Soil seed banks are important to the maintenance and restoration of floras. Extant seed banks exhibit unique characteristics with regard to the distribution of seed size and seed density. Seeds were recovered from the Upper Pennsylvanian Wise Formation in southwest Virginia. Structurally preserved seeds were also examined from coal balls of the Pennsylvanian Pottsville and Allegheny Groups, Ohio. The size distribution of the seeds from the Wise Formation is similar to that of structurally preserved seeds of the Upper Pennsylvanian Pottsville and Allegheny Group coal balls. In contrast, the seed size distributions in extant wetland, grassland, woodland and forest habitats are significantly narrower than that of seeds from the Pennsylvanian seed banks. Larger seeds are less dependent on light for germination, and aid in seedling establishment more than smaller seeds, especially in dense stable forests where disturbance events are rare. Large seed size may contribute to increased seed longevity, which reduces the effect of environmental variability on seed germination and development. The significantly larger size of the Palaeozoic seeds may have imparted an advantage for seedling establishment in the dense Palaeozoic forests. The preponderance of large seeds may be a result of the absence of large seed predators (e.g. herbivorous tetrapods), and may have been an evolutionary strategy to minimize damage to the embryo from a predator population dominated by small invertebrates with chewing or sucking mouthparts. The estimated seed density of 192 seeds/m2 in the Palaeozoic seed bank falls within the range of modern seed banks, but at the lower end of modern seed bank densities in a variety of habitats.

Vegetation in the San Cristobal Valley of Barry M. Goldwater Range-East was mapped using a combination of field surveys and aerial imagery interpretation to contribute to ongoing inventory of natural resources for the BMGR-East as well as assist in resource management decisions. Eighteen vegetation associations were identified and mapped through collection of 186 samples to characterize vegetation associations. The most common vegetation association was Larrea tridentata monotype, covering 29% of the area mapped. Larrea tridentata is a widely spread shrub throughout the Sonoran, Chihuahuan and Mojave deserts; therefore understanding germination and seedling survival patterns is crucial. Ambrosia dumosa and A. deltoidea exhibit nurse plant-protégé interactions with L. tridentata. Seed density of L. tridentata was studied under Ambrosia species to determine factors controlling germination and seedling density. As expected seed density was greater under Ambrosia canopy than areas with no canopy. Ambrosia species and canopy type did not affect seed density.

Soil seed banks are a reservoir of viable seeds present in the soil in plant communities. They have been studied and characterized in various ways in different habitats. However, these studies are limited to modern seed banks. This study extends seed bank studies to the Paleozoic Era. It was hypothesized that size distribution and seed density in Paleozoic seed banks exhibit similar patterns as in modern seed banks. Seed sizes and seed density of fossil seed from Wise Virginia were estimated. Modern seed bank information was obtained from published data. Data were analyzed using one-way ANOVA and Kruskal-Wallis test. The Paleozoic size distribution was predominated by larger seeds and the estimated seed density of 19 200 seeds m-3 falls within the range of modern seed banks but at a higher end of modern seed bank densities. During the Paleozoic they were sufficient to insure regeneration of these economically important forests.

