Non-random distribution of biocrust in a natural arid environment in the northern mexican plateau

Abstract. Biocrust, as photosynthetic organisms, has been considered to show an inversely proportional relationship with vascular plant cover. However, some studies report association and facilitation relationships between them. This research explores whether i) biocrust is associated with shrub species, ii) biocrust cover is higher in undershrub microenvironments than in open areas between plants and, iii) soil moisture and solar radiation affect biocrust distribution. Biocrust cover was analyzed by morphotype in microenvironments under the canopy of two dominant shrub species (Larrea tridentata and Parthenium incanum) and in open areas. Soil moisture and solar radiation were recorded at each microenvironment. Thirty-three interception lines (975 points) were used to analyze the association between vascular plants and biocrust and 20 sampling plots to estimate morphotype cover. Results reveal a positive association between biocrust and plant species compared to open areas. Lichens and cyanobacteria showed a higher cover under L. tridentata than under P. incanum and in open areas, suggesting a species-specific facilitative association with L. tridentata, maybe due to a higher soil water content in this microenvironment. Mosses had lower cover in the open area where the highest solar radiation was recorded. Lichens and cyanobacteria distribution appeared to be related to soil moisture. Keywords: creosote bush, cyanobacteria, lichens, mosses, northeastern Mexic

DIMENSIONES CONCEPTUALES DEL BIENESTAR DE PERSONAS CON PADECIMIENTOS CRÓNICOS

Se explora las dimensiones conceptuales del bienestar de personas con padecimientos crónicos de la ciudad de Guadalajara, México, a fin de generar propuestas de intervención educativa en salud en materia de enfermedades crónicas. Estudio transversal exploratorio realizado entre marzo y mayo de 2006 con 40 personas con Diabetes Mellitus e Hipertensión Arterial que participan en grupos de apoyo en Centros de Salud de la ciudad de Guadalajara, México, seleccionadas por muestreo propositivo. Se aplicaron entrevistas semiestructuradas mediante técnicas de listados libres y sorteo de montones. Se indagaron términos asociados al concepto de bienestar y grupos de dimensiones conceptuales. Se aplicó análisis de consenso mediante factorización de componentes principales y análisis dimensional, mediante conglomerados jerárquicos y escalas multidimensionales. El modelo de consenso mostró alta homogeneidad en las concepciones del bienestar (valor de 8.22). Las dimensiones comunes en las concepciones fueron: ser responsable, la felicidad (con las subdimensiones de tranquilidad, tener fe y tener salud), la disciplina (subdimensiones: desarrollo y mantenimiento así como prolongar la vida) y el vivir a gusto (valor de verosimilitud: stress<0.28). Las personas participantes mostraron en dichas dimensiones una visión holística del concepto de bienestar. Las dimensiones de responsabilidad y disciplina hacen referencia decisiones voluntarias de tipo más bien personal, donde la familia y el aspecto comunitario no son incluidos. La segunda dimensión es sobre elementos de tipo mental y social donde se incluyó a la felicidad y el vivir a gusto. Ello implica la práctica de acciones y cuidados de la salud mental, la vida espiritual y social. Se encontró además asociación del concepto de bienestar con el de salud mental.Palabras clave: bienestar, enfermedad crónica, concepciones culturaleswell-being, chronic illness, cultural conception

Probing Iceland\u27s dust-emitting sediments: particle size distribution, mineralogy, cohesion, Fe mode of occurrence, and reflectance spectra signatures

