Made available in DSpace on 2016-01-26T18:56:32Z (GMT). No. of bitstreams: 1 Jessica Fontes Fileti.pdf: 657960 bytes, checksum: d27058552310d001b7d5b1306d3396dd (MD5) Previous issue date: 2015-08-04 / Orchid seeds are the smallest and rich in lipids, which turn them in an ideal model to deterioration studies as large populations can be worked in small samples. Controlled deterioration (CD) is a procedure that uses a control in the seed water content during ageing process. The objective of this work was to verify the controlled deterioration effect over orchid seeds. This work was done by the first time with five tropical orchid species: Cattleya brevicaulis, C. tenebrosa, C. amethystoglossa, C. tigrina and Encyclia granitica submitted to three temperatures 41, 43 and 45ºC during the periods of 0, 1, 3, 6, 9, 15, 24 and 48 hours. The variables Total germination, Germination Velocity Index (GVI), Tetrazolium test, MDA content, SOD and PRX activities were evaluated. Results were more expressive after 15 horas of exposition to temperatures of 43 and 45ºC. Total germination, GVI and Tetrazolium test exhibited decreases with the increase in the controlled deterioration. Cattleya tigrina and C. tenebrosa showed expressive increase of MDA content after 48h of controlled deterioration, the other species (C. amethystoglossa, C. brevicaulis and Encyclia granitica) did not. Enzyme activities (SOD and PRX) showed decreases in all temperatures. Total germination, GVI and Tetrazolium test were more efficient to detect variations in the aged seeds. / Sementes de orquídeas são diminutas e constituídas em grande parte por lipídeos, o que as torna um modelo ideal para estudos de deterioração, uma vez que grandes populações podem ser trabalhadas em pequenas amostras. A deterioração controlada é um tratamento que apresenta controle do teor de água das sementes durante o envelhecimento. O objetivo deste trabalho foi avaliar o efeito da deterioração controlada sobre sementes de orquídeas. Este trabalho foi conduzido pela primeira vez em cinco espécies de orquídeas: Cattleya brevicaulis, C. tenebrosa, C. amethystoglossa, C. tigrina e Encyclia granítica submetidas a três temperaturas 41, 43 e 45ºC durante os períodos de 0, 1, 3, 6, 9, 15, 24 e 48 horas. As variáveis de germinação total, índice de velocidade de germinação (IVG), teste de tetrazólio, além dos testes bioquímicos como acúmulo de Malondialdeído (MDA), atividade enzimática de Superóxido Dismutase (SOD) e Peroxidase (PRX), foram avaliadas. Os resultados foram mais expressivos a partir de 15 horas de exposição às temperaturas de 43 e 45ºC. A germinação total, o IVG e o teste de tetrazólio apresentaram decréscimos com o aumento da deterioração controlada para todas as espécies. Cattleya tigrina e C. tenebrosa apresentaram incrementos expressivos de MDA após 48 h de deterioração controlada, ao contrário de C. amethystoglossa, C. brevicaulis e Encyclia granitica. A atividade enzimática das duas enzimas testadas (SOD e PRX) apresentaram decréscimos nas três temperaturas. A germinação total, o IVG e o teste de tetrazólio foram mais eficientes para detectar as variações de viabilidade e vigor nas sementes deterioradas.

