decumbens (S2-BR) in between rows. A contaminated, non-rehabilitated (NR) site and two contamination-free sites [Cerrado (C) and pasture (P)] were used as controls. Cmic, densities of bacteria and actinobacteria, and enzymatic activities (β-glucosidase, acid phosphatase, and urease) were significantly higher in the rehabilitated sites of system 2 (S2-R and S2-BR). However, even under high heavy metal contents (S1-R), the rehabilitation with eucalyptus was also effective. DGGE analysis revealed similarity in the diversity and structure of bacteria and fungi communities between rehabilitated sites and C site (uncontaminated). Principal component analysis showed clustering of rehabilitated sites (S2-R and S2-BR) with contamination-free sites, and S1-R was intermediate between the most and least contaminated sites, demonstrating that the soil replacement and revegetation improved the biological condition of the soil. The attributes that most explained these clustering were bacterial density, acid phosphatase, β-glucosidase, fungal and actinobacterial densities, Cmic, and induced respiration. PMID:26662102

  6. Crusting cause changes in soil erodibility: assessment and consequences for erosion modeling. An example from the Loess Plateau (China)

    Wang, Bin; Darboux, Frédéric; Zheng, Fenli; Li, Guifang; Duval, Odile


    Water erosion is a major threat to soil sustainability. In the context of global change, erosion intensity could be dramatically increased, hence decreasing the capability of soils to sustain agriculture. We evaluated soil sustainability to water erosion in two watersheds (about 100 km2 each) located in Southern France and Northern Tunisia. Erosion both at present time and in the future (about 100 years) was assessed using the STREAM model. The ARPEGE model was used to simulate climate change...

  7. The long-term fertilization effect on biological activity of different genesis soils

    Grigaliūnienė, Kristina


    The effect of organic and mineral fertilizers on biological activity of different genesis soils in long-term crop rotation trials was determined. Biological activity was diverse in the soils of different genesis and it activity correlated with some soil chemical properties. Organic and mineral fertilizers and their combinations more increased biological activity in the soil than only mineral fertilizers. Mineral fertilizers suppressed dehydrogenase and alkaline phosphatase activity (180 kg ha...

  8. Effect of the fungicides carbendazim and metalaxyl on the biological activity of soils

    Metalaxyl and carbendazim at 10 and 100 ppm concentration have no influence on the biological activity of Humic Gley and Yellow Red Latosol soils as measured by respirometry. Carbendazim added to the Humic Gley soil at concentration of 500 ppm showed an inhibitory influence on the biological activity of this soil. (Author)

  9. Effect of mineralogical, geochemical and biological properties on soils reflectance to assess temporal and spatial dynamics of BSCs in Sahelian ecosystems

    Bourguignon, A.; Cerdan, O.; Desprats, J. F.; Marin, B.; Malam Issa, O.; Valentin, C.; Rajot, J. L.


    Land degradation and desertification are among the major environmental problems, resulting in reduced productivity and development of bare surfaces in arid and semi-arid areas of the world. One important factor that acts to increase soil stability and nutrient content, and thus to prevent water and wind erosion and enhance soil productivity of arid environment, is the presence of biological soil crusts (BSCs). They are the dominant ground cover and a key component of arid environments built up mainly by cyanobacteria. They enhance degraded soil quality by providing a stable and water-retaining substratum and increasing fertility by N and C fixations. The BioCrust project, funded by ANR (VMCS 2008), focuses on BSCs in the Sahelian zone of West Africa (Niger), a highly vulnerable zone facing soil degradation due to the harsh climatic conditions, with variable rainfall, and high anthropic pressure on land use. Unlike arid areas of developed countries (USA, Australia and Israel) or China where BSCs have been extensively studied, studies from Sahelian zone (Africa) are limited (neither the inventory of their different form nor the estimation of their spatial extension has been carried out). The form, structure and composition of BSCs vary depending on characteristics related to soils and biological composition. This study focuses on the soils characterisation using ground-based spectroradiometry. An extensive database was built included spectral measurements on BSCs, bare soils and vegetation that occur in the same area, visual criteria, in situ and laboratory measurements on the physical, chemical and biological characteristics of BSCs and their substratum. The work is carried out on geo-statistical processing of data acquired in sites along a north-south climatic gradient and three types of representative land uses. The investigated areas are highly vulnerable zone facing soil degradation due to the harsh climatic conditions, with variable rainfall, and high anthropic

  10. Estimation of the Biological Methods of Assessing Soil N-Supplying Capacity in Calcareous Soil

    JIN Fa-hui; LI Shi-qing; LU Hong-ling; LI Sheng-xiu


    Although many biological methods are used to determine soil nitrogen supplying capacity, there are certain differences in the results for different types of soils and various ways of measurement due to the complexity of soil N conformation, the high variance of soil and microorganism, and the difference of environment. Therefore, it is not clear about which biologic incubation method is better for calcareous soil. In this study, pot experiments were performed by using 25 different calcareous surface soil samples on the Loess Plateau and taking the N uptake of wheat and corn with leaching soil initial nitrate and without leaching in pot experiments as the control to investigate the difference of eight biological incubation methods for reflecting soil nitrogen supply capacity. The eight biological methods are waterlogged incubation, aerobic incubation for 2 weeks and for 4 weeks, dry-wet alternation aerobic incubation for 2 weeks, long-term alternate leaching aerobic incubation (and N mineralization potential, N0), short-term leaching aerobic incubation, microbial biomass carbon (BC), and microbial biomass nitrogen (BN) method, respectively. Among these methods, the dry-wet alternation aerobic incubation and aerobic incubation for 4 weeks were the modification of the method of aerobic incubation for 2 weeks according to the actual farmland moisture. The results showed that the correlation coefficients between these methods and crop uptake N with leaching soil initial nitrate were 0.530, 0.700, 0.777, 0.768, 0.764 (and 0.790, N0), 0.650, 0.555, and 0.465, respectively (r0.05 = 0.369, r0.01 = 0.505). While without leaching soil initial nitrate, their coefficients were 0.351, 0.963, 0.962, 0.959, 0.825 (and 0.812, N0), 0.963, 0.289, and 0.095, respectively (r0.05=0.369, r0.01 =0.505). In conclusion,excluding the soil initial nitrate, the correlation coefficients between the eight methods and crop uptake N were, from high to low, N0, aerobic incubation for 4 weeks, dry

  11. Crop production in salt affected soils: A biological approach

    Plant are susceptible to deleterious effects of various abiotic and biotic stresses, thus grossly affecting the growth and productivity. Amongst the abiotic stresses, soil salinity is most significant and prevalent in both developed and developing countries. As a consequences, good productive lands are being desertified at a very high pace. To combat this problem various approaches involving soil management and drainage are underway but with little success. It seems that a durable solution of the salinity and water-logging problems may take a long time and we may have to learn to live with salinity and to find other ways to utilize the affected lands fruitfully. A possible approach could be to tailor plants to suit the deleterious environment. The saline-sodic soils have excess of sodium, are impermeable, have little or no organic matter and are biologically almost dead. Introduction of a salt tolerant crop will provide a green cover and will improve the environment for biological activity, increase organic matter and will improve the soil fertility. The plant growth will result in higher carbon dioxide levels, and would thus create acidic conditions in the soil which would dissolve the insoluble calcium carbonate and will help exchange sodium with calcium ions on the soil complex. The biomass produced could be used directly as fodder or by the use of biotechnological and other procedures it could be converted into other value added products. However, in order to tailor plants to suit these deleterious environments, acquisition of better understanding of the biochemical and genetic aspects of salt tolerance at the cellular/molecular level is essential. For this purpose model systems have been carefully selected to carry out fundamental basic research that elucidates and identifies the major factors that confer salt tolerance in a living system. With the development of modern biotechnological methods it is now possible to introduce any foreign genetic material known

  12. Wildfire effects on biological properties of soils in forest-steppe ecosystems of Russia

    Maksimova, E.; Abakumov, E.


    Soils affected by forest wildfires in 2010 in Russia were studied on postfire and mature plots near the Togljatty city, Samara region. Soil biological properties and ash composition dynamics were investigated under the forest fire affect: a place of local forest fire, riding forest fire and unaffected site by fire-control (mature) during 3 yr of restoration. Soil samples were collected at 0–15 cm. Soil biological properties was measured by the fumigation me...

  13. Effects of organic amendment on soil quality as assessed by biological indicators

    Sultana, Salma


    Soil quality decline is one of the most predominant effect deriving from human activities. In particular, intensive agricultural management can affect negatively soils, principally due to rapid depletion of soil organic matter, that affects, in turn, soil physical, chemical and biological properties. The declining trend of soil quality coupled with mismanagement of agricultural production is pose a serious threat to sustainability of intensive agriculture. Sustainable intensive agriculture is...

  14. Deep ancient fluids in the continental crust and their impact on near-surface economic, environmental and biological systems.

    Ballentine, Christopher; Warr, Oliver; Sutcliffe, Chelsea; McDermott, Jill; Fellowes, Jonathan; Holland, Greg; Mabry, Jennifer; Sherwood Lollar, Barbara


    With a few exceptions the mobility of water, oil and gas, provides for an ephemeral view of subsurface fluids relative to geological or planetary timescales. Aquifers supplying water for drinking and irrigation have mean residence ages from hundreds to tens of thousands of years; Hydrothermal systems can be active for hundreds of thousands to millions of years forming key mineral reserves; Sedimentary basin formation expels fluids during compaction and generates oil and gas on times scales of millions to hundreds of millions of years. Within these exemplar systems biological activity can play a crucial role by mediating system oxidation state: releasing arsenic into shallow groundwaters; precipitating ore bodies; generating methane; and biodegrading oil. It is becoming increasingly apparent that fluids resident in fractures and porespace in the crystalline basement underlying many of these systems can have a mean residence time that ranges from tens to hundreds of millions of years [1,2] to billions of years [3,4]. These fluids are highly saline and trace element rich; they are abundant in nitrogen, hydrogen, methane and helium and can contain microbes that have uniquely adapted to these isolated environments [5]. We are actively expanding discovery of sites with fluids exhibiting extreme age and have recently shown that these systems contribute to half of the terrestrial hydrogen production; a key component in biosphere energy and carbon cycles [6]. Tectonic or thermal release of these fluids can result in helium deposits; possible ore body generation and the inoculation of near-surface systems with microbial biota protected in the deep surface; the controls and rate of fluid release to shallow systems can fundamentally change the nature of some shallow systems. These deep ancient fluids represent a little tapped scientific resource for understanding how life survives and evolves in such isolation, how life is transported and communicates in extremis together and

  15. Modelagem da infiltração em solos com encrostamento superficial. Parte II: condutividade hidráulica variando no tempo Modelling of the soil water infiltration in crusting soil. Part II: variable hydraulic conductivity over time

    João H. Zonta


    Full Text Available RESUMO Este trabalho objetivou avaliar o desempenho do modelo de Green-Ampt-Mein-Larson (GAML na simulação do processo de infiltração em solos com encrostamento superficial. Os ensaios de infiltração foram realizados num Cambissolo com a utilização de simulador de chuvas, em solo nu. O valor da condutividade hidráulica na zona de transmissão (Kt foi considerado igual a Kt* que, por sua vez, é igual à taxa de infiltração estável (Tie multiplicada pelo fator f, que representa o decaimento da Tie em função da energia cinética acumulada da chuva (Ec, ou seja, o valor de Kt variando ao longo do tempo. O modelo GAML com o valor de Kt constante ao longo do tempo não obteve bom desempenho superestimando, na maioria dos casos, os valores da taxa de infiltração (Ti enquanto com o uso de Kt* o modelo apresentou bom desempenho, em que os melhores resultados foram obtidos com a combinação de Kt* com o potencial matricial (jf calculado com uso da equação de Cecílio et al. (2007. O modelo de GAML com valor da condutividade hidráulica na zona de transmissão (Kt variando no tempo apresentou bons resultados na simulação do processo de infiltração em solos sujeitos ao encrostamento superficial.ABSTRACT The soil crust affects significantly the soil water infiltration rate. Thus, the infiltration simulation models must somehow consider the effect of crust layer to obtain good results.The objective of this work was to evaluate the performance of the Green-Ampt-Mein-Larson (GAML model to simulate the soil water infiltration for crusting soils. The trials were carried out in a Podzol Tb distrophic Haplic Cambisol, using a rain simulator, on a bare soil. The GAML model parameters were determined , being proposed for the hydraulic conductivity of transmission zone (Kt value the use of Kt*, which is equal to Tie x f, where Tie is stable infiltration rate and f is a decrease factor of the Tie as a function of cumulative kinetic energy of


    Kutuzova I. V.