Submitted by Rafael De Graaf Correa null (rafadegraaf@gmail.com) on 2018-03-06T19:56:08Z No. of bitstreams: 1 Final.pdf: 2078647 bytes, checksum: f204c353d549b17c80ed1a4e013c4539 (MD5) / Approved for entry into archive by Alexandra Maria Donadon Lusser Segali null (alexmar@fcav.unesp.br) on 2018-03-08T17:35:07Z (GMT) No. of bitstreams: 1 correa_rdg_me_jabo.pdf: 2078647 bytes, checksum: f204c353d549b17c80ed1a4e013c4539 (MD5) / Made available in DSpace on 2018-03-08T17:35:07Z (GMT). No. of bitstreams: 1 correa_rdg_me_jabo.pdf: 2078647 bytes, checksum: f204c353d549b17c80ed1a4e013c4539 (MD5) Previous issue date: 2018-02-16 / Entre os fatores que definem a produtividade do milho estão a disponibilidade de nutrientes, água e luminosidade, sendo esse último definido pelo adensamento da cultura, e direção da operação de semeadura, que podem interferir no sombreamento entre as plantas na lavoura. Outro fator que interfere sobre a produtividade do milho é a variação da dosagem de sementes ao longo da lavoura, que quando superior ou inferior ao potencial máximo da área para determinado híbrido afeta os resultados da cultura. A variação na dosagem de sementes ocorre entre outros motivos devido a erros na operação de semeadura, como aumento de velocidade e operação em curvas, no entanto, há escassez de estudos que definem a partir de que ponto a variação na dosagem de sementes passa a ser prejudicial a produção do milho, e por isso os produtores e a indústria te dificuldades para buscar soluções para esse problema. Com isso, foram realizados dois estudos, o primeiro com intuito de verificar os efeitos da direção de semeadura e da população de plantas sobre a produtividade do milho, e o segundo para estudar os efeitos da variação na dosagem de sementes sobre a produtividade do milho. No primeiro estudo verificou-se que o direcionamento da semeadura não exerceu influência sobre a produtividade de grãos e que menores densidades de plantas apresentam maiores resultados individuais em relação ao número e comprimento de espigas e número de grãos por fileira, porém resultados inferiores quanto à produtividade. No segundo estudo observou-se que a cada 1% de variação negativa na dosagem de sementes perdeu-se 1,06% na produtividade do milho. As variações positivas, no entanto apresentaram alterações que foram de 0 a -2,59% na produtividade. Concluiu-se que maiores densidades populacionais trouxeram ganhos na produtividade do híbrido estudado, e variações negativas na dosagem de sementes reduzem a produtividade do híbrido em até 28%. A variação positiva afeta de forma menos acentuada a produtividade da lavoura, com redução na produtividade que chega a 2,59% nas maiores variações, e pode até causar resultados positivos à produtividade dependendo do potencial máximo da área. / Among the factors that define maize productivity are availability of resources, water and luminosity, the latter being defined by the crop density and direction of the sowing operation, which may interfere with the shading between the plants in the crop. Another factor that interferes with maize productivity is seed dosage variation throughout the crop, which when higher or lower than the maximum potential of the area affects crop results. The variation in seed dosage occurs among other reasons due to errors in the sowing operation, such as speed increase and curved operation, however, there is a shortage of studies that define from which point the variation in seed dosage becomes production and therefore producers and industry find it difficult to find solutions to this problem. Thus, two studies were carried out in order to verify the effects of the direction of sowing and of the plant population on maize productivity, and the second to study the effects of variation in seed dosage on corn yield. In the first study, it was verified that the direction of sowing had no influence on grain yield and that lower plant densities presented higher individual results in relation to number of ears, length of heads and number of grains per row, and lower productivity. In the second study it was observed that every 1% of negative variation in the seed dosage was lost 1.06% in corn yield. The positive variations however presented changes that were 0 to -2.59% in productivity. It was concluded that higher population densities brought gains in the productivity of the hybrid studied, and negative variations in seed dosage reduced hybrid productivity by up to 28%. The positive variation affects crop productivity less dramatically, with a reduction in productivity that reaches 2.59% in the highest variations, and may even cause positive productivity results depending on the maximum potential of the area.