Characterising the physico-chemical properties of dust-emitting sediments in arid regions is fundamental to understanding the effects of dust on climate and ecosystems. However, knowledge regarding high-latitude dust (HLD) remains limited. This study focuses on analysing the particle size distribution (PSD), mineralogy, cohesion, iron (Fe) mode of occurrence, and visible–near infrared (VNIR) reflectance spectra of dust-emitting sediments from dust hotspots in Iceland (HLD region). Extensive analysis was conducted on samples of top sediments, sediments, and aeolian ripples collected from seven dust sources, with particular emphasis on the Jökulsá basin, encompassing the desert of Dyngjunsandur. Both fully and minimally dispersed PSDs and their respective mass median particle diameters revealed remarkable similarities (56 ± 69 and 55 ± 62 µm, respectively). Mineralogical analyses indicated the prevalence of amorphous phases (68 ± 26 %), feldspars (17 ± 13 %), and pyroxenes (9.3 ± 7.2 %), consistent with thorough analyses of VNIR reflectance spectra. The Fe content reached 9.5 ± 0.40 wt %, predominantly within silicate structures (80 ± 6.3 %), complemented by magnetite (16 ± 5.5 %), hematite/goethite (4.5 ± 2.7 %), and readily exchangeable Fe ions or Fe nano-oxides (1.6 ± 0.63 %). Icelandic top sediments exhibited coarser PSDs compared to the high dust-emitting crusts from mid-latitude arid regions, distinctive mineralogy, and a 3-fold bulk Fe content, with a significant presence of magnetite. The congruence between fully and minimally dispersed PSDs underscores reduced particle aggregation and cohesion of Icelandic top sediments, suggesting that aerodynamic entrainment of dust could also play a role upon emission in this region, alongside saltation bombardment. The extensive analysis in Dyngjusandur enabled the development of a conceptual model to encapsulate Iceland\u27s rapidly evolving high dust-emitting environments

Characterization of the particle size distribution, mineralogy, and Fe mode of occurrence of dust-emitting sediments from the Mojave Desert, California, USA

Constraining dust models to understand and quantify the effect of dust upon climate and ecosystems requires comprehensive analyses of the physiochemical properties of dust-emitting sediments in arid regions. Building upon previous studies in the Moroccan Sahara and Iceland, we analyse a diverse set of crusts and aeolian ripples (n=55) from various potential dust-emitting basins within the Mojave Desert, California, USA. Our focus is on characterizing the particle size distribution (PSD), mineralogy, aggregation/cohesion state, and Fe mode of occurrence. Our results show differences in fully and minimally dispersed PSDs, with crusts exhibiting average median diameters of 92 and 37 µm, respectively, compared to aeolian ripples with 226 and 213 µm, respectively. Mineralogical analyses unveiled strong variations between crusts and ripples, with crusts being enriched in phyllosilicates (24 % vs. 7.8 %), carbonates (6.6 % vs. 1.1 %), Na salts (7.3 % vs. 1.1 %), and zeolites (1.2 % and 0.12 %) and ripples being enriched in feldspars (48 % vs. 37 %), quartz (32 % vs. 16 %), and gypsum (4.7 % vs. 3.1 %). The size fractions from crust sediments display a homogeneous mineralogy, whereas those of aeolian ripples display more heterogeneity, mostly due to different particle aggregation. Bulk Fe content analyses indicate higher concentrations in crusts (3.0 ± 1.3 wt %) compared to ripples (1.9 ± 1.1 wt %), with similar proportions in their Fe mode of occurrence: nano-sized Fe oxides and readily exchangeable Fe represent ∼1.6 %, hematite and goethite ∼15 %, magnetite/maghemite ∼2.0 %, and structural Fe in silicates ∼80 % of the total Fe. We identified segregation patterns in the PSD and mineralogy differences in Na salt content within the Mojave basins, which can be explained by sediment transportation dynamics and precipitates due to groundwater table fluctuations described in previous studies in the region. Mojave Desert crusts show similarities with previously sampled crusts in the Moroccan Sahara in terms of the PSD and readily exchangeable Fe yet exhibit substantial differences in mineralogical composition, which should significantly influence the characteristic of the emitted dust particles.</p

Airborne dust and high temperatures are risk factors for invasive bacterial disease