    Full Text Available Negative impact of oil on biological properties of soils right after pollution is shown in the article. Eventually, there is their restoration. However, even in some years after pollution, the biological properties of soils aren't restored completely

  17. Changes and recovery of soil bacterial communities influenced by biological soil disinfestation as compared with chloropicrin-treatment

    Mowlick, Subrata; Inoue, Takashi; Takehara, Toshiaki; Kaku, Nobuo; Ueki, Katsuji; Ueki, Atsuko


    Soil bacterial composition, as influenced by biological soil disinfestation (BSD) associated with biomass incorporation was investigated to observe the effects of the treatment on the changes and recovery of the microbial community in a commercial greenhouse setting. Chloropicrin (CP) was also used for soil disinfestation to compare with the effects of BSD. The fusarium wilt disease incidence of spinach cultivated in the BSD- and CP-treated plots was reduced as compared with that in the untre...

  18. Physical, chemical, and biological properties of soils in the city of Mariupol, Ukraine

    Shekhovtseva, O. G.; Mal'tseva, I. A.


    Physicochemical and biological properties of urbanized soils in the city of Mariupol have been considered in comparison with the background soils. The parametrical characteristics (abundance and biomass) of soil algal groups, the content of humus, the reaction of soil solution, the content of heavy metals, and the particle size distributions of soils under different anthropogenic impacts have been assessed. The physicochemical properties of soils developing under urboecosystem conditions affect the number of structure-forming species, biomass, and proportions of soil algae. According to the particle size distribution, urban soils are classified among the medium and heavy loamy soils with the predominance of the clay and coarse silt fractions. The fractions of physical clay and clay are of highest importance for the existence of algae. The accumulation of heavy metals in the surface horizons of soils can stimulate or inhibit the development of algae depending on the metal concentration.

  19. Temporal and spatial variability of soil biological activity at European scale

    Mallast, Janine; Rühlmann, Jörg


    The CATCH-C project aims to identify and improve the farm-compatibility of Soil Management Practices including to promote productivity, climate change mitigation and soil quality. The focus of this work concentrates on turnover conditions for soil organic matter (SOM). SOM is fundamental for the maintenance of quality and functions of soils while SOM storage is attributed a great importance in terms of climate change mitigation. The turnover conditions depend on soil biological activity characterized by climate and soil properties. Soil biological activity was investigated using two model concepts: a) Re_clim parameter within the ICBM (Introductory Carbon Balance Model) (Andrén & Kätterer 1997) states a climatic factor summarizing soil water storage and soil temperature and its influence on soil biological activity. b) BAT (biological active time) approach derived from model CANDY (CArbon and Nitrogen Dynamic) (Franko & Oelschlägel 1995) expresses the variation of soil moisture, soil temperature and soil aeration as a time scale and an indicator of biological activity for soil organic matter (SOM) turnover. During an earlier stage both model concepts, Re_clim and BAT, were applied based on a monthly data to assess spatial variability of turnover conditions across Europe. This hampers the investigation of temporal variability (e.g. intra-annual). The improved stage integrates daily data of more than 350 weather stations across Europe presented by Klein Tank et al. (2002). All time series data (temperature, precipitation and potential evapotranspiration and soil texture derived from the European Soil Database (JRC 2006)), are used to calculate soil biological activity in the arable layer. The resulting BAT and Re_clim values were spatio-temporal investigated. While "temporal" refers to a long-term trend analysis, "spatial" includes the investigation of soil biological activity variability per environmental zone (ENZ, Metzger et al. 2005 representing similar

  20. Potential of Biological Agents in Decontamination of Agricultural Soil

    Javaid, Muhammad Kashif; Ashiq, Mehrban; Tahir, Muhammad


    Pesticides are widely used for the control of weeds, diseases, and pests of cultivated plants all over the world, mainly since the period after the Second World War. The use of pesticides is very extensive to control harm of pests all over the globe. Persistent nature of most of the synthetic pesticides causes serious environmental concerns. Decontamination of these hazardous chemicals is very essential. This review paper elaborates the potential of various biological agents in decontamination of agricultural soils. The agricultural crop fields are contaminated by the periodic applications of pesticides. Biodegradation is an ecofriendly, cost-effective, highly efficient approach compared to the physical and chemical methods which are expensive as well as unfriendly towards environment. Biodegradation is sensitive to the concentration levels of hydrogen peroxide and nitrogen along with microbial community, temperature, and pH changes. Experimental work for optimum conditions at lab scale can provide very fruitful results about specific bacterial, fungal strains. This study revealed an upper hand of bioremediation over physicochemical approaches. Further studies should be carried out to understand mechanisms of biotransformation. PMID:27293964

  1. Potential of Biological Agents in Decontamination of Agricultural Soil.

    Javaid, Muhammad Kashif; Ashiq, Mehrban; Tahir, Muhammad


    Pesticides are widely used for the control of weeds, diseases, and pests of cultivated plants all over the world, mainly since the period after the Second World War. The use of pesticides is very extensive to control harm of pests all over the globe. Persistent nature of most of the synthetic pesticides causes serious environmental concerns. Decontamination of these hazardous chemicals is very essential. This review paper elaborates the potential of various biological agents in decontamination of agricultural soils. The agricultural crop fields are contaminated by the periodic applications of pesticides. Biodegradation is an ecofriendly, cost-effective, highly efficient approach compared to the physical and chemical methods which are expensive as well as unfriendly towards environment. Biodegradation is sensitive to the concentration levels of hydrogen peroxide and nitrogen along with microbial community, temperature, and pH changes. Experimental work for optimum conditions at lab scale can provide very fruitful results about specific bacterial, fungal strains. This study revealed an upper hand of bioremediation over physicochemical approaches. Further studies should be carried out to understand mechanisms of biotransformation. PMID:27293964

  2. Potential of Biological Agents in Decontamination of Agricultural Soil

    Muhammad Kashif Javaid


    Full Text Available Pesticides are widely used for the control of weeds, diseases, and pests of cultivated plants all over the world, mainly since the period after the Second World War. The use of pesticides is very extensive to control harm of pests all over the globe. Persistent nature of most of the synthetic pesticides causes serious environmental concerns. Decontamination of these hazardous chemicals is very essential. This review paper elaborates the potential of various biological agents in decontamination of agricultural soils. The agricultural crop fields are contaminated by the periodic applications of pesticides. Biodegradation is an ecofriendly, cost-effective, highly efficient approach compared to the physical and chemical methods which are expensive as well as unfriendly towards environment. Biodegradation is sensitive to the concentration levels of hydrogen peroxide and nitrogen along with microbial community, temperature, and pH changes. Experimental work for optimum conditions at lab scale can provide very fruitful results about specific bacterial, fungal strains. This study revealed an upper hand of bioremediation over physicochemical approaches. Further studies should be carried out to understand mechanisms of biotransformation.

  3. 人工生物质结皮在黄土山区公路边坡应用的初探%The Application of Artificial Biological Crust in the Highway Slope of Loess Mountainous Area

    舒鑫; 王百田; 曹远博; 魏婷婷; 王鲜鲜


    Objective]The aim of the study was to evaluate the application of artificial crust in the highway slope of loess mountainous area. [Method ] In the highway slope of the Lvliang mountains,5 experimental groups (natural slope (T1 ),crust (T2 ),crust and fertilizer (T3 ), crust and seeds (T4),curst,fertilizer and seeds (T5))were set.Temperature and humidity of soil,rill erosion of soil and plant growth condition (plant emergence,coverage,Shannon weaver diversity index,Shannon wiener diversity index and the Pielou evenness index)were investigated.[Results]Compared with the natural slope,artificial crust increased soil temperature and humidi-ty in Spring and maintained soil temperature in the rainy season.The temperature of crust was significantly lower than that of the natural slope at noon.Soil moistures of crust groups were sig-nificantly higher than that of natural slope throughout the day and T5 was the highest.The order of erosion degree was T5crust reduced the formation of erosion gully.Artificial crust improved soil seed germination rate and utilization efficiency of soil seed banks.The species diversity,evenness and fresh weight biomass of crust groups were higher compared to the natural slope.The aboveground fresh biomass of T5,T4,T3 and T2 was 2.44, 1.99,1.95 and 1.68 times larger than T1.[Conclusion]Therefore,artificial biomass skin in-creased soil seed banks,biodiversity and coverage by improving soil temperature,humidity and stability.Thus,it could enhance the steady and greening of road slope in the loess mountainous area.%【目的】探讨人工结皮在黄土山区公路边坡的应用效果。【方法】选用吕梁山区人为破坏过的公路边坡进行治理,设置5个试验组(T1自然边坡、T2结皮、T3结皮+肥料、T4结皮+种子、T5结皮+肥料+种子)。对每个试验组的土壤温湿度、土壤细沟侵蚀、植物生长状况(植物出苗株数、覆盖度、Shannon-weaver

  4. Effect of soil type and soil management on soil physical, chemical and biological properties in commercial organic olive orchards in Southern Spain

    Gomez, Jose Alfonso; Auxiliadora Soriano, Maria; Montes-Borrego, Miguel; Navas, Juan Antonio; Landa, Blanca B.


    One of the objectives of organic agriculture is to maintain and improve soil quality, while simultaneously producing an adequate yield. A key element in organic olive production is soil management, which properly implemented can optimize the use of rainfall water enhancing infiltration rates and controlling competition for soil water by weeds. There are different soil management strategies: eg. weed mowing (M), green manure with surface tillage in spring (T), or combination with animal grazing among the trees (G). That variability in soil management combined with the large variability in soil types on which organic olive trees are grown in Southern Spain, difficult the evaluation of the impact of different soil management on soil properties, and yield as well as its interpretation in terms of improvement of soil quality. This communications presents the results and analysis of soil physical, chemical and biological properties on 58 soils in Southern Spain during 2005 and 2006, and analyzed and evaluated in different studies since them. Those 58 soils were sampled in 46 certified commercial organic olive orchards with four soil types as well as 12 undisturbed areas with natural vegetation near the olive orchards. The four soil types considered were Eutric Regosol (RGeu, n= 16), Eutric Cambisol (CMeu, n=16), Calcaric Regosol (RGca, n=13 soils sampled) and Calcic Cambisol (CMcc), and the soil management systems (SMS) include were 10 light tillage (LT), 16 sheep grazing (G), 10 tillage (T), 10 mechanical mowing (M), and 12 undisturbed areas covered by natural vegetation (NV-C and NV-S). Our results indicate that soil management had a significant effect on olive yield as well as on key soil properties. Among these soil properties are physical ones, such as infiltration rate or bulk density, chemical ones, especially organic carbon concentration, and biological ones such as soil microbial respiration and bacterial community composition. Superimpose to that soil

  5. Biochar and biological carbon cycling in temperate soils

    McCormack, S. A.; Vanbergen, A. J.; Bardgett, R. D.; Hopkins, D. W.; Ostle, N.