Thesis (MScConEcol)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Acacia saligna, or Port Jackson, is an Australian Acacia which has spread throughout the Western and Eastern Cape provinces of South Africa where it has become invasive and a prominent feature of the vegetation. In areas where A. saligna establishes it replaces natural vegetation, alters ecosystem processes and interferes with agricultural practices. Consequently large management efforts have been made to eradicate this invasive alien tree. However, its large and persistent soil stored seed bank, even in the presence of management and biological control agents, poses a serious obstacle to its successful removal. Furthermore the reproductive output and the size of the seed bank of A. saligna over its whole distribution as well as the variation of seed production and the seed bank with environmental conditions in time and space is poorly known. Understanding the seed bank dynamics of A. saligna in time and space is essential for reducing invasive success and achieving management objectives. This study has filled this knowledge gap through studying the seed production and seed bank of A. saligna over its invaded range in South Africa, including how environmental factors influence these factors in time and space. The seed rain of A. saligna was assessed at 10 sites across its distribution in South Africa. The seed rain of A. saligna at the sites was determined through the use of seed rain traps. Twenty five traps were placed out at every site during November 2010 (pre-dehiscence) which was collected again during April 2011 (postdehiscence). The seed bank of A. saligna was estimated through sampling at 25 sites across its distribution range in South Africa. The seed bank was sampled during April 2010 (postdehiscence), November 2010 (pre-dehiscence) and April 2011 (post-dehiscence) through taking 50 litter and soil samples at every site which gave a total sampling size of 3 750 for both the seed in the soil and litter over its distribution in South Africa. In addition the average tree diameter, tree density, average number of Uromycladium tepperianum induced galls per tree, the summer aridity index, De Martonne aridity index, winter concentration of precipitation, temperature of coldest month and the soil texture for every site was determined. The damage done by the seed feeding weevil, Melanterius compactus, was also estimated for the seed rain study sites. Water availability during the hot summer months was assessed as the most important factor governing seed production and seed bank size. Riparian and non-riparian water regimes were shown to be important in understanding the seed bank dynamics of A. saligna over its distribution range in the Cape Floristic Region. In non-riparian A. saligna populations the seed production and consequently the size of the seed bank and its rate of accumulation is limited by both water and temperature and in riparian A. saligna populations, only by temperature. Therefore, two environmental gradients influence the seed bank dynamics of Port Jackson in South Africa. In non-riparian A. saligna populations the number of seed produced and the accumulation of seed in the seed bank generally increases along the west coast of South Africa from Clanwilliam towards Cape Town and along the south coast from Cape Town towards Port Elizabeth. Seed banks are larger closer to the coast, when A. saligna populations of similar age are compared. In riparian A. saligna populations, the number of seed produced generally increases from Port Elizabeth towards Cape Town and from Cape Town towards Clanwilliam, again, with larger seed banks being accumulated closer to the coast, when populations of similar age are compared. This study provides managers with a useful tool for prioritising management efforts. / AFRIKAANSE OPSOMMING: Acacia saligna of Port Jackson is ‘n indringerplant in Suid-Afrika wat afkomstig is uit Suid-Wes Australië. Acacia saligna is ‘n onmisbare kenmerk van die plantegroei in die Wes en Oos-Kaap. Waar Port Jackson vestig, verplaas dit natuurlike plantegroei, verander dit ekosisteem prossesse en verhinder dit landbou praktyke. Gevolglik is groot bestuurspogings aangewend om hierdie indringer plant uit te roei. In die teenwoordigheid van bestuursprogramme en biologiese beheer bly A. saligna lewensvatbaar as ‘n gevolg van die plant se groot blywende grond saadreserwes. Verder is die saad produksie en saadbank grootte van A. saligna oor sy verspreiding bereike asook hoe dit met omgewingstoestande in tyd en ruimte interreageer en varieer grootendeels onbekend. ‘n Goeie en