63 research outputs found
Ips Pini (Curculionidae: Scolytinae) is a Vector of the Fungal Pathogen, Sphaeropsis Sapinea (Coelomycetes), to Austrian Pines, Pinus Nigra (Pinaceae)
Sphaeropsis sapinea (Fr.:Fr.) Dyko and Sutton, is among the most common and widely distributed pathogens of conifers worldwide. S. sapinea is disseminated over short distances by rain splash and moist wind, but significant knowledge gaps regarding long-range dispersal remain. Our objective was to determine whether or not the pine engraver beetle, Ips pini Say, is a vector of the pathogen onto Austrian pines (Pinus nigra Arnold). In 2004 and 2005, individuals of I. pini were collected with pheromone traps at two locations in central Ohio (197 and 1,017 individuals for 2004 and 2005, respectively) and screened for the presence of S. sapinea. In the field, fresh logs of Austrian pine were baited with pheromone lures, mechanically wounded, or left undisturbed. After 2 mo, logs were evaluated for insect feeding and the presence of S. sapinea along beetle galleries. Fresh logs were also inoculated in the greenhouse with adult I. pini that were either artificially infested or uninfested with S. sapinea spores to determine vectoring potential. Phoresy rates for individual collections ranged from 0 to 4.1%; average rates were 1.5 and 2.0% for 2004 and 2005, respectively. Isolation frequencies of S. sapinea from baited (15 ± 5%) and unbaited logs (3 ± 1%) differed significantly (P = 0.009). I. pini was also capable of transmitting the pathogen under controlled conditions. Based on phoresy rates, association, and artificial inoculation studies, we conclude that I. pini is able to transmit S. sapinea to Austrian pine stems
Toward an internally consistent astronomical distance scale
Accurate astronomical distance determination is crucial for all fields in
astrophysics, from Galactic to cosmological scales. Despite, or perhaps because
of, significant efforts to determine accurate distances, using a wide range of
methods, tracers, and techniques, an internally consistent astronomical
distance framework has not yet been established. We review current efforts to
homogenize the Local Group's distance framework, with particular emphasis on
the potential of RR Lyrae stars as distance indicators, and attempt to extend
this in an internally consistent manner to cosmological distances. Calibration
based on Type Ia supernovae and distance determinations based on gravitational
lensing represent particularly promising approaches. We provide a positive
outlook to improvements to the status quo expected from future surveys,
missions, and facilities. Astronomical distance determination has clearly
reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press
(chapter 8 of a special collection resulting from the May 2016 ISSI-BJ
workshop on Astronomical Distance Determination in the Space Age
Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
We review HB stars in a broad astrophysical context, including both variable
and non-variable stars. A reassessment of the Oosterhoff dichotomy is
presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of
globular clusters (GCs) in the HB morphology-metallicity plane both exclude,
with high statistical significance, the possibility that the Galactic halo may
have formed from the accretion of dwarf galaxies resembling present-day Milky
Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the
second-parameter problem is presented. A technique is proposed to estimate the
HB types of extragalactic GCs on the basis of integrated far-UV photometry. The
relationship between the absolute V magnitude of the HB at the RR Lyrae level
and metallicity, as obtained on the basis of trigonometric parallax
measurements for the star RR Lyrae, is also revisited, giving a distance
modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are
studied. Finally, the conductive opacities used in evolutionary calculations of
low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and
Space Scienc
Consistent patterns of common species across tropical tree communities
Trees structure the Earthâs most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10âcm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earthâs 800 billion tropical trees with trunk diameters of at least 10âcm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the worldâs most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees
Corrigendum to "Biochar effects on methane emissions from soils: A meta-analysis" : [Soil Biol. Biochem. 101 (2016) 251-258]
Corrigendum to âBiochar effects on methane emissions from soils: AÂ meta-analysisâ [Soil Biol. Biochem. 101 (2016) 251â258]
An old puzzle in a new light: PG 1336-018
Contains fulltext :
35118.pdf (publisher's version ) (Open Access)We present the first preliminary results from VLT photometric and spectroscopic observations of PG 1336-018, a rapidly pulsating eclipsing sdB binary
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