Changes in frost frequency and desert vegetation assemblages in Grand Canyon, Arizona

The effect of decreasing frost frequency on desert vegetation was documented in Grand Canyon by replication of historical photographs. Although views by numerous photographers of Grand Canyon have been examined, 400 Robert Brewster Stanton and Franklin A. Nims views taken in the winter of 1889-1890 provide the best information on recent plant distribution. In Grand Canyon, where grazing is limited by the rugged topography, vegetation dynamics are controlled by climate and by demographic processes such as seed productivity, recruitment, longevity and mortality. The replicated photographs show distribution and abundance of several species were limited by severe frost before 1889. Two of these, brittlebush (Encelia farinosa) and barrel cactus (Ferocactus cylindraceus), have clearly expanded their ranges up-canyon and have increased their densities at sites where they were present in 1890. In 1890, brittlebush was present in warm microhabitats that provided refugia from frost damage. Views showing desert vegetation in 1923 indicate that Encelia expanded rapidly to near its current distribution between 1890 and 1923, whereas the expansion of Ferocactus occurred more slowly. The higher frequency of frost was probably related to an anomalous increase in winter storms between 1878 (and possibly 1862) and 1891 in the southwestern United States

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Rab11-FIP1C and Rab14 Direct Plasma Membrane Sorting and Particle Incorporation of the HIV-1 Envelope Glycoprotein Complex

The incorporation of the envelope glycoprotein complex (Env) onto the developing particle is a crucial step in the HIV-1 lifecycle. The long cytoplasmic tail (CT) of Env is required for the incorporation of Env onto HIV particles in T cells and macrophages. Here we identify the Rab11a-FIP1C/RCP protein as an essential cofactor for HIV-1 Env incorporation onto particles in relevant human cells. Depletion of FIP1C reduced Env incorporation in a cytoplasmic tail-dependent manner, and was rescued by replenishment of FIP1C. FIP1C was redistributed out of the endosomal recycling complex to the plasma membrane by wild type Env protein but not by CT-truncated Env. Rab14 was required for HIV-1 Env incorporation, and FIP1C mutants incapable of binding Rab14 failed to rescue Env incorporation. Expression of FIP1C and Rab14 led to an enhancement of Env incorporation, indicating that these trafficking factors are normally limiting for CT-dependent Env incorporation onto particles. These findings support a model for HIV-1 Env incorporation in which specific targeting to the particle assembly microdomain on the plasma membrane is mediated by FIP1C and Rab14. © 2013 Qi et al.Link_to_subscribed_fulltex

A Debt to the Future: Scientific Achievements of the Desert Laboratory, Tumamoc Hill, Tucson, Arizona

In 1903 the Carnegie Institution of Washington established a Desert Laboratory on Tumamoc Hill, Tucson, Arizona. For the next thirty -seven years the Desert Laboratory was the site of pioneering research into the biology and ecology of desert plants and animals. The more than sixty scientists who worked on Tumamoc Hill published some 350 papers and books based on research there. William A. Cannon and Volney M. Spalding share credit for successfully launching the new facility. Daniel T. Mac - Dougal, who became the first director in 1906, hired an enthusiastic, able staff and recruited many visiting scientists. His untiring promotional efforts gave the laboratory a national reputation, and when he transferred his research projects to a second laboratory at Carmel, California, the Desert Laboratory entered a nine -year decline. Promotion of Forrest Shreve to head the laboratory in 1928 brought about a renewed focus on the ecology of desert plants. The Carnegie Institution closed the facility in 1940, ostensibly because of the depression and consequent financial cutbacks, but actually because institution administrators no longer found it worthwhile to support descriptive ecological research.Desert Plants is published by The University of Arizona for the Boyce Thompson Southwestern Arboretum. For more information about this unique botanical journal, please email the College of Agriculture and Life Sciences Publications Office at [email protected]

Reproductive Potential and Minimum Reproductive Size of Ferocactus wislizeni (Cactaceae)