omvattende begrip van die saadbankdinamika is belangrik om die indringings vermoë van die plant te verlaag en om bestuursdoelwitte te bereik. Hierdie studie vul die bestaande gaping in die kennis aangaande die saadbank dinamika van A. saligna aan deur die saadproduksie en die saadreserves van die indringerplant oor sy verspreiding in Suid-Afrika te bestudeer, insluitend hoe omgewingstoestande die saadbankdinamika beïnvloed in tyd en ruimte. Die saadreën vir 10 A. saligna populasies was bepaal deur die gebruik van saadlokvalle. Vyf-entwintig lokvalle was uitgeplaas in elke bestudeerde Port Jackson perseel gedurende November 2010 (voor-saadval) wat weer gaan haal is gedurende April 2011 (na-saadval). Die saadbank van A. saligna was bepaal in 25 populasies van die boom gedurende April 2010 (na-saadval), November 2010 (voor-saadval) en April 2011 (na-saadval) deur die neem van 50 blaar- en grondmonsters by elke perseel wat ‘n totaal van 3 750 blaar- en grondmonster gee oor die hele verspreiding van A. saligna in Suid-Afrika. Verder is die gemiddelde boomdeursnee, boomdigtheid, gemiddelde Uromycladium tepperianum geinduseerde galle per boom, die somers droogtheids indeks, De Martonnes droogtheids indeks, die winter konsentrasie van presipitasie, die temperatuur van die koudste maand en die grond tekstuur van elke Port Jackson stand bepaal. Die skade wat die saad voedende kewer, Melanterius compactus, aanrig aan die sade van A. saligna is ook vir die persele waar die saadreën eksperiment uitgevoer is, bepaal. Die beskikbaarheid van water vir A. saligna in die droë somermaande is bepaal as die belangrikste faktor wat die grootte van die saadproduksie en saadbank beïnvloed. Oewer en nie-oewer water omgewings is bevind as noodsaaklik om die saadbank dinamika van A. saligna oor die indringerplant se verspreidingareas in die Kaap Floristiese Streek te verstaan. In nie-oewer A. saligna populasies word saadproduksie en gevolglik die grootte en tempo van akkumulasie van die saadbank deur beide water en temperatuur omstandighede beperk, terwyl in oewer A. saligna populasies word die indringerplant slegs deur temperatuur omstandighede beperk. Gevolglik blyk dit dat twee water beskikbaarheids gradiënte bestaan waarop die plant reageer wat dan uitgedruk word in die plant se saad produksie en gevolglik ook die plant se saadbank. In nie-oewer Port Jackson populasies neem die saadproduksie en die tempo waarteen die saadbank akkumuleer algemeen toe langs die weskus van Clanwilliam na Kaapstad en van Kaapstad na Port Elizabeth, met grootter saadproduksie en saadbank akkumulasie nader aan die kusgebiede, wanneer A. saligna populasies van dieselfde ouderdom vergelyk word. In oewer Port Jackson populasies neem die saadproduksie en die tempo waarteen die saadbank akkumuleer algemeen toe van Port Elizabeth na Kaapstad en van Kaapstad na Clanwilliam, met grootter saadproduksie en saadbank akkumulasie nader aan die kusgebiede, wanneer A. saligna populasies van dieselfde ouderdom vergelyk word. Hierdie studie verskaf bestuursplanne met ‘n nuttige raamwerk waarvolgens uitroeiing en beheer programme vir A. saligna beplan kan word.

O número de ações de restauração ecológica no bioma Mata Atlântica tem crescido, e a semeadura direta tem sido apontada como uma técnica complementar ao plantio de mudas de árvores, especialmente devido à possibilidade de diminuição dos custos. O presente experimento buscou testar o uso dessa técnica em larga escala, ao propor a rápida ocupação e cobertura (preenchimento) de duas áreas agrícolas degradadas com baixa resiliência através da semeadura direta de espécies de rápido crescimento e boa cobertura de copa. Em um segundo momento buscou-se utilizar a semeadura direta para enriquecimento dessas áreas. A implantação ocorreu na Usina São João, Araras, estado de São Paulo, em duas Áreas de Preservação Permanente abandonadas após uso agrícola (Área 1 e Área 2). Para a semeadura direta de preenchimento foram utilizadas 16 espécies arbóreas nativas, em cujos lotes de sementes foram realizados testes de germinação em laboratório. O delineamento experimental foi o inteiramente aleatorizado na Área 1 (48 parcelas de 200m2 0,96ha) e o de blocos casualizados na Área 2 (30 parcelas de 300m² 0,90ha). Foram aplicados três tratamentos em campo, baseados em três diferentes densidades de sementes, calculadas com base em uma projeção de indivíduos esperada no campo (Área 1 16 repetições / Área 2 10 repetições). Ao longo de 15 meses após a semeadura (A.S.) na Área 1 e 6 meses A.S. na Área 2 foi monitorado o número de indivíduos sobreviventes. Na Área 1 também ocorreu o monitoramento