Made available in DSpace on 2015-03-26T13:53:30Z (GMT). No. of bitstreams: 1 texto completo.pdf: 3489877 bytes, checksum: 5fd786c548b56c14dd73d2e3780ec87a (MD5) Previous issue date: 2013-03-28 / The Iron Quadrangle (IQ) in Minas Gerais State is a mountainous region with rather peculiar ecosystems, conditioned by the heterogeneity of the landscape, composed of various geological substrates. The more resistant and prominent rocks in the landscape, such as quartzites and itabirites, support diverse rocky environments with high number of endemics. Despite the importance of ecosystems conservation, for many years the iron ore has been mined in IQ, removing the lateritic surface (canga) and the associated vegetation growing on it. However, the ecological studies of this peculiar vegetation are scarce and necessary to understand its environmental importance. The region posseses several IQ conservation units, such as the Private Natural Reserves (PNR), belonging to mining companies, requiring integrated environmental studies, needed for the appropriate management of these areas and promoting long-term ecological research. This project aimed to enhance the knowledge about the relationship between soil and vegetation in the IQ. For this purpose, two separate chapters were developed. In the first chapter, we made the geoenvironmental stratification of the PNR Capivari II, in which the geoenvironmental units were described, mapped and identified using high-resolution Ikonos image, geological map in ArcGIS 10 program and field campaings. In chapter 2, we characterized and compared the thermic and water dynamics of soils on canga and quartzite substrates, in IQ. For this purpose, we conducted for in situ monitoring of soil moisture, soil temperature and air temperature in four different environments for 14 months, namely: Rocky Field on Canga (CC), Forest on Canga (MC), Rocky Field on Quartzite (CQ) and Forest on Quartzite (MQ). The soil moisture monitoring method was based on the TDR (Time Domain Reflectometer), by means of calibration of sensors in laboratory, in which the propagation time of electromagnetic pulse detected by sensors installed in the soil were converted into gravimetric moisture values. Representative soil profiles at each environment sampled, both in the PNR as the monitoring sites were described and classified according to the Brazilian System of Soil Classification and soil samples were subjected to physical and chemical routine analysis at the Soil Science Department of UFV. The PNR Capivari II presented 10 different geoenvironmental units, mostly represented by shallow, rocky and nutrient-poor soils and grassy vegetation; geoenviroments with forest and shruby vegetation are restricted to areas with greater moisture, provided by soil depth and landscape position, or protected areas from the action of fire, due to the soil rockiness/stoniness. The mapping also revealed its environmental fragility, and showed how diverse is the landscape in IQ, even in areas of limited size. The thermic and hydric dynamic characterization showed the influence of temperature, soil moisture and depth on vegetation physiognomies in canga and quartzite. The data also revealed the magnitude of temperature and soil moisture variations, highlighting the extreme environmental conditions to which these plant comunities are subjected. Results allowed a deeper understanding of the pedoclimatic dynamics in these environments. The use of TDR equipment for the soil moisture determination presents some methodological challenges, like its correct installation on the field, as well as the soil density determination, required for sensors calibration. Finally, the studies illustrated the close relationship between soil and vegetation in IQ, a region with considerable environmental fragility, offering new challenges for further investigations on the adaptation mechanisms of plants that are naturally adapted to these environments. / O Quadrilátero Ferrífero (QF) é uma região montanhosa de ecossistemas bastante