Encroachment of woody plants has occurred in many of the world's grasslands within the past 3 centuries. Mechanisms underlying these physiognomic shifts have not been adequately described. My objectives were to elucidate the roles of interference, herbivory, acorn maturation date and timing of precipitation on emergence and survival of Emory oak (Quercus emoryi Torr.) at lower treeline; and to evaluate how different frequencies of monitoring influence the results of demographic studies with woody plants. Seedling emergence was negatively affected by delays in precipitation and decreased soil moisture content. Seedling survival was negatively affected by overstory and understory interference and vertebrate herbivory. Most seedling mortality was attributed to desiccation. Woody plants should be monitored at least monthly to evaluate emergence and survival after one year. These results indicate that abiotic constraints are the primary factors structuring southwestern oak woodlands and savannas.

I monitored and recorded human activities in bighorn sheep habitat to determine the role of human activity in the decline of an indigenous population of bighorn sheep in the Pusch Ridge Wilderness, Santa Catalina Mountains, Arizona. I recorded hiker activity, sound levels, presence of dogs, and hunting activity in off-trail areas of bighorn sheep habitat from June 1995 to June 1996. Eighteen percent of hiker-groups entering the study area hiked off-trails in bighorn sheep habitat, and 8% were accompanied by dogs. Although I observed very little hunting activity in the area, noise disturbance may be a factor in the decline of the population. The cumulative affect of these and other activities probably contributed to the decline of the herd.

I examined the efficacy of a mitigation project in Avra Valley, Arizona that was established to provide wildlife access across the barrier created by the Central Arizona Project aqueduct. I monitored movements of 17 radiocollared desert mule deer (Odocoileus hemionus crooki) to determine if deer were using the corridor for access across the aqueduct and the 26 km wide valley. I also examined deer use of vegetation associations and proximity to landscape features. Four deer crossed the canal but stayed within 500 m of the crossing site. One deer traversed the valley via the corridor. Overall, 22.4% of deer locations were in the corridor land system. Female mule deer generally used the mesquite (Prosopis velutina)-burroweed (Isocoma tenuisecta) vegetation association more than it was available and the palo verde (Cercidium spp.)-mixed cacti association less than it was available. Female deer were generally closer to the CAP, housing developments, roads, and permanent water than random points.

I surveyed parts of Tucson, Arizona to determine numbers of burrowing owl (Speotyto cunicularia) burrows present, identify characteristics associated with burrow sites, and assess reproductive success. I measured habitat characteristics at 48 winter, 58 breeding, and 48 random burrows. Random burrows were closer to perches (P) and farther from wash banks (P) than were active burrows, and had smaller entrance dimensions (P). Winter burrows were farther from human activity than were breeding burrows (P). Active sites had less total vegetation, and less visual obscurity than did random sites. Owls may have selected open sites to facilitate detection of predators or prey. Urbanization sometimes created conditions which appeared to attract owls, but also destroyed burrows. An average of 2.31 young fledged from 116 active burrows during 1997-1998. While comparable to other studies of burrowing owls occupying urban environments, this was lower than rates typically reported for the species.

<p> Lightweight thermal paper (LWTP) is a noteworthy import commodity with wide usage and large import value in the United States. In this study, the trade pattern and market dynamics of the LWTP import market in the U.S. has been examined based on almost ideal demand system. The results revealed that both the trade volume and import source of LWTP had changed during last decade. Competition relationships were found among major suppliers in both the short run and long run, and the long-run competition is stronger than that in the short run. The repeal of restriction on conducting countervailing investigation against non-market economy temporarily stimulated the import of LWTP products from China, but the following antidumping/countervailing investigation and the corresponding punitive duties generated trade depression effect on the imports. In addition, positive trade diversion effect was found on German products, which raises doubt on the effectiveness of this trade remedy policy. </p>

