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Green cover and air quality are important components of life quality and human ecology in arid lands. In the Sonoran Desert of Mexico, Hermosillo is the largest city with a population of 710,000. This city is currently affected by dust pollution and a large part of its population suffers respiratory diseases. Moreover, Hermosillo is considered highly vulnerable to climate change. The objective of this work was to correlate socio-economic variables such as population density and unpaved cover to total suspended particles (TSP), daily temperature oscillation (DTO), and vegetation cover (VC) to establish priority zones for reforestation for the city government. We divided Hermosillo in 440 sampling areas corresponding to Basic Geostatistics Urban Areas (AGEB) as defined by Instituto Nacional de Estadistica Geografia e Informatica (INEGI). We estimated TSP and DTO for each AGEB by spatial interpolation using the splines with barriers from 3 and 7 sampling stations, respectively. We obtained population density for each AGEB from the 2010 Population and Housing Census by INEGI and percentage of unpaved cover for each AGEB from municipal government records. We mapped VC analyzing digital aerial ortho-photos (resolution 15 × 15 cm per pixel) using GIS and manual digitization. We estimated VC at the AGEB level by sampling. Average VC percentage for Hermosillo is 6.4%. We also found that VC is negatively associated with TSP and DTO, highlighting the importance of further increasing green cover to enhance urban life quality in arid lands. Population density (PD) and unpaved cover (UC) were also positively correlated to DTO and marginally with TSP. Our research approach at a local scale, using an accessible methodology and inexpensive data inputs, can be easily applied to other arid cities around the world. We produced a map of prioritization reforestation zones for Hermosillo.

Environmental conditions and human-landscape interaction during the onset of the irrigated agriculture in Oasisamerica are not clear yet. In la Playa site (Sonora, NW Mexico), the evidences of sedentary population, land cultivation, and water management developed after the end of Altithermal period (around 4500 yr BP) include more than 550 archaeological features including hundreds of human cremations and a net of buried artificial channels. These findings were closely associated with several palaeosol levels alternating with sediments within a large alluvial fan. We studied micromorphological features, physical characteristics (color, texture, rock magnetic properties), and composition of organic matter, from three profiles (Maravillas, Zanja, and Cuatro Suelos), to reconstruct pedogenesis and sedimentary environment of the palaeosol sequences. Additional paleoenvironmental information was extracted from pollen assemblages, extracted from the Cuatro Suelos profile. The results pointed to a long period of geomorphic and climatic stability in the early-middle Holocene marked by a well-developed red Cambisol. This period was followed by an unstable interval around 4.5 kyr BP marked by severe erosion of earlier soil profiles and sedimentation of different kind: channel, floodplain, and fluvio-eolian. Later synsedimentary Fluvisols were formed showing signs of predominantly arid pedogenesis, interrupted by occasional flooding; indicators of human impact were also encountered. We conclude that the shift to irrigated agriculture as the main subsistence activity occurred during the period of major climatic and geomorphic fluctuation and then irrigation developed further under dry environment with limited water resources during the Late Holocene.

Studies focused on the seasonal distribution of pollen and spores in semiarid cities are scarce. At these sites, climate change potentiates the emission and transport of fine (PM10) to ultrafine particles (PM2.5), easily attached to pollen surfaces, causing allergen's release. This study examines the potential correlation of seasonal variations of pollen, fungal spores, PM10, and meteorological parameters with allergic reactions of 150 people living in a Sonoran desert city. We collected PM10, airborne pollen, and spores during a year. We also studied topsoil and road dust samples as potential PM-emission sources. We obtained dust-mineralogy, chemistry, and particle size attached to pollen by X-ray diffraction and scanning electron microscope. Results show that seasonal high PM-loading in the urban atmosphere coincides with aeroallergens promoting micro- to nanoparticles' attachment to pollen's surface. A collapsed membrane was observed in several samples after individual grains show the following maximum wall coverage: Poaceae 28%, Asteraceae 40%, Chenopodiaceae-Amaranthacea 29%, Fabaceae 18%. Most of the particles covering pollen's surface have a geogenic origin mixed with metals linked to traffic (bromide, chlorine, and antimony). Mineralogical, granulometric analysis, and main wind-direction show that two local soil-types are the main contributors to PM. A high frequency of positive sensitization to pollen with high particle loading was detected. These results suggest that climate-driven dust emissions may alter pollen and spore surfaces' physicochemical characteristics with the further consequences in their allergenic potential.

