The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Naci Görür - One of the best experts on this subject based on the ideXlab platform.
-
Deep structure of the Mid Black Sea High (offshore Turkey) imaged by multi-channel seismic survey (BLACKSIS cruise)
Marine Geology, 2002Co-Authors: Claude Rangin, A. G. Bader, B. Ecevitoǧlu, G. Pascal, Naci GörürAbstract:The Black Sea is considered to be a Mesozoic-Early Cenozoic marginal basin related to the north-dipping subduction of Tethys beneath Europe. However deformation of this basin during the successive Eocene to Neogene collisions of African-derived continental fragments (Kirshehir and Arabian micro plates) remains poorly understood. A multi-channel seismic survey conducted in the Central part of the Black Sea has shed light on the superimposed tectonic fabrics of the Central Ridge (the Mid Black Sea High, MBSH) in response to these successive collisions. The MBSH is formed by a series of large NW-SE trending anticlines and synclines, and possible northeast-verging thrusts were identified at the boundary with the deep East Black Sea Basin northeast of the Ridge. These buried folds and thrusts, blanketed by 3 to 8 s TWT of undeformed sediments, are interpreted as the offshore extension of the Early Cenozoic tectonic belt resulting from the collision between the Pontides in the north and the Kirshehir block to the south. The offshore part of the belt forming the Ridge could have then collapsed when collision ended. Neogene structures also affect the MBSH. A recent graben (the Sinop Trough) extends between this Central high and mainland Turkey. This graben could have been formed during the late Miocene incipient dextral strike slip motion of the North Anatolian Fault that was initiated during extrusion of the Anatolian microplate. Active tectonic inversion of deep-seated normal faults present along the Pontides passive margin was also observed along the northeastern flank of the Eastern Pontides. This deformation is the westernmost extension of the Lesser Caucasus front that outlines the suturing of the Eastern Black Sea Basin in easternmost Turkey and in Georgia. © 2002 Elsevier Science B.V. All rights reserved.
Larry W. Duncan - One of the best experts on this subject based on the ideXlab platform.
-
Geospatial patterns of soil properties and the biological control potential of entomopathogenic nematodes in Florida citrus groves
Soil Biology & Biochemistry, 2013Co-Authors: Raquel Campos-herrera, James H. Graham, Ekta Pathak, Fahiem E. El-borai, Robin J. Stuart, Carmen Gutiérrez, Jose Antonio Rodríguez-martín, Larry W. DuncanAbstract:Entomopathogenic nematodes (EPNs) are widely distributed in natural and managed ecosystems worldwide. Due to the cryptic nature of soil food webs, EPN ecology and their role in modulating insect population dynamics remain largely a matter of speculation. A weevil pest of citrus, Diaprepes abbreviatus, is less abundant in orchards on the Central Ridge (hilly topography, deep, coarse sand soils) than in the flatwoods (flat topography, fine sand soils with a high water table). We speculate that native EPNs are a key factor regulating these weevils and thus hypothesized that EPNs are most abundant and/or species diverse in Central Ridge orchards. In this study, we measured and analyzed the natural distributions of EPNs in these two regions concomitantly with those of selected abiotic and biotic soil components. Our objective was to identify physical properties that can potentially be manipulated to conserve native EPNs that serve to control D. abbreviatus. We used species-specific qPCR probes for i) 13 EPN species, ii) two species of Paenibacillus that are ectoparasitically associated with EPNs, iii) free-living bacteriophagous nematodes (Acrobeloides-group) that might compete with EPNs, and iv) oomycete pathogens of citrus roots, Phytophthora nicotianae and Phytophthora palmivora. Citrus orchards were surveyed in eco-regions categorized as Central Ridge (23 localities) and flatwoods (30 localities). EPNs and Acrobeloides-group were detected in all sites and the abundances of the two guilds were positively related. Heterorhabditids comprising two species occurred in more localities at higher numbers than did five steinernematid species. Heterorhabditis indica dominated flatwoods communities, whereas communities with abundant Steinernema diaprepesi, Heterorhabditis zealandica and H. indica occurred on the Central Ridge. Spatial patterns of S. diaprepesi were more aggregated than those of H. indica and other dominant species. The Central Ridge supported greater EPN evenness, diversity and species richness. For the first time, quantitative natural positive associations between EPNs and two species of Paenibacillus bacteria were assessed. The oomycete pathogen P. palmivora was only detected in the flatwoods, whereas P. nicotianae was widespread and equally abundant in both regions. Four variables that affect soil water potential (groundwater depth, available water capacity, clay and organic matter content) significantly contributed to explain the variability in a redundancy analysis of the selected soil communities. Management of soil water potential may aid in establishing and conserving diverse EPN communities that provide more effective control of Diaprepes root weevils.
