The black cottonwood, Populus trichocarpa, provides the foundtaion for the riparian woodlands throughout southern British Columbia (B.C.) and western Montana (MT). To study the interaction of riparian dynamics and cottonwood ecology, the present study investigated the influence of the extreme 1995 Elk River flood on the riparian zone and cottonwood ecology, and the effects of flood flow attenuation by the Libby Dam on riparian processess and cottonwoodland ecology of the Kootenai(y) River. Four river reaches were studied: the free-flowing Elk River near Fernie, B.C., the free-flowing Upper Kootenay River, B.C., upstream from the Koocanusa Reservoir, the free-flowing Fisher River, MT, near the Kootenai junction, and the flow-attenuated Lower Kootenai River near Libby, MT. Air photos from 1930, 1962, 1992 and/or 1994 revealed substantial channel change and the development of barren point bars that served as recruitment sites for willos and cottonwoods along the free-flowing reaches. Conversely, the Lower Kootenai had a relatively static channel after damming. In total, thirty-five transects were studied in 1996 and 1997 at 3 sites along each river reach to assess elevation profiles, substrate composition, scour and deposition, vegatation patterns, and aspects of cottonwood reproduction. Abundant cottonwood recruitment occurred in 1996 and even more so in 1997, producing mean densities of 153, 536, and 142 seedlings/m2 along the Elk, Upper Kootenay, and Fisher river transects, respectively. In marked contrast, no seedlings were successful along the Lower Kootenai River, downstream from the Libby Dam. The free-flowing river reaches experienced extensive sediment deposition in the riparian zone after the 1997 high water, whereas the Lower Kootenai experienced little change in stream bank configuration. The Elk River study revealed that the 1995 flood caused considerate geomorphic change and the resultant unconsolidated deposits were easily scoured and transported during the subsequent two years providing abundant sites for new cottonwoods. The Kootenay River study revealed limited meandering and deposition along the flow-attenuated Lower Kootenai River compared to the hydrologically, geomorphologically, and ecologically dynamic, free-flowing upstream reach. Along the Lower Kootenai River, there was a deficiency in black cottonwood population age structure due to limited recruitment. Flood-intolerant, upland plants have encroached to the river's edge, further eliminating cottonwood recruitment opportunities along the Lower Kootenai River. The vegetation encroachment, the static channel configuration, the minimal scour and sediment deposition and the lack of the essential stream stage pattern, combine to underlie the lack of seedling recruitment and the consequent deficiency in cottonwood population structure along the Lower Kootenai River. The studies demonstrate that black cottonwoods require a dynamic hydrologic and geomorphic system with periodic flood events for continued replenishment. The observed loss of cottonwood recruitment along the Lower Kootenai River is thus the consequence of the flood flow attenuation due to the operation of the Libby Dam. The restoration of the Lower Kootenai cottonwoods will probably rely on a partial recovery of more natural and more dynamic instream flow patterns that include occasional high flows in late spring followed by gradual stage recession. Such flows would exclude upland vegetation, recover more dynamic geomorphic processes and provide the stream stage patterns that are directly essential for cottonwood seedling recruitment. / 1 v. (various pagings) : ill. (some col.), maps ; 28 cm.

I evaluated the spatial and temporal patterns of the avian communities in the Colorado River delta, Mexico, and their relationship with vegetation type and surface water. I also developed plausible conservation and restoration guidelines for riparian areas and native birds in the region. The study included monthly point counts at 30 transects (240 points) from May 2002 to July 2003, breeding counts at 175 sites (3 times per year) during 2002 and 2003, and habitat measurements at the survey points.The most common species were Mourning Doves, Red-winged Blackbirds, and Brown-headed Cowbirds, but another 64 species were commonly found, including Verdins, Song Sparrows, Yellow-breasted Chats and Abert's Towhees. Surface water was the most important habitat feature related to avian richness and density regardless of vegetation type or land cover (P < 0.005). During summer, species richness was explained by variations in water and the cover of cottonwoods (r2 = 0.56, P < 0.001), and the variation in bird densities was explained by variations in water and the cover of willows (r2 = 0.35, P = 0.003).When comparing native versus saltcedar dominated sites, both with the presence (wet) or absence (dry) of surface water, the diversity of birds was more influenced by the presence of water than by vegetation type. Bird abundance was more influenced by vegetation type, but water also had an important effect, as wet sites had higher bird abundance than dry sites with the same vegetation type, and saltcedar wet areas had similar avian abundance to native dry sites. On all cases, the presence of water was an important factor determining the ecological value, in terms of avian richness, abundance, and diversity, of both native riparian and saltcedar areas. Saltcedar areas with surface water had avian characteristics similar to native riparian sites.The dedication of instream flows and pulse floods, the maintenance of vegetation cover and structural diversity, and an increase of older riparian stands will secure the viability of existing bird populations and will increase the probability of recovery of the species that are still extirpated from the floodplain of the Colorado River in Mexico.