International audience; We present a multiproxy record from magnetic susceptibility, loss on ignition and chemical analysis of a sediment core collected from ``Cienega Las Taunas'', a peatland in the northwest of the Sierra Madre Occidental in Mexico. The oldest sediments were dated to 12,850 cal yr BP. The relatively cool and wet Younger Dryas (YD) shows higher concentrations of TiO2 and Chemical Index of Alteration (CIA), suggesting higher runoff into the cienega. The transition from the YD to the early Holocene is marked by a decrease in susceptibility, pointing to weakened erosional processes during a period of closed forest vegetation, suggesting a predominantly winter rainfall regime. A change in seasonality likely occurred after ca. 9200 cal yr BP, as shown by: 1) an increase in most major elements, suggesting increased dust fallout from distant sources, and 2) more pollen assemblages from temperate vegetation (pine-oak forest). We related these changes to increased summer rains and monsoons in NW Mexico. A possible hiatus or a very slow sedimentation period occurred during the middle Holocene at this site. Finally, high-frequency changes in sediment properties were especially observed in the Late Holocene, suggesting contrasting sediment inputs controlled by an unstable water table and/or related to ENSO. (C) 2016 Elsevier B.V. All rights reserved.

International audience; The last glacial-interglacial transition encompassed rapid climate oscillations that affected both hemispheres. At low latitudes, the pattern of oscillations is not well established. To address this issue, pollen analysis was performed at Cienega San Marcial, a monsoon-influenced site located on the southeastern edge of the Sonoran Desert at the limit of the tropical thornscrub. The pollen record covers the Late Wisconsinan glacial termination II, from 15650 to 13400cal. a BP, including GS-2 and the Lateglacial interstadial, and a recent historical period (AD c.1919 to 2004). We applied the modern analogue technique, in which pollen taxa are assigned to plant functional types (PFTs), to reconstruct the past climates. At the end of GS-2, a Juniperus-Pinus woodland is indicative of annual temperatures 10 +/- 2 degrees C colder than present and higher annual precipitation dominated by winter rains. The onset of the Lateglacial interstadial occurs at c.15500cal. a BP, resulting in a lower sedimentation rate and the spread of a xeric grassland. This period is associated with an increase in summer insolation. A weak signal of summer monsoon intensification is dated to 14825cal. a BP but is associated with colder winter temperatures. A wider spread of tropical taxa occurs after 13800cal. a BP, along with the loss of Juniperus, suggesting a temperature increase of approximately 3 degrees C. In spite of the earlier Lateglacial warming, the transition from glacial to interstadial conditions seems to be related to North Atlantic atmospheric variations. We conclude that during the last glacial-interglacial transition, the Sonoran Desert at 28.5 degrees latitude was sensitive to climate variations originating in northern latitudes. The recent historical sequence displays summer-dominant precipitation and additional drivers of climate change, including anthropogenic factors and El Nino, thus showing a stronger Pacific circulation influence in the subrecent period.