Made available in DSpace on 2016-07-18T17:51:13Z (GMT). No. of bitstreams: 1 Jessica Fontes Fileti.pdf: 657960 bytes, checksum: d27058552310d001b7d5b1306d3396dd (MD5) Previous issue date: 2015-08-04 / Orchid seeds are the smallest and rich in lipids, which turn them in an ideal model to deterioration studies as large populations can be worked in small samples. Controlled deterioration (CD) is a procedure that uses a control in the seed water content during ageing process. The objective of this work was to verify the controlled deterioration effect over orchid seeds. This work was done by the first time with five tropical orchid species: Cattleya brevicaulis, C. tenebrosa, C. amethystoglossa, C. tigrina and Encyclia granitica submitted to three temperatures 41, 43 and 45ºC during the periods of 0, 1, 3, 6, 9, 15, 24 and 48 hours. The variables Total germination, Germination Velocity Index (GVI), Tetrazolium test, MDA content, SOD and PRX activities were evaluated. Results were more expressive after 15 horas of exposition to temperatures of 43 and 45ºC. Total germination, GVI and Tetrazolium test exhibited decreases with the increase in the controlled deterioration. Cattleya tigrina and C. tenebrosa showed expressive increase of MDA content after 48h of controlled deterioration, the other species (C. amethystoglossa, C. brevicaulis and Encyclia granitica) did not. Enzyme activities (SOD and PRX) showed decreases in all temperatures. Total germination, GVI and Tetrazolium test were more efficient to detect variations in the aged seeds. / Sementes de orquídeas são diminutas e constituídas em grande parte por lipídeos, o que as torna um modelo ideal para estudos de deterioração, uma vez que grandes populações podem ser trabalhadas em pequenas amostras. A deterioração controlada é um tratamento que apresenta controle do teor de água das sementes durante o envelhecimento. O objetivo deste trabalho foi avaliar o efeito da deterioração controlada sobre sementes de orquídeas. Este trabalho foi conduzido pela primeira vez em cinco espécies de orquídeas: Cattleya brevicaulis, C. tenebrosa, C. amethystoglossa, C. tigrina e Encyclia granítica submetidas a três temperaturas 41, 43 e 45ºC durante os períodos de 0, 1, 3, 6, 9, 15, 24 e 48 horas. As variáveis de germinação total, índice de velocidade de germinação (IVG), teste de tetrazólio, além dos testes bioquímicos como acúmulo de Malondialdeído (MDA), atividade enzimática de Superóxido Dismutase (SOD) e Peroxidase (PRX), foram avaliadas. Os resultados foram mais expressivos a partir de 15 horas de exposição às temperaturas de 43 e 45ºC. A germinação total, o IVG e o teste de tetrazólio apresentaram decréscimos com o aumento da deterioração controlada para todas as espécies. Cattleya tigrina e C. tenebrosa apresentaram incrementos expressivos de MDA após 48 h de deterioração controlada, ao contrário de C. amethystoglossa, C. brevicaulis e Encyclia granitica. A atividade enzimática das duas enzimas testadas (SOD e PRX) apresentaram decréscimos nas três temperaturas. A germinação total, o IVG e o teste de tetrazólio foram mais eficientes para detectar as variações de viabilidade e vigor nas sementes deterioradas.

The encroachment of rangelands by woody plants causes an imbalance in the grass:bush ratio leading to decline in ecosystem services including grazing capacity, biodiversity, and water yield. This study assessed the historical changes in woody cover, and the effects of bush clearing on water loss, atmospheric carbon uptake, herbaceous vegetation, and soil seed bank (SSB) dynamics. The study was conducted at Makapanstad (Radi and Maseding) and Kgomokgomo rangelands, North-West Province, South Africa. Landsat imagery was used to assess woody cover over 34 years (1984 - 2018) in a total area of 16 397 ha. Evapotranspiration (ET) and gross primary productivity (GPP) were assessed in cleared sites and their adjacent uncleared sites from 2013 to 2018. Woody plant densities, herbaceous composition, ground cover and biomass production were assessed in 24, 5×5-m plots distributed equally in three 2500-m2 bush-encroached blocks in each rangeland in February 2016. Three samples for soil nutrient analysis were collected 20-cm deep in each plot. Thereafter, half (1250-m2) of each block was mechanically cleared to make three replicates of cleared and uncleared microsites. Post-treatment survey of vegetation was conducted in February 2017. SSB was assessed for samples collected in April 2016 before bush clearing and in August, October and December 2016, and April and August 2017 in paired microsites. In 1984, herbaceous cover (humid + arid grasslands) dominated, accounting for 36% of the total area followed by woody cover (shrublands + bushlands) and unvegetated cover (bare soils + abandoned croplands), with respective proportions of 33 and 31%. There were substantial land cover changes over time, with shrub cover increasing linearly (r2 = 0.94, p < 0.05) at a rate of 0.26% year-1, increasing the total woody cover (TWC) to 38% in 2018. Cropland abandonment was the main driver of increase in shrub cover in the study area. Herbaceous cover declined with increase in TWC (r2 = 0.69), whereas bare soil cover increased (r2 = 0.70) with TWC over time. The main encroachers were Vachellia tenuispina at Radi, Vachellia tortilis at Maseding and Dichrostachys cinerea and V. tortilis at Kgomokgomo. Most of the woody species correlated with total N and clay content (r = 0.96; p < 0.05) in black vertic clay soils of Radi and Maseding, whereas non-leguminous species correlated with total N and C:N in the red-yellow apedal soils of Kgomokgomo. ET and GPP varied interannually in all rangelands and both declined significantly (p < 0.05) after bush clearing at Radi and Kgomokgomo but not at Maseding. ET increased with GPP in cleared (r2 = 0.50-0.59) and uncleared sites (r2 = 0.82-0.93) at Radi and they showed a strong relationship (r2 >0.70) in both sites at Maseding and Kgomokgomo. ET ranged from 0.26-0.46 and 0.48-0.97 Kg H2O m-2 day-1 in cleared and uncleared sites, respectively, at Radi and from 0.44-0.98 and 0.63-1.24 Kg H2O m-2 day-1 at Kgomokgomo. Total SSB densities (constituted mostly by early successional species) increased significantly (p < 0.05) to 2470, 1872 and 693 seeds m-2 at Radi, Maseding and Kgomokgomo, respectively, in cleared microsites in August 2017. Similarly, biomass production (BP) and basal cover (BC) were highest in cleared relative to uncleared microsites. Overall, increase in woody cover reduced herbaceous cover and this calls for bush control in the studied rangelands. The decline in ET after bush clearing suggested that bush clearing could be used to increase rangeland water yield. Increased SSB densities, BP and BC indicated that bush clearing facilitates passive restoration. / Thesis (PhD (Pasture Science))--University of Pretoria, 2020. / Agricultural Research Council / National Research Foundation / Plant Production and Soil Science / PhD (Pasture Science) / Unrestricted