    Production of biochar, the recalcitrant residue formed by pyrolysis of plant matter, is suggested as a means of increasing storage of stable carbon (C) in the soil (1). Biochar has also been shown to act as a soil conditioner, increasing the productivity of certain crops by reducing nutrient leaching and improving soil water-holding capacity. However, the response of soil carbon pools to biochar addition is not yet well understood. Studies have shown that biochar has highly variable effects on microbial C cycling and thus on soil C storage (2,3,4). This discrepancy may be partially explained by the response of soil invertebrates, which occupy higher trophic levels and regulate microbial activity. This research aims to understand the role of soil invertebrates (i.e. Collembola and nematode worms) in biochar-mediated changes to soil C dynamics across a range of plant-soil communities. An open-air, pot-based mesocosm experiment was established in May, 2011 at the Centre for Ecology and Hydrology, Edinburgh. Three treatments were included in a fully-factorial design: biochar (presence [2 % w/w] or absence), soil type (arable sandy, arable sandy loam, grassland sandy loam), and vegetation type (Hordeum vulgare, Lolium perenne, unvegetated). Monitored parameters include: invertebrate and microbial species composition, soil C fluxes (CO2 and trace gas evolution, leachate C content, primary productivity and soil C content), and soil conditions (pH, moisture content and water-holding capacity). Preliminary results indicate that biochar-induced changes to soil invertebrate communities and processes are affected by pre-existing soil characteristics, and that soil texture in particular may be an important determinant of soil response to biochar addition. 1. Lehmann, 2007. A handful of carbon. Nature 447, 143-144. 2. Liang et al., 2010. Black carbon affects the cycling of non-black carbon in soil. Organic Geochemistry 41, 206-213. 3. Van Zwieten et al., 2010. Influence of

  6. Wildfire effects on biological properties of soils in forest-steppe ecosystems of Russia

    E. Maksimova


    Full Text Available Soils affected by forest wildfires in 2010 in Russia were studied on postfire and mature plots near the Togljatty city, Samara region. Soil biological properties and ash composition dynamics were investigated under the forest fire affect: a place of local forest fire, riding forest fire and unaffected site by fire-control (mature during 3 yr of restoration. Soil samples were collected at 0–15 cm. Soil biological properties was measured by the fumigation method. The analytical data obtained shows that wildfires lead to serious changes in a soil profile and soil chemistry of upper horizons. Wildfires change a chemical composition of soil horizons and increase their ash-content. Fires lead to accumulation of biogenic elements' content (P and K in the solum fine earth. Calcium content is increased as a result of fires that leads to an alkaline pH of the solum. The values of nutrients decreased as a result of leaching out with an atmospheric precipitation during the second year of restoration. Thus, when the upper horizons are burning the ash arriving on a soil surface enrich it with nutrients. The mature (unaffected by fire soils is characterized by the greatest values of soil microbial biomass in the top horizon and, respectively, the bigger values of basal respiration whereas declining of the both parameters was revealed on postfire soils. Nevertheless this influence does not extend on depth more than 10 cm. Thus, fire affect on the soil were recognized in decreasing of microbiological activity.

  7. Wildfire effects on biological properties of soils in forest-steppe ecosystems of Russia

    Maksimova, E.; Abakumov, E.


    Soils affected by forest wildfires in 2010 in Russia were studied on postfire and mature plots near the Togljatty city, Samara region. Soil biological properties and ash composition dynamics were investigated under the forest fire affect: a place of local forest fire, riding forest fire and unaffected site by fire-control (mature) during 3 yr of restoration. Soil samples were collected at 0-15 cm. Soil biological properties was measured by the fumigation method. The analytical data obtained shows that wildfires lead to serious changes in a soil profile and soil chemistry of upper horizons. Wildfires change a chemical composition of soil horizons and increase their ash-content. Fires lead to accumulation of biogenic elements' content (P and K) in the solum fine earth. Calcium content is increased as a result of fires that leads to an alkaline pH of the solum. The values of nutrients decreased as a result of leaching out with an atmospheric precipitation during the second year of restoration. Thus, when the upper horizons are burning the ash arriving on a soil surface enrich it with nutrients. The mature (unaffected by fire) soils is characterized by the greatest values of soil microbial biomass in the top horizon and, respectively, the bigger values of basal respiration whereas declining of the both parameters was revealed on postfire soils. Nevertheless this influence does not extend on depth more than 10 cm. Thus, fire affect on the soil were recognized in decreasing of microbiological activity.

  8. Effects of gentle remediation technologies on soil biological and biochemical activities - a review.

    Marschner, B.; Haag, R.; Renella, G.


    Remediation technologies for contaminated sites are generally designed to reduce risks for human health, groundwater or plant quality. While some drastic remediation measures such as soil excavation, thermal treatment or soil washing eliminate or strongly reduce soil life, in-situ treatments involving plants or immobilizing additives may also restore soil functionality by establishing or promoting a well structured and active community of soil organisms. Biological parameters that are sensitive to contaminants and other pedo-environmental conditions and which contribute to biogeochemical nutrient cycles, can be used as synthetic indicators of the progress and also the efficiency of given remediation approaches. Data from long-term studies on re-vegetated mine spoils show that biological and biochemical activity is enhanced with increasing plant density and diversity. Among the soil amendments, most measures that introduce organic matter or alkalinity to the contaminated soils also improve microbial or faunal parameters. Only few amendments, such as phosphates and chelators have deleterious effects on soil biota. In this review, soil microbial biomass and the activity of the enzymes phosphatase and arylsulphatase are identified as suitable and sensitive biological indicators for soil health. The results and future research needs are are summarized.

  9. Physicochemical and biological quality of soil in hexavalent chromium-contaminated soils as affected by chemical and microbial remediation.

    Liao, Yingping; Min, Xiaobo; Yang, Zhihui; Chai, Liyuan; Zhang, Shujuan; Wang, Yangyang


    Chemical and microbial methods are the main remediation technologies for chromium-contaminated soil. These technologies have progressed rapidly in recent years; however, there is still a lack of methods for evaluating the chemical and biological quality of soil after different remediation technologies have been applied. In this paper, microbial remediation with indigenous bacteria and chemical remediation with ferrous sulphate were used for the remediation of soils contaminated with Cr(VI) at two levels (80 and 1,276 mg kg(-1)) through a column leaching experiment. After microbial remediation with indigenous bacteria, the average concentration of water-soluble Cr(VI) in the soils was reduced to less than 5.0 mg kg(-1). Soil quality was evaluated based on 11 soil properties and the fuzzy comprehensive assessment method, including fuzzy mathematics and correlative analysis. The chemical fertility quality index was improved by one grade using microbial remediation with indigenous bacteria, and the biological fertility quality index increased by at least a factor of 6. Chemical remediation with ferrous sulphate, however, resulted in lower levels of available phosphorus, dehydrogenase, catalase and polyphenol oxidase. The result showed that microbial remediation with indigenous bacteria was more effective for remedying Cr(VI)-contaminated soils with high pH value than chemical remediation with ferrous sulphate. In addition, the fuzzy comprehensive evaluation method was proven to be a useful tool for monitoring the quality change in chromium-contaminated soils. PMID:23784058


    Various biological amendments, including commercial biocontrol agents, microbial inoculants, mycorrhizae, and an aerobic compost tea (CT), were evaluated, alone and in conjunction with different crop rotations, for their efficacy in introducing beneficial microorganisms, affecting soil microbial com...

  11. The Impact of Olive Mill Wastewater on the Physicochemical and Biological Properties of Soils in Northwest Jordan

    Mohammad Wahsha; Claudio Bini; Mandana Nadimi-Goki


    Soil contamination may influence negatively soil health, which often limits and sometimes disqualifies soil biodiversity and decreases plant growth. Soil health is the continued capacity of the soil to function as a vital living system, providing essential ecosystem services. Within soils, all bio-geo-chemical processes of the different ecosystem components are combined. These processes are able to sustain biological productivity of soil, to maintain the quality of surrounding air and water e...

  12. Characterization of PAH-contaminated soils focusing on availability, chemical composition and biological effects

    Bergknut, Magnus


    The risks associated with a soil contaminated by polycyclic aromatic hydrocarbons (PAHs) are generally assessed by measuring individual PAHs in the soil and correlating the obtained amounts to known adverse biological effects of the PAHs. The validity of such a risk estimation is dependent on the presence of additional compounds, the availability of the compounds (including the PAHs), and the methods used to correlate the measured chemical data and biological effects. In the work underlying t...

  13. Soil properties and biological activity as influenced by nutrient management in rice- fallow sorghum

    N Goutami


    A field experiment was conducted to observe the effect of inorganics, bio-fertilizers and FYM applied to rice-fallow sorghum on soil properties and biological activity at Agricultural College Farm, Bapatla during 2012. Soil samples were collected at flowering and harvest of the crop and were analysed for bulk density (BD), porosity, pH, electrical conductivity (EC), organic carbon, N, P, K and micronutrients by standard methods. Results indicated that the soil properties viz., bulk density, p...

  14. Proliferation of diversified clostridial species during biological soil disinfestation incorporated with plant biomass under various conditions

    Mowlick, Subrata; Takehara, Toshiaki; Kaku, Nobuo; Ueki, Katsuji; Ueki, Atsuko


    【Abstract】 Biological soil disinfestation (BSD) involves the anaerobic decomposition of plant biomass by microbial communities leads to control of plant pathogens. We analyzed bacterial communities in soil of a model experiment of BSD, as affected by biomass incorporation under various conditions, to find out the major anaerobic bacterial groups emerged after BSD treatments. The soil was treated with Brassica juncea plants, wheat bran or Avena strigosa plants, irrigated at 20% or 30% moisture...

  15. Effect of Organic Amendments and Inorganic Nitrogen on Biological and Chemical Degradation of Atrazine in Soil

    E Ranjbar; G.H. Haghnia; A. Lakzian; A Fotovat


    This study was conducted to compare the impact of various organic amendments with different C/N ratios and chemical compositions on biological and chemical degradation of Atrazine in sterile and non-sterile soils. The experiment was carried out in a factorial arrangement (2×6×2) including two soil types (sterile and non sterile soils), six types of organic amendments (vermicompost, cow manure, glucose, starch and sawdust and without organic matter) and two levels of inorganic nitrogen fertili...

  16. Remediation of Pb contaminated soils by phytoextraction and amendment induced immobilization : biological aspects

    GEEBELEN, Wouter


    This study examines the biological aspects related to alternative remediation strategies for Pb contaminated soils: EDTA induced Pb phytoextraction and amendment induced immobilization of soil Pb by means of inorganic soil amendments. The physiological effects of Pb-EDTA and EDTA were studied on bean plants (Phaseolus vulgaris L. Limburgse vroege), grown under strictly controlled conditions on a Hoagland nutrient solution. Addition of Pb-EDTA to the growth medium increased the capacity of enz...

  17. Neutron star crusts

    The formation, structure, composition, and the equation of state of neutron star crusts are described. A scenario of formation of the crust in a newly born neutron star is considered and a model of evolution of the crust composition during the early neutron star cooling is presented. Structure of the ground state of the crust is studied. In the case of the outer crust, recent nuclear data on masses of neutron rich nuclei are used. For the inner crust, results of different many-body calculations are presented, and dependence on the assumed effective nucleon-nucleon interaction is discussed. Uncertainties concerning the bottom layers of the crust and crust-liquid interface are illustrated using results of various many-body calculations based on different effective nucleon-nucleon interactions. A scenario of formation of a crust of matter-accreting neutron star is presented, and evolution of the crust-matter element under the increasing pressure of accreted layer is studied. Within a specific dense matter model, composition of accreted crust is calculated, and is shown to be vastly different from the ground-state one. Non-equilibrium processes in the crust of mass-accreting neutron star are studied, heat release due to them is estimated, and their relevance to the properties of X-ray sources is briefly discussed. Equation of state of the ground-state crust is presented, and compared with that for accreted crust. Elastic properties of the crust are reviewed. Possible deviations from idealized models of one-component plasmas are briefly discussed. (orig.)

