2,380 research outputs found
Population status and habitat preferences of critically endangered Dipterocarpus littoralis in West Nusakambangan, Indonesia
The conservation of the endemic tree species Dipterocarpus littoralis (Bl.) Kurz. is hampered by the paucity of information on its population biology and ecology. Consequently, a targeted survey was carried out in the West Nusakambangan Nature Reserve to assess its population size and structure as well as habitat preferences. In total, 676 individuals of D. littoralis were located at 52 locations, with an extent of occurrence of 3.66 km2 and an area of occupancy of 1.71 km2. The population had an inverse-J-shaped distribution of diameter at breast height (DBH), with 63% of individuals in the 0-5 cm class and another 21% in the 5-10 cm class; only 11 (1.6%) mature individuals (DBH≥30) were found. D. littoralis was associated with steep, low, southwest-facing sites and sites that had high litter cover and thickness. Illegal logging and fuel-wood chopping were the main threats to D. littoralis and its habitat. In addition, an invasive shrub, Langkap (Arenga obtusifolia, Arecaceae), was a potential competitor with the seedlings throughout the reserve. In view of its endemism, narrow range and localized distribution, small population, environmental preferences, and the severe threats from anthropogenic activities and invasive species, D. littoralis appears to more than justify its conservation status of Critically Endangered
Analysis of 1995 survey data. Phase 2 post survey appraisal. R&D progress report EMA 036/pr4 for the period from 1st November 1998 to 31st January 1999
Discovery of 11 New T Dwarfs in the Two Micron All-Sky Survey, Including a Possible L/T Transition Binary
We present the discovery of 11 new T dwarfs, found during the course of a
photometric survey for mid-to-late T dwarfs in the 2MASS Point Source Catalog
and from a proper motion selected sample of ultracool dwarfs in the 2MASS
Working Database. Using the NASA Infrared Telescope Facility SpeX spectrograph,
we obtained low-resolution (R~150) spectroscopy, allowing us to derive
near-infrared spectral types of T2-T8. One of these new T dwarfs, 2MASS
J13243559+6358284, was also discovered independently by Metchev et al., in
prep. This object is spectroscopically peculiar and possibly a binary and/or
very young (<300 Myr). We specifically attempted to model the spectrum of this
source as a composite binary to reproduce its peculiar spectral
characteristics. The latest-type object in our sample is a T8 dwarf, 2MASS
J07290002-3954043, now one of the four latest-type T dwarfs known. All 11 T
dwarfs are nearby given their spectrophotometric distance estimates, with 1 T
dwarf within 10 pc and 8 additional T dwarfs within 25 pc, if single. These new
additions increase the 25 pc census of T dwarfs by ~14%. Their proximity offers
an excellent opportunity to probe for companions at closer separations than are
possible for more distant T dwarfs.Comment: 45 pages, 9 figures, 9 tables. Published in AJ. Replacement: Fixed
typos in 3 tables (some reported photometry was from the 2MASS Working
Database instead of the 2MASS All Sky Catalog) and updated Fig.
Serendipitous Discovery and Parallax of a Nearby L Dwarf
A field star serendipitously observed in a parallax program proved to have a
proper motion of 562 mas/yr and a parallax of 82 +- 2 mas. The star is
identified with 2MASS J07003664+3157266. A Keck LRIS spectrum shows its
spectral type to be L3.5, as expected from its infrared and optical colors and
absolute magnitude. This object had not been previously recognized as an L
dwarf, perhaps because of crowding at its relatively low Galactic latitude (b =
+15.8 degrees).Comment: PASP, in press. 8 pages incl.2 postscript figures, plus one jpeg
figur
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