No description available.

Knowledge of post-dispersal seed fates and other regeneration characteristics is crucial for predicting abundances and distributions of populations and, ultimately, community species composition and diversity. Seed fate studies, however, are rare primarily due to the difficulty of determining seed fates and causes of mortality. This thesis investigated post-dispersal seed fates for four species common to western Oregon native prairies: Bromus carinatus Hook and Am. var. carinatus, Cynosurus echinatus L., Daucus carota L., and Prunella vulgaris var. lanceolata (Barton) Fern. The general approach was to sow seeds of these species into experimentally manipulated field plots for each of two years, and to recover these seeds from the soil one year later to determine their fates (persistence, death, or establishment as seedlings). The effect of mowing on seedling establishment was also addressed. Additional studies focused on the effects of a single mortality factor, fungal disease, on seed and seedling deaths. The fate of most seeds was death (44%-80%). Few seeds established as seedlings (4%-17%), and mowing did not significantly increase seedling establishment. Only Daucus carota formed a persistent seed bank. Fungal disease generally caused less than 10% mortality. Pot studies corroborated these field results. Other investigators have suggested higher levels of disease in natural vegetation. Vertebrate predation significantly reduced seed numbers for only Bromus carinatus (21%). The largest cause of death for all species for both years was the combined group of other mortality causes (invertebrate predation, interference, and abiotic factors) (52%-73%). The components of this combined group, however, differed among species. The most likely components for Bromus carinatus and Cynosurus echinatus were interference (competition plus allelopathy) and abiotic factors, although invertebrate predation cannot be ruled out for Bromus carinatus. Seedling death due to abiotic factors was most likely the largest component for Daucus carota. The most probable components for Prunella vulgaris were invertebrate predation and abiotic factors. Implications of these findings for population patterns and for restoration of native prairies are discussed. / Graduation date: 1996

The lesser prairie chicken (Tympanuchus pallidicinctus; LPC) has declined in numbers since the late 1800s. Reasons for this decline have been attributed to habitat degradation (decreased forb and grass cover and increased woody cover) and fragmentation caused by overgrazing and conversion of native rangelands to croplands. The herbicide, Tebuthiuron, has been used extensively throughout the LPC’s range to reduce dominance of woody shrubs and allow growth of forbs and grasses. Tebuthiuron treatment of shinnery oak (Quercus havardii) rangelands has been reported as being both beneficial and detrimental to LPC populations. My study evaluated the effects of Tebuthiuran treatment of shinney oak on LPC survival, movement, and reproduction. I trapped (48), radio-tagged (38), and monitored LPC survival, movements, reproduction, and habitat use during spring and summer 2006 and 2007. I also determined potential LPC nest predators using dummy nests (domestic chicken eggs) and motion-sensitive infrared cameras. No differences were found in survival between ages, sexes, or years. Range size did not differ by age, sex, or year. Female LPC moved greater distances from lek of capture than did males. Females nested almost exclusively in non-grazed rangeland and under sand sagebrush (Artemisia filifolia). Nest-sites had higher obstruction of vision (OV), higher (%) woody cover, and lower (%) bare ground than surrounding areas. All LPC were found to use non-grazed rangeland areas more than all other vegetation types, and to use tebuthiuron-treated, grazed areas slightly more than non-treated, grazed areas. Non-grazed rangeland had higher OV than all other vegetation types. Tebuthiuron treatment lowered woody plant dominance and increased forbs and grasses. Fire reduced vegetation height and OV and increased growth of grasses and forbs, but did not kill woody vegetation as did tebuthiuron-treatment. The most common dummy nest predator found was the Chihuahuan raven (Corvus cryptoleucus).