  18. Environmental implications of herbicide resistance: soil biology and ecology

    Soil microbial community structure and activity are clearly linked to plant communities established in natural and agricultural ecosystems. A limited number of studies confirm that weeds alter their soil environment and select for specific microbial communities in the rhizosphere. Such rhizosphere m...

  19. Soil Biological Parameters Influenced By Cocoa Management Systems

    Cropping systems have a profound influence on the soil micro-fauna and they are responsible for nutrient cycling, and add stability to the soil. At Tarapoto, Peru, two field experiments were established on acidic medium fertility Alfisol to assess the influence of management systems on cacao rhizosp...

  20. Soil Biological Engineering to Enhance your Bottom Line

    Despite the importance of soil to all life on Earth, soil is the not-well-understood ‘big black box’. Therefore, the next revolution in agriculture needs not to be a green revolution or an iron (i.e. equipment) revolution; it needs to be a brown revolution. In this brown revolution, the root of th...

  1. Application of radiochemical methods for development of new biological preparation designed for soil bioremediation

    Full text: Internationally the bioremediation of agricultural lands contaminated by persistent chloroorganic compounds by means of the microbial methods are used as the most low-cost and the most effective. One of the factors reducing efficacy of microbial degradation, is often the low quantity of microorganisms - destructors in the soil. Therefore, we have designed bioremediation technology of soils, contaminated by organochlorine compounds, with use of the alive microorganisms as active agent. We developed the biological preparation containing 5 aboriginal active strains of bacteria - destructors of persistent chloroorganic compounds and investigated the ability of biological preparation to increase the bioremediation potential of contaminated soils. To carry out the investigation we developed the complex of radiochemical methods with use of tritium labeled PCBs, including the following methods: 1.The method to define the accumulation and degradation of PCBs in soil bacteria in culture allows determination of quantitative characteristics of bacterial strains. 2. The method to define the PCBs degradation by soil bacteria strains in model conditions in the soil allows to estimate the PCB-destructive activity of strains after introducing in soil. 3. A method to define the PCB-destructive activity of own microbiota of contaminated soil. 4. A method to define the effect of stimulation of the PCB-destructive activity of biological preparation and own microbiota of soil with the help of biofertilizers. By using the developed radiochemical methods we have carried out investigation on creation of new biological preparation on the basis of strains of soil bacteria - destructors of PCBs. We also determined the quality and quantity characteristics of HCCH and PCBs-destructive activity of new biological preparation. It is shown that the new biological preparation is capable of accumulation and destruction of the PCBs in culture and in soil at model conditions. Thus, the

  2. The accumulation of 137Cs in the biological compartment of forest soils

    Soil samples were collected in various forest stands, located about 40 km north-west from Uppsala. The various stands were: (1) Clear cut area made in 1987, (2) Normal forest with 50-100 old Norway spruce and Scots pine and with a thick humic layer of about 10 cm; (3) Raised bog with 50-year-old Scots pine and Sphagnum moss layer over peat soil. (4) Rocky area with old Scots pine, growing on a shallow soil, mainly of organic origin. (5) Normal forest with nearly 100-year-old spruce and pine, growing a shallow humic layer over sandy soil. Soil blocks of about 20x20 cm and down to a depth of 10-15 cm were collected on each site. The soil samples were mechanically separated into various fractions: bulk, rhizosphere and soil-root interface. The results showed that 137Cs was unevenly distributed between the three soil fractions. The highest activity concentrations -- 3-4 times higher than in the other two fractions -- as well as the highest organic content -- usually more than 95% -- were found in the soil-root interface fraction. Of the total 137Cs activity in the soil, 18% as a mean value was found in the soil-root interface fraction. The results thus show that a substantial fraction of the 137Cs in the soils in some way associated with the biological part of the soil, probably with the fungal component

  3. 苔藓结皮影响干旱半干旱植被指数的稳定性%Impact of Moss Soil Crust on Vegetation Indexes Interpretation

    房世波; 张新时


    Vegetation indexes were the most common and the most important parameters to characterizing large-scale terrestrial ecosystems. It is vital to get precise vegetation indexes for running land surface process models and computation of NPP change, moisture and heat fluxes over surface Biological soil crusts (BSC) are widely distributed in arid and semi-arid, polar and sub-polar regions. The spectral characteristics of dry and wet BSCs were quite different, which could produce much higher vegetation indexes value for the wet BSC than for the dry BSC as reported. But no research was reported about whether the BSC would impact on regional vegetation indexes and how much dry and wet BSC had impact on regional vegetation indexes. In the present paper, the most common vegetation index NDVI were used to analyze how the moss soil crusts (MSC) dry and wet changes affect regional NDVI values. It was showed that 100% coverage of the wet MSC have a much higher NDVI value (0. 657) than the dry MSC NDVI value (0. 320), with increased 0. 337. Dry and wet MSC NDVI value reached significant difference between the levels of 0. 000. In the study area, MSC, which had the average coverage of 12.25%, would have a great contribution to the composition of vegetation index. Linear mixed model was employed to analyze how the NDVI would change in regional scale as wet MSC become dry MSC inversion. The impact of wet moss crust than the dry moss crust in the study area can make the regional NDVI increasing by 0. 04 (14. 3%). Due to the MSC existence and rainfall variation in arid and semi-arid zones, it was bound to result in NDVI change instability in a short time in the region. For the wet MSC's spectral reflectance curve is similar to those of the higher plants, misinterpretation of the vegetation dynamics could be more severe due to the “maximum value composite” (MVC) technique used to compose the global vegetation maps in the study of vegetation dynamics. The researches would be

  4. Biological Treatment of Petroleum in Radiologically Contaminated Soil



    This chapter describes ex situ bioremediation of the petroleum portion of radiologically co-contaminated soils using microorganisms isolated from a waste site and innovative bioreactor technology. Microorganisms first isolated and screened in the laboratory for bioremediation of petroleum were eventually used to treat soils in a bioreactor. The bioreactor treated soils contaminated with over 20,000 mg/kg total petroleum hydrocarbon and reduced the levels to less than 100 mg/kg in 22 months. After treatment, the soils were permanently disposed as low-level radiological waste. The petroleum and radiologically contaminated soil (PRCS) bioreactor operated using bioventing to control the supply of oxygen (air) to the soil being treated. The system treated 3.67 tons of PCRS amended with weathered compost, ammonium nitrate, fertilizer, and water. In addition, a consortium of microbes (patent pending) isolated at the Savannah River National Laboratory from a petroleum-contaminated site was added to the PRCS system. During operation, degradation of petroleum waste was accounted for through monitoring of carbon dioxide levels in the system effluent. The project demonstrated that co-contaminated soils could be successfully treated through bioventing and bioaugmentation to remove petroleum contamination to levels below 100 mg/kg while protecting workers and the environment from radiological contamination.

  5. Biological responses of agricultural soils to fly-ash amendment.

    Singh, Rajeev Pratap; Sharma, Bhavisha; Sarkar, Abhijit; Sengupta, Chandan; Singh, Pooja; Ibrahim, Mahamad Hakimi


    The volume of solid waste produced in the world is increasing annually, and disposing of such wastes is a growing problem. Fly ash (FA) is a form of solid waste that is derived from the combustion of coal. Research has shown that fly ash may be disposed of by using it to amend agricultural soils. This review addresses the feasibility of amending agricultural field soils with fly ash for the purpose of improvings oil health and enhancing the production of agricultural crops. The current annual production of major coal combustion residues (CCRs) is estimated to be -600 million worldwide, of which about 500 million t (70-80%) is FA (Ahmaruzzaman 2010). More than 112 million t of FA is generated annually in India alone, and projections show that the production (including both FA and bottom ash) may exceed 170 million t per annum by 2015 (Pandey et al. 2009; Pandey and Singh 20 I 0). Managing this industrial by-product is a big challenge, because more is produced each year, and disposal poses a growing environmental problem.Studies on FA clearly shows that its application as an amendment to agricultural soils can significantly improve soil quality, and produce higher soil fertility. What FA application method is best and what level of application is appropriate for any one soil depends on the following factors: type of soil treated, crop grown, the prevailing agro climatic condition and the character of the FA used. Although utilizing FA in agricultural soils may help address solid waste disposal problems and may enhance agricultural production, its use has potential adverse effects also. In particular, using it in agriculture may enhance amounts of radionuclides and heavy metals that reach soils, and may therefore increase organism exposures in some instances. PMID:24984834

  6. Biological Activity of Autochthonic Bacterial Community in Oil-Contaminated Soil

    Wolińska, Agnieszka; Kuźniar, Agnieszka; Szafranek-Nakonieczna, Anna; Jastrzębska, Natalia; Roguska, Eliza; Stępniewska, Zofia


    Soil microbial communities play an important role in the biodegradation of different petroleum derivates, including hydrocarbons. Also other biological factors such as enzyme and respiration activities and microbial abundance are sensitive to contamination with petroleum derivates. The aim of this study was to evaluate the response of autochthonic microbial community and biological parameters (respiration, dehydrogenase and catalase activities, total microorganisms count) on contamination wit...

  7. Geochemistry of U and Th and its Influence on the Origin and Evolution of the Crust of Earth and the Biological Evolution

    Bao, Xuezhao


    We have investigated the migration behaviors of uranium (U) and thorium (Th) in the Earth and other terrestrial planets. Theoretical models of U and Th migration have been proposed. These models suggest that the unique features of the Earth are closely connected with its unique U and Th migration models and distribution patterns. In the Earth, U and Th can combine with oxidative volatile components and water, migrate up to the asthenosphere position to form an enrichment zone (EZ) of U and Th first, and then migrate up further to the crusts through magmatism and metamorphism. We emphasize that the formation of an EZ of U, Th and other heat-producing elements is a prerequisite for the formation of a plate tectonic system. The heat-producing elements, currently mainly U and Th, in the EZ are also the energy sources that drive the formation and evolution of the crust of Earth and create special granitic continental crusts. In other terrestrial planets, including Mercury, Venus, and Mars, an EZ can not be formed ...

  8. Rich in life but poor in data: the known knowns and known unknowns of modelling how soil biology drives soil structure

    Hallett, Paul; Ogden, Mike


    Soil biology has a fascinating capacity to manipulate pore structure by altering or overcoming hydrological and mechanical properties of soil. Many have postulated, quite rightly, that this capacity of soil biology to 'engineer' its habitat drives its diversity, improves competitiveness and increases resilience to external stresses. A large body of observational research has quantified pore structure evolution accompanied by the growth of organisms in soil. Specific compounds that are exuded by organisms or the biological structures they create have been isolated and found to correlate well with observed changes to pore structure or soil stability. This presentation will provide an overview of basic mechanical and hydrological properties of soil that are affected by biology, and consider missing data that are essential to model how they impact soil structure evolution. Major knowledge gaps that prevent progress will be identified and suggestions will be made of how research in this area should progress. We call for more research to gain a process based understanding of structure formation by biology, to complement observational studies of soil structure before and after imposed biological activity. Significant advancement has already been made in modelling soil stabilisation by plant roots, by combining data on root biomechanics, root-soil interactions and soil mechanical properties. Approaches for this work were developed from earlier materials science and geotechnical engineering research, and the same ethos should be adopted to model the impacts of other biological compounds. Fungal hyphae likely reinforce soils in a similar way to plant roots, with successful biomechanical measurements of these micron diameter structures achieved with micromechanical test frames. Extending root reinforcement models to fungi would not be a straightforward exercise, however, as interparticle bonding and changes to pore water caused by fungal exudates could have a major impact on

  9. Natural physical and biological processes compromise the long-term performance of compacted soil caps

    Compacted soil barriers are components of essentially all caps placed on closed waste disposal sites. The intended functions of soil barriers in waste facility caps include restricting infiltration of water and release of gases and vapors, either independently or in combination with synthetic membrane barriers, and protecting other manmade or natural barrier components. Review of the performance of installed soil barriers and of natural processes affecting their performance indicates that compacted soil caps may function effectively for relatively short periods (years to decades), but natural physical and biological processes can be expected to cause them to fail in the long term (decades to centuries). This paper addresses natural physical and biological processes that compromise the performance of compacted soil caps and suggests measures that may reduce the adverse consequences of these natural failure mechanisms


    Radu Lacatusu


    Full Text Available Urban soil is an material that has been manipulated, disturbed or transported by man’s activities in the urban environment and is used as a medium for plant growth and for constructions. The physical, chemical, and biological properties are generally less favorable as a rooting medium than soil found on the natural landscape. The main characteristics of urban soils are: great vertical and spatial variability; modified soil structure leading to compaction; presence of a surface crust; modified soil reaction, usually elevated; restricted aeration and water drainage; modified abundance of chemical elements, interrupted nutrient cycling and soil organism activity; presence of anthropic materials contaminants and pollutants; modified soil temperature regime. The urbic horizon is designated as U (always capital letter and for indication of processes are used different small letters. It is necessary elaboration a new classification of urban soils for our country.