de altura e cobertura de copa nas linhas de semeadura (CL) por 34 meses A.S. As taxas de emergência foram cerca de 70-90% menores que as obtidas em laboratório. Mesmo assim, as densidades de indivíduos foram elevadas e diretamente relacionadas às diferentes densidades de sementes utilizadas, alcançando-se projeções de 1.215 ind.ha-1 a 13.002 ind.ha-1. Em um a três meses A.S. a densidade de indivíduos já tinha alcançado valores próximos aos obtidos no final dos monitoramentos. Aos 34 meses A.S. houve registro de indivíduos com <0,50m a 7,01-8,0m de altura, com o maior percentual (29,05%) na faixa dos 3,01m 4,0m de altura. Também aos 34 meses A.S., mais de 70% das linhas de semeadura apresentaram valores de CL acima de 101%. O custo para aquisição de sementes para obter uma muda no campo a partir de semeadura direta da maioria das espécies utilizadas pode ser duas a três vezes menor que o preço de uma muda em viveiro. Após o preenchimento das duas áreas experimentais, foram implantadas as semeaduras diretas de enriquecimento, com 30 espécies na Área 1 e 35 espécies na Área 2. Problemas relacionados à infestação por plantas daninhas, revolvimento do solo por animais e predação por formigas dificultaram a emergência das plântulas. A semeadura direta de espécies arbóreas nativas de preenchimento mostrou-se efetiva tanto técnica como economicamente para a ocupação inicial de áreas agrícolas em restauração. Porém, a efetividade é dependente das espécies utilizadas e das condições específicas do local, como o solo, sendo necessário realizar diagnósticos prévios à implantação e mesmo considerar o plantio de mudas como técnica complementar. / The number of restoration projects in the Atlantic Forest biome is increasing, and direct seeding has been identified as a complement technique to the planting of tree seedlings, especially considering the possibility of reducing the costs of the activity. This experiment sought to test the large scale use of this technique, by proposing the fast occupation and coverage (filling) of two degraded agricultural lands with low resilience through direct seeding of fast growing and wide canopy tree species. In a second moment, it was tested the use of direct seeding to increase plant richness of these areas. The experiment was set at the Usina São João, Araras, São Paulo state, in two Permanent Preservation Areas (riparian areas) abandoned after agricultural use (Area 1 and Area 2). For the filling direct seeding, 16 native tree species were used, in which seed germination tests were carried out in laboratory. The experimental design was the completely randomized in Area 1 (48 plots of 200m² 0,96ha) and the randomized blocks in Area 2 (30 plots of 300m² 0,90ha). Three treatments were tested in the field, based on three different densities of seed sowing, calculated according to an expected projection of individuals number (Area 1 16 repetitions / Area 2 10 repetitions). The number of surviving individuals was monitored over 15 months after seeding (A.S.) in Area 1 and 6 months A.S. in Area 2. Tree height and canopy cover were also monitored in Area 1 in the seeded lines (CL) during 34 months A.S. Emergence rates were about 70-90% lower than those obtained in laboratory. Even so, the densities of individuals were elevated and directly related to the different densities of seeds used, reaching a projected density on the experimental plots of 1,215 ind.ha-1 to 13,002 ind.ha-1. In one to three months A.S., the density of individuals had already reached levels close to those obtained at the end of monitoring. Thirty four months A.S., individuals of <0.50m to 7.0m-8.0m high were recorded, with the largest percentage (29.05%) in the range of 3.01m-4.0m. In this evaluation, over 70% of seeded lines showed CL above 101%. The expenses with seed acquisition to obtain a single seedling in the field from direct seeding of most species used was two to three times lower than the price of an individual seedling in nurseries. After covering the two experimental areas, direct seeding was implanted to increase plant richness, with 30 species in Area 1 and 35 species in Area 2. Problems related to weed infestation, soil disturbance by animals and predation by ants hindered seedling emergence. Direct seeding of native tree species was both technically and economically effective to the initial occupation of agricultural lands through restoration. However, effectiveness is dependent on the species used and the local site conditions, such as soils, being necessary a pre-implantation diagnosis and even the need of seedling plantation as a complementary technique.