peculiares, condicionados pela heterogeneidade da paisagem, composta de substratos geológicos diversos. As rochas mais resistentes e salientes na paisagem, tais como quartzitos e itabiritos, sustentam ambientes rupestres diversificados e com elevado grau de endemismo. A despeito da importância de conservação destes ecossistemas, há muitos anos o minério de ferro é explorado no QF, suprimindo as áreas de canga ferrífera, sendo que ainda são escassos os estudos sobre sua vegetação peculiar, sua relação com o solo e importância ambiental. A região do QF abrange várias unidades de conservação, como por exemplo as Reservas de Proteção ao Patrimônio Natural (RPPN), pertencentes a empresas mineradoras, e que ainda carecem de estudos ambientais integrados, importantes para o manejo adequado dessas áreas e para o fomento de novas pesquisas. Esta pesquisa teve como objetivo geral aprofundar o conhecimento acerca das relações entre solo e vegetação no QF e, nesse sentido, dois capítulos distintos foram desenvolvidos. No primeiro capítulo, foi feita a estratificação geoambiental da RPPN de Capivari II, na qual as unidades geoambientais foram descritas, mapeadas e identificadas, utilizando imagem Ikonos de alta resolução, mapa geológico em programa ArcGIS 10 e viagens de campo. No capítulo 2, objetivouse caracterizar e comparar a dinâmica térmica e hídrica do solo em área de canga e quartzito no QF. Para tal, foi realizado, durante o período de 14 meses, o monitoramento in situ da umidade e da temperatura do solo e da temperatura do ar em quatro ambientes distintos, a saber: Campo Rupestre sobre Canga (CC), Mata sobre Canga (MC), Campo Rupestre sobre Quartzito (CQ) e Mata sobre Quartzito (MQ). O monitoramento da umidade do solo foi baseado no método TDR (do inglês Time Domain Reflectometer), através do qual, por meio de calibração dos sensores em laboratório, valores de tempo de propagação do pulso eletromagnético detectado por sensores instalados no solo foram convertidos em valores de umidade gravimétrica. Perfis de solo representativos de cada ambiente amostrado, tanto na RPPN quanto nos sítios de monitoramento, foram descritos e classificados de acordo com o Sistema Brasileiro de Classificação de Solos e as amostras de solo coletadas foram submetidas às análises físicas e químicas de rotina do Departamento de Solos da UFV. A RPPN de Capivari II apresentou 10 unidades geoambientais distintas, em sua maioria representada por solos rasos, pobres, cascalhentos e vegetação campestre; os geoambientes com feições de vegetação florestais e arbustivas ficam restritas às áreas com maior umidade do solo, proporcionada pela profundidade do solo e posição na paisagem, ou às áreas protegidas contra a ação do fogo, devido à rochosidade/pedregosidade do solo. O mapeamento da área revelou também sua fragilidade ambiental, bem como mostrou o quanto é diversificada a paisagem no QF, mesmo em áreas de dimensões restritas. A caracterização da dinâmica térmica e hídrica mostrou a influência da temperatura, da umidade do solo e da profundidade sobre as fitofisionomias de vegetação de canga e quartzito, além da profundidade do solo. Os dados também revelaram a magnitude das variações de temperatura e umidade do solo, que denuncia condições ambientais extremas às quais estão submetidas a vegetação naturalmente adaptada aos ecossistemas rupestres do QF, além de permitir o entendimento mais detalhado da dinâmica pedoclimática destes ambientes. Este estudo mostrou que a utilização do equipamento TDR para a determinação da umidade do solo apresenta alguns desafios metodológicos, desde sua correta instalação no campo até a determinação da densidade do solo, necessária para a calibração dos sensores. Por fim, os estudos aqui detalhados ilustraram as estreitas relações existentes entre solo e vegetação no QF, uma região com notável fragilidade ambiental, ao mesmo tempo em que abrem novos caminhos para investigações mais detalhadas acerca dos mecanismos de adaptação das plantas, naturalmente adaptadas a estes ambientes.

