The twospotted spider mite (TSSM), Tetranychus urticae Koch, is a common polyphagous pest in peanut agroecosystems. The mite has caused serious economic losses to peanut farmers in the Virginia-Carolina area, where approximately 20% of the peanuts are produced annually in the United States. Peanut farmers depend on pesticides to control mite populations. Because TSSM has developed resistance to many acaricides and there are restrictions on the use of pesticides, an alternative approach, such as precision pest management, is needed that would reduce the amount of pesticides that must be applied. This study was initiated to determine whether precision pest management is a feasible management strategy for use against TSSM populations in peanut. Two requirements of the precision management approach are that maps of the spatial distribution of TSSM populations can be developed and the pattern of distribution changes little over time to allow management strategies to be implemented. To this end, a study of four commercial peanut fields located in two counties of southeastern Virginia was conducted to characterize the spatial distribution of TSSM populations. Intensive sampling of TSSM populations was conducted within each of the fields. The results showed that there was a general increase in TSSM populations during the early phases of sampling. Fields with low densities of TSSM populations had a spatial distribution that was either uniform or random; in fields with relatively higher densities, TSSM populations usually were aggregated. Little or no change in the spatial distribution of TSSM occurred from week to week in all fields that were sampled. Where changes in the distribution were observed, these were apparently caused by the application of a pesticide by the grower. The study also looked at remote sensing technology as an alternative to intensive sampling within peanut fields. Research was conducted under laboratory conditions to determine whether damage caused by feeding TSSM could be detected spectrally before symptoms become visible. The study showed that after eight days leaves of peanut plants subjected to low soil moisture levels had significantly lower reflectance ratios (mean = 9.4766; a = 0.05) than plants given medium (mean = 10.0186) or high (mean = 10.5413) soil moisture levels. After 10 days, there were significant differences (P < 0.05) in the mean reflectance ratios of peanut leaves exposed to four levels of spider mite densities (0, 5, 10, 20 mites/leaf) and the three levels of soil moisture. However, no significant interaction was observed between soil moisture and spider mite density (P = 0.8710). The mean reflectance ratio for 20 TSSM per leaf was found to be significantly lower than 0, 5, and 10 TSSM per leaf at all levels of moisture (low, medium, and high). The results suggested that remote sensing could be used to detect and map plant damage caused by feeding of spider mites before visual symptoms of damage are observed. The study also attempted to develop a platform for using remote sensing technology in the field. An Unmanned Air Vehicle (UAV) was evaluated that carried a remote sensing system. The UAV remote sensing system was flown over peanut fields where it captured images, which were analyzed to show the spatial distribution of plant stress. Further studies are needed to relate the distribution of plant stress or damage observed by the UAV with the distribution of TSSM densities within peanut fields. Once this has been accomplished, low-altitude remote sensing could be used as an alternative to sampling for building maps of the spatial distribution of TSSM populations for precision pest management. / Master of Science

This study involves seismic monitoring of a deep coal mine. The purpose is to examine the processes responsible for induced seismicity. A seismic network consisting of five three-component short-period seismometers located above the mine recorded the seismic data. The events discussed here occurred from March 1, 2009 until April 7, 2011 during the mining of three longwall panels and the data was telemetered to Blacksburg, Virginia. A correlation equation was developed to relate local magnitude estimated by automatic data processing software in near real-time to seismic moment for well-recorded events. Local magnitude is a relative measure of relative size for a suite of earthquakes, while seismic moment is an objective measure of the actual physical size. Using the calculated seismic moments, we calculated "moment magnitudes" (Mw) for all events, which allowed us to do further studies in terms of their absolute size as a function of both time and space. The results indicate that there are two distinct classes of seismic events at the mine. The first class consists of small (M<=0) earthquakes recorded near the moving mine face. The second class of seismicity occurs in the mined-out "gob" area of the longwall panel at a greater distance behind the moving face. Their occurrence and relation to the mining history, depth of overburden and geology of the roof rocks is a significant interest. Results show that thick overburden due to elevated topography has a positive correlation with the number of seismic events but is not the only controlling factor; other factors include gob size and geological variability. Another important observation is the high seismic attenuation of the rock mass above the mine. This appears to be the result of the fracturing and caving processes associated with the creation of the gob and the resulting subsidence of the ground surface. / Master of Science

