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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

The effects of fire and salvage logging on early post-fire succession in mixedwood boreal forest communities of Saskatchewan

Guedo, Dustin C 13 September 2007
This study compared the effects of fire severity and salvage logging on early successional vegetation in the mixedwood boreal forest upland of Saskatchewan. The effects of salvage logging on post-fire forest stands are poorly understood. Few studies have investigated the short-term effects of salvage logging on the regeneration of boreal plant species or the long-term impact on overall forest composition and diversity. This study examines salvage logged and wildfire leave stands across three burn severity classes (no burn, low/moderate burn, and high burn) over two time periods (1 year post-fire and 10 years post-fire). The results indicate that salvage logging has a significant impact on the early regeneration of burned mixedwood boreal plant communities with the effect still evident in forest stands ten years post-fire. Salvage logging has long-lasting residual effects on boreal forest plant community development. Salvage logging one year post-fire reduced the number, diversity, and abundance of species within each of the burn severities, creating a less abundant and simplified plant community. It was also shown that salvage logging one year post-fire tended to create more homogenous plant communities similar to those communities typical of areas of moderate burn severity, constraining the effects of burn severity and decreasing the range of the vegetation communities. These findings are less pronounced, but still evident, within salvage logged stands ten years post-fire as three regrowth cover types have developed, characterised by no disturbance, moderate disturbance either by fire or salvage logging, and severe disturbance. The convergence of plant community characteristics between burn severity classes across logging treatments suggests that the effects of salvage logging do not have long lasting effects within areas of high burn severity.
32

Diversity of birds in relation to area, vegetation structure and connectivity in urban green areas in La Paz, Bolivia

Hiding, Camilla January 2012 (has links)
With a   growing human population, cities keep growing worldwide altering ecosystem   and thereby affecting the species living in these areas. Most studies of   urbanization and its effect on ecosystem have been conducted in the western   world and little is known about its effect in the neotropical part of the   world. I examined effects of fragment size, vegetation structure and   connectivity of urban green areas on bird species richness, mean abundance,   diversity and biomass in La Paz, Bolivia. Additionally, the effects of   different disturbance variables on bird community were evaluated. In total,   36 bird species were found in 24 fragment of varying size, connectivity and   level of disturbance. Bird species richness decreased with increasing   disturbance while connectivity and fragment size did not contribute   significantly to explain the variation in species richness at count point scale (p>0.005, multiple linear regression). At fragment   scale, however, species richness increased with fragment sizes,   which has been shown in other studies from neotrophical regions. Variation in   abundance, diversity or biomass could not be explained by connectivity,   fragment size or disturbance.     Furthermore, coverage of construction had a negative effect on species   richness while coverage of bushes and coverage of herbs were negatively   related to biomass and diversity, respectively. The composition of bird   species differed with size and disturbance of the fragments, so that more   omnivorous and granivorous species such as Zonotrichia capensis, Turdus chiguanco and Zenaida auriculata, were present in areas highly affected by human activities. Larger fragments,   less affected by human presence held a larger proportion of insectivorous   species.
33

The effects of fire and salvage logging on early post-fire succession in mixedwood boreal forest communities of Saskatchewan

Guedo, Dustin C 13 September 2007 (has links)
This study compared the effects of fire severity and salvage logging on early successional vegetation in the mixedwood boreal forest upland of Saskatchewan. The effects of salvage logging on post-fire forest stands are poorly understood. Few studies have investigated the short-term effects of salvage logging on the regeneration of boreal plant species or the long-term impact on overall forest composition and diversity. This study examines salvage logged and wildfire leave stands across three burn severity classes (no burn, low/moderate burn, and high burn) over two time periods (1 year post-fire and 10 years post-fire). The results indicate that salvage logging has a significant impact on the early regeneration of burned mixedwood boreal plant communities with the effect still evident in forest stands ten years post-fire. Salvage logging has long-lasting residual effects on boreal forest plant community development. Salvage logging one year post-fire reduced the number, diversity, and abundance of species within each of the burn severities, creating a less abundant and simplified plant community. It was also shown that salvage logging one year post-fire tended to create more homogenous plant communities similar to those communities typical of areas of moderate burn severity, constraining the effects of burn severity and decreasing the range of the vegetation communities. These findings are less pronounced, but still evident, within salvage logged stands ten years post-fire as three regrowth cover types have developed, characterised by no disturbance, moderate disturbance either by fire or salvage logging, and severe disturbance. The convergence of plant community characteristics between burn severity classes across logging treatments suggests that the effects of salvage logging do not have long lasting effects within areas of high burn severity.
34