Lesser prairie-chickens (Tympanuchus pallidicinctus) have declined throughout their range because of overgrazing and loss or fragmentation of habitat from conversion of native prairie to agricultural cropland. Lesser prairie-chickens were radio-marked (n = 225) as part of 2 separate field studies in the Texas Panhandle (2001–2003, 2003– 2007). These data were used to evaluate whether differences in demographic parameters existed between populations occurring in 2 areas dominated by different vegetation types (sand sagebrush [Artemisia filifolia] versus shinnery oak [Quercus havardii]) in the Texas Panhandle from 2001–2007. A model-selection approach was used to test hypotheses explaining differences in survival and reproductive success of lesser prairiechickens. Additionally, a population viability analysis was constructed using the above demographic parameters to evaluate effects of harvest and no harvest scenarios on viability and population persistence of lesser prairie-chickens in Texas. Overall, survival, reproduction, and population viability were lower in the shinnery oak compared to the sand sagebrush vegetation type. Lesser prairie-chicken survival differed between breeding and non-breeding periods. I estimated annual survival of lesser prairiechickens at 31% in the shinnery oak and 52% in the sand sagebrush vegetation type. Nest success was (41%, 95% CI = 25–56%) in the shinnery oak population compared to the sand sagebrush population (75%, 95% CI = 54–94%). Population viability analysis predicted continued declines in lesser prairie-chicken populations in Texas. Estimates of local occupancy indicated lesser prairie-chicken populations would go extinct in the southwestern shinnery oak vegetation type more quickly compared to the northeastern sand sagebrush vegetation type (approximately 10 years compared to 30 years, respectively) without changes in population vital rates. Harvest at all levels increased risk of extinction. Results suggest that differences in survival and reproduction of lesser prairie-chickens within sand sagebrush and shinnery oak vegetation types throughout the Texas Panhandle should be evaluated, especially during the breeding season. Improvements to vegetation conducive for successful nesting are important to the viability of lesser prairie-chickens. Conservation and recovery strategies for lesser prairie-chicken populations should address variables that increase survival and nest success and consideration of no harvest.

Thesis (M.S.)--University of Wisconsin--Stevens Point, 2003. / Includes bibliographical references (leaves 168-174).

No description available.

Grassland bird species have declined more than birds of any other region in North America, and industrial development may exert additional pressure on these species. I evaluated the effects of natural gas infrastructure on the relative abundances of grassland songbirds in southeastern Alberta, Canada using point counts at sites with well densities ranging from 0 to 20 per 1×1 mile. Generalized Linear Mixed Models were used to evaluate effects of infrastructure on birds, and parsimonious models were selected using Akaike’s Information Criterion. Vegetation near infrastructure was shorter and sparser than locations farther away, but was unlikely to have driven responses to infrastructure by birds. Gas wells may have acted as “artificial shrubs” attracting species such as vesper sparrow (Pooecetes gramineus) and western meadowlark (Sturnella neglecta) that use vegetation for perching, while other species, such as Sprague’s pipit (Anthus spragueii) and chestnut-collared longspur (Calcarius ornatus), had higher abundances farther from wells.

Grassland bird species have declined more than birds of any other region in North America, and industrial development may exert additional pressure on these species. I evaluated the effects of natural gas infrastructure on the relative abundances of grassland songbirds in southeastern Alberta, Canada using point counts at sites with well densities ranging from 0 to 20 per 1×1 mile. Generalized Linear Mixed Models were used to evaluate effects of infrastructure on birds, and parsimonious models were selected using Akaike’s Information Criterion. Vegetation near infrastructure was shorter and sparser than locations farther away, but was unlikely to have driven responses to infrastructure by birds. Gas wells may have acted as “artificial shrubs” attracting species such as vesper sparrow (Pooecetes gramineus) and western meadowlark (Sturnella neglecta) that use vegetation for perching, while other species, such as Sprague’s pipit (Anthus spragueii) and chestnut-collared longspur (Calcarius ornatus), had higher abundances farther from wells.

Thesis (M.S.)--University of Wyoming, 2007. / Title from PDF title page (viewed on June 10, 2009). Includes bibliographical references.

Thesis--Wisconsin. / Includes bibliographical references (leaves 96-99).