Background The Sahel region of West Africa has the highest bacterial meningitis attack and case fatality rate in the world. The effect of climatic factors on patterns of invasive respiratory bacterial disease is not well documented. Objective We aimed to assess the link between climatic factors and occurrence of invasive respiratory bacterial disease in a Sahel region of Niger. Methods We conducted daily disease surveillance and climatic monitoring over an 8-year period between January 1, 2003, and December 31, 2010, in Niamey, Niger, to determine risk factors for bacterial meningitis and invasive bacterial disease. We investigated the mechanistic effects of these factors on Streptococcus pneumoniae infection in mice. Results High temperatures and low visibility (resulting from high concentrations of airborne dust) were identified as significant risk factors for bacterial meningitis. Dust inhalation or exposure to high temperatures promoted progression of stable asymptomatic pneumococcal nasopharyngeal carriage to pneumonia and invasive disease. Dust exposure significantly reduced phagocyte-mediated bacterial killing, and exposure to high temperatures increased release of the key pneumococcal toxin pneumolysin through increased bacterial autolysis. Conclusion Our findings show that climatic factors can have a substantial influence on infectious disease patterns, altering density of pneumococcal nasopharyngeal carriage, reducing phagocytic killing, and resulting in increased inflammation and tissue damage and consequent invasiveness. Climatic surveillance should be used to forecast invasive bacterial disease epidemics, and simple control measures to reduce particulate inhalation might reduce the incidence of invasive bacterial disease in regions of the world exposed to high temperatures and increased airborne dust

Probing Iceland's dust-emitting sediments: Particle size distribution, mineralogy, cohesion, Fe mode of occurrence, and reflectance spectra signatures

Characterising the physico-chemical properties of dust-emitting sediments in arid regions is fundamental to understanding the effects of dust on climate and ecosystems. However, knowledge regarding highlatitude dust (HLD) remains limited. This study focuses on analysing the particle size distribution (PSD), mineralogy, cohesion, iron (Fe) mode of occurrence, and visible-near infrared (VNIR) reflectance spectra of dustemitting sediments from dust hotspots in Iceland (HLD region). Extensive analysis was conducted on samples of top sediments, sediments, and aeolian ripples collected from seven dust sources, with particular emphasis on the Jökulsá basin, encompassing the desert of Dyngjunsandur. Both fully and minimally dispersed PSDs and their respective mass median particle diameters revealed remarkable similarities (56±69 and 55±62 μm, respectively). Mineralogical analyses indicated the prevalence of amorphous phases (68±26 %), feldspars (17±13 %), and pyroxenes (9.3±7.2 %), consistent with thorough analyses of VNIR reflectance spectra. The Fe content reached 9.5±0.40 wt %, predominantly within silicate structures (80±6.3 %), complemented by magnetite (16±5.5 %), hematite/goethite (4.5±2.7 %), and readily exchangeable Fe ions or Fe nano-oxides (1.6±0.63 %). Icelandic top sediments exhibited coarser PSDs compared to the high dust-emitting crusts from mid-latitude arid regions, distinctive mineralogy, and a 3-fold bulk Fe content, with a significant presence of magnetite. The congruence between fully and minimally dispersed PSDs underscores reduced particle aggregation and cohesion of Icelandic top sediments, suggesting that aerodynamic entrainment of dust could also play a role upon emission in this region, alongside saltation bombardment. The extensive analysis in Dyngjusandur enabled the development of a conceptual model to encapsulate Iceland's rapidly evolving high dust-emitting environments.This research has been supported by the European Research Council, EU H2020 European Research Council (grant no. 773051), the AXA Research Fund (AXA Chair on Sand and Dust Storms), the Agència de Gestió d'Ajuts Universitaris i de Recerca (grant no. 2020_FI B 00678), the Deutsche Forschungsgemeinschaft (grant nos. 264907654 and 416816480), and the Helmholtz Association (grant no. VH-NG-1533). The article processing charges for this open-access publication were covered by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).Peer reviewe

Characterization of the particle size distribution, mineralogy, and Fe mode of occurrence of dust-emitting sediments from the Mojave Desert, California, USA