  11. Dynamic Relationship Between Biologically Active Soil Organic Carbon and Aggregate Stability in Long-Term Organically Fertilized Soils

    LI Cheng-Liang; XU Jiang-Bing; HE Yuan-Qiu; LIU Yan-Li; FAN Jian-Bo


    Biologically active soil organic carbon (BASOC) is an important fraction of soil organic carbon (SOC),but our understanding of the correlation between BASOC and soil aggregate stability is limited.At an ecological experimental station (28° 04′-28° 37′ N,116°41′-117° 09′ E) in Yujiang County,Jiangxi Province,China,we analyzed the dynamic relationship between soil aggregate stability and BASOC content over time in the red soil (Udic Ferrosols) fertilized with a nitrogen-phosphorus-potassium chemical fertilizer (NPK)without manure or with NPK plus livestock manure or green manure.The dynamics of BASOC was evaluated using CO2 efflux,and soil aggregates were separated according to size using a wet-sieving technique.The soils fertilized with NPK plus livestock manure had a significantly higher content of BASOC and an improved aggregate stability compared to the soils fertilized with NPK plus green manure or NPK alone The BASOC contents in all fertilized soils decreased over time The contents of large aggregates (800-2000μm) dramatically decreased over the first 7 d of incubation,but the contents of small aggregates (< 800.μm) either remained the same or increased,depending on the incubation time and specific aggregate sizes.The aggregate stability did not differ significantly at the beginning and end of incubation,but the lowest stability inall fertilized soils occurred in the middle of the incubation,which implied that the soils had a strong resilience for aggregate stability.The change in BASOC content was only correlated with aggregate stability during the first 27 d of incubation.

  12. Biological and chemical assessments of zinc ageing in field soils

    As zinc (Zn) is both an essential trace element and potential toxicant, the effects of Zn fixation in soil are of practical significance. Soil samples from four field sites amended with ZnSO4 were used to investigate ageing of soluble Zn under field conditions over a 2-year period. Lability of Zn measured using 65Zn radioisotope dilution showed a significant decrease over time and hence evidence of Zn fixation in three of the four soils. However, 0.01 M CaCl2 extractions and toxicity measurements using a genetically modified lux-marked bacterial biosensor did not indicate a decrease in soluble/bioavailable Zn over time. This was attributed to the strong regulatory effect of abiotic properties such as pH on these latter measurements. These results also showed that Zn ageing occurred immediately after Zn spiking, emphasising the need to incubate freshly spiked soils before ecotoxicity assessments. - Ageing effects were detected in Zn-amended field soils using 65Zn isotopic dilution as a measure of lability, but not with either CaCl2 extractions or a lux-marked bacterial biosensor.

  13. The search for biologically inert and lithogenic carbon in recent soil organic matter

    The search for the existence of biologically inert carbon in recent soil samples, as suggested by Gerasimov, led to soil fraction dating, followed by various fractionation techniques. 6N HC1-hydrolysis residues were most consistently superior in age to the untreated soil sample. The age gradient from repeated steps of 6N HC1-hydrolysis indicates that by an extended continuous treatment of soil samples with synchronous replacement of the acid medium the starting position for recent soil dating can be considerably improved. The gap between the radiocarbon dates of recent soil samples, representing AMRT (apparent mean residence time) values and the true age of the soil formation, can be further minimized. A collection of 26 soil samples from soils with free carbonates and bicarbonate dynamics did not indicate a deviation from the Δ13C-range, characteristic for Calvin-type carbon. On the basis of Δ13C this excludes aging of such soils by introduction of lithogenic dead carbon into the soil organic matter. (author)

  14. Deforestation effects on biological and other important soil properties in an upland watershed of Bangladesh

    S.M. Sirajul Haque; Sanatan Das Gupta; Sohag Miah


    Deforestation occurs at an alarming rate in upland watersheds of Bangladesh and has many detrimental effects on the environment. This study reports the effects of deforestation on soil biological proper-ties along with some important physicochemical parameters of a southern upland watershed in Bangladesh. Soils were sampled at 4 paired sites, each pair representing a deforested site and a forested site, and having similar topographical characteristics. Significantly fewer (p≤0.001) fungi and bacteria, and lower microbial respiration, active microbial biomass, metabolic and microbial quotients were found in soils of the deforested sites. Soil physical properties such as moisture content, water holding capacity, and chemical properties such as organic matter, total N, avail-able P and EC were also lower in deforested soils. Bulk density and pH were significantly higher in deforested soils. Available Ca and Mg were inconsistent between the two land uses at all the paired sites. Re-duced abundance and biomass of soil mesofauna were recorded in defor-ested soils. However, soil anecic species were more abundant in defor-ested soils than epigeic and endogeic species, which were more abundant in forested soils than on deforested sites.

  15. Changes and recovery of soil bacterial communities influenced by biological soil disinfestation as compared with chloropicrin-treatment.

    Mowlick, Subrata; Inoue, Takashi; Takehara, Toshiaki; Kaku, Nobuo; Ueki, Katsuji; Ueki, Atsuko


    Soil bacterial composition, as influenced by biological soil disinfestation (BSD) associated with biomass incorporation was investigated to observe the effects of the treatment on the changes and recovery of the microbial community in a commercial greenhouse setting. Chloropicrin (CP) was also used for soil disinfestation to compare with the effects of BSD. The fusarium wilt disease incidence of spinach cultivated in the BSD- and CP-treated plots was reduced as compared with that in the untreated control plots, showing effectiveness of both methods to suppress the disease. The clone library analyses based on 16S rRNA gene sequences showed that members of the Firmicutes became dominant in the soil bacterial community after the BSD-treatment. Clone groups related to the species in the class Clostridia, such as Clostridium saccharobutylicum, Clostridium tetanomorphum, Clostridium cylindrosporum, Oxobacter pfennigii, etc., as well as Bacillus niacini in the class Bacilli were recognized as the most dominant members in the community. For the CP-treated soil, clones affiliated with the Bacilli related to acid-tolerant or thermophilic bacteria such as Tuberibacillus calidus, Sporolactobacillus laevolacticus, Pullulanibacillus naganoensis, Alicyclobacillus pomorum, etc. were detected as the major groups. The clone library analysis for the soil samples collected after spinach cultivation revealed that most of bacterial groups present in the original soil belonging to the phyla Proteobacteria, Acidobacteria, Bacteroidetes, Gemmatimonadetes, Planctomycetes, TM7, etc. were recovered in the BSD-treated soil. For the CP-treated soil, the recovery of the bacterial groups belonging to the above phyla was also noted, but some major clone groups recognized in the original soil did not recover fully. PMID:23958081

  16. Short-term effects of different organic amendments on soil chemical, biochemical and biological indicators

    Mondelli, Donato; Aly, Adel; Yirga Dagnachew, Ababu; Piscitelli, Lea; Dumontet, Stefano; Miano, Teodoro


    The limited availability of animal manure and the high cost of good quality compost lead to difficult soil quality management under organic agriculture. Therefore, it is important to find out alternative organic soil amendments and more flexible strategies that are able to sustain crop productivity and maintain and enhance soil quality. A three years study was carried out in the experimental fields of the Mediterranean Agronomic Institute of Bari located in Valenzano, Italy. The main objective of this research is to investigate the effects of different fertility management strategies on soil quality in order to estimate the role of innovative matrices for their use in organic farming. The experiment consists of seven treatments applied to a common crop rotation. The treatments include alternative organic amendments (1- olive mill wastewater OMW, 2- residues of mushroom cultivation MUS, 3- coffee chaff COF), common soil amendments (4- compost COM, 5- faba bean intercropping LEG, 6- cow manure - MAN) and as a reference treatment (7- mineral fertilizer COV). The soil quality was assessed before and after the application of the treatments, through biological (microbial biomass carbon and nitrogen, soil respiration and metabolic quotient), biochemical (soil enzymatic activities: β-glucosidase, alkaline phospatase, urease, fluorescein diacetate (FDA) hydrolysis), and chemical (pH, soil organic carbon, soil organic matter, total nitrogen, available phosphorous, exchangeable potassium, dissolved organic carbon and total dissolved nitrogen) indicators. Based on the results obtained after the second year, all treatments were able to improve various soil chemical parameters as compared to mineral fertilizer. The incorporation of COF and OMW seemed to be more effective in improving soil total N and exchangeable K, while MAN significantly increased available P. All the amendments enhance dissolved organic C, soil respiration, microbial biomass and metabolic quotient as

  17. Chemical and biological attributes of a lowland soil affected by land leveling

    José Maria Barbat Parfitt


    Full Text Available The objective of this work was to evaluate the relationship between soil chemical and biological attributes and the magnitude of cuts and fills after the land leveling process of a lowland soil. Soil samples were collected from the 0 - 0.20 m layer, before and after leveling, on a 100 point grid established in the experimental area, to evaluate chemical attributes and soil microbial biomass carbon (MBC. Leveling operations altered the magnitude of soil chemical and biological attributes. Values of Ca, Mg, S, cation exchange capacity, Mn, P, Zn, and soil organic matter (SOM decreased in the soil profile, whereas Al, K, and MBC increased after leveling. Land leveling decreased in 20% SOM average content in the 0 - 0.20 m layer. The great majority of the chemical attributes did not show relations between their values and the magnitude of cuts and fills. The relation was quadratic for SOM, P, and total N, and was linear for K, showing a positive slope and indicating increase in the magnitude of these attributes in cut areas and stability in fill areas. The relationships between these chemical attributes and the magnitude of cuts and fills indicate that the land leveling map may be a useful tool for degraded soil recuperation through amendments and organic fertilizers.


    Irina RUSAKOVA


    Full Text Available Estimation of changes of a biological condition (status soddy-podzolic sandy soil under the influence of use of mineral fertilizers and biological resources (straw of a winter wheat and stubble green manure, separately and in a combination was an objective of this research. Among the investigated kinds of fertilizers the strongest influence on the mortmass and mortmass carbon, number, activity of soil microflora and the content of soil microbial biomass have rendered straw in a combination with , postharverst green manure (intermediate culture, at the expense of increase in an input of the easily accessible for soil microflora organic matter. In this research mineral fertilizers without additives of organic materials essentially have not affected microbiаl activity

  19. Biological treatment of polluted soils; Tratamiento biologico de suelos contaminados

    Gorostiza, I.