We determined the effect of the seasonal distribution of summer rainfall and associated seasonal changes in vegetation on the timing of reproduction and reproductive success of the Rufous-winged Sparrow (Peucaea carpalis) in the plains of central Sonora, Mexico, and influence of exotic buffelgrass (Pennisetum ciliare). We monitored 302 nests twice weekly from early July to early October of 2012–2014. We fitted Bayesian logistic-exposure models for nest survival data using covariables year, nest stage, date, normalized difference vegetation index, shrub cover, buffelgrass cover, and nest height. Mean daily nest survival probability equaled 95.9% (95% CRI 95.1%–96.1%), with nest survival probability averaging 36.3% (95% CRI 30.2%–42.5%) during the nesting season.We found evidence that daily nest survival probability differed between nest stages but variation in environmental explanatory variables among nests did not explain variation in daily nest survival probability, despite suggestive evidence of a positive association between NDVI and daily nest survival probability. Daily nest survival probability seemed unaffected by the habitat alteration in buffelgrass prairies, suggesting that the Rufous-winged Sparrow may be resilient to habitat transformation in the center of its distribution.

International audience; A modem pollen rain study was performed in a 300 km-long altitudinal transect (similar to 28 degrees N latitude) from 300 to 2300 m elevation. The higher elevation modem communities: epithermal oak-pines, pine-oak forest, pine forest, and mixed conifer forest were easy to distinguish from their pollen content. In contrast, lower elevation subtropical communities: thornscrub and tropical deciduous forest were difficult to separate, because they share many pollen taxa. Nevertheless we identify high frequencies of Bursera laxiflora as an important component of the tropical deciduous forest. Additionally, fossil pollen was analyzed at three sites located between 1700 and 1950 m altitude at similar to 28 degrees latitude north in the Sierra Madre Occidental of northwestern Mexico. The sites were in pine-oak (Pinus-Quercus), pine, and mixed-conifer forests respectively. Shifts in the altitudinal distribution of vegetation belts were recorded for the last 12,849 cal yr BP, and climate changes were inferred. The lowest site (pine-oak forest) was surrounded by pine forest between 12,849 and 11,900 cal yr BP, suggesting a cold and relatively dry Younger Dryas period. The early Holocene was also cold but wetter, with mixed conifer forest with Abies (fir) growing at the same site, at 1700 m elevation, 300 m lower than today. After 9200 cal yr BP, a change to warmer/drier conditions caused fir migration to higher elevations and the expansion of Quercus at 1700 m. At 5600 cal yr BP Abies was growing above 1800 m and Picea (spruce) that is absent today, was recorded at 1950 m elevation. Fir and spruce disappeared from the 1950 m site and reached their present distribution (scattered, above 2000 m) after 1000 cal yr BP; we infer an episodic Holocene migration rate to higher elevations for Abies of 23.8 m/1000 cal yr and for Picea of 39.2 m/1000 cal yr. The late Holocene reflects frequent climate oscillations, with variations in the representation of forest trees. A tendency towards an openness of the forest is recorded for the last 2000 yrs, possibly reflecting human activities along with short-term climate change. (C) 2008 Elsevier B.V All rights reserved.