Resumo: A região ocidental do estado de São Paulo abriga a maior área contínua remanescente da Floresta Estacional Semidecidual Atlântica que recobria esta região. Grande parte desta região está protegida no Parque Estadual do Morro do Diabo (PEMD), considerada insuficientemente conhecida, mas de provável importância biológica em relação a herpetofauna. O presente estudo objetivou-se por estudar os padrões de distribuição espacial e temporal da anurofauna do PEMD, e também verificar como a heterogeneidade dos corpos d'água influencia na composição e riqueza de espécies de anfíbios. De maneira geral, as espécies de anfíbios registradas no PEMD (tanto adultos em atividade de vocalização quanto girinos) ocorreram diferentemente entre os variados tipos de corpos d'água amostrados, sendo principalmente relacionado com tipo de correnteza e hidroperíodo dos corpos d'água. Assim, a composição da anurofauna foi diferente entre corpos d'água lóticos, lênticos permanentes/semi-permanentes e lênticos temporários. A ocorrência temporal das espécies foi restrita aos meses quente e úmido do ano (com exceção de uma espécie que ocorreu durante os meses frio e seco), o que resultou em alta sobreposição temporal no período de vocalização dos machos e ocorrência de girinos. Grupos de espécies ocorreram diferentemente ao longo dos meses quente e úmido, com espécies características de início, meio e fim da estação chuvosa. A análise macro-espacial da distribuição da anurofauna no PEMD evidenciou uma baixa similaridade entre as diferentes fitofisionomias amostradas. Na verdade, esta baixa similaridade faunística foi consequência da baixa eficiência de captura das armadilhas de interceptação e queda, o que resultou em uma baixa riqueza de espécies nas fitofisionomias estudadas. No entanto, alta similaridade na composição de espécies foi encontrada... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Occidental region of São Paulo state shelters the largest continuous remnant of Mesophytic Semideciduous Forest (Atlantic domain). Most of this region is legally protected by the Morro do Diabo State Park (MDSP), considered insufficient known but with probable biological importance concerning amphibians and reptiles. The present study aimed to study the spatio-temporal patterns of anuran distribution at MDSP, as well as to verify how environmental heterogeneity of breeding ponds influences on richness and anuran species composition. In general, recorded species (either calling males or tadpoles) occurred differentially among the studied breeding habitats, which was mainly related to the water flow and hidroperiod of breeding habitats. Thus, lotic, lentic permanent/semipermanent, and lentic temporary breeding habitats presented different anuran species composition. Temporal distribution of individuals was restricted to the moist and hot months (with exception to one species that occurred during the dry and cold months), resulting in a high temporal overlap of calling males and tadpoles distribution. Groups of species distributed differentially through the hot and moist months, where typical species of beginning, middle, and end of the rainy season could be identified. A macro-spatial analysis of anuran distribution evidenced low similarity among different sampled phytophysiognomies. Actually, the low faunistic similarity is rather a consequence of the low efficiency of capture by pitfall traps with drift fences, resulting in low species richness in the phytophysiognomies studied. However, a high similarity on species composition was found only among the most preserved areas of MDSP, due to the presence of Rhinella ornata. This species was indicative of the most preserved area of the MDSP, while two other species from the Leiuperidae family (Eupemphix nattereri and Physalaemus cuvieri)... (Complete abstract click electronic access below) / Orientador: Célio Fernando Baptista Haddad / Coorientador: Denise de Cerqueira Rossa-Feres / Banca: João Miguel de Barros Alexandrino / Banca: Itamar Alves Martins / Banca: José Perez Pombal Junior / Banca: Cinthia Aguirre Brasileiro / Doutor