Constraining dust models to understand and quantify the effect of dust upon climate and ecosystems requires comprehensive analyses of the physiochemical properties of dust-emitting sediments in arid regions. Building upon previous studies in the Moroccan Sahara and Iceland, we analyse a diverse set of crusts and aeolian ripples (n=55) from various potential dust-emitting basins within the Mojave Desert, California, USA. Our focus is on characterizing the particle size distribution (PSD), mineralogy, aggregation/cohesion state, and Fe mode of occurrence. Our results show differences in fully and minimally dispersed PSDs, with crusts exhibiting average median diameters of 92 and 37 µm, respectively, compared to aeolian ripples with 226 and 213 µm, respectively. Mineralogical analyses unveiled strong variations between crusts and ripples, with crusts being enriched in phyllosilicates (24 % vs. 7.8 %), carbonates (6.6 % vs. 1.1 %), Na salts (7.3 % vs. 1.1 %), and zeolites (1.2 % and 0.12 %) and ripples being enriched in feldspars (48 % vs. 37 %), quartz (32 % vs. 16 %), and gypsum (4.7 % vs. 3.1 %). The size fractions from crust sediments display a homogeneous mineralogy, whereas those of aeolian ripples display more heterogeneity, mostly due to different particle aggregation. Bulk Fe content analyses indicate higher concentrations in crusts (3.0 ± 1.3 wt %) compared to ripples (1.9 ± 1.1 wt %), with similar proportions in their Fe mode of occurrence: nano-sized Fe oxides and readily exchangeable Fe represent ∼1.6 %, hematite and goethite ∼15 %, magnetite/maghemite ∼2.0 %, and structural Fe in silicates ∼80 % of the total Fe. We identified segregation patterns in the PSD and mineralogy differences in Na salt content within the Mojave basins, which can be explained by sediment transportation dynamics and precipitates due to groundwater table fluctuations described in previous studies in the region. Mojave Desert crusts show similarities with previously sampled crusts in the Moroccan Sahara in terms of the PSD and readily exchangeable Fe yet exhibit substantial differences in mineralogical composition, which should significantly influence the characteristic of the emitted dust particles

Characterization of the particle size distribution, mineralogy, and Fe mode of occurrence of dust-emitting sediments from the Mojave Desert, California, USA

Constraining dust models to understand and quantify the effect of dust upon climate and ecosystems requires comprehensive analyses of the physiochemical properties of dust-emitting sediments in arid regions. Building upon previous studies in the Moroccan Sahara and Iceland, we analyse a diverse set of crusts and aeolian ripples (nCombining double low line55) from various potential dust-emitting basins within the Mojave Desert, California, USA. Our focus is on characterizing the particle size distribution (PSD), mineralogy, aggregation/cohesion state, and Fe mode of occurrence. Our results show differences in fully and minimally dispersed PSDs, with crusts exhibiting average median diameters of 92 and 37 μm, respectively, compared to aeolian ripples with 226 and 213 μm, respectively. Mineralogical analyses unveiled strong variations between crusts and ripples, with crusts being enriched in phyllosilicates (24 % vs. 7.8 %), carbonates (6.6 % vs. 1.1 %), Na salts (7.3 % vs. 1.1 %), and zeolites (1.2 % and 0.12 %) and ripples being enriched in feldspars (48 % vs. 37 %), quartz (32 % vs. 16 %), and gypsum (4.7 % vs. 3.1 %). The size fractions from crust sediments display a homogeneous mineralogy, whereas those of aeolian ripples display more heterogeneity, mostly due to different particle aggregation. Bulk Fe content analyses indicate higher concentrations in crusts (3.0 ± 1.3 wt %) compared to ripples (1.9 ± 1.1 wt %), with similar proportions in their Fe mode of occurrence: nano-sized Fe oxides and readily exchangeable Fe represent ĝ1/41.6 %, hematite and goethite ~15 %, magnetite/maghemite ~2.0 %, and structural Fe in silicates ~80 % of the total Fe. We identified segregation patterns in the PSD and mineralogy differences in Na salt content within the Mojave basins, which can be explained by sediment transportation dynamics and precipitates due to groundwater table fluctuations described in previous studies in the region. Mojave Desert crusts show similarities with previously sampled crusts in the Moroccan Sahara in terms of the PSD and readily exchangeable Fe yet exhibit substantial differences in mineralogical composition, which should significantly influence the characteristic of the emitted dust particles.This research has been supported by the European Research Council, EU H2020 (Consolidator Grant FRAGMENT, grant no. 773051); the AXA Research Fund (AXA Chair on Sand and Dust Storms BSC); the Agència de Gestió d'Ajuts Universitaris i de Recerca (grant no. 2020_FI B 00678); the Deutsche Forschungsgemeinschaft (grant nos. 264907654 and 416816480); the Helmholtz Association (grant no. VH-NG-1533); and the Earth Sciences Division (NASA Earth Venture Instrument – Science Mission Directorate). The article processing charges for this open-access publication were covered by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).Peer reviewe