The model of rejuvenation of a near-solidus crystal mush to produce large volumes of crystal-rich magma is tested here by analyzing the mineralogical, chemical, modal, and physical characteristics of the 31.1 Ma super-eruptive (2000 km3) Cottonwood Wash Tuff. It is the oldest in a series of three so-called "monotonous intermediate" ignimbrites from the Indian Peak-Caliente volcanic field in southern Utah and Nevada. A crystal-rich (~50% Pl > Qz ≈ Hbl ≈ Bt > Mag ≈ Ilm > Cpx + Zrn + Ap+ Po) dacite (62 - 69 wt% SiO2), the Cottonwood Wash Tuff is similar in age, volume, mineralogy, crystallinity, and elemental composition to the 28.0 Ma, ~5000 km3 Fish Canyon Tuff (~45% Pl + Kfs + Qz + Hbl + Bt + Ttn + Mag + Ilm + Ap + Zrn + Po, 66 - 68 wt% SiO2), used as the basis of the rejuvenation model, which suggests that magma chambers remain in a near-solidus state until a late heating event melts the magma enough to allow eruption. The Cottonwood Wash magma chamber was compositionally varied, as shown by the composition of mineral and juvenile clast compositions. Most of the whole-rock compositional variations are likely due to the variation of mineral proportions induced by shear in the magma chamber. A volumetrically minor component with evolved mineral compositionss, is represented by "evolved" juvenile clasts. Mineral compositions and experimental phase relationships show the pre-eruption magma crystallized at 800°C, 2.3 kb under water-undersaturated but oxidized conditions (delta QFM = 2.1). The majority of plagioclase and amphibole grains exhibit small-scale oscillatory zonation; where systematic compositional zonation exists, normal and reverse zonation are equally present. Cathodoluminescence of quartz reveals typically normally zoned phenocrysts with late resorption, considered to be the result of eruptive decompression. Many of the characteristics used to identify the warming of a near-solidus mush for the Fish Canyon Tuff are not present in the Cottonwood Wash Tuff [i.e., reversely zoned hornblende or plagioclase, partially remelted mineral aggregates, evidence of fluid saturation, resorption textures not related to decompression, rapakivi mantles, and hybrid andesite inclusions]. The Cottonwood Wash Tuff magma system did not undergo rejuvenation from a near-solidus state. Instead, the magma was apparently cooling and crystallizing just prior to eruption.

