Microstructure profiling measurements taken on a shallow Black Sea shelf and in Lake Banyoles and Boadella reservoir （Both in Spain） are analyzed to investigate the influence of boundary-layer-induced turbulence of ...Microstructure profiling measurements taken on a shallow Black Sea shelf and in Lake Banyoles and Boadella reservoir （Both in Spain） are analyzed to investigate the influence of boundary-layer-induced turbulence of various sources on mixing in the water interior. The state of turbulence in shallow waters is examined and details of microstructure data processing and error analysis are discussed. The dependence between averaged activity parameter A6 and buoyancy Reynolds number Reb for the shelf turbulence indicates that for Reb 〈 1 the state of turbulence can be described by the fossil turbulence model, which postulates AG - Re b^1/2. For Reb 〉 1, however, the influence of Reb on Ao is weak, signifying that the buoyancy Reynolds number can no longer serve as the governing parameter for active turbulent mixing. The generation of turbulence by a one-minute long wind bursts （the Boadella reservoir） increases the averaged dissipation rate （ε） of the surface mixed layer by more than 5 times （up to 3 × 10^-6 W kg^-1）. The influence of the wind bursts was also traced below the thermocline, where turbulent patches with （ε） = （10^-7 - 10^-6） W kg^-1 were generated. It is shown that the geothermal convection in Lake Banyoles produces intermittent turbulent patches with characteristic dissipation rate （ε） = （2 × 10^-8- 3 × 10^-7） W kg^-1, which influences the overall vertical mixing in the basin.展开更多
Dental microwear textures have proven to be a valuable tool for reconstructing the diets of a wide assortment of fossil vertebrates.Nevertheless,some studies have recently questioned the efficacy of this approach,sugg...Dental microwear textures have proven to be a valuable tool for reconstructing the diets of a wide assortment of fossil vertebrates.Nevertheless,some studies have recently questioned the efficacy of this approach,suggesting that aspects of habitat unrelated to food preference,especially environmental grit load,might have a confounding effect on microwear patterning that obscures the diet signal.Here we evaluate this hypothesis by examining microwear textures of 3 extant sympatric rodent species that vary in diet breadth and are found in a variety of habitat types:Mastomys coucha,Micaelamys namaquensis and Rhabdomys pumilio.We sample each of these species from 3 distinct environmental settings in southern Africa that differ in rainfall and vegetative cover:Nama-Karoo shrublands(semi-desert)and Dry Highveld grasslands in the Free State Province of South Africa,and Afromontane(wet)grasslands in the highlands of Lesotho.While differences between habitat types are evident for some of the species,inconsistency in the pattern suggests that the microwear signal is driven by variation in foods eaten rather than grit-level per se.It is clear that,at least for species and habitats sampled in the current study,environmental grit load does not swamp diet-related microwear signatures.展开更多
Rivers are revered worldwide for their ecologic,scenic,and recreational value.The capacity to communicate effectively among human groups with vested interest in rivers hinges on understanding the nature of human perce...Rivers are revered worldwide for their ecologic,scenic,and recreational value.The capacity to communicate effectively among human groups with vested interest in rivers hinges on understanding the nature of human perceptions of water quality and the extent to which they vary intraculturally.Recognizing the intersection between measured water quality and the characteristics of rivers that influence human perceptions facilitates potential for better communication across disciplines and among stakeholders.We conducted interviews and a pile-sort task with water quality experts and nonexperts.Our analysis suggested human evaluation of water quality is guided by culturally constructed criteria,regardless of respondent expertise,experience,or demographics.Cluster analysis results implied that measured physical and chemical parameters of rivers were directly related to the visible attributes used in human judgments.We suggest that,regardless of variability among individual stakeholders,observable characteristics may be the foundation for a common understanding of water quality in rivers.展开更多
Conservation agriculture seeks to reduce environmental degradation through sustainable management of agricultural land.Since the 1990s,agricultural research has been conducted using remote sensing technologies;however...Conservation agriculture seeks to reduce environmental degradation through sustainable management of agricultural land.Since the 1990s,agricultural research has been conducted using remote sensing technologies;however,few previous reviews have been conducted focused on different conservation management practices.Most of the previous literature has focused on the application of remote sensing in agriculture without focusing exclusively on conservation practices,with some only providing a narrative review,others using biophysical remote sensing for quantitative estimates of the bio-geo-chemical-physical properties of soils and crops,and few others focused on single agricultural management practices.This paper used the preferred reporting items for systematic review(PRISMA)methodology to examine the last 30 years of thematic research,development,and trends associated with remote sensing technologies and methods applied to conservation agriculture research at various spatial and temporal scales.A set of predefined key concepts and keywords were applied in three databases:Scopus,Web of Science,and Google Scholar.A total of 188 articles were compiled for initial examination,where 68 articles were selected for final analysis and grouped into cover crops,crop residue,crop rotation,mulching,and tillage practices.Publications on conservation agriculture research using remote sensing have been increasing since 1991 and peaked at 10 publications in 2020.Among the 68 articles,94%used a pixel-based,while only 6%used an object-based classification method.Prior to 2005,tillage practices were abundantly studied,then crop residue was a focused theme between 2004 and 2012.From 2012 to 2020,the focus shifted again to cover crops.Ten spectral indices were used in 76%of the 68 studies.This examination offered a summary of the new potential and identifies crucial future research needs and directions that could improve the contribution of remote sensing to the provision of long-term operational services for various conservation agriculture applications.展开更多
基金The work was supported by the US Office of Naval Research(N00014-97-1-0140 and N00014-05-l-0245)by the Spanish Government(GL2004-02027/HID).