Potatoes in the Eastern Shore of Virginia are traditionally planted between late February and early April and harvested between early June and late August. Potato prices are usually higher early into the harvest season and decrease slowly as the season progresses. Early planting dates are desirable for farmers, as it allows them to perceive higher prices for their product, but early planting is also associated with lower air temperature during the early season, which in turn can affect plant development, water and nutrient uptake, and overall yield. Additionally, variations in soil properties often affect nutrient and water availability for plants, as well as the distribution of soil-borne insect pests. Additionally, several techniques are available to map the variations of soil properties in commercial potato fields, but little effort has been made to relate this information to the potential presence of soil-borne pests. Hence, the objective of this project was to evaluate the effect of planting dates, nitrogen (N) rates, and irrigation regimes on potato production. Two comprehensive studies were conducted between February and July 2022 and 2023. The objective of the first study was to evaluate the effect of N rates, planting dates, and soil physicochemical properties in potato production and the presence of soil-borne pests. This study was established in a split-plot design with four replications, with planting dates on the main plot and N rates and time of application on the sub-plot. Late March planting resulted in the highest total tuber yield, while early planting produced significantly larger tubers. Early March planting reduced plant development and emergence, probably due to lower air and soil temperatures. There was no interaction between planting dates and N applications. Using N rates higher than 147 kg ha-1 resulted in no significant differences in total tuber yield. Regression analyses showed that the Normalized Differences Red Edge (NDRE) is an excellent predictor of N content in plant tissue and tuber yield. Moreover, Ca and H saturation percentages were linked to wireworm damage levels using classification algorithms. Similarly, K saturation percentage was identified as a potential predictor of nematode presence in this region. A second study was established with the objective of evaluating the effect of N rates and irrigation regimes on potato production. The study was established in a split-plot design with four replications, with the irrigation method on the main plot and total N rate on the subplot. Results from these experiments showed higher growth and tuber yield when combining overhead irrigation with crop evapotranspiration (ETc) estimation. Moreover, there were no significant differences when using N rates higher than 112 kg ha-1. Overall, results from these experiments suggest no changes in current N rate recommendations for this region. Additionally, these results suggest planting in late March and using irrigation regimes based on evapotranspiration with overhead irrigation systems. Future research should focus on adaptive fertilization based on growing degree days and refinement irrigation determination practices. / Master of Science in Life Sciences / In the Eastern Shore of Virginia, nearly 4,000 acres are annually dedicated to fresh white potato farming. The established planting window extends from early March to early April, aligned with peak market demands in late April. However, this traditional planting strategy exposes crops to varying temperatures, potentially affecting water and nutrient demands, as well as overall yield. A research project consisting of two studies was conducted with the objective of evaluating the effect of planting dates, nitrogen (N) rates, and irrigation regimes on potato production. The first study was conducted with the aim of optimizing yield and nutrient management by exploring the interplay between planting dates, N rates, and application timing. The second study evaluated overhead and subsurface drip irrigation systems with irrigation regimes determined either by crop evapotranspiration (ETc) or by soil moisture content through soil water sensors (SWS). Results demonstrated that early March planting resulted in delayed emergence and overall growth due to colder temperatures, while late March plantings produced the highest tuber yields. On the irrigation front, overhead irrigation integrated with ETc estimation consistently improved plant health and augmented yield. In addition, the Normalized Differences Red Edge (NDRE) index, obtained from multispectral drone imaging, produced a significant correlation with N content in plant tissue and with total tuber yields for both studies. This suggests its high potential as a yield prediction tool. Overall, results from these studies reinforce current N rate recommendations for Virginia. Furthermore, they not only refine regional potato cultivation practices but also suggest the need for research pivoting around adaptive fertilization based on growing degree days and the potential refinement of irrigation regimens.

