Keck Planet Finder: design updates

The Keck Planet Finder (KPF) is a fiber-fed, high-resolution, high-stability spectrometer in development at the UC Berkeley Space Sciences Laboratory for the W.M. Keck Observatory. KPF is designed to characterize exoplanets via Doppler spectroscopy with a goal of a single measurement precision of 0.3 m s-1 or better, however its resolution and stability will enable a wide variety of astrophysical pursuits. Here we provide post-preliminary design review design updates for several subsystems, including: the main spectrometer, the fabrication of the Zerodur optical bench; the data reduction pipeline; fiber agitator; fiber cable design; fiber scrambler; VPH testing results and the exposure meter

Keck Planet Finder: design updates

The Keck Planet Finder (KPF) is a fiber-fed, high-resolution, high-stability spectrometer in development at the UC Berkeley Space Sciences Laboratory for the W.M. Keck Observatory. KPF is designed to characterize exoplanets via Doppler spectroscopy with a goal of a single measurement precision of 0.3 m s-1 or better, however its resolution and stability will enable a wide variety of astrophysical pursuits. Here we provide post-preliminary design review design updates for several subsystems, including: the main spectrometer, the fabrication of the Zerodur optical bench; the data reduction pipeline; fiber agitator; fiber cable design; fiber scrambler; VPH testing results and the exposure meter

Reading between the rings: climatic and biotic controls of shrub growth and expansion in the tundra biome

The tundra biome has undergone dramatic vegetation shifts in recent decades, which have been partly attributed to climate warming. Shrub species in particular are expanding widely throughout the Pan-Arctic region, and are involved in complex vegetation-atmosphere interactions that have important implications for the global energy balance and carbon budget. However, projections of vegetation change and associated feedbacks are complicated by the high variability in the sensitivity of shrub growth to temperature among sites and species. A mechanistic understanding of the individual-to-regional controls of climate sensitivity is therefore needed to accurately predict future vegetation change at the biome scale. This thesis quantifies the influence of environmental and ecological factors, and especially of plant-plant interactions, on the growth response of Arctic shrub communities to climate change. Climate change in the Arctic has resulted in warmer, but also longer growing seasons in many locations due to earlier snowmelt. These two factors are often treated as one single control of plant growth, but with scarce records of green-up and senescence dates for the Arctic, few studies have measured the sensitivity of shrub growth to changes in growing season length. Using radial growth time series from over 300 shrubs collected at four sites of contrasting climatic regimes and greening trajectories in Northern Canada, I measured the sensitivity of shrub growth to summer temperature and satellite-derived growing season length. I found that growing season length and summer temperature were decoupled within sites and had inconsistent effects on growth across the four sites. My findings indicate that longer and warmer growing seasons do not necessarily act as combined drivers of vegetation change across the biome. My research also demonstrated that growth at the root collar of shrubs is more climate sensitive than stem growth, possibly indicating differential internal resource allocation strategies, and highlighting the importance of standardised protocols when comparing dendroecological data across multiple sites. Individual and species traits are thought to play an important role in the response of tundra vegetation to climate change. Taller shrub species have been shown to be more climate-sensitive than dwarf shrubs, but whether this relationship holds at the individual level is unknown. I tested whether plant size, as a proxy for competitive ability, explained variation in the climate sensitivity of shrub growth using 1085 individual size and growth-ring records from 16 species at 18 sites across the tundra biome. I did not find evidence that taller shrubs were more climate sensitive, and found that height became a progressively poorer predictor of other growth dimensions at higher latitudes. This suggests that predictions of functional and structural change based on allometric equations from boreal or sub-Arctic populations may not be valid for the tundra biome as a whole. Plant-plant interactions are a strong driver of community dynamics. With increasing shrub densities in the circumpolar region, competition could have an increasingly important influence on shrub growth, potentially limiting climate-driven expansion. I found that competition with trees might slow down shrub expansion in the boreal forest biome, as the climate sensitivity of shrub growth was much lower in a boreal forest in southwest Yukon compared to shrubs growing in the alpine tundra in the same region. However, my findings did not indicate a strong control of shrub-shrub competition on growth. A canopy removal experiment did not reveal any difference in the growth rate of shrubs having experienced a decrease in aboveground competition compared to shrubs growing in intact shrub patches. Additionally, shrubs experiencing more competition were generally as climate sensitive as those with fewer or more distant neighbours, as I demonstrated through spatial analysis at four sites across the Canadian Arctic. However, their spatial arrangement, with positive size-distance relationships between pairs of neighbours, suggested that competition does play a role in the life history of these shrubs, especially at more productive sites. Finally, I found evidence of physical and chemical interference of ground vegetation on the germination of deciduous shrub seeds, indicating that interactions with other plant functional groups may control rates of shrub expansion. Shrub expansion at the plot to landscape scale has been heavily documented over multiple decades through several lines of evidence including long-term monitoring, remote sensing, and experimental studies. The increase in shrub biomass in the tundra has high certainty both in detection and in attribution to climate warming. However, my thesis highlights the complexity and variability of growth responses when using radial growth as an indicator of climate sensitivity. I detected this variability at multiple scales, from plant parts within an individual showing inconsistent climatic signals, to site-scale sensitivity responding to different facets of global change. I did not find strong or consistent influences of biotic and abiotic controls on the growth responses of tundra shrubs; however, these relationships may change over time as shrub densities continue to increase and exacerbate resource limitations. With 80% of tundra biomass potentially located below ground, understanding whole-plant and community-level responses to climate will be critical to improve projections of tundra plant community responses to global change. Understanding the different drivers of primary and secondary growth will be key to using estimates of climate sensitivity derived from growth-ring records to project biomass change and associated feedbacks across the tundra biome