O número de ações de restauração ecológica no bioma Mata Atlântica tem crescido, e a semeadura direta tem sido apontada como uma técnica complementar ao plantio de mudas de árvores, especialmente devido à possibilidade de diminuição dos custos. O presente experimento buscou testar o uso dessa técnica em larga escala, ao propor a rápida ocupação e cobertura (preenchimento) de duas áreas agrícolas degradadas com baixa resiliência através da semeadura direta de espécies de rápido crescimento e boa cobertura de copa. Em um segundo momento buscou-se utilizar a semeadura direta para enriquecimento dessas áreas. A implantação ocorreu na Usina São João, Araras, estado de São Paulo, em duas Áreas de Preservação Permanente abandonadas após uso agrícola (Área 1 e Área 2). Para a semeadura direta de preenchimento foram utilizadas 16 espécies arbóreas nativas, em cujos lotes de sementes foram realizados testes de germinação em laboratório. O delineamento experimental foi o inteiramente aleatorizado na Área 1 (48 parcelas de 200m2 0,96ha) e o de blocos casualizados na Área 2 (30 parcelas de 300m² 0,90ha). Foram aplicados três tratamentos em campo, baseados em três diferentes densidades de sementes, calculadas com base em uma projeção de indivíduos esperada no campo (Área 1 16 repetições / Área 2 10 repetições). Ao longo de 15 meses após a semeadura (A.S.) na Área 1 e 6 meses A.S. na Área 2 foi monitorado o número de indivíduos sobreviventes. Na Área 1 também ocorreu o monitoramento de altura e cobertura de copa nas linhas de semeadura (CL) por 34 meses A.S. As taxas de emergência foram cerca de 70-90% menores que as obtidas em laboratório. Mesmo assim, as densidades de indivíduos foram elevadas e diretamente relacionadas às diferentes densidades de sementes utilizadas, alcançando-se projeções de 1.215 ind.ha-1 a 13.002 ind.ha-1. Em um a três meses A.S. a densidade de indivíduos já tinha alcançado valores próximos aos obtidos no final dos monitoramentos. Aos 34 meses A.S. houve registro de indivíduos com <0,50m a 7,01-8,0m de altura, com o maior percentual (29,05%) na faixa dos 3,01m 4,0m de altura. Também aos 34 meses A.S., mais de 70% das linhas de semeadura apresentaram valores de CL acima de 101%. O custo para aquisição de sementes para obter uma muda no campo a partir de semeadura direta da maioria das espécies utilizadas pode ser duas a três vezes menor que o preço de uma muda em viveiro. Após o preenchimento das duas áreas experimentais, foram implantadas as semeaduras diretas de enriquecimento, com 30 espécies na Área 1 e 35 espécies na Área 2. Problemas relacionados à infestação por plantas daninhas, revolvimento do solo por animais e predação por formigas dificultaram a emergência das plântulas. A semeadura direta de espécies arbóreas nativas de preenchimento mostrou-se efetiva tanto técnica como economicamente para a ocupação inicial de áreas agrícolas em restauração. Porém, a efetividade é dependente das espécies utilizadas e das condições específicas do local, como o solo, sendo necessário realizar diagnósticos prévios à implantação e mesmo considerar o plantio de mudas como técnica complementar. / The number of restoration projects in the Atlantic Forest biome is increasing, and direct seeding has been identified as a complement technique to the planting of tree seedlings, especially considering the possibility of reducing the costs of the activity. This experiment sought to test the large scale use of this technique, by proposing the fast occupation and coverage (filling) of two degraded agricultural lands with low resilience through direct seeding of fast growing and wide canopy tree species. In a second moment, it was tested the use of direct seeding to increase plant richness of these areas. The experiment was set at the Usina São João, Araras, São Paulo state, in two Permanent Preservation Areas (riparian areas) abandoned after agricultural use (Area 1 and Area 2). For the filling direct seeding, 16 native tree species were used, in which seed germination tests were carried out in laboratory. The experimental design was the completely randomized in Area 1 (48 plots of 200m² 0,96ha) and the randomized blocks in Area 2 (30 plots of 300m² 0,90ha). Three treatments were tested in the field, based on three different densities of seed sowing, calculated according to an expected projection of individuals number (Area 1 16 repetitions / Area 2 10 repetitions). The number of surviving individuals was monitored over 15 months after seeding (A.S.) in Area 1 and 6 months A.S. in Area 2. Tree height and canopy cover were also monitored in Area 1 in the seeded lines (CL) during 34 months A.S. Emergence rates were about 70-90% lower than those obtained in laboratory. Even so, the densities of individuals were elevated and directly related to the different densities of seeds used, reaching a projected density on the experimental plots of 1,215 ind.ha-1 to 13,002 ind.ha-1. In one to three months A.S., the density of individuals had already reached levels close to those obtained at the end of monitoring. Thirty