Doctor of Philosophy / Department of Entomology / James F. Campbell / Phillip E. Sloderbeck / Robert "Jeff" J. Whitworth / Knowledge of factors influencing the establishment, persistence and distribution of stored-product pests aids the development of effective Integrated Pest Management (IPM) programs in food storage and processing facilities. This research focused primarily on Tribolium castaneum, which is one of the most important pests of mills. Populations of T. castaneum from different food facilities can potentially be interconnected by either their own dispersal behavior or by human transportation. Population genetic structure analyses based on microsatellites and other insertion-deletion polymorphisms (“indels”) showed that populations from different mills around the US are genetically distinct from each other, but the level of differentiation was not correlated with the geographic distance. A potential source of insect infestation within a food facility is spillage that accumulates outside or movement from bulk storage facilities on site. Results from three facilities showed that most stored-product species were captured both inside and outside buildings, but T. castaneum was rarely captured outside of the facilities. Spatial distribution of all species outside was associated with the proximity of buildings, not necessarily with areas with accumulated spillage. T. castaneum populations inside facilities are potentially exposed to frequent genetic bottlenecks resulting from structural fumigations. Changes in allele frequencies through time, based on the analysis of microsatellites and other indels in individuals collected in a mill, confirmed bottleneck effects. To understand how spatial distribution of T. castaneum within a mill could be influenced by environmental and physical factors, a range of variables were measured at each trap location. There was significant variation among trap locations regarding beetle captures and the variables measured, but increase in beetle captures correlated only with increase in temperature and spillage production. Tribolium castaneum response to visual cues could influence attraction to pheromone and kairomone olfactory cues used in traps. Results of laboratory experiments showed that adults respond to tall narrow black shapes and placing traps in front of these shapes can increase captures. This research provides new insights into factors influencing the spatial distribution of T. castaneum and could help in improving monitoring programs for this important pest of the food industry.

Benthic invertebrates inhabiting boreal rivers are exposed to very large seasonal variations in their physical environment. The extremes are in winter when the littoral area freezes solid and in spring when water flow increases rapidly. In the North Swedish river Vindelälven, the invertebrates fell into three main categories according to their seasonal lateral distribution. One category of animals was stationary in the littoral zone and let itselt freeze into the ice, adopting a "take it" alternative. The category consisted of many species belonging to several higher taxa. By overwintering in ice, the animals avoided predation for nearly half the year and they were in the productive littoral at the same time as they thawed out from the ice in spring. On the other hand the animals had to withstand sub-zero temperatures. A typical representative for this category of animals was the semivoltine snail Gyraulus acronicus. It is a less mobile species connected to dense stands of macrophytes, which are found only in the littoral zone of the river. Nearly the whole population was found overwintering successfully enclosed in ice. Its shell and epiphragm could serve as mechanical protection when frozen into the ice. G. acronicus was cold-hardy only during late autumn and early winter, but it could stand prolonged sub-zero exposure during the proper time. A second category of animlas avoided being frozen by performing lateral movements to deeper parts of the river, adopting the Vleave it" alternative. No species tested in this category were found cold-hardy. It consisted of mobile species known to utilize sedimentated detritus which was only found in greater amounts in the littoral zone of the river. In springtime, prior to spring flood peak, these species colonized promptly the former frozen zone. This behaviour was most pronounced in several lentie mayfly species. An extreme case of migratory behaviour was found in the mayfly Pararneletus chelifer which not only moved towards the river bank but continued up into small tributaries. The shoreward movements of mayflies both allowed the nymphs to avoid the high current velocities in the central part of the river during spring flood time and to utilize the food resources in the flooded areas. A third category of animals avoided the ice by living stationary in the sublittoral zone, adopting the "never face it" alternative. This category was dominated by filter feeders. / <p>Diss. (sammanfattning) Umeå : Umeå university, 1982, härtill 5 uppsatser</p> / digitalisering@umu