Desert Plants is published by The University of Arizona for the Boyce Thompson Southwestern Arboretum. For more information about this unique botanical journal, please email the College of Agriculture and Life Sciences Publications Office at [email protected]

The Making of a Flora for Arizona, 1901-1951, or, Why Arizona Flora is Published by the University of California

Desert Plants is published by The University of Arizona for the Boyce Thompson Southwestern Arboretum. For more information about this unique botanical journal, please email the College of Agriculture and Life Sciences Publications Office at [email protected]

Plant Geography of Southwestern Sand Dunes

Patterns of plant distribution among eight dune fields in the southwestern USA and northwestern Mexico are analyzed and discussed. Each dune flora is characterized by three to five geographic components; the regional flora in which each dune field occurs is the dominant component. Endemic species, that is, species restricted to sand dunes, comprise ten percent or more of five of the eight floras. All possible combinations of the eight dune floras taken two at a time (28 pairs) were analyzed using Sorensen's similarity index. Only seven have a similarity value of 0.200 or greater. The lack of similarity among dune floras is due in part to their distribution among four floristically distinct biogeographic provinces and in part to localized recruitment of species from adjacent, non -dune plant communities. Geographic, edaphic and temporal barriers to dispersal and establishment also promote high dissimilarity among the eight floras. Eighty -three of the 533 species composing the eight dune floras are either endemic to sand dunes or occur at three or more of the dune fields studied. These 83 species fall into two subgroups: a group of 36 species characteristic of southwestern sand dunes east of 113° Longitude, and a group of 57 species characteristic of sand dunes west of 113° Longitude. Ten species are common to both groups. In the Southwest, dune fields are habitat islands, but dune floras do not behave in all respects as predicted by the MacArthur and Wilson theory of island biogeography. Southwestern sand dunes are not now floristic islands, but additional insular characteristics may develop over time.Desert Plants is published by The University of Arizona for the Boyce Thompson Southwestern Arboretum. For more information about this unique botanical journal, please email the College of Agriculture and Life Sciences Publications Office at [email protected]

A Career of Her Own: Edith Shreve at the Desert Laboratory

Desert Plants is published by The University of Arizona for the Boyce Thompson Southwestern Arboretum. For more information about this unique botanical journal, please email the College of Agriculture and Life Sciences Publications Office at [email protected]

Catastrophic Freezes in the Sonoran Desert

Desert Plants is published by The University of Arizona for the Boyce Thompson Southwestern Arboretum. For more information about this unique botanical journal, please email the College of Agriculture and Life Sciences Publications Office at [email protected]

A Debt to the Future: Achievement of the Desert Laboratory, Tumamoc Hill, Tucson, Arizona

In 1903 the Carnegie Institution of Washington established a Desert Laboratory on Tumamoc Hill, Tucson, Arizona. For the next thirty-seven years the Desert Laboratory was the site of pioneering research into the biology and ecology of desert Plants and animals. More than sixty scientists who worked on Tumamoc Hill published some 350 papers and books based on research there. William A. Cannon and Volney M. Spalding share credit for successfully launching the new facility. Daniel T. MacDougal, who became the first director in 1906, hired an enthusiastic, able staff and recruited many visiting scientists. His untiring promotional efforts gave the laboratory a national reputation, and when he transferred his research projects to a second laboratory at Carmel, California, the Desert Laboratory entered a nine year decline. Promotion of Forrest Shreve to head the laboratory in 1928 brought about a renewed focus on the ecology of desert plants. The Carnegie Institution closed the facility in 1940, ostensibly because of the depression and consequent financial cutbacks, but actually because institution administrators no longer found it worthwhile to support descriptive ecological research.Desert Plants is published by The University of Arizona for the Boyce Thompson Southwestern Arboretum. For more information about this unique botanical journal, please email the College of Agriculture and Life Sciences Publications Office at [email protected]