    Bio remediation has proven to be a promising low-cost treatment technology for a wide range of contaminated soils. Apart from the well-known aspect of environmental parameters control (pH, water content, aeration, temperature,...), R and D on strategies to enhance bioavailability, and on serious approaches to bio augmentation will surely expand the applicability of this technology in the near future. One of the current research topics at GAIKER deals with these two aspects of Bioremediation technology. (Author)

  20. Blade-mixing reactors in the biological treatment of contaminated soils

    The application of mixing reactors was expected to have a positive effect on the biological turnover of contaminants, especially for cohesive soils. During investigations using blade-mixing reactors, it appeared to be of utmost importance to inhibit or reduce pellet formation during the dynamic treatment of soils. In this connection, a comparison of the degradation kinetics in static and dynamic reactors is of great interest. Contaminants of concern were diesel fuel and lubricating oil

  1. Phytoecological indicators for biological recultivation of soils polluted with oil in the Absheron peninsula

    E. M. Gurbanov; A. A. Akhundova


    Phytoecological indicators of polluted soils of Amirov Oil-and-Gas Production Department (Garadag district, Baku) were studied. Phytocenological and biomorphological analysis of flora was done with the aim of further biological rehabilitation of Absheron peninsula. Oil products (black oil, boring waters, etc.) pollution turns the plant cover into a dead mass. Decontamination of soil and rehabilitation of microbial community improve the soil’s fertility. Wild and cultured plant indicators may ...

  2. Biological nitrogen fixation by lucerne (Medicago sativa L.) in acid soils.

    Pijnenborg, J.W.M.


    Growth of lucerne( Medicago sativa L.) is poor in soils with values of pH-H2O below 6. This is often due to nitrogen deficiency, resulting from a hampered performance of the symbiosis withRhizobium meliloti. This thesis deals with the factors affecting biological nitrogen fixation by lucerne in acid soils.In a field experiment, lucerne seeds were either inoculated withR.meliloti only,or inoculated and pelleted with lime, before sowing in a sandy soil of pH 5.2. Lime-pelleting significantly im...

  3. Phytoecological indicators for biological recultivation of soils polluted with oil in the Absheron peninsula

    E. M. Gurbanov


    Full Text Available Phytoecological indicators of polluted soils of Amirov Oil-and-Gas Production Department (Garadag district,Baku were studied. Phytocenological and biomorphological analysis of flora was done with the aim of further biological rehabilitation of Absheron peninsula. Oil products (black oil, boring waters, etc. pollution turns the plant cover into a dead mass. Decontamination of soil and rehabilitation of microbial community improve the soil’s fertility. Wild and cultured plant indicators may be used in biopurification of the soils polluted with oil products. Sowing of the fodder crops followed by the technical remediation forms the clean areas of higher productivity.

  4. The effect of biological activity on soil water retention and diffusivity

    Choudhury, Burhan U.; Ferraris, Stefano; Ashton, Rhys W.; Powlson, David S.; Whalley, William R.


    soil microbial activity, with the addition of mercuric chloride, soil water diffusivity increased in comparison with biologically active soils.

  5. Behaviour of oxyfluorfen in soils amended with edaphic biostimulants/biofertilizers obtained from sewage sludge and chicken feathers. Effects on soil biological properties.

    Rodríguez-Morgado, Bruno; Gómez, Isidoro; Parrado, Juan; Tejada, Manuel


    We studied the behaviour of oxyfluorfen herbicide at a rate of 4 l ha(-1) on biological properties of a Calcaric Regosol amended with two edaphic biostimulants/biofertilizers (SS, derived from sewage sludge; and CF, derived from chicken feathers). Oxyfluorfen was surface broadcast on 11 March 2013. Two days after application of oxyfluorfen to soil, both biostimulants/biofertilizers (BS) were also applied to the soil. An unamended soil without oxyfluorfen was used as control. For 2, 4, 7, 9, 20, 30, 60, 90 and 120 days of the application of herbicide to the soil and for each treatment, the soil dehydrogenase, urease, β-glucosidase and phosphatase activities were measured. For 2, 7, 30 and 120 days of the application of herbicide to the soil and for each treatment, soil microbial community was determined. The application of both BS to soil without the herbicide increased the enzymatic activities and soil biodiversity, mainly at 7 days of beginning the experiment. However, this stimulation was higher in the soil amended with SS than for CF. The application of herbicide in organic-amended soils decreased the inhibition of soil enzymatic activities and soil biodiversity. Possibly, the low-molecular-weight protein content easily assimilated by soil microorganisms is responsible for less inhibition of these soil biological properties. PMID:24859703

  6. Potential of Biological Agents in Decontamination of Agricultural Soil

    Javaid, Muhammad Kashif; Ashiq, Mehrban; Tahir, Muhammad


    Pesticides are widely used for the control of weeds, diseases, and pests of cultivated plants all over the world, mainly since the period after the Second World War. The use of pesticides is very extensive to control harm of pests all over the globe. Persistent nature of most of the synthetic pesticides causes serious environmental concerns. Decontamination of these hazardous chemicals is very essential. This review paper elaborates the potential of various biological agents in decontaminatio...

  7. Biological nitrogen fixation by lucerne (Medicago sativa L.) in acid soils.

    Pijnenborg, J.W.M.


    Growth of lucerne( Medicago sativa L.) is poor in soils with values of pH-H2O below 6. This is often due to nitrogen deficiency, resulting from a hampered performance of the symbiosis withRhizobium meliloti. This thesis deals with the factors affecting biological nitrogen fixat

  8. Research results in the field of biological soil decontamination in the Netherlands

    Soczo, E.R.; Staps, J.J.M.; Visscher, K.


    Biological soil decontamination is also considered within efforts for the sanifation of abandoned waste sites. Research activities of varying scope were performed in Holland to study the applicability of these methods. The article reports in detail on the results and experience gained with different methods. Results encourage further pertinent studies.

  9. Tree species traits influence soil physical, chemical, and biological properties in high elevation forests.

    Edward Ayres

    Full Text Available BACKGROUND: Previous studies have shown that plants often have species-specific effects on soil properties. In high elevation forests in the Southern Rocky Mountains, North America, areas that are dominated by a single tree species are often adjacent to areas dominated by another tree species. Here, we assessed soil properties beneath adjacent stands of trembling aspen, lodgepole pine, and Engelmann spruce, which are dominant tree species in this region and are distributed widely in North America. We hypothesized that soil properties would differ among stands dominated by different tree species and expected that aspen stands would have higher soil temperatures due to their open structure, which, combined with higher quality litter, would result in increased soil respiration rates, nitrogen availability, and microbial biomass, and differences in soil faunal community composition. METHODOLOGY/PRINCIPAL FINDINGS: We assessed soil physical, chemical, and biological properties at four sites where stands of aspen, pine, and spruce occurred in close proximity to one-another in the San Juan Mountains, Colorado. Leaf litter quality differed among the tree species, with the highest nitrogen (N concentration and lowest lignin:N in aspen litter. Nitrogen concentration was similar in pine and spruce litter, but lignin:N was highest in pine litter. Soil temperature and moisture were highest in aspen stands, which, in combination with higher litter quality, probably contributed to faster soil respiration rates from stands of aspen. Soil carbon and N content, ammonium concentration, and microbial biomass did not differ among tree species, but nitrate concentration was highest in aspen soil and lowest in spruce soil. In addition, soil fungal, bacterial, and nematode community composition and rotifer, collembolan, and mesostigmatid mite abundance differed among the tree species, while the total abundance of nematodes, tardigrades, oribatid mites, and prostigmatid

  10. Does the different mowing regime affect soil biological activity and floristic composition of thermophilous Pieniny meadow?

    Józefowska, Agnieszka; Zaleski, Tomasz; Zarzycki, Jan


    The study area was located in the Pieniny National Park in the Carpathian Mountain (Southern Poland). About 30% of Park's area is covered by meadows. The climax stage of this area is forest. Therefore extensive use is indispensable action to keep semi-natural grassland such as termophilous Pieniny meadows, which are characterized by a very high biodiversity. The purpose of this research was to answer the question, how the different way of mowing: traditional scything (H), and mechanical mowing (M) or abandonment of mowing (N) effect on the biological activity of soil. Soil biological activity has been expressed by microbial and soil fauna activity. Microbial activity was described directly by count of microorganisms and indirectly by enzymatic activity (dehydrogenase - DHA) and the microbial biomass carbon content (MBC). Enchytraeidae and Lumbricidae were chosen as representatives of soil fauna. Density and species diversity of this Oligochaeta was determined. Samples were collected twice in June (before mowing) and in September (after mowing). Basic soil properties, such as pH value, organic carbon and nitrogen content, moisture and temperature, were determined. Mean count of vegetative bacteria forms, fungi and Actinobacteria was higher in H than M and N. Amount of bacteria connected with nitrification and denitrification process and Clostridium pasteurianum was the highest in soil where mowing was discontinued 11 years ago. The microbial activity measured indirectly by MBC and DHA indicated that the M had the highest activity. The soil biological activity in second term of sampling had generally higher activity than soil collected in June. That was probably connected with highest organic carbon content in soil resulting from mowing and the end of growing season. Higher earthworm density was in mowing soil (220 and 208 individuals m‑2 in H and M respectively) compare to non-mowing one (77 ind. m‑2). The density of Enchytraeidae was inversely, the higher

  11. Assessing the Soil Physiological Potential Using Pedo-Biological Diagnosis Under Minimum-Tillage System and Mineral Fertilization

    Lazar Bireescu; Geanina Bireescu; Michele Vincenzo Sellitto


    The main objective of sustainable agriculture is the protection of environment and natural vegetal and soil resources. Accordingly, the objective of this research was to assess the impact of technological systems by minimum tillage on soil biological activity, using the Pedo-Biological Diagnosis of Soil Resources. Our research was conducted on haplic chernozem from Experimental Station of UASVM of Iasi, Romania, during the seasonal dynamic, to the soybean crop, on unfertilized and fertilized ...


    Kandashova K. A.


    Full Text Available The article presents the results of laboratory modeling of gleyisation and its effect on the biological properties of soils with stagnant regime in ordinary black soils. Gleyisation is a complex biochemical process that occurs under oxygen reduction conditions. Anaerobic microorganisms, the presence of organic substances, and the constant or prolonged waterlogging of individual horizons or the entire soil profile promote gleyisation. Model experiments revealed that gleyisation increase the total number of bacteria and suppresses number of actinomycetes, micromycetes and growth of fungal mycelium. Gleyisation decreases the activity of oxidoreductases and increases the hydrolases activity. In addition, the second content of humus slightly increases and active acidity (pH changes to neutral. Accumulation of large amounts of iron oxide (II in soil is revealed

  13. Proliferation of diversified clostridial species during biological soil disinfestation incorporated with plant biomass under various conditions.