Cheatgrass (Bromus tectorum) is an invasive annual grass common in several semiarid plant communities in the western U.S. B. tectorum presence increases fire frequency and size, reducing species diversity, and leading to annual species-dominated systems with inconsistent livestock forage potential and degraded wildlife habitat value. Most efforts to manage B. tectorum-dominated rangelands have focused on controlling the plant itself rather than addressing the causes of vegetation change. An alternative approach, ecologically-based invasive plant management (EBIPM), identifies treatments that can alter factors associated with the causes of succession, leading to a more desirable vegetation state. This study utilized the EBIPM framework to design a large-scale demonstration project, which implemented a series of manipulation treatments (mowing, prescribed fire, imazapic herbicide, and seeding with perennial species) to suppress B. tectorum and promote desirable species. The treatments were implemented at two semiarid shrubland sites in northwestern Utah. Treatments were evaluated by measuring resident vegetation cover, density, aboveground biomass, and litter and soil seed banks. Herbicide was most effective in reducing B. tectorum cover, density, and biomass, while fire was effective in reducing seed density in the litter seed bank. Treatment interactions were rarely significant; however, by combining fire and herbicide, increased B. tectorum control was achieved. Seedlings of seeded perennial grasses emerged in all treatments; however, establishment by the end of the first growing season was greatest in treatments involving fire. The results of this study indicate that using a decision-making framework to select a series of treatments that alter the causes of succession can improve the management of B. tectroum-dominated rangelands.

Astragalus ampullarioides and A. holmgreniorum are two rare endemics of southwestern Utah. Over two consecutive field seasons (2009-2010) we examined pre-emergent reproductive success, based on F/F and S/O ratios, from populations of both Astragalus ampullarioides and A. holmgreniorum, estimated the density of the soil seed bank of A. holmgreniorum as a measure of potential post-emergent reproductive success, and estimated seed persistence within the soil seed bank. Fruit/flower (F/F) ratios and seed/ovule (S/O) ratios varied significantly between populations and among years in both species, and showed low reproductive output in both taxa. In Astragalus ampullarioides F/F and S/O were 0.06±0.01 and 0.16±0.02, respectively (2009), and 0.14±0.01 and 0.41±0.02, respectively (2010). For Astragalus holmgreniorum F/F and S/O ratios were 0.11±0.01 and 0.38±0.02, respectively (2009), and 0.23±0.01 and 0.66±0.02, respectively (2010). Although Astragalus holmgreniorum exhibited a low soil seed bank density (4.3 seeds m-2), seed persistence data showed low a low percentage of seeds germinated during the first year in the soil seed bank. Seeds remaining in the seed bank maintained high percent viability. Soil seed persistence of Astragalus ampullarioides differed from A. holmgreniorum in that a high percentage of seeds germinated during the first year in the soil seed bank. A high percentage of viability in ungerminated seeds was also maintained in A. ampullarioides. Although these species differ in life histories and dependence on soil seed banks, an understanding of the strategies unique to each species will prove useful in management plans.