The model of rejuvenation of a near-solidus crystal mush to produce large volumes of crystal-rich magma is tested here by analyzing the mineralogical, chemical, modal, and physical characteristics of the 31.1 Ma super-eruptive (2000 km3) Cottonwood Wash Tuff. It is the oldest in a series of three so-called “monotonous intermediate” ignimbrites from the Indian Peak-Caliente volcanic field in southern Utah and Nevada. A crystal-rich (~50% Pl > Qz ≈ Hbl ≈ Bt > Mag ≈ Ilm > Cpx + Zrn + Ap+ Po) dacite (62 – 69 wt% SiO2), the Cottonwood Wash Tuff is similar in age, volume, mineralogy, crystallinity, and elemental composition to the 28.0 Ma, ~5000 km3 Fish Canyon Tuff (~45% Pl + Kfs + Qz + Hbl + Bt + Ttn + Mag + Ilm + Ap + Zrn + Po, 66 – 68 wt% SiO2), used as the basis of the rejuvenation model, which suggests that magma chambers remain in a near-solidus state until a late heating event melts the magma enough to allow eruption. The Cottonwood Wash magma chamber was compositionally varied, as shown by the composition of mineral and juvenile clast compositions. Most of the whole-rock compositional variations are likely due to the variation of mineral proportions induced by shear in the magma chamber. A volumetrically minor component with evolved mineral compositionss, is represented by “evolved” juvenile clasts. Mineral compositions and experimental phase relationships show the pre-eruption magma crystallized at 800°C, 2.3 kb under water-undersaturated but oxidized conditions (delta QFM = 2.1). The majority of plagioclase and amphibole grains exhibit small-scale oscillatory zonation; where systematic compositional zonation exists, normal and reverse zonation are equally present. Cathodoluminescence of quartz reveals typically normally zoned phenocrysts with late resorption, considered to be the result of eruptive decompression. Many of the characteristics used to identify the warming of a near-solidus mush for the Fish Canyon Tuff are not present in the Cottonwood Wash Tuff [i.e., reversely zoned hornblende or plagioclase, partially remelted mineral aggregates, evidence of fluid saturation, resorption textures not related to decompression, rapakivi mantles, and hybrid andesite inclusions]. The Cottonwood Wash Tuff magma system did not undergo rejuvenation from a near-solidus state. Instead, the magma was apparently cooling and crystallizing just prior to eruption.

Thesis (M.S.)--University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 7, 2007) Includes bibliographical references.

No description available.

In this research, I describe the use of false rings to reconstruct local histories of seasonal drought in riparian ecosystems in semiarid regions. In tree-ring analysis, false rings are boundary-like features often formed as a response to drought within the growing season. Drought can be a common feature in hydrologic regimes of dryland rivers but in recent decades drought has been intensifying due to climate change and increasing water use by cities, agriculture and industry. Identifying when and where water availability has decreased along the river course is critical for understanding, and therefore managing, these generally endangered ecosystems. The higher density of trees compared to instrumental data make them ideal candidates for reconstructing site-specific drought patterns.The first part of this dissertation is an observational study conducted on the San Pedro River in southeastern Arizona during 2002. I used dendrometer data and local hydrological data to show that a period of negligible radial growth in cottonwood during the middle of the growing season coincided with a channel drying event. Tree-ring core samples confirmed that false-rings had formed in each of the instrumented trees. The second part of this dissertation is an experimental study designed to evaluate the effect of different levels of water stress on false-ring formation in cottonwood and willow. I showed that experimental decreases in water availability for periods as short as ten days were enough to induce false-ring formation in willow. Longer periods of reduced water availability were generally required to induce false-ring formation in cottonwood. In the final part of this dissertation, I reconstructed false-ring occurrence in Fremont cottonwoods at three sites along the San Pedro River. I infer from false-ring frequencies that the severity of summer drought has been increasing over the last four to six decades but that the drought severity varies along a hydrological gradient. Overall, the findings in this body of research confirm that false rings in riparian tree species can be used as indicators of seasonal drought and underscore the importance of identifying site-specific responses to reduced water availability along the riparian corridor.

In this study the former mining town and present ski resort of Alta, Utah, and the Little Cottonwood Canyon (in which Alta is located) are treated as one unit of study. After a brief treatment of the natural setting, man's earliest activities in the region are traced through the winter of 1966. Activities which are examined include: exploring, trapping, logging, grazing, milling with the major emphasis upon quarrying, mining, skiing and settlement. Until 1864 the region was utilized for non-mining activities. By the 1870's, mining "boomed" and various settlements were established in the canyon. The most famous of these was Alta. Although not formally chartered, Alta was typical of frontier mining camps. Following the decline of mining, the area lay somewhat dormant until the advent of organized skiing in 1937. Now Alta's wealth is found in the snow that falls upon surrounding mountains and not in the silver that was mined from them.

Thesis (M.S.)--University of Alabama at Birmingham, 2006. / Description based on contents viewed Feb. 12, 2009; title from PDF t.p. Includes bibliographical references (p. 40-41).

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb. 24, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dr. Frank Thompson and Dr. Mickey Heitmeyer, Dissertation Supervisors. Vita. Includes bibliographical references.