-
Modifying orchard planting sites conserves entomopathogenic nematodes, reduces weevil herbivory and increases citrus tree growth, survival and fruit yield
Biological Control, 2012Co-Authors: Larry W. Duncan, Raquel Campos-herrera, Ekta Pathak, Fahiem E. El-borai, Robin J. Stuart, Mihai C. Giurcanu, James H. GrahamAbstract:Abstract In Florida, a root weevil pest of citrus, Diaprepes abbreviatus , is more damaging and attains higher population density in some orchards on fine textured, poorly drained “flatwoods” soils than in those on the deep, coarse sandy soils of the Central Ridge. Previous research revealed that sentinel weevil larvae were killed by indigenous entomopathogenic nematodes (EPNs) at significantly higher rates in an orchard on the Central Ridge, compared to one in the flatwoods. We hypothesized that filling tree planting holes in a flatwoods orchard with sandy soil from the Central Ridge would provide a more suitable habitat for EPNs, thereby reducing weevil numbers and root herbivory. Fifty trees were planted in oversized planting holes filled with coarse sand and 50 trees were planted in native soil in a split plot design where whole plots were species of introduced EPNs and split plots were soil type. Each of Steinernema diaprepesi , Steinernema riobrave , Heterorhabditis indica , Heterorhabditis zealandica , or no EPNs were introduced into the rhizospheres in 10 plots of each soil type. During four years, EPN numbers in soil samples and the relative abundance of seven species of nematophagous fungi associated with nematodes were measured three times using real-time PCR. The efficacy of EPNs against sentinel weevil larvae was also measured three times by burying caged weevils in situ . EPN species richness ( P = 0.001) and diversity ( P = 0.01) were always higher in sand than native soil. Soil type had no effect on numbers of EPNs in samples, but EPNs were detected more frequently ( P = 0.01) in plots of sandy soil than native soil in 2011. Two nematophagous fungi species, Paecilomyces lilacinus and Catenaria sp. were significantly more abundant in nematode samples from sandy soil on all three sampling dates. Efficacy of EPNs against weevil larvae was greater in sandy soil inoculated with S. diaprepesi ( P = 0.03) in June 2010 and in all treatments in sandy soil in May 2011 ( P = 0.03). Sixty-eight percent more adult weevils ( P = 0.01) were trapped emerging from native soil during two years than from sandy soil. By May 2011, the cumulative number of weevils emerging from each plot was inversely related ( P = 0.01) to the numbers of EPNs detected in plots and to EPN efficacy against sentinels. Three trees in sandy soil died as a result of root herbivory compared to 21 trees in native soil. Surviving trees in sandy soil had trunk diameters that were 60% larger ( P = 0.001) and produced 85% more fruit ( P = 0.001) than those in native soil. Although it is not possible to characterize all of the mechanisms by which the two soil treatments affected weevils and trees, substitution of sand for native soil was an effective means of conserving EPNs and shows promise as a cultural practice to manage D. abbreviatus in flatwoods citrus orchards with a history of weevil damage to trees.
-
From Augmentation to Conservation of Entomopathogenic Nematodes: Trophic Cascades, Habitat Manipulation and Enhanced Biological Control of Diaprepes abbreviatus Root Weevils in Florida Citrus Groves
Journal of Nematology, 2008Co-Authors: Robin J. Stuart, Fahiem E. El-borai, Larry W. DuncanAbstract:The use of entomopathogenic nematodes (EPN) for management of the root weevil, Diaprepes abbreviatus, in Florida citrus groves is considered a biological control success story and typically involves augmentation in which EPN are applied inundatively as biopesticides to quickly kill the pest. However, recent evidence indicates that efficacy of EPN applications in Florida citrus depends on soil type. They are very effective in the well drained coarse sands of the Central Ridge but often less so in poorly drained fine-textured soils of the Flatwoods. Moreover, groves on the Central Ridge can harbor rich communities of endemic EPN that might often suppress weevil populations below economic thresholds, whereas Flatwoods groves tend to have few endemic EPN and frequent weevil problems. Current research is examining the ecological dynamics of EPN in Florida citrus groves, the potential impact of EPN augmentation on soil food webs, especially endemic EPN, and whether habitat manipulation and inoculation strategies might be effective for conserving and enhancing EPN communities to achieve long-term control in problem areas. Conservation biological control could extend the usefulness of EPN in Florida citrus and be especially appropriate for groves with persistent weevil problems.