<p>Oak (<i>Quercus</i>) forests in the Arkansas Ozarks have been important culturally, ecologically and environmentally for centuries. Historically these forests were fire dependent and dominated by oak species. In the past century, fire suppression and land management have caused these forests to densify. As a result, oaks are increasingly less abundant following disturbance in natural hardwood stands. Many applied ecological studies have explored methods and practices to maintain oak species in newly developing stands. This study attempted to link the mechanistic physiology of oak and non-oak reproduction to the applied ecological work. Varying stand conditions were generated in an undisturbed mature hardwood forest. Photosynthesis physiology was evaluated through direct and in-direct measures for six upland hardwood species in the Springfield Plateau of the Arkansas Ozarks. Environmental conditions, including sunlight canopy penetration, were significantly different based on treatment/slope position combinations. Corresponding differences in photosynthesis, development and abundance of hardwood reproduction were also significant across treatments, topographic position, and species. In conclusion, this study demonstrates that <i>in situ</i> measurements of photosynthetic performance are a valuable tool in predicting stand performance in oaks growing in their natural environment. </p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3273. Adviser: Edward J. Heske. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Expanding urbanization into undisturbed Sonoran Desert vegetation has led to public concern over the removal and destruction of large saguaro cacti (Carnegia gigantea). Development mitigation plans were established requiring transplantation, salvage and replacement of saguaros in certain development sites. However, no research has assessed whether native birds use transplanted saguaros at the same rate as non-transplanted cacti. The objective of this study was to determine the effects of saguaro transplantation on nest use. In Tucson, Arizona, 87 transplanted and 28 non-transplanted saguaros on a developed site and 26 non-transplanted saguaros on an undisturbed site were selected for observation of bird nesting activity during the breeding seasons of 1997 and 1998. Birds showed a preference for saguaros, transplanted or non-transplanted, which were surrounded by native vegetation and in areas with low human activity. I suggest that guidelines be revised for development mitigation standards and saguaro transplanting.

Ponderosa pine (Pinus ponderosa Laws.) forests have changed considerably during the past century, partly because recurrent fires have been absent for a century or more. In dense stands of ponderosa pine in the Black Hills of South Dakota, a layer of pine needles has replaced understory vegetation. I examined the disturbance history, soil seed bank, and effects of prescribed burning and overstory reduction on understory vegetation in a ponderosa pine stand in the northern Black Hills. Cessation of fires, prolific ponderosa pine regeneration, and logging led to a dense, even-aged stand with very little understory vegetation and few viable seeds in the soil seed bank. Understory vegetation did not respond to restoration treatments the first growing season, but did respond the second growing season. Paucity of viable seeds in the soil seed bank does not appear to constrain recruitment of understory vegetation in dense ponderosa pine forests of South Dakota.

I studied bat activity at 13 artificial and 4 natural water sources in southern Arizona from May 1995 through August 1996 using mist-nets and ultrasonic detectors. I used 2 indices of bat activity, capture rates, calculated from mist-netting data, and bat passes/30 minutes, calculated from ultrasound data. Both methods provided similar information on temporal patterns of bat activity. Indices of bat activity were highest during the reproductive season (May through August) compared to the non-reproductive season (September through April). Bat activity did not differ between any of the 2-week time periods within the reproductive season. During the reproductive season, bat activity was bimodal with peaks during the first 2 hours after sunset and the 2 hours preceding sunrise. During the non-reproductive season, bat activity was unimodal, with the majority of activity occurred within 2 hours of sunset. I captured six bat species within the study area. Sex ratios tended to be male biased during the non-reproductive season but close to 1:1 during the reproductive season. Sex ratios did not differ between natural and artificial water sources for any of the bat species compared. Age ratios did differ significantly between natural and artificial water sites. A higher percentage of the total captures at natural water sources were juveniles compared to artificial water sources, possibly indicating higher reproductive output in areas surrounding natural sites. Indices of activity during the reproductive season were significantly higher at natural compared to artificial water sources. However, this difference was not due to higher insect biomass at natural water sources. I developed stepwise multiple regression models to explain variation in bat activity and species richness at water sources. Elevation, type of water source and distance to the nearest cliff or rock outcrop were significant variables in explaining variation in overall capture rates at water sources. Type of water source was the only significant variable explaining variation in ultrasonic activity (passes/30 min), while distance to the nearest source of permanent water and size of the water source explained 33% of the variation in species richness.