文摘Microstructure profiling measurements taken on a shallow Black Sea shelf and in Lake Banyoles and Boadella reservoir （Both in Spain） are analyzed to investigate the influence of boundary-layer-induced turbulence of various sources on mixing in the water interior. The state of turbulence in shallow waters is examined and details of microstructure data processing and error analysis are discussed. The dependence between averaged activity parameter A6 and buoyancy Reynolds number Reb for the shelf turbulence indicates that for Reb 〈 1 the state of turbulence can be described by the fossil turbulence model, which postulates AG - Re b^1/2. For Reb 〉 1, however, the influence of Reb on Ao is weak, signifying that the buoyancy Reynolds number can no longer serve as the governing parameter for active turbulent mixing. The generation of turbulence by a one-minute long wind bursts （the Boadella reservoir） increases the averaged dissipation rate （ε） of the surface mixed layer by more than 5 times （up to 3 × 10^-6 W kg^-1）. The influence of the wind bursts was also traced below the thermocline, where turbulent patches with （ε） = （10^-7 - 10^-6） W kg^-1 were generated. It is shown that the geothermal convection in Lake Banyoles produces intermittent turbulent patches with characteristic dissipation rate （ε） = （2 × 10^-8- 3 × 10^-7） W kg^-1, which influences the overall vertical mixing in the basin.
基金funded by US National Science Foundation Grant SBR0948283 to PSU.
文摘Dental microwear textures have proven to be a valuable tool for reconstructing the diets of a wide assortment of fossil vertebrates.Nevertheless,some studies have recently questioned the efficacy of this approach,suggesting that aspects of habitat unrelated to food preference,especially environmental grit load,might have a confounding effect on microwear patterning that obscures the diet signal.Here we evaluate this hypothesis by examining microwear textures of 3 extant sympatric rodent species that vary in diet breadth and are found in a variety of habitat types:Mastomys coucha,Micaelamys namaquensis and Rhabdomys pumilio.We sample each of these species from 3 distinct environmental settings in southern Africa that differ in rainfall and vegetative cover:Nama-Karoo shrublands(semi-desert)and Dry Highveld grasslands in the Free State Province of South Africa,and Afromontane(wet)grasslands in the highlands of Lesotho.While differences between habitat types are evident for some of the species,inconsistency in the pattern suggests that the microwear signal is driven by variation in foods eaten rather than grit-level per se.It is clear that,at least for species and habitats sampled in the current study,environmental grit load does not swamp diet-related microwear signatures.
基金supported in part by the U.S.Geological Survey 104B Program and the Arkansas Water Resources Center(project#2014AR351B)by a research grant awarded by The Geological Society of America.
文摘Rivers are revered worldwide for their ecologic,scenic,and recreational value.The capacity to communicate effectively among human groups with vested interest in rivers hinges on understanding the nature of human perceptions of water quality and the extent to which they vary intraculturally.Recognizing the intersection between measured water quality and the characteristics of rivers that influence human perceptions facilitates potential for better communication across disciplines and among stakeholders.We conducted interviews and a pile-sort task with water quality experts and nonexperts.Our analysis suggested human evaluation of water quality is guided by culturally constructed criteria,regardless of respondent expertise,experience,or demographics.Cluster analysis results implied that measured physical and chemical parameters of rivers were directly related to the visible attributes used in human judgments.We suggest that,regardless of variability among individual stakeholders,observable characteristics may be the foundation for a common understanding of water quality in rivers.
基金This research is based upon funding supported by the Natural Resources Conservation Service(NRCS)-U.S.Department of Agriculture(USDA),under agreement number NR1871003XXXXC054.
文摘Conservation agriculture seeks to reduce environmental degradation through sustainable management of agricultural land.Since the 1990s,agricultural research has been conducted using remote sensing technologies;however,few previous reviews have been conducted focused on different conservation management practices.Most of the previous literature has focused on the application of remote sensing in agriculture without focusing exclusively on conservation practices,with some only providing a narrative review,others using biophysical remote sensing for quantitative estimates of the bio-geo-chemical-physical properties of soils and crops,and few others focused on single agricultural management practices.This paper used the preferred reporting items for systematic review(PRISMA)methodology to examine the last 30 years of thematic research,development,and trends associated with remote sensing technologies and methods applied to conservation agriculture research at various spatial and temporal scales.A set of predefined key concepts and keywords were applied in three databases:Scopus,Web of Science,and Google Scholar.A total of 188 articles were compiled for initial examination,where 68 articles were selected for final analysis and grouped into cover crops,crop residue,crop rotation,mulching,and tillage practices.Publications on conservation agriculture research using remote sensing have been increasing since 1991 and peaked at 10 publications in 2020.Among the 68 articles,94%used a pixel-based,while only 6%used an object-based classification method.Prior to 2005,tillage practices were abundantly studied,then crop residue was a focused theme between 2004 and 2012.From 2012 to 2020,the focus shifted again to cover crops.Ten spectral indices were used in 76%of the 68 studies.This examination offered a summary of the new potential and identifies crucial future research needs and directions that could improve the contribution of remote sensing to the provision of long-term operational services for various conservation agriculture applications.