    Mowlick, Subrata; Takehara, Toshiaki; Kaku, Nobuo; Ueki, Katsuji; Ueki, Atsuko


    Biological soil disinfestation (BSD) involves the anaerobic decomposition of plant biomass by microbial communities leading to control of plant pathogens. We analyzed bacterial communities in soil of a model experiment of BSD, as affected by biomass incorporation under various conditions, to find out the major anaerobic bacterial groups which emerged after BSD treatments. The soil was treated with Brassica juncea plants, wheat bran, or Avena strigosa plants, irrigated at 20 or 30 % moisture content and incubated at 25-30 °C for 17 days. The population of Fusarium oxysporum f. sp. spinaciae incorporated at the start of the experiment declined markedly for some BSD conditions and rather high concentrations of acetate and butyrate were detected from these BSD-treated soils. The polymerase chain reaction-denaturing gradient gel electrophoresis analysis based on the V3 region of 16S rRNA gene sequences from the soil DNA revealed that bacterial profiles greatly changed according to the treatment conditions. Based on the clone library analysis, phylogenetically diverse clostridial species appeared exceedingly dominant in the bacterial community of BSD soil incorporated with Brassica plants or wheat bran, in which the pathogen was suppressed completely. Species in the class Clostridia such as Clostridium saccharobutylicum, Clostridium acetobutylicum, Clostridium xylanovorans, Oxobacter pfennigii, Clostridium pasteurianum, Clostridium sufflavum, Clostridium cylindrosporum, etc. were commonly recognized as closely related species of the dominant clone groups from these soil samples. PMID:23132344

  14. Soil biological attributes in arsenic-contaminated gold mining sites after revegetation.

    Dos Santos, Jessé Valentim; de Melo Rangel, Wesley; Azarias Guimarães, Amanda; Duque Jaramillo, Paula Marcela; Rufini, Márcia; Marra, Leandro Marciano; Varón López, Maryeimy; Pereira da Silva, Michele Aparecida; Fonsêca Sousa Soares, Cláudio Roberto; de Souza Moreira, Fatima Maria


    Recovery of arsenic contaminated areas is a challenge society faces throughout the world. Revegetation associated with microbial activity can play an essential role in this process. This work investigated biological attributes in a gold mining area with different arsenic contents at different sites under two types of extant revegetation associated with cover layers of the soil: BS, Brachiaria sp. and Stizolobium sp., and LEGS, Acacia crassicarpa, A. holosericea, A. mangium, Sesbania virgata, Albizia lebbeck and Pseudosamanea guachapele. References were also evaluated, comprising the following three sites: B1, weathered sulfide substrate without revegetation; BM, barren material after gold extraction and PRNH (private reserve of natural heritage), an uncontaminated forest site near the mining area. The organic and microbial biomass carbon contents and substrate-induced respiration rates for these sites from highest to lowest were: PRNH > LEGS > BS > B1 and BM. These attributes were negatively correlated with soluble and total arsenic concentration in the soil. The sites that have undergone revegetation (LEGS and BS) had higher densities of bacteria, fungi, phosphate solubilizers and ammonium oxidizers than the sites without vegetation. Principal component analysis showed that the LEGS site grouped with PRNH, indicating that the use of leguminous species associated with an uncontaminated soil cover layer contributed to the improvement of the biological attributes. With the exception of acid phosphatase, all the biological attributes were indicators of soil recovery, particularly the following: microbial carbon, substrate-induced respiration, density of culturable bacteria, fungi and actinobacteria, phosphate solubilizers and metabolic quotient. PMID:24114185

  15. The Effect of Peat and Vermicompost Cavitation Products on the Soil Biological Activity

    Steinberga Vilhelmine


    Full Text Available Commercial products with humic substances have often been recommended for plant growth stimulation and yield improvement. The aim of this study was to clarify the effects of two products, containing cavited peat and vermicompost respectively on the soil biological activity. Vegetation experiments with garden cress and cucumbers were arranged in pots with a peat substratum in the greenhouses of the Latvia University of Agriculture. The plants were treated with the preparations once a month. The first treatment was done at sowing. Dose of 20, 2, 0.2 mL per m2 during each treatment time were used. A control variant was without peat or vermicompost preparation. Field experiments with onions were carried out in the organic farming experimental field of the Latvia State Institute of Cereal Breeding. Plant growth and soil (substratum biological activity (respiration and enzymatic activity were tested. Plant growth and response to the different preparations depended on the plant species and its development stage. The effect of preparations decreases during plant development. The impact of peat or vermicompost preparation on soil biological activity depended not only on the concentration of preparation, but was influenced by the soil or growth media type. The decrease of onion yield in field conditions as a result of preparations was observed.

  16. Afforestation using micro-catchment water harvesting system with microphytic crust treatment on semi-arid Loess Plateau: A preliminary result

    YANG Xiao-hui; WANG Ke-qin; WANG Bin-rui; YU Chun-tang


    Water harvesting is one of main measures to solve water shortage resulting from less precipitation and erratically seasonal distribution in arid and semi-arid areas. Different types of anti-infiltration treatments including mechanical and chemical to micro-catchment and their runoff efficiencies had been reported. This paper, through 5 years experiment from 1992 to 1996, is aimed at studying the impacts of microcatchment water-harvesting system (MCWHS) with microphytic crust treatment on afforestation on semi-arid Loess Plateau. The results showed that after 3 years of crust inoculation, crust had covered majority of MCWHS and the function of water harvesting had also been demonstrated partially, there were significant difference in soil moisture of shallow soil layer in three typical spring stages between crust cover and control treatments (0.05 level), and about 0.9%-6.04% increase of monthly mean soil moisture within 1m soil layer in spring of late 3 years. The impact of severe spring drought can be alleviated effectively. In the meanwhile, as crust developed on the treated surface, there are significant differences (0.05 level) for tree height (H), diameter at breast height (DBH) and diameter at ground level (DGL) at the end of the study period (1996) with the increases by 22.38%, 17.34%, and 20.49% respectively compared with the control treatment. Microphytic crust, as one of biological infiltration-proof materials, may become the optimized option for revegetation in Chinese Great West Development Strategy due to its self-propagation, non-pollution to water qualities, long use duration and relatively cost effective. Further work should be focused on the selection of endemic crust species and their batch-culture in arid environment.

  17. Effect of Pesticides On Certain Soil Biological and Biochemical Indices of a Paddy Soil

    LIAO; Min; XIE; Xiao-mei; HUANG; Chang-yong


    A 21-day laboratory incubation experiment was conducted to investigate the impact of pesticides (Triazophos, Butaehlor and Jinggangmycin) on a paddy field soil health under controlled moisture (flooded soil) and temperature (25℃ ) conditions. The electron transport system (ETS)/dehydrogenase activity displayed a negative correlation with pesticides concentrations, and the activity was affected adversely as the concentration of the pesticides increased. The higher doses of pesticides,5 and 10 folds field rates, significantly inhibited ETS activity, while lower rates failed to produce any significant reducing effect against the control. The relative toxicity level of pesticides in decreasing the ETS activity was in the following order:Triazophos>Jinggangmycin>Butachlor, irrespective of their rates of application. The pesticides caused an improvement in the soil phenol content and it increased with increasing the concentration of agrochemicals. The pesticide incorporation did not produce any significant change in soil protein content. The response of biomass phospholipid content was nearly similar to ETS activity. The phospholipid content was decreased with the addition of pesticides in the given order of Triazophos>Jinggangmycin>Butachlor; and the toxicity was in the order: 10 FR (times of field rate)>5 FR>1.0 FR>0.5 FR>control.

  18. Biological and chemical tests of contaminated soils to determine bioavailability and environmentally acceptable endpoints (EAE)

    The understanding of the concept of bioavailability of soil contaminants to receptors and its use in supporting the development of EAE is growing but still incomplete. Nonetheless, there is increased awareness of the importance of such data to determine acceptable cleanup levels and achieve timely site closures. This presentation discusses a framework for biological and chemical testing of contaminated soils developed as part of a Gas Research Institute (GRI) project entitled ''Environmentally Acceptable Endpoints in Soil Using a Risk Based Approach to Contaminated Site Management Based on Bioavailability of Chemicals in Soil.'' The presentation reviews the GRI program, and summarizes the findings of the biological and chemical testing section published in the GRI report. The three primary components of the presentation are: (1) defining the concept of bioavailability within the existing risk assessment paradigm, (2) assessing the usefulness of the existing tests to measure bioavailability and test frameworks used to interpret these measurements, and (3) suggesting how a small selection of relevant tests could be incorporated into a flexible testing scheme for soils to address this issue

  19. Soil quality evaluation following the implementation of permanent cover crops in semi-arid vineyards. Organic matter, physical and biological soil properties

    Virto, I.; Imaz, M. J.; Fernandez-Ugalde, O.; Urrutia, I.; Enrique, A.; Bescansa, P.


    Changing from conventional vineyard soil management, which includes keeping bare soil through intense tilling and herbicides, to permanent grass cover (PGC) is controversial in semi-arid land because it has agronomic and environmental advantages but it can also induce negative changes in the soil physical status. The objectives of this work were (i) gaining knowledge on the effect of PGC on the soil physical and biological quality, and (ii) identifying the most suitable soil quality indicators for vineyard calcareous soils in semi-arid land. Key soil physical, organic and biological characteristics were determined in a Cambic Calcisol with different time under PGC (1 and 5 years), and in a conventionally managed control. Correlation analysis showed a direct positive relationship between greater aggregate stability (WSA), soil-available water capacity (AWC), microbial biomass and enzymatic activity in the topsoil under PGC. Total and labile organic C concentrations (SOC and POM-C) were also correlated to microbial parameters. Factor analysis of the studied soil attributes using principal component analysis (PCA) was done to identify the most sensitive soil quality indicators. Earthworm activity, AWC, WSA, SOC and POM-C were the soil attributes with greater loadings in the two factors determined by PCA, which means that these properties can be considered adequate soil quality indicators in this agrosystem. These results indicate that both soil physical and biological attributes are different under PGC than in conventionally-managed soils, and need therefore to be evaluated when assessing the consequences of PGC on vineyard soil quality. (Author) 65 refs.

  20. Cementing mechanism of algal crusts from desert area


    34-, 17-, 4-, 1.5-year old natural algal crusts were collected from Shapotou Scientific Station of the Chinese Academy of Sciences, 40-day old field and greenhouse artificial algal crusts were in situ developed in the same sandy soil and the same place (37°27′N, 104°57′E). Their different cohesions both against wind force and pressure were measured respectively by a sandy wind-tunnel experiment and a penetrometer. On the basis of these algal crusts, the cementing mechanism was revealed from many subjects and different levels. The results showed that in the indoor artificial crusts with the weakest cohesion bunchy algal filaments were distributed in the surface of the crusts, produced few extracellular polymers (EPS), the binding capacity of the crusts just accomplished by mechanical bundle of algal filaments. For field crusts, most filaments grew toward the deeper layers of algal crusts, secreted much more EPS, and when organic matter content was more than 2.4 times of chlorophyll a, overmuch organic matter (primarily is EPS) began to gather onto the surface of the crusts and formed an organic layer in the relatively lower micro-area, and this made the crust cohesion increase 2.5 times. When the organic layer adsorbed and intercepted amounts of dusts, soil particles and sand grains scattered down from wind, it changed gradually into an inorganic layer in which inorganic matter dominated, and this made the crusts cohesion further enhanced 2-6 times. For crust-building species Microcoleus vaginatus, 88.5% of EPS were the acidic components, 78% were the acidic proteglycan of 380 kD. The uronic acid content accounted for 8% of proteglycan, and their free carboxyls were important sites of binding with metal cations from surrounding matrix.

  1. Impact of HydroPolymers on the soil biological components in mediterranean drylands

    Dvořáčková, Helena; Hueso González, Paloma; Záhora, Jaroslav; Mikajlo, Irina; Damián Ruiz Sinoga, Jose


    Soil degradation affects more than 52 million ha of land in counties of the European Union. This problem is particularly serious in Mediterranean areas, where the effects of anthropogenic activities (tillage on slopes, deforestation, and pasture production) add to problems caused by prolonged periods of drought and intense and irregular rainfall. Soil microbiota can be used as an indicator of the soil healthy in degraded areas. This is because soil microbiota participates in the cycle elements and in the organic matter decomposition. All this helps to the young plants establishment and in long term protect the soils against the erosion. During dry periods in the Mediterranean areas, the lack of water entering the soil matrix leads to a loss of soil microbiological activity and it turns into a lower soil production capabilities. Under these conditions, the aim of this study was to evaluate the positive effect on soil biological components produced by an hydro absorbent polymer (Terracottem). The aim of the experiment was to evaluate the impact assessment of an hydropolymer (Terracottem) on the soil biological components. An experimental flowerpot layout was established in June 2015 and 12 variants with different amount of Terracottem were applied as follow: i) 3.0 kg.m3 ; ii) 1.5 kg.m3 and; iii) 0 kg.m3. In all the variants were tested the further additives: a) 1% of glucose, b) 50 kg N.ha-1 of Mineral nitrogen, c) 1% of Glucose + 50 kg N.ha-1 of Mineral nitrogen d) control (no additive). According to natural conditions, humidity have been kept at 15% in all the variants. During four weeks, mineral nitrogen leaching and soil respiration have been measured in each flowerplot. Respiration has been quantified four times every time while moistening containers and alkaline soda lime has been used as a sorbent. The amount of CO2 increase has been measured with the sorbent. Leaching of mineral nitrogen has been quantified by ion exchange resins (IER). IER pouches have been

