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Jayne Belnap - One of the best experts on this subject based on the ideXlab platform.
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Table_2_Chronic Physical Disturbance Substantially Alters the Response of Biological Soil Crusts to a Wetting Pulse, as Characterized by Metatranscriptomic Sequencing.xls
2018Co-Authors: Blaire Steven, Jayne Belnap, Cheryl R KuskeAbstract:Biological soil crusts (biocrusts) are microbial communities that are a feature of arid surface soils worldwide. In drylands where precipitation is pulsed and ephemeral, the ability of biocrust microbiota to rapidly initiate metabolic activity is critical to their survival. Community gene expression was compared after a short duration (1 h) wetting pulse in both intact and soils disturbed by chronic foot trampling. Across the metatranscriptomes the majority of transcripts were cyanobacterial in origin, suggesting that cyanobacteria accounted for the bulk of the transcriptionally active cells. Chronic trampling substantially altered the functional profile of the metatranscriptomes, specifically resulting in a significant decrease in transcripts for nitrogen fixation. Soil depth (biocrust and below crust) was a relatively small factor in differentiating the metatranscriptomes, suggesting that the metabolically active bacteria were similar between shallow soil horizons. The dry samples were consistently enriched for hydrogenase genes, indicating that molecular hydrogen may serve as an energy source for the desiccated soil communities. The water pulse was associated with a restructuring of the metatranscriptome, particularly for the biocrusts. Biocrusts increased transcripts for photosynthesis and carbon fixation, suggesting a rapid resuscitation upon wetting. In contrast, the trampled surface soils showed a much smaller response to wetting, indicating that trampling altered the metabolic response of the community. Finally, several biogeochemical cycling genes in carbon and nitrogen cycling were assessed for their change in abundance due to wetting in the biocrusts. Different transcripts encoding the same gene product did not show a consensus response, with some more abundant in dry or wet biocrusts, highlighting the challenges in relating transcript abundance to biogeochemical cycling rates. These observations demonstrate that metatranscriptome sequencing was able to distinguish alterations in the function of arid soil microbial communities at two varying temporal scales, a long-term ecosystems Disturbance through foot trampling, and a short term wetting pulse. Thus, community metatranscriptomes have the potential to inform studies on the response and resilience of biocrusts to various environmental perturbations.
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Chronic Physical Disturbance Substantially Alters the Response of Biological Soil Crusts to a Wetting Pulse, as Characterized by Metatranscriptomic Sequencing
Frontiers Media S.A., 2018Co-Authors: Blaire Steven, Jayne Belnap, Cheryl R KuskeAbstract:Biological soil crusts (biocrusts) are microbial communities that are a feature of arid surface soils worldwide. In drylands where precipitation is pulsed and ephemeral, the ability of biocrust microbiota to rapidly initiate metabolic activity is critical to their survival. Community gene expression was compared after a short duration (1 h) wetting pulse in both intact and soils disturbed by chronic foot trampling. Across the metatranscriptomes the majority of transcripts were cyanobacterial in origin, suggesting that cyanobacteria accounted for the bulk of the transcriptionally active cells. Chronic trampling substantially altered the functional profile of the metatranscriptomes, specifically resulting in a significant decrease in transcripts for nitrogen fixation. Soil depth (biocrust and below crust) was a relatively small factor in differentiating the metatranscriptomes, suggesting that the metabolically active bacteria were similar between shallow soil horizons. The dry samples were consistently enriched for hydrogenase genes, indicating that molecular hydrogen may serve as an energy source for the desiccated soil communities. The water pulse was associated with a restructuring of the metatranscriptome, particularly for the biocrusts. Biocrusts increased transcripts for photosynthesis and carbon fixation, suggesting a rapid resuscitation upon wetting. In contrast, the trampled surface soils showed a much smaller response to wetting, indicating that trampling altered the metabolic response of the community. Finally, several biogeochemical cycling genes in carbon and nitrogen cycling were assessed for their change in abundance due to wetting in the biocrusts. Different transcripts encoding the same gene product did not show a consensus response, with some more abundant in dry or wet biocrusts, highlighting the challenges in relating transcript abundance to biogeochemical cycling rates. These observations demonstrate that metatranscriptome sequencing was able to distinguish alterations in the function of arid soil microbial communities at two varying temporal scales, a long-term ecosystems Disturbance through foot trampling, and a short term wetting pulse. Thus, community metatranscriptomes have the potential to inform studies on the response and resilience of biocrusts to various environmental perturbations
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climate change and Physical Disturbance manipulations result in distinct biological soil crust communities
Applied and Environmental Microbiology, 2015Co-Authors: Blaire Steven, Sasha C Reed, Cheryl R Kuske, La Verne Gallegosgraves, Jayne BelnapAbstract: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.