Cattle grazing has been a historic use of rangelands in Utah since Pioneer settlement in the mid 1800's. Wright fishhook cactus is a small globose cactus endemic to an area of 280,000 ha in south-central Utah and was listed as endangered in October of 1979, by the U.S. Fish and Wildlife Service (USFWS). By 2010, concerns were expressed that soil compaction in proximity to the cactus posed a threat to this species, though there was no empirical data to support such concern. In order to assess the impact of cattle traffic on Wright fishhook cactus, we used an imprint device to simulate a cow track's impact. We applied a treatment of either zero, one, or four hoof imprints within 15 cm evenly of 146 cacti within the same population cluster on the same day. We monitored subsequent plant survival as well as reproductive success. Each cactus in the study was visited multiple times and all developed seed was collected. We found that cattle traffic of any amount had no effect on plant survival or seed production and therefore concluded that cattle traffic poses no threat to Wright fishhook cactus. The status of this cactus yields no justification for changing the historic land management use of cattle grazing on these rangelands. Seedbank abundance and location has not been examined for any species within the genus Sclerocactus. Over a one-day period, we took 500 soil samples from various locations near the cactus and potential nurse-plants. We found that approximately 1% of annual seed production makes it into the seedbank, a number in line with other species in the Cactaceae family. Seedbank densities were highest immediately adjacent to, and downslope from, parent plants. Understanding the dynamics of the seedbank of this species could lead to more informed management practices.

In the face of unprecedented anthropogenic change, we increasingly turn to emergent technologies and extensive data sets for solutions that complement much needed systemic changes in our societies. These technological solutions, however, must be approached with care. We must recognize and address biases in the way data has been accumulated. In demographic studies, dormant life stages, such as seed banks, and other cryptic factors have often been neglected. The potential consequences of these omissions have been extensively described in the literature. In the first chapter, I analyze patterns of seed bank omissions in demographic models, finding unjustified omissions are widespread across ecoregions, growth forms, and taxonomic groups. More importantly, studies with longer duration and accounting for a greater range of conditions were less likely to neglect the seed bank. Unfortunately, most demographic studies are conducted for relatively short periods and are limited to one or a few sites. In addition, modeling tools often focus on mean behavior and do not properly characterize variability. In the second chapter, I explore the use of Bayesian generalized linear mixed models to characterize vital rates and compare their variation across growing conditions. Using wild and translocated populations of Dicerandra christmanii,this study tests the ability of this approach to evaluate early translocation success and site suitability.In chapter 3, I expand the demographic analysis of Dicerandra christmaniiand provide an example of the use of Bayesian-fitted Integral Projection Models (IPMs) to combine data sources and incorporate seed dynamics into demographic models. By propagating uncertainty from vital rates to derived population metrics, this study illustrates the consequences of accounting for the seed bank stage and site condition to our assessment of population viability. In the final part of this work, I present potential routes to expand field and modeling tools to help address the inclusion of dormant and cryptic life stages into demographic studies. Among these, I recommend exploring more complex sampling schemes, informed priors, and expanded IPMs.