A Study of Plant Species Richness in Taiwan Forestry Research Institute Tai-Ma-Lee Experimental Forest

Tzi, Ting-Yi 21 July 2005 (has links)
Many ecologists are struggling to quantify the species richness in a particular landscape or region. The number of species increases with sample area. Species-area relationship is often used to estimate species richness of a particular region. This study used species-log (area) curves, corrected with Jaccard¡¦s coefficients for within-vegetation type heterogeneity, to estimate species richness and to describe vascular plant species composition in Taiwan Forestry research Institute Tai-Ma-Lee Experimental Forest. In the study area, the author recorded 748 plant species, including 98 endemic species, 21 rare species and 36 naturalized species. There are estimation of 701 species (95¢H CI¡×651~758 species) in the 583-ha natural forest area, 819 species (95¢H CI¡×744~889 species) in the 291-ha plantation area, 560 species (95¢H CI¡×508~641 species) in 8.1-ha forest road. As plantation area is not well-sampled, the total species number in the 947-ha study area could not be estimated. When use 0.1 Modified-Whittaker sampling techniques to assess plant diversity, it is possible to use elevation division, instead of vegetation type, to estimate species richness.
35

Adaptive Diversification of Interaction Networks

Stegen, James January 2009 (has links)
Understanding the processes responsible for gradients in biodiversity is a central goal of ecological research. In order to elucidate the processes responsible for community assembly and structure, it is useful to adopt a functional trait approach to community ecology. This is because species names provide little information regarding how constituent species interact. In addition, assembly rules based on species names are likely to become intractably complex with increasing species richness but rules based on traits can provide simple, broadly applicable. In turn, generality is gained by emphasizing functional traits. Here I first build from a previously published model that merged metabolic theory with a model of community evolution and assembly to derive a general assembly rule based on a continuous functional trait and compare this rule with a broad suite of empirical data (Chapter 1). However, linking metabolism to macroevolutionary rates and patterns has thus far been limited to non-ecological, static models. These models are not inconsistent with empirical data, but are relatively limited in their predictive ability (Chapter 2). I thus next develop a fully dynamic `metabolic theory of biodiversity' (MTB) that explicitly implements the qualitative framework proposed in Allen et al. (2007). With this model I examine the influence of temperature dependent mutation rate on speciation rate, extinction rate and species richness (Chapter 2). The model predicts a variable influence of temperature, but the processes responsible for this variation are not immediately clear. I subsequently conduct a detailed analysis elucidating the key processes that allow/constrain a strong influence of temperature dependent mutation rate on species richness (Chapter 3). In addition to mutation rate, temperature-dependent metabolism can influence ecological (feeding and mortality) and ecosystem (e.g. decomposition and in turn nutrient supply) rates. As such, I extend the model developed in chapters 1-3 to incorporate these additional temperature dependencies and derive predictions for the influence of temperature over species richness (Chapter 4).
36

The effects of natural and anthropogenic disturbances on the structure and composition of early-successional plant communities in the Interior Cedar-Hemlock (ICH) zone of southern British Columbia