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climate change and Physical Disturbance cause similar community shifts in biological soil crusts
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Scott Ferrenberg, Sasha C Reed, Jayne BelnapAbstract: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.
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response and resilience of soil biocrust bacterial communities to chronic Physical Disturbance in arid shrublands
The ISME Journal, 2012Co-Authors: Cheryl R Kuske, Chris M Yeager, Shannon L Johnson, Lawrence O Ticknor, Jayne BelnapAbstract:The impact of 10 years of annual foot trampling on soil biocrusts was examined in replicated field experiments at three cold desert sites of the Colorado Plateau, USA. Trampling detrimentally impacted lichens and mosses, and the keystone cyanobacterium, Microcoleus vaginatus, resulting in increased soil erosion and reduced C and N concentrations in surface soils. Trampled biocrusts contained approximately half as much extractable DNA and 20–52% less chlorophyll a when compared with intact biocrusts at each site. Two of the three sites also showed a decline in scytonemin-containing, diazotrophic cyanobacteria in trampled biocrusts. 16S rRNA gene sequence and terminal restriction fragment length polymorphism (T-RFLP) analyses of soil bacteria from untrampled and trampled biocrusts demonstrated a reduced proportion (23–65% reduction) of M. vaginatus and other Cyanobacteria in trampled plots. In parallel, other soil bacterial species that are natural residents of biocrusts, specifically members of the Actinobacteria, Chloroflexi and Bacteroidetes, became more readily detected in trampled than in untrampled biocrusts. Replicate 16S rRNA T-RFLP profiles from trampled biocrusts at all three sites contained significantly more fragments (n=17) than those of untrampled biocrusts (n⩽6) and exhibited much higher variability among field replicates, indicating transition to an unstable disturbed state. Despite the dramatic negative impacts of trampling on biocrust Physical structure and composition, M. vaginatus could still be detected in surface soils after 10 years of annual trampling, suggesting the potential for biocrust re-formation over time. Physical damage of biocrusts, in concert with changing temperature and precipitation patterns, has potential to alter performance of dryland ecosystems for decades.
Sulaiman Wadi Harun - One of the best experts on this subject based on the ideXlab platform.
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s band q switched fiber laser using molybdenum disulfide mos2 saturable absorber
Laser Physics Letters, 2016Co-Authors: Harith Ahmad, M Suthaskumar, M Z Zulkifli, Sathiyan Samikannu, M. A. Ismail, Sulaiman Wadi Harun, Sivabalan SivarajAbstract:In this letter, a molybdenum disulfide (MoS2) saturable absorber (SA) is fabricated using a simple drop cast method to generate Q-switched fiber laser operating in the S-band region (1460 nm-1530 nm). The MoS2 solution was prepared using the liquid phase exfoliation (LPE) method where MoS2 crystals were added into dimethylformamide (DMF) solvent and subsequently sonicated and centrifuged. They were then repeatedly dripped onto fiber ferrules and dried in an oven. The resultant Q-switched fiber laser starts with some Physical Disturbance when the pump power was set at 40 mW and continues to operate until the pump power reaches 120 mW. The resultant repetition rate varies with pump power between 27.17 to 101.17 kHz while the changes in pulse widths are from 3.0 to 1.4 μs.