Tyrimo tikslas – nustatyti armens apvertimo kokybės įtaką vasarinių miežių (Hordeum vulgare L.) pasėlio piktžolėtumui modeliniame lauko tyrime. Modelinis lauko tyrimas vykdytas LŽŪU bandymų stotyje 2009-2010. Tirti keturi armens apvertimo variantai: armuo apverstas 135° (kontrolinis variantas), 157,5º ir 180° kampu bei neverčiamas (0°). Įrengti stacionarūs 0,25 m2 modeliniai laukeliai Nustatyta piktžolių vasarinių miežių derliuje, rūšinė sudėtis, biomasė ir skaičius, miežių antžeminės dalies biomasė ir stiebų skaičius, derlius, 1000 grūdų masė ir kiti parametrai. Pasėlio piktžolėtumo ir piktžolių sėklų pasiskirstymo armenyje duomenys vertinami dispersinės analizės metodu, nustatant esminio skirtumo ribą (R05, R01) ir vidurkių vidutinę kvadratinę paklaidą Apibendrinus tyrimo duomenis, gauti rezultatai parodė, kad esant skirtingam armens apvertimo kampui piktžolių biomasė pasėlyje skyrėsi iki 3 kartų. Piktžolių sėklų atsargose dirvoje vyravo trumpaamžės piktžolės, daugiausiai baltoji balanda (Chenopodium album L.). Paviršiniame dirvos sluoksnyje piktžolių sėklų pasiskirstymas tarp variantų buvo nevienodas (skyrėsi kelis kartus) skirtingais metais. Eksperimento rezultatai iš esmės patvirtino hipotezę, kad nuo armens apvertimo kampo priklauso pasėlio piktžolėtumas, tačiau reikėtų atlikti papildomus tyrimus ir nustatyti optimalų armens apvertimo kampą mūsų klimato ir dirvožemių sąlygomis. / The aim of the investigation was to estimate the influence of arable soil turnover angle on spring barley (Hordeum vulgare L.) crop yield and weediness in model field experiment. The model field experiment carried out at the Experimental Station of LŽŪU in 2009-2010. Four arable soil turnover angle treatments were investigated: 135° (control treatment), 157.5° and 180° and not overturned (0°). Stationary 0.25 m-2 model fields were equipped. The following parameters were measured: weeds harvested along with barley (weed species composition, weed biomass and number), spring barley density, and stem density, yield, 1000 grain weight and other parameters. Weediness and weed seed distribution in the arable soil layer were assessed by variance method by determining the LSD05, LSD01 and the average SEM Summarized survey data revealed that weed biomass in the spring barley crop differed by three times at the different arable soil turnover angle, short-living weeds dominated in the seed bank, mostly Chenopodium album L., weed seed distribution in top soil layer as well as spring barley yield has been uneven between the treatments (several times) in different years. Experimental results broadly confirmed the hypothesis that the arable soil overturning angle has influence on the crop yield and weediness, but further studies should be carried out to determine the optimum turnover angle for our climate and soil conditions.

Ecological restoration of a converted wetland was characterized within a recently drained impoundment along the James River in Charles City County, Virginia. Colonizing vegetation was assessed over three growing seasons in both tidal and non-tidal environments. Study objectives were to (1) examine geospatial relations of recruitment patterns among colonizing species over three growing seasons, (2) quantify species composition and potential differences between extant species cover and soil seed banks across restored and natural wetland habitats and (3) assess geospatial patterns to develop a GIS model of bald cypress (Taxodium distichum L.) recruitment. The two most common native colonizing species during 2009, 2010 and 2011 growing seasons were narrow-leaf cattail (Typha angustifolia L.) and rice cutgrass (Leersia oryzoides L.). Vegetative communities dominated by these two species covered 72% of the basin in each growing season. Differences were observed between extant species cover in the field and seed bank species across habitats. Two hundred and eighty T. distichum individuals have been located in wetland habitats at the VCU Rice Center. Using a GIS weighted suitability model we identified potential areas within the restored wetland for natural and facilitated bald cypress recruitment. At the VCU Rice Center ~9.7 ha have potential for natural regeneration and ~48.5 ha have potential for facilitated restoration of T. distichum.

Organisms are often adapted to their local environment, but the role of early life stages in adaptive differentiation among populations remains poorly known. The aim of my thesis was to investigate the contribution of early life stages to the magnitude and genetic basis of local adaptation, and to identify the underlying adaptive traits. For this, I used two natural populations of the annual plant Arabidopsis thaliana from Italy and Sweden, and a Recombinant Inbred Line (RIL) population derived from a cross between these populations. By combining greenhouse and field experiments, Quantitative Trait Loci (QTL) mapping, and path analysis, I examined (1) the genetic basis of seed dormancy, (2) the contribution of differential seedling establishment to local adaptation, (3) among-year variation in selection during seedling establishment, (4) direct and indirect effects of seed dormancy and timing of germination on fitness, and (5) the adaptive value of the seed bank. I found that both the level and the genetic basis of seed dormancy were affected by the maternal environment. One major-effect QTL was identified in all maternal environments, which overlaps with the dormancy gene DELAY OF GERMINATION 1 (DOG1). Selection through seedling establishment success contributed strongly to local adaptation and genetic tradeoffs, and varied among years. Variation in seedling establishment and overall fitness among RILs could be explained by genetically based differences in seed dormancy and timing of germination. Seed dormancy affected fitness throughout the life cycle, by affecting the proportion of germinated seeds, and indirectly via effects on timing of germination, plant size and flowering time. My results suggest that a considerable portion of A. thaliana seeds enter the seed bank. I found genetic differences in dormancy cycling behaviour between the two populations, which could contribute to local adaptation. The value of a seed bank should be higher at the Swedish study site than at the Italian study site due to lower rate of seed mortality in the soil. Overall, the results of this thesis demonstrate that early life stages contribute strongly to both the magnitude and the genetics of local adaptation.