The wettability and phase change phenomena of water are ubiquitous on biological and artificial surfaces. Properties like water repellency, self-cleaning, coalescence induced condensation jumping, anti-frosting, and dew harvesting arise on surfaces with particular structures and chemistry and are of particular interest for energy and water saving. This thesis collects different studies of wettability and phase change on natural and artificial surfaces: growth and self-ejection of condensation droplets on micro and nanostructured surfaces we fabricated, their applications, the Sliding on Frost of condensation droplets observed on the Cotinus Coggygria leaf, the dew harvesting property of the Old Man of the Andes Cactus enhanced by distance coalescence through microgrooves and finally, a theoretical study of viruses viability in sessile droplets. The first chapter introduces the theoretical framework of wettability and phase changes on surfaces. In the second chapter, we present the self-ejection of condensation droplets from hydrophobic nanostructured microstructures. We modelled analytically the droplets jumping and fabricated surfaces to verify the predictions. The fabricated geometry was inspired by the modelling and the available fabrication techniques. We tested the surfaces in condensation conditions. Using a high frame rate camera coupled with a long working distance microscopy objective, we investigated the growth and ejection transient. We then compared the experimental self-ejection velocity for various structures geometry with our analytical models. In Chapter 3, we investigated the applications of the fabricated surfaces reported in Chapter 2. In Chapter 4, we explore the condensation frosting on the leaf of Cotinus Coggygria, native of our woods and with interesting hydrophobic properties. Covered by wax nanotubules, it exhibits coalescence-induced condensation jumpings that may be a useful cleaning tool. Furthermore, the frost is delayed but not only for the jumping. Surprisingly, at temperatures some degrees below zero, we observed what we called ‘droplet Sliding on Frost bridges’, that further delays frosting. We described the feasibility of this sliding in terms of dynamic contact angles of the surface and contact angles of supercooled water on ice. By capturing high temporal and spatial resolution videos we investigated the sliding on frost and droplet recalescence (fast dendrite growth that partially solidify the liquid). The responsible for the failure of sliding for temperatures from about -8 ° C down appears to be the advancing angle of water on ice that increases with the subcooling rather than the recalescence that blocks the drop in place. These results add a piece to the fundamental research on the supercooled water-ice-vapour interfaces. As it often happens, biological surfaces offer a starting point for the study of fundamental mechanisms and the development of artificial surfaces with optimized properties. In the Chapter 5, the multifunctional roles of hairs and spines in Old Man of the Andes Cactus (Oreocereus trolli) are studied. We study the morphology of the appendages, the hairs wettability, mechanical properties of both, and the dew formation on spines. The longitudinal microgrooves on the spines cause a particular phenomenon of distant coalescence (DC), in which smaller droplets flow totally or partially into larger ones through the microgrooves, with consequent accumulation of water in a few large drops. An earlier study has shown artificial micro-grooved surfaces that exhibit DC are more efficient than flat ones at collecting and sliding dew, and thus these cactus spines could act as soil dew conveyors. The agreement between our analytical model and experimental data verifies that the flow is driven by the Laplace pressure difference between the drops. This allowed us to obtain a general criterion for predicting the total or partial emptying of the smaller drops as a function of the dynamic contact angles of a surface. Based on this criterion, an hydrophilic material with small contact angle hysteresis would allow a greater number of complete drops emptying. The COVID-19 pandemic has raised the problem of contagion from airborne and deposited droplets. In the last chapter, we report the state of the art of experiments on the viability of viruses in deposited droplets. Up to date, it has been experimentally highlighted that the relative viability of some viruses (RV) depends on the material chemistry, temperature, and interestingly, on relative humidity (RH) with a U-shaped trend. One of the current hypotheses is that the cumulative dose of salt concentration (CD) affects RV. We model the RV of viruses in sessile droplets by inserting a RV-CD relation in a model of droplet evaporation. By considering a saline water droplet (one salt) as the simplest approximation of real solutions, we analytically simulate the time evolution of salt concentration, vapor pressure, and droplet volume varying contact angles, droplet sizes, and RH in the range 0–100%. The results elucidate some previously not yet well-understood dynamics, demonstrating how three main regimes—directly implicated in nontrivial experimental trends of virus RV—can be recognized as the function of RH. The proposed approach could suggest a chart of a virus fate by predicting its survival time at a given temperature as a function of RH and contact angle. We found a good agreement with experimental data for various enveloped viruses and predicted in particular for the Phi6 virus, a surrogate of coronavirus, the characteristic U-shaped dependence of RV on RH. Given the generality of the model, once experimental data are available that link the vulnerability of a certain virus (such as SARS-CoV-2) to the concentrations of salts or other substances in terms of CD, it is envisioned that this approach could be employed for antivirus strategies and protocols for the prediction/reduction of human health risks associated with SARS-CoV-2 and other viruses.

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