  2. Assessing Soil Biological Properties of Natural and Planted Forests in the Malaysian Tropical Lowland Dipterocarp Forest

    Daljit S. Karam


    Full Text Available Problem statement: A study was conducted to evaluate and compare the soil biological properties of a natural forest and an 18-year-old stand of Shorea leprosula in Chikus Forest Reserve, Perak, Malaysia. Approach: Soils were sampled at depths of 0-15 cm (topsoil and 15-30 cm (subsoil in six subplots (20×20 m of natural forest (C1 and of a planted S. leprosula (C2 plot. Fresh composite soil samples were kept in UV-sterilized polyethylene bags prior to analysis in the laboratory. The microbial population count was determined using a spread-plate count technique. The microbial enzymatic activity was elucidated using a Fluorescein Diacetate (FDA hydrolysis assay; microbial biomass was extracted using a rapid chloroform fumigation extraction method. The Microbial Biomass C (MBC was determined by wet dichromate oxidation; Kjeldahl digestion and a distillation method were used for evaluation of Microbial Biomass N (MBN. Results: Results indicate that only the microbial biomass N and the population count in the soil at the 0-15 cm depth were found to be higher in C1 compared to C2. The higher microbial population count in the soil at the 0-15 cm depth of C1 compared to C2 was enhanced by the large amount of organic matter that serves as a suitable medium for soil microbial growth. The higher MBN in the C1 soil was also influenced by the high content of organic material available that encourages activities of decomposing bacteria to take place. Similarities in the soil biological properties of the plots with regard to enzymatic activity and microbial biomass Care believed to be influenced by the same topographic gradient. The higher MBC/MBN ratios found in soils of C2 compared to C1 were due to the low availability of N compared to C, might result from N utilization by soil microbes for organic material decomposition. Conclusion: There are similarities in microbial enzymatic activity and biomass C, but not in microbial population counts and biomass N

  3. Investigations involving oxidation-reduction (REDOX) pretreatment in conjunction with biological remediation of contaminated soils

    Oxidation-reduction (REDOX) reactions are among the most important reactions involved in the environmental engineering field. Oxidation is a reaction in which the oxidation state of the treated compound is increased, i.e., the material loses electrons. Reduction involves the addition of a chemical (reducing) agent which lowers the oxidation state of a substance, i.e., the material gains electrons. Both processes of oxidation and reduction occur together. All REDOX reactions are thermodynamically based. There are a number of oxidizing agents which have been reported in the technical literature for treatment of refractory organic compounds. Common oxidizing agents include: hydrogen peroxide, ozone, ultraviolet (UV) irradiation, and combinations thereof, such as UV/ozone and UV/peroxide. A gradient of REDOX reactions is possible, depending on such factors as the oxidation-reduction reaction conditions, the availability of electron donors and acceptors, and the nature of the organic compounds involved. A review of the technical literature revealed that the majority of the oxidation-reduction applications have been in the areas of wastewater treatment and groundwater remediation, with very little attention devoted to the potential of using REDOX technologies for remediation of hydrocarbon contaminated soils. In this particular study, feasibility studies were performed on gasoline- contaminated soil. These studies focused on three major phases: 1) containment of the contamination by addition of tailoring agents to the soil, 2) biological remediation either performed in situ or on-site (using a slurry reactor system), and 3) pretreatment of the contaminated soils using REDOX systems, prior to biological remediation. This particular paper focuses on the third phase of the project, aimed at ''softening'' the refractory organics resulting in the formation of organic compounds which are more amenable to biological degradation. This paper focuses its attention on the use of

  4. The early terrestrial crust

    Bourdon, Bernard; Caro, Guillaume


    Recent geochemical evidence based on the ^(146)Sm–^(142)Nd system and Hadean zircons shows that the Earth's mantle experienced depletion approximately 100 Ma after the formation of the solar system, and possibly even before (earlier than 30 Ma), due to the extraction of a crust enriched in incompatible elements. Depending on the model ^(142)Nd abundance assumed for the Bulk Earth, the early crust may have been stored in the deep mantle, or may have been remixed in the mantle with a timescale ...

  5. Biological soil loosening by grasses from genus Brachiaria in crop-livestock integration

    José Flávio Neto; Eduardo da Costa Severiano; Kátia Aparecida de Pinho Costa; Wellingthon Silva Guimarães Junnyor; Wainer Gomes Gonçalves; Renata Andrade


    Soil compaction associated with pastures degradation can decrease animal productivity, forage longevity and compromise environmental sustainability. To confront this serious issue, the loosening potential of forages should be recognized. We evaluated the least limiting water range as indicator of biological loosening potential in relation to cultivation of grasses the genus Brachiaria in crop-livestock integration. We also evaluated the water availability to soybean crop that succeeded these ...

  6. Bioremediation of oil contaminated soil from service stations. Evaluation of biological treatment

    Biological treatment of contaminated soil has received much attention during the last decade. Microbes are known to be able to degrade many oil hydrocarbons. However, research is needed to ensure that new technologies are implemented in a safe and reliable way under Finnish climatic conditions. The main points of interest are the rate of the degradation as well as the survival and efficiency of microbial inoculants possibly introduced during the treatment. During 1993 the biotreatability of oil-contaminated soil from service stations was investigated in cooperation with the Finnish Petroleum Federation. The goal of this field-scale study was to test how fast lubrication oil can be composted during one Finnish summer season and to find out whether microbial inoculants would enhance the degradation rate. The soil was excavated from three different service stations in the Helsinki metropolitan area and was transported to a controlled composting area. The soil was sieved and compost piles, also called biopiles, were constructed on the site. Bark chips were used as the bulking agent and nutrients and lime were added to enhance the biological activity. Two different commercial bacterial inoculants were added to two of the piles. The piles were turned by a tractor-drawn screw-type mixer at two to four weeks interval. Between the mixings, the piles were covered with tarpaulins to prevent evaporation and potential excessive wetting. Several microbiological parameters were determined during the test period as well as the temperature and mineral oil content

  7. The validation of forensic DNA extraction systems to utilize soil contaminated biological evidence.

    Kasu, Mohaimin; Shires, Karen


    The production of full DNA profiles from biological evidence found in soil has a high failure rate due largely to the inhibitory substance humic acid (HA). Abundant in various natural soils, HA co-extracts with DNA during extraction and inhibits DNA profiling by binding to the molecular components of the genotyping assay. To successfully utilize traces of soil contaminated evidence, such as that found at many murder and rape crime scenes in South Africa, a reliable HA removal extraction system would often be selected based on previous validation studies. However, for many standard forensic DNA extraction systems, peer-reviewed publications detailing the efficacy on soil evidence is either lacking or is incomplete. Consequently, these sample types are often not collected or fail to yield suitable DNA material due to the use of unsuitable methodology. The aim of this study was to validate the common forensic DNA collection and extraction systems used in South Africa, namely DNA IQ, FTA elute and Nucleosave for processing blood and saliva contaminated with HA. A forensic appropriate volume of biological evidence was spiked with HA (0, 0.5, 1.5 and 2.5 mg/ml) and processed through each extraction protocol for the evaluation of HA removal using QPCR and STR-genotyping. The DNA IQ magnetic bead system effectively removed HA from highly contaminated blood and saliva, and generated consistently acceptable STR profiles from both artificially spiked samples and crude soil samples. This system is highly recommended for use on soil-contaminated evidence over the cellulose card-based systems currently being preferentially used for DNA sample collection. PMID:25690910

  8. Biological quality of soils containing hydrocarbons and efficacy of ecological risk reduction by bioremediation alternatives

    Stewart, A.J.; Napolitano, G.E.; Sample, B.E.


    This project provides technical support to the Petroleum Environmental Research Forum (PERF; a consortium of petroleum companies) on environmentally acceptable endpoints that may be used to help assess the ecological risk of petroleum hydrocarbon residuals in soils. The project, was designed in consultation with PERF representatives and focuses on the relationship between {open_quotes}chemically available{close_quotes} and {open_quotes}biologically available{close_quotes} measurements of petroleum hydrocarbon compounds in soils, a discrepancy of considerable interest to the petroleum industry. Presently, clean-up standards for soils contaminated with total petroleum hydrocarbon (TPH) constituents are based on concentrations of TPH, as measured in solvent extracts of soil samples. Interestingly, TPH includes a complex mixture of compounds which differ from one another in molecular weight and toxicity. Based on various studies with insecticides, herbicides and metals, some compounds apparently can slowly permeate into soil particles. If this situation occurs, the particle-embedded compounds may be extractable by use of organic solvents, and yet be unavailable biologically. This hypothesis serves as the central focus for our study. If this hypothesis is correct, then soil clean-up standards based on solvent-extractable TPH data may be more stringent than necessary to achieve a desired level of environmental risk. The economic significance of this possibility is considerable, because clean-up costs to achieve a low-risk status would, in most cases, be lower than those needed to achieve a standard based on present limits, which are based on measurements of {open_quotes}extractable{close_quotes} TPH.

  9. Chemical properties of soils treated with biological sludge from gelatin industry

    Rita de Cássia Melo Guimarães


    Full Text Available The impact of agro-industrial organic wastes in the environment can be reduced when used in agriculture. From the standpoint of soil fertility, residue applications can increase the organic matter content and provide nutrients for plants. This study evaluated the effect of biological sludge from gelatin industry on the chemical properties of two Ultisols (loamy sand and sandy clay and an Oxisol (clay. The experiment lasted 120 days and was carried out in laboratory in a completely randomized design with factorial arrangement, combining the three soils and six biological sludge rates (0, 100, 200, 300, 400, and 500 m³ ha-1, with three replications. Biological sludge rates of up to 500 m³ ha-1 decreased soil acidity and increased the effective cation exchange capacity (CEC and N, Ca, Mg, and P availability, without exceeding the tolerance limit for Na. The increase in exchangeable base content, greater than the effective CEC, indicates that the major part of cations added by the sludge remains in solution and can be lost by leaching.

  10. The influence of competition between lichen colonization and erosion on the evolution of soil surfaces in the Tabernas badlands (SE Spain) and its landscape effects

    Lázaro, R.; Cantón, Y.; Solé-Benet, A.; Bevan, J.; Alexander, R.; Sancho, L. G.; Puigdefábregas, J.


    Badlands often contain a mosaic of soil surface types with contrasting hydrological behaviour which drives their short term geomorphic evolution. The Tabernas badlands, in semiarid SE Spain, show a complex mosaic of bare ground, biological soil crusts and plant covered patches, and high variability of covers and morphologies. Previous work has identified the surfaces that act as sources of runoff and sediments and those that act as sinks; the pathways of runoff between surfaces, and the runoff and erosion at catchment scale. However, surfaces without vascular plants, can be quite dynamic, with important effects on geomorphic processes. This work aims to generate hypotheses about the dynamics of both bare soil (34% of the area) and biological soil crusts (33%), and to provide a first estimation of the growth rate of terricolous lichens (as increase of coverage) and their geomorphological implications. The dynamics of ten representative soil surfaces were photographically monitored over 13 years, recording the cover and pattern of bare soil and of the two main kinds of biological soil crust: 'brown crust' and 'white crust'. Erosion/deposition were measured by erosion pins in unbounded plots, and the hydrological and erosional behaviour monitored in bounded plots under natural and simulated rainfall. Biological colonization and crust growth were studied from 2004 within cleared plots in four crust communities. Microclimate was continuously monitored in each community. After 13 years, net erosion was recorded only in previously eroded slopes and divides. Vegetated sites and those covered by biological soil crust remained more or less invariant or recorded sedimentation. In all white crust surfaces, whole crust cover increased by 3% on average, while macrolichen cover increased by nearly 30%. Within the driest brown crust, macrolichen cover increased by 7%, while the whole crust decreased by 3%. According to previous work, lichen cover, particularly of white crust, is