-
Validation of an area-wide extension program to estimate the seasonal abundance of adult citrus root weevils with un-baited pyramidal traps
2004Co-Authors: Stephen H. Futch, Larry W. Duncan, Mongi ZekriAbstract:One hundred modified Tedders traps were monitored weekly for 2.5 years in each of seven citrus orchards located throughout Florida. Temporal patterns of the prevalence of adult Diaprepes abbreviatus at each site were compared to determine the feasibility of using insect abundance in sentinel orchards to schedule pest management activities within a region. Weevil abundance in three orchards on Florida's Central Ridge exhibited no consistent temporal patterns between years or among sites. In three Central and eastern flatwoods sites, the abundance of weevils tended to be highest during the spring and early summer, but the variation in this pattern was high between sites and years. The mean abundance of weevils in the flatwoods sites was more than five-fold greater (P = 0.02) than that for sites on the Central Ridge. These data suggest the need for site-specific monitoring programs to aid in management of D. abbreviatus. Causes of regional variation in the abundance of D. abbreviatus merit additional research.
-
Spatial Patterns of Belonolaimus spp. Among and Within Citrus Orchards on Florida's Central Ridge
Journal of Nematology, 1996Co-Authors: Larry W. Duncan, J. W. Noling, Renato N. Inserra, D. DunnAbstract:A survey was initiated to determine the incidence of Belonolaimus spp. (sting nematodes) in citrus orchards in the Central Ridge region of Florida, following widespread damage by these nematodes to young trees replanted after freezing weather in 1989-90. Sting nematodes were detected in 50% of 210 samples and in 64% of 84 orchards surveyed. More orchards in Polk County were infested with sting nematodes (82%) than in counties to the north (36%) or south (48%). Principal component analysis of morphometric data separated six of seven sting nematode populations in northeastern Polk County from six populations in adjacent regions. Stylet:tail ratio for nematodes in northeastern Polk County tend to be 1.0 and were 1.0 for all other populations. Patchiness of nematodes within an orchard was associated with stunted trees (23% smaller), reduced root mass density (25% lower), and low fruit yield (57% reduction). Soil texture did not vary among trees of different size in the orchard, but soil water potential between irrigation events was highest beneath small trees with low root mass density. Results of the survey indicate that the incidence of sting nematodes in orchards on the Central Ridge is much higher than previously estimated and that sting nematodes can cause substantial damage in replanted orchards. Further research is needed to evaluate the significance of sting nematode population variability and its relationship to citrus crop loss in Florida. Key words: Belonolaimus longicaudatus, citrus, crop loss assessment, ecology, nematode, nematode survey, soil moisture, spatial distribution, spatial pattern, sting nematode.
Liao Chang - One of the best experts on this subject based on the ideXlab platform.
-
Characterizing magnetofossils from first‐order reversal curve (FORC) Central Ridge signatures
Geochemistry Geophysics Geosystems, 2014Co-Authors: David Heslop, Andrew P Roberts, Liao ChangAbstract:The Central Ridge structure of a first-order reversal curve (FORC) distribution is indicative of uniaxial noninteracting single domain magnetic particles, which provides the opportunity to identify and characterize biogenic magnetic mineral remains (magnetofossils) in sediments. Recent studies have shown that magnetofossils are widespread in the geological record and that they carry useful environmental information and contribute to paleomagnetic recording, which makes it essential to quantify how these biogenic components contribute to the magnetic properties of sediments. We present results from six sedimentary sequences whose magnetic mineral assemblages contain a significant magnetofossil contribution. Using principal component analysis, we find that the Central Ridge properties exhibit both intra-sequnce and inter-sequence variability that may be ascribed to external environmental factors. While samples from individual sediment sequences tend to cluster together, there is a continuum of inter-sequence behavior that appears to be related to a variety of magnetofossil properties. We demonstrate the complexity of biogenic magnetic components in sedimentary environments, but also the power and potential of FORC Central Ridges for understanding magnetic mixtures and unraveling environmental information.
-
characterizing magnetofossils from first order reversal curve forc Central Ridge signatures
Geochemistry Geophysics Geosystems, 2014Co-Authors: David Heslop, Andrew P Roberts, Liao ChangAbstract:The Central Ridge structure of a first-order reversal curve (FORC) distribution is indicative of uniaxial noninteracting single domain magnetic particles, which provides the opportunity to identify and characterize biogenic magnetic mineral remains (magnetofossils) in sediments. Recent studies have shown that magnetofossils are widespread in the geological record and that they carry useful environmental information and contribute to paleomagnetic recording, which makes it essential to quantify how these biogenic components contribute to the magnetic properties of sediments. We present results from six sedimentary sequences whose magnetic mineral assemblages contain a significant magnetofossil contribution. Using principal component analysis, we find that the Central Ridge properties exhibit both intra-sequnce and inter-sequence variability that may be ascribed to external environmental factors. While samples from individual sediment sequences tend to cluster together, there is a continuum of inter-sequence behavior that appears to be related to a variety of magnetofossil properties. We demonstrate the complexity of biogenic magnetic components in sedimentary environments, but also the power and potential of FORC Central Ridges for understanding magnetic mixtures and unraveling environmental information.