This thesis consists of a summary and five self-contained papers addressing dynamics of firms in the Swedish wholesale trade sector. Paper [1] focuses upon determinants of new firm formation in the Swedish wholesale trade sector, using two definitions of firms’ relevant markets, markets defined as administrative areas, and markets based on a cost minimizing behavior of retailers. The paper shows that new entering firms tend to avoid regions with already high concentration of other firms in the same branch of wholesaling, while right-of-the-center local government and quality of the infrastructure have positive impacts upon entry of new firms. The signs of the estimated coefficients remain the same regardless which definition of relevant market is used, while the size of the coefficients is generally higher once relevant markets delineated on the cost-minimizing assumption of retailers are used. Paper [2] analyses determinant of firm relocation, distinguishing between the role of the factors in in-migration municipalities and out-migration municipalities. The results of the analysis indicate that firm-specific factors, such as profits, age and size of the firm are negatively related to the firm’s decision to relocate. Furthermore, firms seems to be avoiding municipalities with already high concentration of firms operating in the same industrial branch of wholesaling and also to be more reluctant to leave municipalities governed by right-of-the- center parties. Lastly, firms seem to avoid moving to municipalities characterized with high population density. Paper [3] addresses determinants of firm growth, adopting OLS and a quantile regression technique. The results of this paper indicate that very little of the firm growth can be explained by the firm-, industry- and region-specific factors, controlled for in the estimated models. Instead, the firm growth seems to be driven by internal characteristics of firms, factors difficult to capture in conventional statistics. This result supports Penrose’s (1959) suggestion that internal resources such as firm culture, brand loyalty, entrepreneurial skills, and so on, are important determinants of firm growth rates. Paper [4] formulates a forecasting model for firm entry into local markets and tests this model using data from the Swedish wholesale industry. The empirical analysis is based on directly estimating the profit function of wholesale firms and identification of low- and high-return local markets. The results indicate that 19 of 30 estimated models have more net entry in high-return municipalities, but the estimated parameters is only statistically significant at conventional level in one of our estimated models, and then with unexpected negative sign. Paper [5] studies effects of firm relocation on firm profits of relocating firms, employing a difference-in-difference propensity score matching. Using propensity score matching, the pre-relocalization differences between relocating and non-relocating firms are balanced, while the difference-in-difference estimator controls for all time-invariant unobserved heterogeneity among firms. The results suggest that firms that relocate increase their profits significantly, in comparison to what the profits would be had the firms not relocated. This effect is estimated to vary between 3 to 11 percentage points, depending on the length of the analyzed period.

This dissertation explores the impact of international trade on the geographic location of manufacturing activities and on regional productivity growth patterns within countries. This study develops models of trade with monopolistic competition in the context of a two-region country. It also provides empirical estimates of the e ect of tari policy on the distribution of industrial activities and on productivity growth di erentials across Colombia's regions. The rst essay investigates the consequences of trade liberalization for the distribution of manufacturing activities between large and small cities. It presents an extension of the Melitz (2003) model of trade with monopolistic competition and heterogeneous rms where producers' location and export market participation decisions depend on their productivity. As a country's exposure to trade shifts, rms and output are reallocated between large and small urban areas. Data from Colombia's manufacturing sector lend support to theoretical predictions concerning tari reduction's impact on the repartition of industrial activities between metro- and nonmetropolitan areas in this country. The second essay extends the New Economic Geography, Footloose-Capital model to examine the e ect of commercial policy on the distribution of industrial activities between regions within a country. This study aims at distinguishing theoretical cases with regard to the nature of the trade policy change or to the source of asymmetry between regions. It shows that trade liberalization can have adverse consequences for the manufacturing sector of a small or isolated region under bilateral liberalization, but a positive impact under unilateral trade liberalization. The third essay adapts the Melitz and Ottaviano (2008) model of trade with monopolistic competition, heterogeneous rms, and variable mark-ups to analyze the relationship between trade openness, regional market size, and regional aggregate industry performance. It demonstrates that the impact of trade liberalization on aggregate industry productivity growth varies across regions as a function of regional market size and proximity to foreign markets. A larger region experiences a greater increase in aggregate productivity through intra-industry reallocation of market shares. Similarly, a region with better access to international markets enjoys a higher productivity growth from tari reduction. Empirical evidence is obtained from the Colombian manufacturing sector.

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The tidal James River, a focus of VCU's Atlantic Sturgeon program, supports both commercial shipping and hydraulic dredging. These anthropogenic threats present documented but preventable sources of mortality to the endangered species. Using three separate VEMCO Positioning System (VPS) receiver arrays, spatial data of previously-tagged fish were collected. ArcGIS and Programita software were used to analyze fish spatial distributions in the presence and absence of potential threats, using additional data including automatic identification system (AIS) vessel locations, vessel passages compiled using camera footage, and dredge records provided by the US Army Corps of Engineers. The data showed a change in distribution associated with vessels that varied according to river width but not vessel type. Dredging was associated with differences in spatial distribution, but more clearly for adults than sub-adults. The responses of Atlantic Sturgeon provide information necessary to propose potential threat mitigations, including seasonal restrictions for both vessels and dredging.