Corriveau, Brit Madelaine 11 1900 (has links)
Wildfire is the primary natural disturbance in Interior Cedar-Hemlock (ICH) forests, and since the mid-20th century, forest harvesting (clearcutting, in this case) has become the primary anthropogenic disturbance type. Forest management in British Columbia is currently governed by a paradigm that maintains that biological diversity can be preserved by utilizing forest harvesting regimes that closely mimic "natural" disturbance regimes, but a question remains as to how closely these regimes mimic wildfire disturbances. More specifically, how do clearcutting and wildfires compare in their effects on the structure and composition of early-successional ICH plant communities? This study compares vegetation structure, composition, relative abundance and diversity among 39 sites that experienced either a stand-replacing fire or a clearcut within the last 40 years. Sites of different ages and disturbance types were located within the wet cool ICHwkl and very-wet cool ICHvk I biogeoclimatic variants near Revelstoke, B.C. For each site, overstory structural characteristics (tree and snag diameters, basal area and density), overstory composition, and surface fuels (volume of coarse woody debris (CWD)) were assessed. Understory vegetation percent cover, species richness, composition and diversity were also determined. Linear regression analysis was used to examine differences in each of these variables between disturbance types, over time. The trends in structural legacies (especially snag and CWD dynamics) varied greatly between wildfire and clearcut sites. Compared to burned sites, clearcut sites exhibited patterns of accelerated succession in several characteristics (overstory tree regeneration, vegetation cover and understory species richness) due to planting treatments and pre-disturbance relicts. Understory species composition also varied between disturbances, with clearcut sites containing more shade-tolerant survivors initially. Both disturbance types had similar levels of floristic diversity during early succession. These results suggest that clearcut harvesting may not emulate stand-replacing fires in terms of impact on early ICH plant succession in any aspect but diversity. However, it is unclear if these early-successional differences will continue through time. There is a need for further research in this ecosystem, as well as any other ecosystems where emulation silviculture is applied, in order to confirm that silvicultural effects mimic those of natural disturbance regimes.
37

Exploring Species Diversity and Molecular Evolution of Arachnida through DNA Barcodes

Young, Monica Rose 11 February 2013 (has links)
This thesis investigates species diversity and patterns of molecular evolution in Arachnida through DNA barcoding. The first chapter assesses mite species richness through comprehensive sampling at a subarctic location in Canada. Barcode analysis of 6279 specimens revealed nearly 900 presumptive species with high rates of turnover between major habitat types, demonstrating the utility of DNA barcoding for biodiversity surveys of understudied taxa. The second chapter explores nucleotide composition, indel occurrence, and rates of amino acid evolution in Arachnida. The results suggest a significant shift in nucleotide composition in the arachnid subclasses of Pulmonata (GC = 37.0%) and Apulmonata (GC = 34.2%). Indels were detected in five apulmonate orders, with deletions being much more common than insertions. Finally, rates of amino acid evolution were detected among the orders, and were negatively correlated with generation length, suggesting that generation time is a significant contributor to variation in molecular rates of evolution in arachnids.
38

A bryophyte perspective on forest harvest: The effects of logging on above- and below-ground bryophyte communities in coastal temperate rainforests

Miyashita, Kesia A. Unknown Date
No description available.
39

Influence of landscape scale and habitat distribution on individual bat species and bat species richness

Brüsin, Martin January 2013 (has links)
Habitat fragmentation is one of the most important factors affecting species extinction and biodiversity loss, Species habitat response expects to differ with habitat feature at different spatial scales and this study was to identify how bat diversity and individual bat species respond to different habitat amounts. The local bat species richness was observed in 156 different locations in Östergötland and the proportion of different habitats were calculated for circular areas with diameters ranging from 400 m. to 12 km. from each location. Although we found that the individual bat species responded differently to the amount of each habitat at different spatial scales, the bat species richness showed a decreasing response with increasing spatial scale. The strongest response of bat species richness to habitat characteristics was at a scale of 939 m.
40

Analysis of Fleet Readiness Center Southwest concept integration: new-employee orientation and communication processes

Clemmons, Francini R., Falconieri, Holly M. 12 1900 (has links)
Approved for public release; distribution is unlimited. / Fleet Readiness Center Southwest has embraced integration of personnel and processes from Aircraft Intermediate Maintenance Departments and Naval Aviation Depots supporting Naval Aviation Maintenance. This transformation marks a change in Naval Aviation Maintenance history and will align Fleet Readiness centers with the Naval Enterprise vision. As civilian and military personnel begin working side-by-side, orientation, communnication, and process relationships are being redefined to combine the previous infrastructure of two organizations under one roof. The new relationsships are designated to be comparable to the aviation maintenance industry's business structure to leverage opportunities for growth as well as sustainability for the industry. The authors analyzed new-employee orientation, personnel integration and communication processes to determine their effectiveness to convey FRCSW's vision and efforts for integration.

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