four months A.S., individuals of <0.50m to 7.0m-8.0m high were recorded, with the largest percentage (29.05%) in the range of 3.01m-4.0m. In this evaluation, over 70% of seeded lines showed CL above 101%. The expenses with seed acquisition to obtain a single seedling in the field from direct seeding of most species used was two to three times lower than the price of an individual seedling in nurseries. After covering the two experimental areas, direct seeding was implanted to increase plant richness, with 30 species in Area 1 and 35 species in Area 2. Problems related to weed infestation, soil disturbance by animals and predation by ants hindered seedling emergence. Direct seeding of native tree species was both technically and economically effective to the initial occupation of agricultural lands through restoration. However, effectiveness is dependent on the species used and the local site conditions, such as soils, being necessary a pre-implantation diagnosis and even the need of seedling plantation as a complementary technique.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Objective was to evaluate the effects of different population arrangements in forage sorghum grazing on forage production, morphogenesis, pasture structure, performance, and animal behavior. They were used 36 crossed heifers between Charolais and Nellore, with initial age of 15 months and 262 kg of body weight (BW). The experimental period lasted 84 days, divided into periods of 28 days. The animals received daily supplementation to the level of 1% of body weight. Treatments consisted of a combination of spacings of 22 or 44 cm in planting spacing with two densities of seeds per hectare, 12 or 24 kg, resulting in arrangements population E44D12; E44D24; E22D12; E22D24. The grazing method was continuous with variable number of regulators animals. The forage mass and the mass of leaf blades did not differ between population arrangements, with average values of 1279.11 and 232.99 kg DM / ha. Similarly the stocking rate, dry matter accumulation rate and weight gain per area, with average values of 1172.32 kg LW / ha, 58.47 kg DM / ha / day and 303.31 kg PV / ha, in that order. The performance and development of the animals were not affected by population arrangements grassland, with weight gain and average final weight between treatments of 0.891 kg / day and 330.36 kg of PV. The relation weight:height among the population arrangements was 2.67 kg / cm, indicating that cross heifers between Charolais and Nellore with 18 months of age have fat thickness and appropriate weight for slaughter. Productive parameters of pasture and animal performance were influenced by evaluation periods. The different population arrangements change the behavioral patterns of animals, E44D24 and E22D12 treatments increase the grazing time. The E44D24 treatment decreases the bit rate when compared to E22D24. The lower density of plants per square meter causes the increase in the number of feeding stations / minute and the displacement rate of the animals. The spacing between rows 22cm promote a larger number of bits/food station. The use of higher density of seeds and larger spacing between lines increases the density of leaf blades in the lower and upper stratum of the pasture, respectively. The E44D12 and E22D24 treatments have higher amounts of stems in the upper stratum of the pasture (over 60 cm). Morphogenic variables were not significantly influenced by the different arrangements of plants used and the evaluation periods, being obtained elongation rate and leaf senescence of 1.43 and 1.11 cm/day/tiller, respectively, leaf appearance rate and leaf appearance interval of 0.28 leaves/day/tiller and 3.81 days phillochron and leaf life span of 72.99 and 351.68 degree day, in that order. Have the structural characteristics of pasture were influenced by evaluation periods, reflecting the forage production decline with advancing the use of the pasture cycle. The first to the third evaluation period was verified a reduction of 65.53% in the number of sheets in elongation and 47.79% in the number of living leaves. / Objetivou-se avaliar os efeitos de diferentes arranjos populacionais em pastagem de sorgo forrageiro na produção forrageira, morfogênese, estrutura do pasto, desempenho e comportamento animal. Foram utilizadas 36 novilhas de corte cruzadas entre as Charolês e Nelore, com idade média inicial de 15 meses e 262 Kg de peso vivo (PV). O período experimental durou 84 dias, divididos em períodos de 28 dias. Os animais receberam suplementação diária à nível de 1% do peso vivo. Os tratamentos consistiram na combinação de espaçamentos de 22 ou 44 cm na entrelinha de plantio com duas densidades de sementes por hectare, 12 ou 24 Kg, resultando nos arranjos populacionais E44D12; E44D24; E22D12; E22D24. O método de pastoreio utilizado foi contínuo, com número variável de animais reguladores. A massa de forragem e a massa de lâminas foliares não diferiram entre os arranjos populacionais, apresentando valores médios de 1279,11 e 232,99 Kg de