This dissertation investigates the structure and topological properties of cyclicallypresented groups. First, a family of groups called groups of type Z is considered. Withfew exceptions, the finiteness, asphericity, fixed point, and 3-manifold spine problemsare solved. Most groups of type Z have a central element of infinite order fixed by theshift....
The spread of medusahead across the western United States has severe implications for a wide range of ecosystem
services. Medusahead invasion reduces biodiversity, wildlife habitat and forage production, and often leads to
increased fire frequency and restoration costs. Medusahead is problematic in the Intermountain West and California
Annual Grasslands. The...
Many exotic annual grasses are believed to increase wildfire frequency to the detriment of native vegetation
by increasing fine fuels and thus, creating a grass-fire cycle. However, information on differences in fuel characteristics
between invaded and non-invaded plant communities is lacking, or is based mainly on speculation and anecdotal evidence....
Several factors currently threaten blue crab (Callinectes sapidus) in the Chesapeake Bay. In addition to poor water quality, degraded habitat, and shifting environmental conditions, derelict gear has recently been recognized as a significant source of mortality for this economically and culturally significant species. From 2008 through 2014, commercial watermen in...
This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the National Academy of Sciences and can be found at: https://doi.org/10.3141/2463-01
Medusahead (Taeniatherum caput-medusae [L.] Nevski), an exotic annual grass, is rapidly spreading and
causing ecological damage across the western United States. Because this exotic plant occupies vast areas and because
management resources are limited, it is critical that land managers prioritize where they direct treatment and monitoring
efforts. Identifying where...
Restoration of exotic annual grass-invaded rangelands is needed to improve ecosystem function and services.
Increasing plant species richness is generally believed to increase resistance to invasion and increase desired
vegetation. However, the effects of species richness and individual plant life forms in seed mixes used to restore
rangelands invaded by...
Monotypic stands of crested wheatgrass (Agropyron cristatum [L] Gaertm. and Agropyron desertorum [Fisch.] Schult.), an
introduced grass, occupy vast expanses of the sagebrush steppe. Efforts to improve habitat for sagebrush-associated wildlife by
establishing a diverse community of native vegetation in crested wheatgrass stands have largely failed. Instead of concentrating
on...
Medusahead (Taeniatherum caput-medusae [L.] Nevski) is an exotic annual grass invading western rangelands. Successful
revegetation of invaded-plant communities can be prohibitively expensive because it often requires iterative applications of
integrated control and revegetation treatments. Prescribed burning has been used to control medusahead and prepare seedbeds
for revegetation, but burning has...
Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis [Beetle & A. Young] S.L. Welsh) plant communities with degraded native herbaceous understories occupy vast expanses of the western United States. Restoring the native herbaceous understory in these communities is needed to provide higher-quality wildlife habitat, decrease the risk of exotic plant invasion,...