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c band q switched fiber laser using titanium dioxide tio 2 as saturable absorber
IEEE Photonics Journal, 2016Co-Authors: Harith Ahmad, M. A. Ismail, S A Reduan, Zainal Abidin Ali, N E Ruslan, C S J Lee, R Puteh, Sulaiman Wadi HarunAbstract:We demonstrate a passively Q-switched erbium fiber laser using titanium dioxide (TiO 2) as a saturable absorber. The TiO 2 saturable absorber was fabricated as a polymer composite film and sandwiched between fiber ferrules. Q-switched pulsing starts with the assistance of Physical Disturbance of the laser cavity (by lightly tapping the cavity to induce instability) at 140 mW and lasts until 240 mW. The repetition rate increases with the pump power from 80.28 to 120.48 kHz. On the other hand, the pulsewidth decreases from $2.054\ \mu\text{s}$ until it reaches a plateau at $1.84\ \mu\text{s}$ . The Q-switched fiber laser exhibits two competing modes: at 1558.1 and 1558.9 nm as the pump power increases. A high signal-to-noise ratio of 49.65 dB is obtained.
Harith Ahmad - One of the best experts on this subject based on the ideXlab platform.
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s band q switched fiber laser using molybdenum disulfide mos2 saturable absorber
Laser Physics Letters, 2016Co-Authors: Harith Ahmad, M Suthaskumar, M Z Zulkifli, Sathiyan Samikannu, M. A. Ismail, Sulaiman Wadi Harun, Sivabalan SivarajAbstract:In this letter, a molybdenum disulfide (MoS2) saturable absorber (SA) is fabricated using a simple drop cast method to generate Q-switched fiber laser operating in the S-band region (1460 nm-1530 nm). The MoS2 solution was prepared using the liquid phase exfoliation (LPE) method where MoS2 crystals were added into dimethylformamide (DMF) solvent and subsequently sonicated and centrifuged. They were then repeatedly dripped onto fiber ferrules and dried in an oven. The resultant Q-switched fiber laser starts with some Physical Disturbance when the pump power was set at 40 mW and continues to operate until the pump power reaches 120 mW. The resultant repetition rate varies with pump power between 27.17 to 101.17 kHz while the changes in pulse widths are from 3.0 to 1.4 μs.
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c band q switched fiber laser using titanium dioxide tio 2 as saturable absorber
IEEE Photonics Journal, 2016Co-Authors: Harith Ahmad, M. A. Ismail, S A Reduan, Zainal Abidin Ali, N E Ruslan, C S J Lee, R Puteh, Sulaiman Wadi HarunAbstract:We demonstrate a passively Q-switched erbium fiber laser using titanium dioxide (TiO 2) as a saturable absorber. The TiO 2 saturable absorber was fabricated as a polymer composite film and sandwiched between fiber ferrules. Q-switched pulsing starts with the assistance of Physical Disturbance of the laser cavity (by lightly tapping the cavity to induce instability) at 140 mW and lasts until 240 mW. The repetition rate increases with the pump power from 80.28 to 120.48 kHz. On the other hand, the pulsewidth decreases from $2.054\ \mu\text{s}$ until it reaches a plateau at $1.84\ \mu\text{s}$ . The Q-switched fiber laser exhibits two competing modes: at 1558.1 and 1558.9 nm as the pump power increases. A high signal-to-noise ratio of 49.65 dB is obtained.
R M Warwick - One of the best experts on this subject based on the ideXlab platform.
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recovery rates of benthic communities following Physical Disturbance
Journal of Animal Ecology, 2003Co-Authors: K M Dernie, Michel J Kaiser, R M WarwickAbstract:1. Despite numerous studies that have investigated the effects of Physical Disturbance on marine benthic communities, deducing the ecological significance of such events has been hampered by the specificity of individual studies. Less stable habitats (coarse, clean sands) are thought to recover more quickly than stable (muddy sands and mud) habitats but so far an empirical test of this paradigm has been lacking. 2. We describe a large-scale field experiment that investigated the response of marine benthic communities within a variety of sediment types (clean sand, silty sand, muddy sand and mud) to Physical Disturbance. Sites were sampled for macrofauna and habitat characteristics (sediment organic content and water content, depth of water within disturbed pits) following Disturbance, in order to examine any relationship between the rate of Physical and biological recovery. 3. There were no detectable changes to the measured Physical parameters following the Disturbance with the exception of the water depth within disturbed areas. It was not possible to derive a linear relationship between the measured habitat characteristics (percentage silt and clay content) and the recovery trajectory of the associated community. However, the rate of sediment infilling of disturbed plots was strongly correlated to the recovery rate of the numbers of individuals within disturbed areas. 4. Clean sand communities had the most rapid recovery rate following Disturbance, whereas communities from muddy sand habitats had the slowest Physical and biological recovery rates. These findings concur with the predictions of a meta analysis of fishing Disturbances for similar habitats. 5. We suggest that Physical and biological recovery rates are mediated by a combination of Physical, chemical and biological factors that differ in their relative importance in different habitats. Monitoring the infilling rate of Physically disturbed patches of sediment has the potential to become a useful tool to predict the recovery rate of associated communities.