MS/ha. Da mesma forma a carga animal, taxa de acúmulo de matéria seca e o ganho de peso por área, apresentando valores médios de 1172,32 Kg de PV/ha, 58,47 Kg de MS/ha/dia e 303,31 Kg de PV/ha, nessa ordem. O desempenho e o desenvolvimento dos animais não foram influenciados pelos arranjos populacionais da pastagem, apresentando ganho de peso e peso final médio entre os tratamentos de 0,891 Kg/dia e 330,36 Kg de PV. Os parâmetros produtivos da pastagem e desempenho animal foram influenciados pelos períodos de avaliação. Os diferentes arranjos populacionais alteraram os padrões comportamentais dos animais, os tratamentos E44D24 e E22D12 aumentam o tempo de pastejo. O tratamento E44D24 diminui a taxa de bocado quando comparado ao E22D24. A menor densidade de plantas por metro quadrado ocasiona o aumento no número de estações alimentares/minuto e a taxa de deslocamento dos animais. O espaçamento 22 cm entrelinhas promove um maior número de bocados/estação alimentar. A utilização de maior densidade de sementes e maiores espaçamentos entrelinhas aumenta a densidade de lâminas foliares no estrato inferior e superior da pastagem, respectivamente. Os tratamentos E44D12 e E22D24 apresentaram maiores quantidades de colmos no estrato superior do pasto (acima de 60 cm). As variáveis morfogênicas não foram influenciadas significativamente pelos diferentes arranjos de plantas utilizados e pelos períodos de avaliação, sendo obtidos taxa de alongamento e senescência foliar de 1,43 e 1,11 cm/dia/afilho, respectivamente, taxa de aparecimento foliar e intervalo de surgimento de folhas de 0,28 folhas/dia/afilho e 3,81 dias, filocrono e duração de vida foliar de 72,99 e 351,68 graus dia, nessa ordem. Já as características estruturais da pastagem foram influenciadas pelos períodos de avaliação, refletindo a queda de produção forrageira com o avançar do ciclo de utilização da pastagem. Do primeiro para o terceiro período de avaliação foi verificado uma redução de 65,53% no número de folhas em alongamento e de 47,79% no número de folhas vivas.

Thesis (M.Sc. Agriculture (Pasture Science)) -- University of Limpopo, 2021 / Savanna rangelands are ecosystems which are characterized by the co-existence of scattered trees and shrubs with a continuous grass layer. However, the grass and tree balance has been highly altered as a result of disturbances caused by bush encroachment. Encroaching woody species have been shown to decrease species richness and abundance of the seed bank and ground‐layer diversity. So far little is known on the effect of bush encroachment and soil depth on the soil seed bank diversity in savanna rangelands. The objectives of this mini-dissertation were to (1) determine the influence of soil depth on soil seed bank diversity in bush encroached savanna rangelands, and (2) determine the relationships between soil seed bank herbaceous vegetation and physicochemical properties in encroached rangeland. In order to address these objectives, a savanna rangeland was demarcated into two encroachment gradients spanning from open to encroached rangeland. Within each encroachment gradient, six plots of 10 m x 10 m were randomly selected, whereby soil sampling and herbaceous vegetation were carried out and determined. In each replicate plot per encroachment level, five soil samples were randomly collected at 0-10 and 10-20 cm depths. The number of seedlings of different species emerging from the soil samples was used as a measure of the number of viable seeds in the soil and the composition of the seed bank using the seedling emergence method. The total seed densities showed significant differences (P<0.05) in the 0-10 cm depth layer in the open rangeland and encroached rangeland. Bush encroachment significantly (P<0.05) decreased the seed density of perennial grasses, specifically in 0-10 cm depth layer. Further, species diversity increased with bush encroachment in the 10-20 cm depth layer. Menhinick’s richness index showed no significant difference in the open and encroached rangeland, while species evenness decreased in the 0-10 cm depth layer and increased at 10-20 cm depth.The study also revealed negative correlations between organic carbon, calcium, clay, silt and forbs while mean weight diameter (MWD), a measure of soil aggregate stability was positively correlated with forbs. The canonical correspondence analysis (CCA) showed that pH, phosphorus, potassium and calcium were positively correlated to Eragrostis curvula and magnesium was negatively correlated to Panicum maximum. In open rangeland, CCA revealed that clay content was negatively correlated with species evenness while xii magnesium was negatively correlated to the Shannon Weiner index. Further, silt content was positively correlated with species richness and evenness. In the encroached rangeland, the CCA showed a negative correlation between magnesium and the Shannon Weiner index. The Sørensen’s index between soil seed banks and aboveground vegetation was low with index values of 0.22 and 0.24 in open and encroached rangeland, respectively. / AgriSeta