Biogenic crust dynamics on sand dunes

Sand dunes are often covered by vegetation and biogenic crusts. Despite their significant role in dune stabilization, biogenic crusts have rarely been considered in studies of dune dynamics. Using a simple model, we study the existence and stability ranges of different dune-cover states along gradients of rainfall and wind power. Two ranges of alternative stable states are identified: fixed crusted dunes and fixed vegetated dunes at low wind power, and fixed vegetated dunes and active dunes at high wind power. These results suggest a cross-over between two different forms of desertification

Activation of Methanogenesis in Arid Biological Soil Crusts Despite the Presence of Oxygen

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 δ13C 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 H2/CO2 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

The global distribution and environmental drivers of the soil antibiotic resistome

Background: Little is known about the global distribution and environmental drivers of key microbial functional traits such as antibiotic resistance genes (ARGs). Soils are one of Earth’s largest reservoirs of ARGs, which are integral for soil microbial competition, and have potential implications for plant and human health. Yet, their diversity and global patterns remain poorly described. Here, we analyzed 285 ARGs in soils from 1012 sites across all continents and created the first global atlas with the distributions of topsoil ARGs. Results: We show that ARGs peaked in high latitude cold and boreal forests. Climatic seasonality and mobile genetic elements, associated with the transmission of antibiotic resistance, were also key drivers of their global distribution. Dominant ARGs were mainly related to multidrug resistance genes and efflux pump machineries. We further pinpointed the global hotspots of the diversity and proportions of soil ARGs. Conclusions: Together, our work provides the foundation for a better understanding of the ecology and global distribution of the environmental soil antibiotic resistome.This project received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement 702057 (CLIMIFUN), a Large Research Grant from the British Ecological Society (agreement no. LRA17\1193; MUSGONET), and from the European Research Council (ERC grant agreement no. 647038, BIODESERT). M. D. B. was also supported by a Ramón y Cajal grant (RYC2018-025483-I). M.D-B. also acknowledges support from the Spanish Ministry of Science and Innovation for the I+D+i project PID2020-115813RA-I00 funded by MCIN/AEI/10.13039/501100011033. M.D-B. is also supported by a project of the Fondo Europeo de Desarrollo Regional (FEDER) and the Consejería de Transformación Económica, Industria, Conocimiento y Universidades of the Junta de Andalucía (FEDER Andalucía 2014-2020 Objetivo temático “01 - Refuerzo de la investigación, el desarrollo tecnológico y la innovación”) associated with the research project P20_00879 (ANDABIOMA). FTM acknowledges support from Generalitat Valenciana (CIDEGENT/2018/041). J. Z. H and H. W. H. are financially supported by Australian Research Council (DP210100332). We also thank the project CTM2015-64728-C2-2-R from the Ministry of Science of Spain. C. A. G. and N. E. acknowledge funding by the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, funded by the German Research Foundation (FZT 118). TG was financially supported by Slovenian Research Agency (P4-0107, J4-3098 and J4-4547)

Geodiversity, biocrust - POC, N-NO3, N-NH3, Protein

Eli Zaady Data set Mendeley Geodiversity_BiocrustsPOC_N-NO3_N-NH3_Protein_Park_Shaked_LTE

Soil particle size and texture Shaked LTER site, Negev Desert, Israel

Weight of sand fractions, g Percentage, % Hydrometer readings Particle Percentage,% Cross-section Shaked LTER site, Negev Desert Israel Biological crusts data summary Shaked LTER site, Negev Desert Israel Hillslope type plot Microhabita

Effect of soil erosion on the biodiversity of soil crust within the Ziporim basin of Israel

The biological soil crust is composed of living microorganisms. In deserts it is mainly the non-vascular plants that constitute the soil crust. Protein, polysaccharide, NDVI and Organic carbon showed significant differences (

Soil particle size and texture Shaked LTER site, Negev Desert, Israel

Weight of sand fractions, g Percentage, % Hydrometer readings Particle Percentage,% Cross-section Shaked LTER site, Negev Desert Israel Biological crusts data summary Shaked LTER site, Negev Desert Israel Hillslope type plot Microhabita

Geodiversity, biocrust - POC, N-NO3, N-NH3, Protein

Eli Zaady Data set Mendeley Geodiversity_BiocrustsPOC_N-NO3_N-NH3_Protein_Park_Shaked_LTE

Growth response of Mediterranean herbaceous swards to inoculation with Azospirillum brasilense

A study was conducted on the effect of the rhizobacterium Azospirillum brasilense strain Cd on the production of herbaceous swards growing at 2 rangeland habitats in Israel. One habitat was the semiarid zone (< 300 mm annual rainfall, calcareous soil on rocky slopes) while the other was a typical Mediterranean zone (approximately-600 mm annual rainfall, karstic rock covered with terra rossa soil). The inoculum was applied in water suspension at a concentration of 109 colony forming units (CFU) ml-1. The effect of inoculation was compared with P-fertilizer application at a rate of 5 g/m2. The same treatments were also applied on potted soil from the 2 sites. The semiarid ecosystem showed a strong response to Azospirillum inoculation, to P-fertilizer and to the combination of these 2 treatments, with aerial biomass production increasing by approximately fourfold in the treatments as compared with the control. The response to inoculation or P-fertilization was similar, with no interaction or additive effect noted for the combined treatment. At the Mediterranean site, the response to inoculation or P-fertilization alone was variable, with only a moderate effect on biomass production as compared with the control; however, the inoculation-fertilization interaction was highly significant and doubled biomass production. In the greenhouse experiment, the response to inoculation or fertilization was significant and the biomass production at the end of the growing season was approximately 50% higher than in the control. At both sites, standing biomass was greater in the treated plots already at early stages of growth, thereby potentially lengthening the effective grazing season. It is suggested that inoculation with Azospirillum brasilense on a commercial scale may offer a means of increasing rangeland production without resorting to costly and ecologically unfavorable fertilizer application.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Long-term impact of agricultural practices on biological soil crusts and their hydrological processes in a semiarid landscape

The natural landscapes of semiarid areas worldwide comprise a series of scattered patches of shrubs within a matrix of biologically crusted soils (BSC). As BSCs are considered ecosystem engineers the relationships between the BSC and the shrub patches determine system functioning. The objective of our study was to investigate long-term effects of agricultural practices on biological soil crusts and their influence on hydrological aspects of a semiarid ecosystem. During 1991, we experimentally simulated five of the area\u27s agricultural practices; 1) Scraping – the topsoil was removed to a depth of 2 cm, 2) Spraying – phototrophic organisms were chemically killed with herbicide, 3) Mowing – perennial vegetation was cut and spread to simulate grazing practices, 4) Car track – a heavy roller was used to simulate car-tracks, 5) Control – undisturbed natural plots. Sixteen years later, in 2007, these agricultural practices were found to have a long-term effect on the crusted soil surface and the related soil-surface properties. Mowing and car-track treatments led to decreased overland runoff and increased hydraulic conductivity, whereas scraping and spraying treatments led to increased overland runoff production and decreased hydraulic conductivity. We conclude that the practices had a long-term residual impact on BSC succession and related soil surface properties, which affected the hydrological processes and system functioning