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recovery of soft sediment communities and habitats following Physical Disturbance
Journal of Experimental Marine Biology and Ecology, 2003Co-Authors: K M Dernie, Michel J Kaiser, Elizabeth A Richardson, R M WarwickAbstract:Physical Disturbance in soft sediment habitats disrupts the sediment structure and can lead to the death or emigration of resident biota. Current methods used to quantify the response of benthic assemblages to Physical Disturbance are time consuming and expensive, requiring the analysis of a time series of samples to ascertain the time taken for a disturbed area to converge on a condition similar to that found in adjacent control areas (the recovery time). We designed an experiment that studied the effects of two intensities of Physical Disturbance on both the habitat and fauna of a sheltered sand flat to ascertain whether the recovery of the biota could be predicted from Physical attributes of the habitat. Benthic community recovery from the lower intensity Disturbance occurred within 64 days of the Disturbance, whereas recovery after higher intensity Disturbance did not occur until 208 days post-Disturbance at this site. Sediment granulometry and percentage organic content did not alter as a result of the Disturbance in either treatment. However, the depth of water that remained in the disturbed pits decreased with time, and correlated with the temporal changes in community structure. Thus although this was the most crude Physical parameter measured it best described the recovery process of the fauna and may encapsulate the entire suite of other more subtle habitat changes that occur at the same time. By quantifying the persistence of Physical features in different soft sediment habitats it might be possible to develop a more amenable and rapid framework for assessing the longevity of the effects of Physical Disturbance.
M. A. Ismail - One of the best experts on this subject based on the ideXlab platform.
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s band q switched fiber laser using molybdenum disulfide mos2 saturable absorber
Laser Physics Letters, 2016Co-Authors: Harith Ahmad, M Suthaskumar, M Z Zulkifli, Sathiyan Samikannu, M. A. Ismail, Sulaiman Wadi Harun, Sivabalan SivarajAbstract:In this letter, a molybdenum disulfide (MoS2) saturable absorber (SA) is fabricated using a simple drop cast method to generate Q-switched fiber laser operating in the S-band region (1460 nm-1530 nm). The MoS2 solution was prepared using the liquid phase exfoliation (LPE) method where MoS2 crystals were added into dimethylformamide (DMF) solvent and subsequently sonicated and centrifuged. They were then repeatedly dripped onto fiber ferrules and dried in an oven. The resultant Q-switched fiber laser starts with some Physical Disturbance when the pump power was set at 40 mW and continues to operate until the pump power reaches 120 mW. The resultant repetition rate varies with pump power between 27.17 to 101.17 kHz while the changes in pulse widths are from 3.0 to 1.4 μs.
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c band q switched fiber laser using titanium dioxide tio 2 as saturable absorber
IEEE Photonics Journal, 2016Co-Authors: Harith Ahmad, M. A. Ismail, S A Reduan, Zainal Abidin Ali, N E Ruslan, C S J Lee, R Puteh, Sulaiman Wadi HarunAbstract:We demonstrate a passively Q-switched erbium fiber laser using titanium dioxide (TiO 2) as a saturable absorber. The TiO 2 saturable absorber was fabricated as a polymer composite film and sandwiched between fiber ferrules. Q-switched pulsing starts with the assistance of Physical Disturbance of the laser cavity (by lightly tapping the cavity to induce instability) at 140 mW and lasts until 240 mW. The repetition rate increases with the pump power from 80.28 to 120.48 kHz. On the other hand, the pulsewidth decreases from $2.054\ \mu\text{s}$ until it reaches a plateau at $1.84\ \mu\text{s}$ . The Q-switched fiber laser exhibits two competing modes: at 1558.1 and 1558.9 nm as the pump power increases. A high signal-to-noise ratio of 49.65 dB is obtained.