International audience; New palcovegetation and paleoclimatic reconstructions from the Sierra Madre Occidental (SMO) in northwestern Mexico are presented. This work involves climate and biome reconstruction using Plant Functional Types (PFT) assigned to pollen taxa. We used fossil pollen data from four Holocene peat bogs located at different altitudes (15002000 m) at the border region of Sonora and Chihuahua at around 28 degrees N latitude (Ortega-Rosas, C.I. 2003. Palinologia de la Cienega de Camilo: datos para la historia de la vegetacion y el clima del Holoceno medio y superior en el NW de la Sierra Madre Occidental, Sonora, Mexico. Master Thesis, Universidad Nacional Autonoma de Mexico, Mexico, D.F.; Ortega-Rosas, C.I., Pefialba, M.C., Guiot, J. Holocene altitudinal shifts in vegetation belts and environmental changes in the Sierra Madre Occidental, Northwestern Mexico. Submitted for publication of Palaeobotany and Palynology). The closest modern pollen data come from pollen analysis across an altitudinal transect from the Sonoran Desert towards the highlands of the temperate SMO at the same latitude (Ortega-Rosas, C.I. 2003. Palinologia de la Cienega de Camilo: datos para la historia de la vegetacion y el clima, del Holoceno medio y superior en el NW de la Sierra Madre Occidental, Sonora, Mexico. Master Thesis, Universidad Nacional Autonoma de M6xico, M6xico D.F.). An additional modem pollen dataset of 400 sites across NW Mexico and the SW United States was compiled from different sources (Davis, O.K., 1995. Climate and vegetation pattern in surface samples from and western U.S.A.: application to Holocene climatic reconstruction. Palynology 19, 95-119, North American Pollen Database, Latin-American Pollen Database, personal data, and different scientific papers). For the biontization method (Prentice, I.C., Guiot, J., Huntley, B., Jolly, D., Cheddadi, R., 1996. Reconstructing biomes from paleoecological data: a general method and its application to European pollen data at 0 and 6 ka. Climate Dynamics 12, 185-194), we modified the pollen-PFT and PFT-biomes assignation of Thompson and Anderson (Thompson, R.S., Anderson, K.H., 2000. Biomes of western North America at 18,000; 6000 and 0 14C yr BP reconstructed from pollen and packrat midden data. Journal of Biogeography 27, 555-584) for a better representation of the modem vegetation of NW Mexico. The biome reconstruction method was validated with the modem pollen sites and applied to the fossil sites. Our results show that, during the early Holocene, a cool conifer forest extended at least down to 1700 m, while today this biome is present above 2000 m in the Chihuahua state. The Younger Dryas event was recorded in one site with cold and dry conditions. The reconstructed annual temperature for this period was 3 degrees-6 degrees C colder than today, and annual precipitation was 250 mm lower than at present (900 mm/yr). The middle Holocene after 9200 cal yr BP was marked by a warming trend, reaching temperatures 2 degrees C warmer than today at 7000 cal yr BP, and by the installation of a warm mixed forest, the present day biome, at 1700 m elevation, while at higher elevations (1900 m) the cool conifer forest was still present. Summer precipitation was 200 mm/yr above the early Holocene values, suggesting that monsoon-like conditions strengthened since 9200 cal yr BP at this region. During the last 4000 yr, the same warm mixed forest was reconstructed below 1700 m and a conifer forest above 1700 m. A great variability of vegetation and climate patterns was recorded for the last 3000 yr particularly at high elevation sites where warming and cooling trends would be coeval of the Medieval warm period and Little Ice Age, likely related to ENSO variability. (c) 2007 Elsevier B.V. All rights reserved.

La Ciénega de Camilo es un humedal con Sphagnum palustre localizado en un bosque denso de pino y encino con cuatro especies de Pinus y siete de Quercus, en la Sierra Madre Occidental, en la región este de Sonora. Los análisis de polen y palinomorfos no polínicos de dos núcleos de sedimento muestran que el bosque de pino y encino ha existido en el lugar durante el último milenio. Sin embargo, hace alrededor de mil años (1058 ±60 y 870 ±70 años cal. BP (años calibrados antes del presente)), el pino era más abundante que hoy día, y además crecía una especie de pino adicional, posiblemente del grupo de Pinus strobiformis, que hoy prospera a mayores elevaciones, en un clima más fresco y húmedo. Había abundancia y diversidad de helechos. Los palinomorfos no polínicos sugieren condiciones más húmedas (presencia de Copepoda) y eu- a mesotróficas en la base, seguidas por condiciones más secas (amerosporas indiferenciadas, tipo 55A, Zygnemataceae y Pediastrum), conducentes al medio ambiente mesotrófico-ombrotrófico más reciente caracterizado por Pleospora y tipo 82E, que refleja la ciénega de Sphagnum palustre. Se infiere que hubo un período húmedo hace alrededor de 1000 años (14C BP), contemporáneo con el máximo desarrollo de las culturas arqueológicas de los desiertos Sonorense y Chihuahuense, que fue seguido por un clima progresivamente más seco y cálido.