Claude Rangin - One of the best experts on this subject based on the ideXlab platform.
-
Deep structure of the Mid Black Sea High (offshore Turkey) imaged by multi-channel seismic survey (BLACKSIS cruise)
Marine Geology, 2002Co-Authors: Claude Rangin, A. G. Bader, B. Ecevitoǧlu, G. Pascal, Naci GörürAbstract:The Black Sea is considered to be a Mesozoic-Early Cenozoic marginal basin related to the north-dipping subduction of Tethys beneath Europe. However deformation of this basin during the successive Eocene to Neogene collisions of African-derived continental fragments (Kirshehir and Arabian micro plates) remains poorly understood. A multi-channel seismic survey conducted in the Central part of the Black Sea has shed light on the superimposed tectonic fabrics of the Central Ridge (the Mid Black Sea High, MBSH) in response to these successive collisions. The MBSH is formed by a series of large NW-SE trending anticlines and synclines, and possible northeast-verging thrusts were identified at the boundary with the deep East Black Sea Basin northeast of the Ridge. These buried folds and thrusts, blanketed by 3 to 8 s TWT of undeformed sediments, are interpreted as the offshore extension of the Early Cenozoic tectonic belt resulting from the collision between the Pontides in the north and the Kirshehir block to the south. The offshore part of the belt forming the Ridge could have then collapsed when collision ended. Neogene structures also affect the MBSH. A recent graben (the Sinop Trough) extends between this Central high and mainland Turkey. This graben could have been formed during the late Miocene incipient dextral strike slip motion of the North Anatolian Fault that was initiated during extrusion of the Anatolian microplate. Active tectonic inversion of deep-seated normal faults present along the Pontides passive margin was also observed along the northeastern flank of the Eastern Pontides. This deformation is the westernmost extension of the Lesser Caucasus front that outlines the suturing of the Eastern Black Sea Basin in easternmost Turkey and in Georgia. © 2002 Elsevier Science B.V. All rights reserved.
David R. Sharpe - One of the best experts on this subject based on the ideXlab platform.
-
Sequence stratigraphy of a glaciated basin fill, with a focus on esker sedimentation
Bulletin of the Geological Society of America, 2011Co-Authors: Don I. Cummings, George Gorrell, Jean Pierre Guilbault, Charles Logan, Dmitri Ponomarenko, André J.m. Pugin, James A. Hunter, Hazen A.j. Russell, Susan E. Pullan, David R. SharpeAbstract:A large integrated data set of cores, outcrop data, and seismic transects from the mud-buried Vars-Winchester esker in the Champlain Sea basin, Canada, was studied to gain insight into how muddy glaciated basins fill with sediment, and how esker sedimentary systems contribute to this process. Three stratigraphic units-a till sheet over carbonate bedrock, the Vars-Winchester esker, and overlying Champlain Sea mud-are identified in the data set. The till is massive, mud rich, carbonate rich, and drumlinized. The esker is also carbonate rich, and rests erosively on till or bedrock. It consists of two elements, a narrow gravelly Central Ridge and a broad sandy carapace. Three units comprise the overlying mud package: gray carbonate-rich rhythmites, massive bioturbated mud, and carbonate-poor, red-andgray rhythmites. A sequence stratigraphic model is proposed to explain these observations. Emphasis is placed on gradual ice-front translation superimposed by rapid meltwater events. The esker is interpreted to have been derived from the underlying till by water that flowed through a subglacial conduit (R-channel), within which the narrow gravelly Central Ridge was deposited. Most mud and finer sand bypassed the conduit and was deposited proglacially on the floor of the Champlain Sea, first as sandy outwash and, farther basinward, as muddy carbonate-rich rhythmites. Gradual ice-front retreat superposed distal facies over proximal facies, generating the upward-fining succession that starts with the esker gravel and ends with muddy rhythmites. Most esker sediment appears to have been deposited during rapid, jokulhlaup-like floods that punctuated gradual retreat. Discharges are estimated to have been high, possibly on the order of several hundred to, perhaps more commonly, several thousand cubic meters per second. The chaotic and random-looking appearance of the resultant sedimentological signatures in the esker sensu stricto is sharply contrasted with the regularity of the muddy rhythmites. If the rhythmites are indeed correlative to the esker, which seems reasonable given their geochemistry and the fact that their volume scales to the volume of mud in the till, the flood events that deposited the esker must have been seasonally mediated, and the basin water must have attenuated the flood signal, resulting in a rhythmic "on-off" signature in more distal portions of the system. The regularity of the rhythmites does not betray the chaotic nature of the esker sensu stricto, and vice versa. Studying either one in isolation would lead to a very different "end-member" impression of how eskers form and how esker sedimentary systems operate during the infilling of glaciated basins.