Treesearch

Basin wildrye [Leymus cinereus (Scribn. & Merr.) Á. Löve] and creeping wildrye [Leymus triticoides (Buckley) Pilg.] are outcrossing perennial grasses native to western North America. These divergent species are generally adapted to different habitats but can form fertile hybrids. Cultivars of both species are used in agriculture and conservation, but little is known about genetic diversity and gene flow among these species. Therefore, multilocus amplified fragment length polymorphism (AFLP) genotypes and chloroplast DNA sequences were evaluated from 536 L. cinereus and 43 L. triticoides...

Sunflower family (Asteraceae). Bigflower agoseris is a short lived perennial forb from a simple or branched taproot. The stems and leaves contain a white milky juice. The leaves are all basal with the flower heads solitary on a naked scape. Leaves are 8 to 25 cm (3 to 10 in) long and 1 to 3 cm (0.4 to 1.2 in) wide, oblanceolate pinnatifid to nearly entire. The flowering stems are 15 to 45 cm (6 to 18 in) tall (Welsh et al. 2003). The floral heads are made of numerous yellow ray flowers (similar to a dandelion). Flowering occurs in spring. The fruit is an achene with a 4 to 7 mm (0.16 to...

During the historic Lewis and Clark expedition, Meriwether Lewis wrote on 20 July 1805, "I saw a black woodpecker (or crow) today it is a distinct species of woodpecker; it has a long tail and flys a good deal like the jay bird" (sic, Thwaites 1905). Subsequent observations of flight and vocalization reminded him of the Red-headed Woodpecker (Melanerpes erythrocephalus) he knew from his home in Virginia. A few years later the ornithologist Alexander Wilson, working with skins that Lewis and Clark's expedition had provided, described this species in his American Ornithology and named it...

Western North American forests are shaped by natural disturbances, which are an important driver of habitat heterogeneity and species diversity. Wildfire and bark beetle infestations are of particular interest to resource managers because of their widespread occurrence and potential economic impacts. These naturally occurring disturbances create habitat for numerous wildlife species, which benefit from abundant food resources in the form of beetle larvae, increased nesting opportunities in dead and dying trees, and increased forage production though reductions in canopy cover. Despite...

Norway spruce is one of the most important conifer tree species in Europe, paramount for timber provision, habitat, recreation, and protection of mountain roads and settlements from natural hazards. Although natural Norway spruce forests exhibit diverse structures, even-aged stands can arise after disturbance or as the result of common silvicultural practice, including off-site afforestation. Many even-aged Norway spruce forests face issues such as senescence, insufficient regeneration, mechanical stability, sensitivity to biotic disturbances, and restoration. We propose the use of Density...

Aspen populations in the south-western portion of the range are consistent with expectations for a historically stable edge, with low within-population diversity, significant geographical population structuring, and little evidence of northward expansion. Structuring within the southwestern cluster may result from distinct gene pools separated during the Pleistocene and reunited following glacial retreat, similar to patterns found in other forest tree species in the western USA. In aspen, populations in the southwestern portion of the species range are thought to be at particularly high...

This study examined the effects of organisational, environmental, group and individual characteristics on five components of safety climate (High Reliability Organising Practices, Leadership, Group Culture, Learning Orientation and Mission Clarity) in the US federal wildland fire management community. Of particular interest were differences between perceptions based on respondents' Incident Position. Those in supervisory positions at the ground level (Type 1 Firefighters) and those at the top (Incident Commanders and operational leads) scored significantly higher than did midlevel superviso...

Falcaria vulgaris Bernh. (sickleweed), native to Eurasia, occurs disjunctly in the Midwest and the East Coast of the United States. In parts of Iowa, Nebraska and South Dakota, it is an aggressive weed potentially turning to invasive. The main objectives of this study were (1) to reconstruct the introduction history and spread of the plant, (2) to develop and apply molecular markers to study the genetics of sickleweed populations in the United States. I used herbarium records and a suite of molecular markers to accomplish the project objectives. I surveyed 178 US herbaria, including those...

Falcaria vulgaris (sickleweed) is native to Eurasia and a potential invasive plant of the United States. No molecular markers have been developed so far for sickleweed. Characterization of molecular markers for this plant would allow investigation into its population structure and biogeography thereby yielding insights into risk analysis and effective management practices of the plant. In order to characterize the molecular markers, DNA samples were collected from eight populations in Iowa, Nebraska and South Dakota. Nuclear microsatellite markers developed for other Apiaceae taxa were...

We report the first detailed field survey of sickleweed (Falcaria vulgaris L.) in the United States. Sickleweed is native to Europe, the Mediterranean, Asia Minor, and Iran and was first reported in the United States in 1922. It is listed by the Nebraska Invasive Species Council as a Category II invasive plant species. In recent years, abundance and distribution of sickleweed has increased dramatically in and around the Fort Pierre National Grassland (FPNG), South Dakota. Management of such a rapidly expanding population is hampered by a general lack of baseline information on the biology...