Global fine-resolution data on springtail abundance and community structure

Springtails (Collembola) inhabit soils from the Arctic to the Antarctic and comprise an estimated ~32% of all terrestrial arthropods on Earth. Here, we present a global, spatially-explicit database on springtail communities that includes 249,912 occurrences from 44,999 samples and 2,990 sites. These data are mainly raw sample-level records at the species level collected predominantly from private archives of the authors that were quality-controlled and taxonomically-standardised. Despite covering all continents, most of the sample-level data come from the European continent (82.5% of all samples) and represent four habitats: woodlands (57.4%), grasslands (14.0%), agrosystems (13.7%) and scrublands (9.0%). We included sampling by soil layers, and across seasons and years, representing temporal and spatial within-site variation in springtail communities. We also provided data use and sharing guidelines and R code to facilitate the use of the database by other researchers. This data paper describes a static version of the database at the publication date, but the database will be further expanded to include underrepresented regions and linked with trait data.</p

Influence of fire prevention management strategies on the diversity of butterfly fauna in the eastern Pyrenees

Fire prevention management is becoming a necessity in many Mediterranean locations to regulate fire of natural or human origin. However, very few studies have determined the real effects of the strategies adopted on local fauna. Butterflies are sensitive to local changes and they can thus serve as indicators of environmental changes. Three different types of fire prevention management approaches in three different localities in the Eastern Pyrenees (France) were performed and the butterfly community composition was investigated. We show that of the 80 species of butterflies observed, 36 % can be considered as biological markers. An original objective treatment of data using hierarchical distance analysis combined with a neural network analysis (Self-Organizing Maps) was applied in this study. Our conclusions are that the overall number of species is maintained independently of the fire prevention type but that some important changes are observed among butterfly communities, with a clear reduction of the numbers of endemic/specialized species in favour of generalist ones for the two most drastic fire prevention management approaches studied here. The influence of such approaches is discussed on the basis of the conservation of Mediterranean species of Lepidoptera

Ecologie et biologie des arthropodes terrestres du milieu souterrain superficiel. Fonctionnement et ecologie evolutive

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : TD 84058 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Diversity of energy fluxes and interactions between arthropod communities: from soil to cave

The vertical distribution of a species may directly indicate the stage of organic matter decomposition in which it takes part. Observations have so far been limited to superficial layers, but studies on the continuum from the litter to underground biotopes, through the recently discovered superficial underground compartment, open new perspectives in the analyses of matter and energy fluxes. Sampling at different levels, from leaf litter to caves, using pitfall traps and sunken tubes, has revealed the existence of exchanges of organic matter and Arthropoda between different layers. The importation of energy from soil to cave follows two routes: passive and active. For the passive route, I measured dissolved substances in water at five levels. For the active route, I evaluated the migrations of insects and other invertebrates (downwards as well as upwards). For the analysis of arthropod communities, using the notion of functional groups, I showed the existence of link between two components, hypogean species, and endogean-epigean species, defining an ecotone along the vertical gradient ‘soil to cave’. The superficial underground compartment is not isolated, but is rather a whole food web with epigean and endogean organisms penetrating and interlinking with another web of hypogean origin

Quand le souterrain fait surface

Gers Charles. Quand le souterrain fait surface. In: Bulletin mensuel de la Société linnéenne de Lyon, 58ᵉ année, n°10, décembre 1989. pp. 325-327

Evolution de la flore, des humus et de la pédofaune associée sous l'effet de perturbations sylvicoles

TOULOUSE3-BU Sciences (315552104) / SudocBRUNOY-Bib. d'ecologie generale (911145101) / SudocSudocFranceF

Tentative de chronologie des formations superficielles du versant sud de la vallée de La Ballongue (Pyrénées ariégeoises) : Applications à la genèse du milieu souterrain superficiel

The MSS (superficial underground compartment) corresponds either to a weathering of the bedrock or to a scree slope regardless of the nature of the bedrock. One of the essential characteristics of the MSS is the presence of heterogeneous voids in the rocky material lying underneath the soil. In order to know the geodynamics and evolution, chronological markers (3 weathering and pedogenesis degrees) were researched in three terraces scraps. These degrees of weathering and pedogenesis allow to propose a slope dynamic. The formation of superficial underground compartment (MSS) appears to be dependent on this slope dynamic. The MSS is originated fiom a morphogenesis phase characterised by a cryoclasty period (Late Glacial), responsible forvoids, and followed by a pedogenesis phase beginning at the Holocene, which produced a soil above the MSS.Le milieu souterrain superficiel (MSS) correspond à un réseau de vides, constitué soit par des fissures dans les roches in situ, soit par les pores d'entassement dans les éboulis de versant. Le MSS existe lorsque roches fissurées et éboulis sont recouverts par un sol. Pour en connaître la géodynamique et l'évolution, des documents de chronologie ont été recherchés au niveau des lambeaux de terrasses, dans des faits d'altération et de pédogenèse plus ou moins intenses. Ceci a permis d'approcher une connaissance dynamique de l'évolution des versants et, par là, du MSS. En effet, pour que le MSS existe, le versant doit subir une phase de morphogenèse accompagnée d'une cryoclastie active, datant apparemment de la fin du dernier glaciaire, suivie d'une pédogenèse débutant à l'Holocène, celle-ci génère une couverture protectrice, sus-jacente, du MSS.Revel Jean-Claude, Gers Charles. Tentative de chronologie des formations superficielles du versant sud de la vallée de La Ballongue (Pyrénées ariégeoises) : Applications à la genèse du milieu souterrain superficiel . In: Quaternaire, vol. 4, n°4, 1993. pp. 175-184